64-slice ct scanners evaluation

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64-Slice

Computed Tomography Systems

Computed tomography systems offering 64 slices are highly popular

because of their fast acquisition time. Any of the four systems cov-

ered in this article is likely to meet your basic CT needs. But each of-fers differing features and capabilities—for example, they’re not all

equally effective at cardiac imaging. Our Evaluation will help you de-cide which product is best for your facility.

We tested and rated the following products:

u GE LightSpeed VCT

u Philips Brilliance 64

u Siemens Sensation 64

u Toshiba Aquilion 64 w




Evaluation at a Glance: 64-Slice CT Systems

GE LightSpeed VCT Philips Brilliance 64 Siemens Sensation 64 Toshiba Aquilion 64

PRODUCT RATING

butsomewhat lessdesirable

than theother systems

IMAGE QUALITY Good Good Good ✪ Excellent

Noise characteristics Good Good Good Good

Slice thickness and

spatial resolution Good Good ✪ Excellent—Ultrahigh-

resolution mode is avail-able (0.3 mm slices)

✪ Excellent—Narrow-

est slices

Uniformity ✪ Excellent intersliceuniformity

Good ✪ Excellent—Best uni-formity performance

✪ Excellent—Goodscores

Temporal resolution ✪ Excellent—Best scoresoverall

✪ Excellent—Highscoresfor phantom images

Good ✪ Excellent—Bestscoresfor narrowest slices

Artifacts Good Good Good Good

DOSE MANAGEMENT ✪ Excellent ✪ Excellent ✪ Excellent ✪ Excellent

Dose ✪ Excellent—CardiacSnapShot Pulse reducesdose by 80%; “Color Cod-ing Kids” used for pediatric

doses; 3 filters automati-cally match image size

✪ Excellent—CardiacStep & Shoot image ac-quisition reduces dose

✪ Excellent ✪ Excellent—Auto-matic selection of filtersbased on image size

Dose modulation ✪ Excellent—Dose is

recorded for all exams asDICOM image

✪ Excellent ✪ Excellent—Uses non-

linear exposure model solarger patients receiveless dose

✪ Excellent—Dose is

recorded within DICOMdata

WORKFLOW

INTEGRATION

✪ Excellent ✪ Excellent Good Good

Clinical experience ✪ Excellent—High-powerx-ray source for obese pa-

tients; descriptive namesfor reconstruction filters

✪ Excellent—Smallfocal spot (high resolu-

tion) available at high mAsettings

Good Good

Image acquisition

performance Good ✪ Excellent—Wide-

coverage stroke detection

and real-time imagedisplay

Good Good

Postprocessing ✪ Excellent—Wide range

of applications, includingwide-coverage stroke de-tection and computer-

assisted reading

✪ Excellent—Remote

users can reprocess im-ages; full range of appli-cations, including ability to

export data to cath lab

✪ Excellent—Automated

postprocessingworkflow;wide range of clinical appli-cations, including true CAD

for lung noduledetection

✪ Excellent—Vitrea

workstation includes ac-cess to lung noduleCAD software

Ease of use Good Good ✪ Excellent—Intelligenthelp for setting parameters

✪ Excellent—Severalfeatures make imageacquisition more consis-

tent regardless of userexperience

Connectivity Good Good Good Good

SERVICE AND

SUPPORT

Good Good Good Good

User feedback ✪ Excellent ✪ Excellent ✪ Excellent ✪ Excellent

Training ✪ Excellent—Remoteusers can control acquisi-

tion parameters

Good ✪ Excellent—Remoteservice and access to ap-

plications specialists

✪ Excellent

Reliability and

maintenance Good Good Good Good

Planning Good ✪ Excellent—Unique in-stallation planningand ar-chitectural services help

reduce patient anxiety

Good Good



saved with the images. In addition, GE’s cardiac dose-sav-

ing feature, Cardiac SnapShot Pulse, demonstrated an 80%

dose saving during our tests, although it has limitations—

such as only being usable for heart rates up to 65 bpm and

producing an image of only one part of the cardiac phase.Extended-coverage brain perfusion imaging is available.

For advanced 3-D processing, GE depends on the Advan-

tage Workstation, which has some unique applications

(e.g., stent planning, pacemaker planning, body perfusion

calculation, colonography, densitometry). For large pa-

tients, the standard configuration has the most powerful

specified x-ray generator. GE also provides a wide range

of training and business-optimization services.

Philips Medical Systems Brilliance 64

u Provides high-quality images and includes some useful

and unique applications, such as remote access to rawdata and large-coverage stroke detection.

The Brilliance 64 provides consistent, high-quality images

in both cardiac and noncardiac applications. Its Extended

Brilliance Workspace feature enables multiple users to ac-

cess and reconstruct raw data remotely, a unique capability

that is likely to benefit radiologists who are not physically

close to the scanner. In departments with Philips cardiol-

ogy imaging equipment, the Brilliance can be closely inte-

grated with Philips’s TrueView technology, which allows

CT cardiac images to be displayed in the cath lab. Philips

offers a function called Step & Shoot that provides ad-

vanced dose saving in cardiac CT, although it has limita-

tions—for example, it cannot be used with higher heart

rates and produces an image of only one part of the cardiac

phase. In stroke imaging, the Jog Mode has been used for

a few years to provide reliable and accurate brain perfu-

sion images.

For imaging obese patients, Philips has an optional ta-

ble with a weight limit of 295 kg (650 lb), which is thehighest capacity available, and the x-ray tube can be used

at maximum power on the small focal spot for short peri-

ods, so high-resolution imaging is possible with larger pa-

tients. In addition, Philips offers good tube warranty terms

and upgrade options, improving the predictability of the

overall cost of ownership. And the company provides all

the information required for installation planning and of-

fers architectural design features—including lighting—

designed to reduce patient anxiety.

LESS DESIRABLE ACCEPTABLE PRODUCT

The remaining system is also rated Acceptable but is not

quite as desirable as the others because its cardiac image

quality—a vital factor when choosing a 64-slice system—

doesn’t quite measure up to that of the other systems.

Siemens Medical Solutions Sensation 64

u Offers excellent performance for noncardiac applica-

tions, including computer-aided detection.

The Sensation 64 is a good choice for noncardiac applica-

tions, as well as for facilities standardizing on the Siemens

multimodality platform (Syngo) for workflow and eco-

nomic considerations. It provides high-quality images witha straightforward user interface. It offers the highest spa-

tial resolution and narrowest slice thickness of the systems

we evaluated; this is useful in some limited applications,

such as inner-ear exams. Also, the image uniformity is ex-

ceptional, and the default dose settings are the lowest of

the systems we tested. However, a disadvantage is the sys-

tem’s narrower coverage, which is only half of that

provided in other systems.

380 HEALTH DEVICES December 2007 ■ www.ecri.org ©2007 ECRIInstitute.Duplication ofthis page by any meansfor any purposeis prohibited.

A Comment on Slices

Why Test 64?

Each supplier covered in this Evaluation offers a

range of systems, providing varying numbers of

slices. In our April 2007 Guidance Article “Com-

puted Tomography—How Many Ways Should You

Slice It?” we concluded that 16-slice systems are ad-

equate for most applications. So why did we concen-

trate on 64-slice products for this Evaluation?

One reason is that 64-slice systems represent the

latest available technology* and are heavily pro-

moted by suppliers, so there is considerable pressure

on facilities to offer them. Another is that in most

cases, suppliers’ 16- and 64-slice systems have

many similarities. This means that facilities looking

at 16-slice systems can use our findings to judge

many of those products’ capabilities, particularly in

areas such as x-ray detection, image reconstruction,and applications software. (However, our actual

product ratings apply only to the specific 64-slice

systems we tested.) ◆

* Systems offering 256 slices are in the late stages of development

butare still several months from being commercially available. We

profiled this technology in our November2007 Technology Timeline

article, “256-Slice Wide-Detector Computed Tomography.”

(continued from page 378)



The Syngo multimodality platform has now been used

for a number of years and has proved popular. The image

display workstation uses the same database as the acquisi-

tion computer, so there are no data transfer penalties, and

data can be reprocessed without interfering with acquisi-

tion. Users can access some of the 3-D image visualization

tools on remote computers over the Internet. Siemens is

the only CT manufacturer to offer computer-aided detec-

tion for lung nodules. Users of Siemens cardiology imag-

ing equipment can display CT cardiac images within the

cath lab.

Siemens also offers some potentially useful service

and monitoring tools. These depend on a CT system being

electronically accessible by Siemens (via a virtual private

network [VPN], usually through a facility’s firewall).

Siemens provides proactive system monitoring, as well as

good tube warranty coverage and unique utilization and

management data.

Desirable Features and HowWe Tested For Them

Multislice CT is used for a wide variety of diagnostic and

screening exams. Not only must the image quality be ade-

quate with minimum x-ray dose, but the systems must al-

low efficient patient throughput and have high reliability.

Our specific tests are listed on this page. In broad outline,

they consisted of the following:

Image Quality

Image quality determines diagnostic accuracy. You need a

scanner that offers the highest-quality images without sig-

nificantly increasing dose. We used standard CT image

quality measurement techniques (noise, uniformity, slice

thickness, spatial resolution, and low-contrast detectability)

to assess the image quality across the full range of clini-

cally relevant imaging parameters. We used either our own

phantom or industry-standard phantoms to ensure compa-rability of the results.

Our measurement methods are widely used, and most

are objective; for example, our criteria are based on indus-

try standards such as the International Electrotechnical

Commission’s IEC 61223-3-5 (Acceptance Tests—Imag-

ing Performance of Computed Tomography X-Ray

Equipment). However, other measurements, such as low-

contrast detectability, are necessarily subjective; in such

cases, all images were anonymized to ensure an unbiased

result.

A particularly important feature of 64-slice CT systems

is the ability to acquire clear images of coronary arteries in

the beating heart. To test this, we designed and built a dy-

namic test phantom that emulated the motion of the coro-nary arteries at various heart rates. The phantom can be

connected to the ECG input of a CT system so that it can

be imaged in exactly the same way that a patient would be.

For more details, see the discussion of ECRI Institute’s

cardiac phantom, below.

Dose Management

Suppliers have made considerable efforts to reduce the

dose of CT scans, in particular controlling the dose based

on the patient’s size. Using phantoms, we evaluated the ef-

fectiveness of dose-reduction technologies and the effect


Tests Performed

Image Quality

■ Noise Characteristics

■ Slice Thickness and Spatial Resolution

■ Uniformity

■ Temporal Resolution

■

Artifacts

Dose Management

■ Dose

■ Dose Modulation

Workflow Integration

■ Clinical Experience

■ Image Acquisition Performance

■ Postprocessing

■ Ease of Use

■ Connectivity

Service and Support

■ User Feedback

■ Training

■ Reliability and Maintenance

■ Planning ◆




on dose when using different beam collimations. We also

looked at dose-control mechanisms for pediatric patients.

Workflow Integration

CT systems must reliably and consistently perform many

different scans on a wide range of patients, and the resulting

data must be processed and interpreted. Efficient workflow

requires adequate equipment and good integration with

other systems.

We ascertained how well systems fit into the workflow

by exploring the application tools available, surveying us-

ers, and examining the compliance to relevant standards

applicable to CT (e.g., DICOM, IHE).

Service and Support

CT systems are complex and will require both routine and

emergency service, making good manufacturer servicingimportant. We surveyed users regarding their experiences

with the manufacturers. In addition, we looked at each

manufacturer’s policies regarding service, particularly

x-ray tube reliability and warranty options.

ECRI Institute’sCardiac Phantom

To assess the dynamic image quality of the evaluated sys-

tems, we designed and built a dynamic phantom that con-

tained three contrast-filled catheters (diameters 1.3 mm,

1.9 mm, and 2.5 mm). The catheters were moved by a

microprocessor-controlled mechanism to simulate cardiac

motion at various heart rates (65 bpm, 75 bpm, 85 bpm,

and irregular). The phantom had an ECG output that con-

nected to a CT scanner in the same way that a patient

would be. Images were acquired and reconstructed using

the manufacturers’ recommended protocols.

The images from our phantom (about 200 for eachheart rate) were processed using a maximum intensity pro-

jection to create composites, some of which can be found

in the product profiles for the individual systems. The im-

ages of the catheters were assessed using the following

scale:

5. Clear and sharp throughout

4. Slight blurring and irregularities

3. Majority of sectors usable

2. Minority of sectors usable

1. Unusable

Schematic of our cardiac phantom, showing mechan-

ical motion.



Evaluation Findings

Overall PerformanceThe evaluated systems are all able to consistently provide

images of suitable quality. All of the users we interviewed

said that they would choose the same system again.* Even

customers who reported some problems answered posi-

tively. At the same time, we found that each manufacturer

had some unique features and technologies, which we de-

tail in this and the following sections.

IMAGE QUALITY

General findings. The tables on pages 384 through 386

summarize our image quality measurements. As our re-

sults show, the image quality provided by all the systems

is within acceptable limits. However, there are some dif-

ferences among the systems that are discussed in the indi-

vidual product profiles.

Dynamic imaging. Perhaps the hardest aspect of modern

CT scanning to evaluate objectively is the quality of an

image captured from a beating heart. Our assessment using

simulated coronary arteries showed clear differences be-

tween the systems (see “ECRI Institute’s Cardiac Phan-

tom” on page 382), particularly at higher and irregular

heart rates: GE’s and Toshiba’s images were clear and

sharp, the other systems’ slightly less so. The images also

demonstrated that manufacturers use significantly differentreprocessing parameters (e.g., reconstruction filters, slice

width). It is possible that these will affect the accuracy of

the cardiac images. Therefore, we believe that more re-

search into those factors is needed.

DOSE MANAGEMENT

Dose modulation based on information retrieved from

scout views is now standard on CT systems. While there

are subtle differences between the approaches used, the

techniques achieve comparable dose savings of 40% to

60%. Absolute dose savings will depend not only on the

technology, but also on how the user configures and usesthe tools provided.

Dose control is a major issue in cardiac imaging. ECG

gating of the x-ray exposure—that is, using the ECG sig-

nal to trigger the beginning and end of a scan—is now

standard, and each manufacturer achieves dose reductions

between 13% and 20%, which represent comparable effec-

tiveness. Even so, cardiac CT remains a high-dose exam.GE, Philips, and Siemens have techniques using axial ac-

quisition that can reduce the dose by 80%. However, there

are limitations to these techniques, and other more signifi-

cant technological innovations may prove to be more ef-

fective at reducing dose without limiting the diagnostic

information—for example, dual-source CT from Siemens

and 256-slice CT from Toshiba. ECRI Institute believes

that dose is becoming a key decision issue when choosing

CT systems for cardiac imaging. It is vital that users

understand the benefits and limitations of any new

techniques being proposed.

WORKFLOW INTEGRATION

It is clear from our study that all the manufacturers have

made considerable efforts to develop intuitive user inter-

faces; all of them define clear steps through which the user

progresses. However, differences emerge when consider-

ing how image acquisition and image reconstruction

coexist. Some manufacturers put scan planning and recon-

struction into one console, while others use separate

consoles. One console is sufficient if it is unlikely that

physicians will ask for additional reconstructions and if

workspace is limited. But in situations with more demand-ing physicians who are likely to request additional pro-

cessing, two separate workstations are preferred so that

scanning is not interrupted. One manufacturer, Philips, has

introduced technology that enables any user to access raw

data remotely; this technology enables radiologists to re-

process images without interrupting workflow and to do so

from different locations.

The huge amount of data produced by CT means that

3-D processing is now indispensable. Picture archiving

and communication system (PACS) workstations are gen-

erally not adequate for this purpose, but few facilities can

afford to purchase sufficient 3-D workstations to handle

their workloads. So the trend today is to use thin-client

technology so that users can access advanced 3-D func-

tionality from personal computers or PACS workstations.

Different pricing models are used for licensing the number

of concurrent users, so overall costs will be variable.


* Note that we did not restrict our user survey to names provided by the

manufacturers. (continued on page 386)




Table 1. Noise Comparison

Spatial frequency,line pairs/cm Noise, %

GE Philips Siemens Toshiba

3 (standard) 0.36 0.38 0.35 NA

5 (chest) 1.7 1.7 1.8 0.9

6 (lung) 2.3 2.3 2.5 3.2

9 (bone) 4.2 4.2 4.7 10.6

Noise limits the visibility of details, so it is widely used as an indicator of image quality—the lower the

noise, the better the image quality. However, noise is strongly affected by the sharpness of the image,

which is determined by the reconstruction kernel. In fact, there is a linear relationship between them.

Therefore, to compare systems, we can interpolate the noise produced by each at specific spatial fre-

quencies. These values show comparable performance for three of the systems; the exception is

Toshiba. In soft-tissue imaging, Toshiba uses a higher spatial resolution and has lower noise. But in bone

imaging (which is a high-resolution technique), Toshiba has higher noise. Keep in mind, however, thatminimizing noise is more important during soft-tissue imaging than during high-resolution imaging.

In addition to the standard reconstruction kernels, manufacturers also include high-resolution kernels

with reduced noise levels, sometimes referred to as adaptive filters. Our results confirm that adaptive fil-

ters allow the dose to be reduced in high-resolution imaging. The main disadvantage with these filters is

that they require a slightly longer reprocessing time.

Table 2. Uniformity Comparison

Results in italics represent the best uniformity. Numbers in parentheses indicate the slice thickness used.


Intraslice axial uniformity, HU 3.7 (5 mm) 3.6 (5 mm) 0.3 (4.8 mm) 0.4 (8 mm)

Interslice axial uniformity, HU

Broad slices 1.0 (5 mm) 3.8 (5 mm) 0.8 (4.8 mm) 0.83 (8 mm)

Narrow slices 2.68 (0.625 mm) 8 (0.6 mm) 2.25 (1 mm) 1.53 (0.5 mm)

Interslice uniformity for 5 mm

spiral slices, HU

1.0 1.0 0.3 1.1

In CT images, voxel values are directly related to the attenuation characteristics of the subject. The voxel

values in a uniform phantom image should be uniform regardless of the position of the phantom. Unifor-

mity depends on good calibration for all the detectors. Low values indicate good uniformity.

For all four systems, the measurements were within acceptable limits. Overall, the Siemens and

Toshiba results demonstrated better performance.




Table 3. Sharpness Comparison

Higher values indicate sharper images. Results in italics represent the best performance.


Soft-tissue imaging Standard kernel UB kernel B31s kernel FC22 kernel

50% 3.6 lp/cm 3.0 lp/cm 3.3 lp/cm 4.4 lp/cm



Lung imaging Lung kernel E kernel B70s kernel FC50 kernel




Bone imaging Edge kernel D kernel B75h kernel FC80 kernel




The sharpness of any imaging device can be measured using the modulation transfer function (MTF). Put

simply, the MTF is a plot of contrast against spatial resolution. In general, MTF decreases with spatial

resolution—in other words, fine detail (high spatial resolution) is more difficult to see. CT manufacturers

typically report the spatial frequencies at specific points along the MTF curve for comparison (e.g., 50%,

10%, and 2%). The 10% values are probably the most indicative of the image sharpness. However, the

MTF is dependent on the reconstruction kernel. This table reports the spatial frequency, in l ine pairs

(lp)/cm for specific points on the MTF response for three kernels for each manufacturer.

Table 4. Nominal versus Measured Slice Thickness

Results in italics indicate closest agreement between nominal and measured values.


Nominal, mm 0.625 0.625 0.6 0.5

FWHM 0.72 0.83 0.69 0.60

FWTM 1.3 1.7 1.5 1.0

Nominal, mm 5 5 5 5

FWHM 5.3 5.0 5.1 5.0 FWTM 8.2 8.6 8.0 5.7

The thickness of helical slices is measured by assessing a profile of a thin object through multiple slices.

The full width half maximum (FWHM) of the profile defines slice thickness and should match the set value,

while the full width tenth maximum (FWTM) shows the spread of the slice profile—a narrower spread is

preferred. Toshiba images show smaller spreads than those of the other systems.



The range of clinical applications available on different

suppliers’ 3-D workstations is broadly similar. The main

differences can be found in the quantitative and automated

tools they provide, such as computer-aided detection and

computer-assisted reading. It is important to keep in mindthat buyers are not limited to choosing a 3-D workstation

from the same manufacturer as the CT system, so they

should carefully consider their options and what is best for

their specific situation.

INSTALLATION AND MAINTENANCE

All the manufacturers have made considerable efforts to

provide installation, training, and maintenance services to

their customers. For example, they all have training

schools and normally include training for two hospital cli-

nicians with the purchase of new equipment. In addition,the companies’ applications specialists will spend some

time on-site after installation.

The users we surveyed were satisfied with the overall

level of service they received. However, one common com-

plaint with CT is the time involved in waiting for replace-

ment parts. This is unavoidable to some extent, since the

high cost of most parts means that it is not feasible to main-

tain spare-parts inventories within healthcare facilities.

Instead, manufacturers maintain distributed parts depots,

which can entail a longer delivery time. However, facili-

ties that allow manufacturers to remotely troubleshoot

their CT systems should benefit from earlier parts

delivery.

The most significant service issue with CT is the x-raytube life. A replacement tube can cost $200,000. There is

no standard method used to determine tube use, so com-

paring manufacturers’ warranties can be challenging. Our

calculations showed a wide variation in warranted tube life

from 120,000 to 250,000 scan seconds. Also, our survey

showed that x-ray tube life span tends to be random: Some

tubes lasted four months, while identical tubes lasted two

years. Based on our pooled data, users should budget to re -

place their tubes at least once per year. However, our sur-

vey found that one manufacturer, Toshiba, showed

consistently more reliable x-ray longevity, with most cus-

tomers still using their first tube after more than a year of operation.

For a fee, all the manufacturers will train hospital or

third-party service technicians in the same way as their

own technicians; most also require substantial additional

annual licensing fees to allow these technicians to service

their equipment. The bottom line is that, for facilities

wanting to service their own equipment, the full costs

must be considered.


Table 5. Low-Contrast Detectability

Results in italics represent best performance.

GE Standardkernel

Philips UBkernel

Siemens B31skernel

Toshiba FC13kernel

Dose CTDIvol, mGy* 53 41 43 35

Minimum visible

diameter, mm

At 1% contrast 2 2 2 2

At 0.5% contrast 2 3 3 2

At 0.3% contrast 3 5 4 2

* Dose calculated using the head phantom CTDIw values and mAs.

The detectability of low-contrast objects of various sizes is often used to visually confirm the other mea-

surements. In CT, the minimum visible diameter is reported at three contrasts. A smaller diameter indicates

better image quality. However, manufacturers differ in how dose is determined, so comparing systems re-

quires close analysis of specifications. The results for the evaluated systems are comparable; Toshiba

shows the best performance overall.

(continued from page 383)



About the Product Profiles

Starting on the next page, we describe each evaluated

product and note the test results that contributed to our rat-

ings. We present only those results from our testing that

we determined to be significant; we don’t discuss results

for tests in which a unit simply met our criteria or had noremarkable features. However, for all tests or test catego-

ries, we present an ECRI Institute judgment of the unit’s

performance according to the following scheme:

■ Excellent. The system possesses a feature or performs

at a level that would likely be considered favorable dur-

ing the selection process.

■ Good. The system performs satisfactorily. In general,

any advantages of the system balance or outweigh any

disadvantages.

■ Fair. The system either does not perform satisfactorily

or has a noteworthy deficiency or limitation. However,

the failure, deficiency, or limitation is not likely to (1)

cause an adverse clinical outcome, (2) significantly af-

fect the overall performance of the system, or (3) place

an excessive burden on those who purchase, use, or

service the system.

■ Poor. The system does not perform satisfactorily, and

its deficiencies or limitations are likely to (1) adversely

affect the clinical outcome, (2) significantly affect the

overall performance of the system, or (3) place an ex-

cessive burden on those who purchase, use, or service

the system.

Note that, in future updates of this study, our judgments

may change as we obtain new information.


Health Devices Evaluations rate products based on their clinical

and technical acceptability and desirability. Ratings are based on

standard commercial products. Suppliers often modify theirprod-

ucts in response to our findings, sometimes before we publishour Evaluations. If the modified product is not available in time for

us to verify the significance of the change, we may include a

statement of thesupplier’s intentions. In future issuesof Health

Devices, we mayupdate the information provided for theevalu-

ated products and may revise our ratings.

We recommend that you use our ratings as a guide for se-

lecting the best products for your healthcare facility. Actual

purchasing decisions should be based on a thorough under-

standing of the article, as well as on your specific clinical

applications, users’ opinions, standardization policies, direct

experience with the supplier, and price.

Ratings Category: Acceptable for Use

The product meets all major performance

and safety criteria. It has no serious shortcomings and offers

significant advantages over other alternatives.

The product meets all major performance

and safety criteria and has no serious shortcomings.

The product does what it is intended to

do, but not at the desired level of performance, or it has sig-

nificant disadvantages compared with other alternatives. For

example, it may be more difficult to use or clean, or it may be

less suitable for a specific application. A product that we rate

Not Recommended is safe to use and does not have to be

withdrawn from service. However, we recommend against

purchasing the product unless overriding considerations

warrant it.

Ratings Category: Unacceptable

The product fails to meet significant criteria

for performance or poses significant safety risks. A healthcare

facility that does not own such a product should not purchase

it. If you have a product that we have rated Unacceptable, re-

view the disadvantages of continuing to use it, and plan to

replace it. If you decide to purchase or continue to use the

product, carefully document the basis for your actions.

Conditional Ratings

Occasionally, our rating for a product depends on whether a

healthcare facility is willing and able to take corrective mea-

sures to overcome a basic performance or safety shortcoming.

Corrective measures range from special training (e.g., stress-

ing the importance of certain operating instructions) to order-

ing an upgrade or modifying a product. If the facility meets the

conditions stated, the product is rated in the category speci-

fied—that is, Preferred, Acceptable, or Not Recommended.

However, if the facility does not or cannot meet the conditions,

the product is Unacceptable.

Health Devices Ratings System



GE Healthcare LightSpeed VCT

Supplier. GE Healthcare [439946], Waukesha, Wisconsin

(USA); +1 (800) 643-6439, +1 (262) 544-3011; www.

gehealthcare.com

Product availability. Introduced in 2005, this product is

marketed worldwide.

The system we tested. We performed our testing on a

LightSpeed VCT with software release 06MW29.7 and

07MW18.4. The system was located in the manufacturer’s

testing and manufacturing facility.

Product DescriptionThe LightSpeed VCT family of CT systems includes sys-

tems with either 32 or 64 slices. In addition, the 16-slice or

4-slice LightSpeed RT and Xtra wide-bore (80 cm) config-

urations are available for oncology and general radiology

applications (e.g., trauma, bariatrics). GE has recently in-

troduced the BrightSpeed family of systems, which are

available with 4 to 16 slices and have a more compact gan-

try so they can be installed in smaller rooms.

The standard scanner configuration includes a dual-

monitor acquisition console to control scanning and im-

age reconstruction. A majority of clinical applications

can be accessed from the console. However, in most sce-

narios a specialized 3-D platform is more appropriate.

GE uses the Advantage Workstation (AW), which can bedirectly connected to GE CT scanners. In addition, the

AW RemoteAccess option allows users to remotely ac-

cess and use an AW.

Significant Test Results

Image quality—Good

Noise characteristics. Good—No significant findings to

report.

Slice thickness and spatial resolution. Good—No sig-

nificant findings to report.Uniformity. Excellent—The uniformity across a 250 mm

diameter phantom was within 3.7 HU, which is within our

criterion of 5 HU. The uniformity between contiguous ax-

ial slices was 1 HU for 5 mm slices and less than 3 HU for

0.625 mm slices. These values are well within our criteria.

Temporal resolution. Excellent—When using our dy-

namic cardiac phantom, the scores (5 = clear and sharp to

1 = unusable) for the 1.3 mm simulated catheter were 5 at

65 bpm, 4 at 75 bpm, 4 at 85 bpm, and 4 for the irregular

heart rate. The larger catheters were easily visible regard-

less of heart rate. (Some of the phantom images are shown

on the next page.)

Artifacts. Good—No significant findings to report.

Dose management—Excellent

Dose. Excellent—We were able to test a feature that

GE recently introduced commercially, Cardiac SnapShot

Pulse. We found that this feature reduced the dose length

product to 102 mGy ● cm compared to 561 mGy ● cm for

an ECG-modulated scan, which is an 80% reduction in

dose. What’s more, the breathhold time was reduced from8 seconds to less than 5 seconds. The technique is limited

to heart rates no greater than 65 bpm, so beta blockers are

normally needed to reduce the heart rate. We interviewed an

early user of this technology to determine the drawbacks.

The main drawback is that only one phase of cardiac data

is acquired. Therefore, the images can only be used to

determine the patency of the coronaries and cannot be

used for functional measurements. Also, the quality of the


Acceptable. The GE LightSpeed VCT offers high-quality

imaging and is very easy to use.



images produced by the first versions of this technique is

susceptible to variations in heart rate. GE informed us that

the full commercial version will be modified to better cope

with varying heart rates. In our opinion, this technique is a

significant step forward in the reduction of dose when CT

is being used to diagnose coronary disease.

Dose in pediatric body imaging is set using the Broselow-

Luten “Color Coding Kids” system, which is commonly

used in emergency rooms to determine appropriate drugdoses. The system is applicable for weights up to 36 kg

(80 lb). In head imaging, three age ranges are used.

The system uses three bow-tie filters to shape the x-ray

beam before it is incident on the patient. The bow-tie filter

is automatically selected to match the field of view. These

filters help optimize the dose to the clinical requirements.

Dose modulation. Excellent—Two dose-modulation

techniques are used, AutomA and SmartmA. AutomA

works just for the z-axis, while SmartmA works in all

three dimensions. The settings are based on the scout im-

age. A dose saving of 42% was demonstrated.

When using dose modulation, each facility specifies the

target standard deviation and the range of acceptable mA

values. Once specified, these settings are built into allstandard protocols, making dose modulation easy to use.

A dose record is made with all studies as an additional

text image within the DICOM data. This report includes

both the dose length product and CT dose index (CTDI vol).

Therefore, dose data can be retrospectively reviewed.

During cardiac exams, the dose is modulated based on

the ECG. Measurements with our cardiac phantom showed

dose savings of about 20% at a heart rate of 65 bpm com -

pared to a non-ECG-modulated exam.

Workflow integration—Excellent

Clinical experience. Excellent—All users surveyed re-

ported that they would choose GE again for a CT system.

The system is equipped with either an 85 kW or 100

kW generator; these are the highest powers available for

any CT system. Higher power means that most obese pa-

tients can be scanned without the need to adjust standard

protocols. Several users commented that this aids

workflow.

The acquisition console uses a standard dual-monitor

configuration. While other manufacturers also offer

dual-monitor configurations, we found that the GE consolemakes the most efficient use of the additional space avail-

able. For example, one monitor is used to display text,

while the second monitor is used just to display images.

GE uses descriptive names for the reconstruction filters.

What’s more, the choices offered to the user are limited to

those that are clinically useful. So while users must usually

choose between multiple coded options (e.g., UB, B31s,

FC22) that often have only subtle differences, GE makes it

easy for the user to select the most appropriate option

(e.g., soft, standard, lung, chest, detail, bone, edge,

boneplus).

Image acquisition performance. Good—No significant

findings to report.

Postprocessing. Excellent—While no second console is

available for postprocessing, it is possible to access a prior

patient without interfering with the present exam.

A comprehensive range of clinical applications is avail-

able on the AW and the acquisition console. These include

full cardiac analysis (including pacemaker planning), brain


GE phantom images. 1.3 mm catheter imaged at simu-

lated 85 bpm (top) and irregular heart rate (middle). Thestationary image (bottom) serves as a baseline.



perfusion (GE is developing a shuttle technique that will

double the coverage possible in stroke detection), vessel

analysis (including thrombus assessment), computer-

assisted lung measurement (not available on the acquisi-

tion console), and virtual colonography (including a dis-

section view).

A standard feature on the LightSpeed systems is exam

split, which enables studies of contiguous body parts to be

split prospectively and given new accession numbers. This

has advantages for billing.

Ease of use. Good—No significant findings to report.

Connectivity. Good—In addition to meeting all our

DICOM requirements, the LightSpeed meets most of the

appropriate IHE profiles, including Scheduled Workflow,

Patient Information Reconciliation, Consistent Presenta-

tion of Images, and Presentation of Grouped Procedures.

Service and support—Good

User feedback. Excellent—All users reported a generally

positive experience regarding service.

Training. Excellent—In addition to the standard training

offerings, GE provides Training in Partnership (TiP) Vir-

tual Assist, in which a GE specialist can remotely controlan AW workstation through a VPN connection. This al-

lows users to access expert help at almost any time. In ad-

dition, GE provides various business analysis services,

such as Imaging Roadmap and Realize VCT, that are de-

signed to optimize the training and clinical services.

Reliability and maintenance. Good—The x-ray tube is

warranted to last for 6,000 patients, which equates to a

year under normal use. Standard warranty conditions re-

flect this. Assuming 20 seconds per patient, this equates to

120,000 scan seconds.

Planning. Good — No significant findings to report.


Specifications for GE CT Systems

Description LightSpeed VCT BrightSpeed Elite BrightSpeed Select

Number of slices 64, 32 16, 8, 4 16, 8, 6

Detector coverage (z-axis), mm 40 20 20

Number of detectors (z-axis) 64 24 24

Minimum slice width, mm 0.625 0.625 0.625

Minimum rotation time, sec 0.4; 0.35 optional 0.5 0.8

Generator power, kW 85; 100 optional 53 42

Large focal spot, mm 0.9 × 0.9 0.9 × 0.7 0.9 × 0.7

Small focal spot, mm 0.6 × 0.7 0.6 × 0.7 0.6 × 0.7

X-ray tube heat storage, MHU 8 6.3 3.5

X-ray tube cooling rate, kHU/min 1,782 840 820

Standard patient table

Weight limit, kg (lb) 227 (500) 180 (400) 205 (451)

Precision of table movement, mm ±0.25 ±0.25 ±1

Optional patient table

Weight limit, kg (lb) NA 205 (451) NA

Precision of table movement, mm NA ±1 NA

Minimum height of patient table,

cm (in)

43 (17) 52 (20) 44 (17)



Philips Medical Systems Brilliance 64

Supplier. Philips Medical Systems International [415450],

Best (The Netherlands); 31 (40) 2763051 n Philips Medi-

cal Systems North America [102120], Bothell, Washing-

ton (USA); +1 (800) 722-7900, +1 (425) 487-7000 n

www.medical.philips.com

Product availability. Introduced in 2005, this product is

marketed worldwide.

The system we tested. We performed our testing on a

Brilliance 64 with software release 2.2.1. The system was

located in the manufacturer’s testing and manufacturing

facility.

Product DescriptionThe Brilliance family of CT systems includes systems of-

fering 6 to 64 slices. In addition, the 16-slice Brilliance

Big Bore (85 cm) configuration is available, primarily for

oncology applications.

The standard Brilliance 64 scanner configuration in-

cludes a dual-monitor acquisition console to control scan-

ning, image reconstruction, and postprocessing. All

clinical applications can be accessed from the console. In

addition, the Extended Brilliance Workspace is an image

analysis workstation and has full access to both the raw

data and processed images, so images can be reprocessed

remotely. In addition, a thin client-server product, knownas the Brilliance Workspace Portal, is available. The portal

enables almost any networked computer to run a suite of

advanced applications.


Image quality—Good

Noise characteristics. Good—No significant findings to

report.

Slice thickness and spatial resolution. Good—No sig-

nificant findings to report.Uniformity. Good—The uniformity across a 250 mm di-

ameter phantom was within 3.6 HU, which is within our

criterion of 5 HU.


namic cardiac phantom, the scores (5 = clear and sharp

to 1 = unusable) for the 1.3 mm simulated catheter were

5 at 65 bpm, 4 at 75 bpm, 3 at 85 bpm, and 2 for the ir-

regular heart rate. The larger catheters were easily visible

regardless of heart rate. (Some of the phantom images are

shown on the next page.)

The cardiac images are reconstructed with a 0.9 mm

slice width and a smooth reconstruction filter (XCB). This

means that the images appear to have low noise. However,

the smooth reconstruction filter will also tend to reduce the

resolution. This may explain why the diameter of the sim-ulated contrast-filled vessel appeared to be too wide (2.4

mm compared to 1.3 mm).



Dose. Excellent—Infant and pediatric protocols are auto-

matically applied when appropriate, based on the patient’s

age.

Philips has just commercially introduced a cardiac

dose-reduction technique called Step & Shoot. While it

was not available during our testing, its technical detailsare similar to those of GE’s Cardiac SnapShot Pulse tech-

nique, which will be commercially introduced soon; we

did test the SnapShot Pulse, finding that it shows signifi-

cant dose savings. Therefore, ECRI Institute expects that

the Philips approach will demonstrate similar results—in-

cluding limitations such as not being usable with higher

heart rates and producing an image of only one part of the

cardiac phase.


Acceptable. The Philips Brilliance 64 provides high-

quality images and includes some useful and unique

applications, such as remote access to raw data and

large-coverage stroke detection.




Dose modulation. Excellent—The dose modulation

function (called DOM) operates in both the 2-D and 3-D

modes based on the Surview (scout) image. A dose saving

up to 60% was demonstrated. The operation of the DOM

is dependent on the automatic current selection (ACS),

which aims for constant noise (standard deviation)

throughout the image. Once ACS is calibrated, the user

simply selects the required noise level.

Dose modulation based on the ECG is standard in car-

diac exams. Measurement with our phantom showed dose

savings of about 15% at a heart rate of 65 bpm.

Workflow integration—Excellent

Clinical experience. Excellent—All users surveyed re-

ported that they would choose Philips again for a CT sys-

tem. Users commented that being able to use the small

focal spot at maximum power (for a limited exposure

time) was an advantage, since it enables high-resolution

imaging even with large patients.

Image acquisition performance. Excellent—The sys-

tem’s Jog Mode (used for brain perfusion imaging) is

useful and well accepted by patients. According to a

long-term user, the images are of similar quality to thosefrom magnetic resonance.

During acquisition, a subset of the images is displayed

to the operator as they are reconstructed (using an optional

feature called Evolve), so the user has feedback and can

terminate and rescan the exam if necessary.

Postprocessing. Excellent—Any user of the Philips 3-D

workstation (Extended Brilliance Workspace) can repro-

cess raw data remotely. In addition, via the Workspace

Portal option, remote users can view and process 3-D CT

data using any networked computer.

A comprehensive range of clinical applications is avail-able on any Brilliance Workspace, including the acquisition

console. These applications include full cardiac analysis,

brain perfusion (Philips has the Jog Mode technique, which

will double the brain volume covered in stroke detection),

vessel analysis, computer-assisted lung measurement

(computer-aided detection is under development), and

colonography (including a dissection view). In addition,

Philips offers its TrueView technology, which exports car-

diac data to a Philips cath lab and shows the cardiologist

how to obtain the projections obtained from CT.

A standard feature on the Brilliance 64 and 40 systems

is split study. This enables studies of contiguous body

parts to be split prospectively and given new accession

numbers. This has advantages for billing.

Ease of use. Good—No significant findings to report.


DICOM requirements, the Brilliance meets some of the

IHE profiles we specified, including Scheduled Workflow

and Patient Information Reconciliation.




Training. Good—Philips has a Web-based NetForum

community for users to ask questions and access instruc-

tional materials (e.g., lectures).

Reliability and maintenance. Good—The x-ray tube is

warranted for 12 months and is not prorated; if the tube

fails at any time during the warranty period, a replacement

will be installed at no cost. The expected life of the tube is

Philips phantom images. 1.3 mm catheter imaged at

simulated 85 bpm (top) and irregular heart rate (middle).

The stationary image (bottom) serves as a baseline.




250,000 scan seconds, which is the longest of the evalu-

ated systems.

Philips offers a co-op agreement for non-Philips techni-

cians to access the same service support as that available

to Philips technicians.

Philips also offers a technology update program toall service customers, in which all applicable software

options are migrated when new versions (including up-

grades) are released, and computer hardware is swapped

after 3 years. The program is available to all Philips ser-

vice customers.

Planning. Excellent—Philips provides complete installa-

tion planning, physicist information, and site surveys (in-

cluding power quality) to the purchaser. Planning includes

provisions for the predictable requirements for future CT

technology upgrades.

Unique to Philips is the availability of Ambient Experi-ence, which is an integrated room design that is intended

to reduce patient anxiety using lighting and curved spaces

that are meant to be less threatening. Users of Ambient

Experience have reported reduced use of sedation in pedi-

atric patients.

Specifications for Philips Brilliance CT Systems

Description Brilliance 64 Brilliance 16

Number of slices 64, 40 16, 6

Detector coverage (z-axis), mm 40 24

Number of detectors (z-axis) 64 24

Minimum slice width, mm 0.625 (2 × 0.5) 0.75 (2 × 0.6)

Minimum rotation time, sec 0.5; 0.4 optional 0.5; 0.4 optional

Generator power, kW 60 60

Large focal spot, mm 1 × 1 1 × 1

Small focal spot, mm 0.5 × 1 0.5 × 1

X-ray tube heat storage, MHU 8 8

X-ray tube cooling rate, kHU/min 1,608 1,608


Weight limit, kg (lb) 204 (450) 204 (450)

Precision of table movement, mm ±0.25 ±0.25


Weight limit, kg (lb) 295 (650) 295 (650)

Precision of table movement, mm ±0.25 ±0.25

Minimum height of patient table, cm (in) 53 (21) 53 (21)



catheters were easily visible regardless of heart rate.

(Some of the phantom images are shown on this page.)



Dose. Excellent—The Sensation’s CareDose 4D dose-modulation application includes provisions for pediatric

patients based on weight.

Siemens is making its forthcoming cardiac step-and-

shoot feature available free of charge to its customers. It is

similar to other axial cardiac dose-reduction techniques,

and Siemens predicts that a 80% dose reduction will be

possible. However, the Sensation’s smaller z-axis cover-

age will likely limit the clinical utility of the technique

with the Sensation 64 compared to other 64-slice systems,

since the Sensation will require twice as many steps as the

others to cover the same anatomy, making dose reduction

more difficult.

Dose modulation. Excellent—The built-in protocols are

initially set up with the lowest dose. What’s more, the dosemodulation feature, CareDose 4D, operates in both the

2-D and 3-D modes based on the topogram (scout) image

and real-time feedback during the scan. A dose saving up

to 40% was demonstrated.

The operation of the CareDose 4D is dependent on the

configured reference point. Unlike other dose-modulation

techniques, CareDose does not aim for constant noise. In-

stead, the dose for smaller patients is not reduced as much,

and the dose for larger patients is not increased as much.

Siemens believes that this approach is more beneficial in

terms of matching the image quality to the clinical need. It

also reduces the mA required for very large patients, so

you are less likely to have problems when scanning obese

subjects.

Dose modulation based on ECG is standard in cardiac

exams. At the time of our testing, Siemens was in the pro-

cess of introducing a revised ECG modulation technique

that is designed to more accurately predict the R-R interval

rather than simply average the previous three intervals.

Results presented by Siemens show that the new approach

achieves an average dose reduction of 39%, which is dou-

ble that normally found. The higher dose reduction is a re-

sult of being able to more reliably set narrower pulsesbased on the ECG.

Workflow integration—Good

Clinical experience. Good—All users surveyed reported

that they would choose Siemens again for a CT system.

Image acquisition performance. Good—During acquisi-

tion, a subset of the images is displayed to the operator as

they are reconstructed, so the user has feedback and can

stop the exam if necessary.

Postprocessing. Excellent—WorkStream 4D automates

most of the routine postprocessing steps so that technolo-gists do not have to manually process the images into the

required projections and views, as would be normally re-

quested by the radiologist. If used properly, this saves time

and should enhance workflow.

Full reprocessing is possible at the Syngo Acquisition

Workplace, which can be fitted with dual monitors as an

option (Syngo is the Siemens interface for all imaging mo-

dalities). In addition, a separate Syngo CT Workplace,


Siemens phantom images. 1.3 mm catheter imaged at

simulated 85 bpm (top) and irregular heart rate (middle).

The stationary image (bottom) serves as a baseline. The

gaps visible in the top two images were caused by air

bubbles that could not be completely purged from the

contrast media; these can be disregarded.



which shares the same database as the main Acquisition

Workplace, can be used for raw data reprocessing and

clinical applications. Since the database is shared, there is

no delay in transferring data. Distributed reading can be

achieved with Syngo MultiModality Workplaces or via the

Syngo WebSpace.

A comprehensive range of clinical applications is avail-

able on any Syngo Workplace, including the acquisition

console. These applications include full cardiac analysis,

brain perfusion, vessel analysis, computer-aided lung-nod-

ule detection (computer-aided detection has premarket ap-

proval from the U.S. Food and Drug Administration

[FDA]), and colonography. In addition, Siemens has re-

cently introduced technology that exports cardiac data to a

Siemens cath lab and shows the cardiologist how to obtain

the projections obtained in CT.

Ease of use. Excellent—If the user sets nonviable study

parameters, the Scan Assist feature displays a window that

shows the interdependence of all the settings. In addition,

the scan parameters (e.g., pitch) are freely selectable.

Therefore, the user can quickly find suitable alternative

settings with minimum compromise.

Connectivity. Good—The Sensation meets all our

DICOM requirements, plus three of the IHE profiles we

specified: Scheduled Workflow, Patient Information Rec-

onciliation, and Consistent Presentation of Images.




Training. Excellent—Siemens runs three training centers

within the United States as part of the Siemens Remote

Services, which are offered at no cost to customers; it re-

quires a VPN connection. Users can contact applications

specialists via the Acquisition Workplace.

Reliability and maintenance. Good—The x-ray tube has

an unlimited 12-month warranty. After 12 months, the

coverage is prorated with a minimum coverage of 160,000

scan seconds. Additional coverage (scan seconds) can be


Specifications for Selected

Siemens Single-Source CT Systems

Description Sensation 64 Emotion 16 Spirit

Number of slices 64 16, 2 2Detector coverage (z-axis), mm 28.8 24 10

Number of detectors (z-axis) 40* 16 2

Minimum slice width, mm 0.6; 0.3 optional 0.6 1

Minimum rotation time, sec 0.37; 0.33 optional 0.6; 0.5 optional 0.8

Generator power, kW 80 50 24

Large focal spot, mm 0.8 x 1.1 0.8 x 0.7 0.8 x 0.7

Small focal spot, mm 0.6 x 0.7 0.8 x 0.5 NA

X-ray tube heat storage, MHU 0** 6 2

X-ray tube cooling rate, kHU/min 5,000 810 700


Weight limit, kg (lb) 205 (450) 200 (440) 220 (480)

Precision of table movement, mm ±0.25 ±0.25 ±0.25


Weight limit, kg (lb) 280 (615) NA NA

Precision of table movement, mm Not specified NA NA

Minimum height of patient table, cm (in) 53 (21) 45 (18) 45 (18)

* Siemens uses a technology it calls z-Sharp to produce 64 slices; 64-slice acquisition is only possible during spiral acquisition.

** Siemens specifies the equivalent heat storage to be 30 MHU based on the tube’s rapid cooling (see next line).



purchased. Customers without tube coverage automatically

have a prorated 160,000-scan-second warranty.

Another warranty-related feature offered by Siemens is

the optional Syngo Evolve Package. Purchasers of this

package receive a computer hardware and software up-

grade after three years. The Syngo Evolve Package is in-

cluded in Gold level service contracts.

Users of Siemens Remote Services are proactively

monitored from Cary, North Carolina. If a problem is

identified, the service center will contact the customer.

Siemens estimates that 50% of problems can be fixed re-

motely. In addition, Siemens can now provide utilization

management and service data direct to users via e-mail.

Planning. Good — No significant findings to report.




Toshiba Medical Systems Aquilion 64

Supplier. Toshiba Corp. Medical Systems Co. Ltd.

[140664], Otawara-shi Tochigi Pref., (Japan); 81 (287)

266301; www.toshiba-medical.co.jp n Toshiba America

Medical Systems Inc. [101894], Tustin, California (USA);

+1 (800) 621-1968, +1 (714) 730-5000; www.medical.

toshiba.com

Product availability. Introduced in 2005; marketed

worldwide

The system we tested. We performed our testing on an

Aquilion 64 with software release V3.00ER003. The sys-

tem was located in the manufacturer’s testing facility.

Product Description

The Aquilion family of CT systems includes systems with 4to 64 slices; apart from the number of slices, the standard

Aquilion systems have identical specifications. Also avail-

able is the 16-slice Aquilion Large Bore (90 cm) configura-

tion, which is intended primarily for oncology and general

radiography applications (e.g., trauma and bariatrics).

The standard scanner configuration includes two inde-

pendent consoles. Both consoles can be used for study man-

agement and raw data processing. In addition, the scan

console is used for scanning, while the display console can be

used for some 3-D processing. Additional 3-D applications

are available on the Vitrea workstation (supplied by Vital

Images Inc. [331069], Minnetonka, Minnesota, www.

vitalimages.com), which is generally sold with the Aquilion.

The Aquilion and Vitrea both support the enhanced DICOM

CT standard, which enables much faster image transfer com-

pared to the normal DICOM CT standard.


Image quality—Excellent

Noise characteristics. Good—No significant findings

to report.

Slice thickness and spatial resolution. Excellent—Theactual slice thickness used for routine imaging is the nar-

rowest we measured (0.6 mm; nominal = 0.5 mm). What’s

more, we found that the slice width profiles had the least

spread—that is, were overall the narrowest—of all the

evaluated systems. Therefore, the actual slice width most

closely matches the resolution set during scan planning.

Uniformity. Excellent—The uniformity across a 250 mm

diameter phantom was less than 1 HU, which is well

within our criterion of 5 HU. Also, the uniformity between

contiguous axial slices was 0.8 HU for 8 mm slices and

1.5 HU for 0.5 mm slices. These values are also well

within our criteria.


namic cardiac phantom, the scores (5 = clear and sharp to

1 = unusable) for the 1.3 mm simulated catheter were 5 at65 bpm, 4 at 75 bpm, 4 at 85 bpm, and 4 for the irregular

heart rate. The larger catheters were easily visible regard-

less of heart rate. These were the best scores of the sys-

tems evaluated. (Some of the phantom images are shown

on the next page.)

Toshiba has two applications that are designed to aid

cardiac image acquisition. SureCardio is used before the

acquisition to record the effects of breathholding on the

patient’s ECG, providing a more accurate ECG record

for gating. Following the exam, the PhaseXact technique

is used to automatically select the phase with the leastcoronary movement. For most patients, the optimal phase

will be predictable; however, it is well established that in

some cases (e.g., higher heart rates), different cardiac

phases are better for imaging. All manufacturers offer the

ability to manually select different phases to reconstruct,

but PhaseXact automates this process. If the results are

not satisfactory, the user can always revert to the manual

technique.


Preferred. Offers superior image quality, most signifi-

cantly for cardiac imaging, as well as tools to help technol-

ogists achieve reproducible, consistent results.




We found that the cardiac images are reconstructed

with a 0.5 mm slice width and a sharp reconstruction filter

(FC43), with the result that the simulated coronaries ap-

peared to be sharp and well defined. As a result, measure-

ment of the diameter closely matched the actual diameter,

which is an advantage. However, any flaw in the image is

also very visible, which is not the case if a smoother filteris used.



Dose. Excellent—The Aquilion offers the SureExposure

3-D dose-modulation technique, which automatically

adjusts the exposure parameters based on the patient’s

measured x-ray composition, operating on the principle of

keeping the noise level constant. In addition, pediatric pro-

tocols are automatically triggered by the patient’s date

of birth.

The system uses two bow-tie filters to shape the x-ray

beam before it is incident on the patient. The bow-tie filteris automatically selected to match the field of view. These

filters help optimize the dose to the clinical requirements.

Dose modulation. Excellent—SureExposure demon-

strated a dose saving up to 40%.

Users define the target standard deviation and the range

of acceptable mA values. These settings are built into all

standard protocols, making dose modulation easy to use.

A dose record is recorded with all studies as an addi-

tional image within the DICOM data. This report includes

both the dose length product and CTDIvol.

Dose modulation based on ECG is standard in cardiac

exams. Measurements with our cardiac phantom showed

dose savings of about 13% at a heart rate of 65 bpm.

Workflow integration—Good

Clinical experience. Good—All users surveyed reported

that they would choose Toshiba again for a CT system.

Two independent workstations are provided as standard.

Both workstations can process raw data. Therefore, a cur-

rent study should not need to be interrupted if any repro-

cessing is required.

Image acquisition performance. Good—During image

acquisition, the SureScan feature displays a subset of the

images to the operator at 12 fps, so the user has feedback

and can stop the exam if necessary.

The SureFluoro feature is used in biopsy cases and dis-

plays three slices in real time instead of the normal single

slice. Therefore, the physician can have more images to

guide the biopsy needle.

Postprocessing. Excellent—Full reprocessing is possible

at the acquisition and display consoles so long as the raw

data remains.Toshiba relies on Vital Images’ Vitrea workstation for

most applications and develops applications in close part-

nership with Vital Images. The Vitrea offers a comprehen-

sive range of clinical 3-D applications. These include

full cardiac analysis, brain perfusion, vessel analysis,

computer-aided lung nodule detection (using the R2 CAD

algorithm, which has FDA premarket approval), and

virtual colonography.

Toshiba phantom images. 1.3 mm catheter imaged at

simulated 85 bpm (top) and irregular heart rate (middle).The stationary image (bottom) serves as a baseline. The

gaps visible in the top two images were caused by air

bubbles that could not be completely purged from the

contrast media; these can be disregarded.



Ease of use. Excellent—A number of “Sure” techniques

are available that automate acquisition and processing.

Unique to Toshiba is SureCardio, which automatically re-

cords the patient’s ECG during a rehearsal scan while pre-

paring for a cardiac scan. The system can then better

predict the ECG during the real scan. Also, SureExposure

shows the user what the image would look like based on

the parameters selected.


DICOM requirements, the Aquilion meets most of the IHE

profiles we specified, including Scheduled Workflow, Pa-

tient Information Reconciliation, Consistent Presentations

of Images, and Presentation of Grouped Procedures.




Training. Excellent—Toshiba has recently expanded its

user training academy in Tustin, California, for both

technologists and radiologists. In addition to the standard

training offerings, Toshiba has started an e-mail service

allowing users to directly contact applications specialists.

Reliability and maintenance. Good—The MegaCool

x-ray tube is warranted to last for 200,000 rotations, which

equates to approximately 100,000 scan seconds. Standard

warranty conditions reflect this. Our survey found that us-ers were consistently achieving more than 12 months’ use

from their tubes. While other manufacturers also often

achieve more than 12 months’ use, the record is far from

consistent. We believe there are a number of reasons for

the high consistency, including the moderate power speci-

fication, which means that high mA is not used routinely;

use of a grounded anode (it is usually at +75 kV), which

allows the anode to be directly cooled; and the larger focal

spot size used. This longer life may translate into consider-

able cost savings over the life of the equipment.

Access to service tools does not require the payment of

licensing fees. Therefore, there are no recurring annual

fees for in-house service.

Planning. Good—No significant findings to report.


Specifications for Toshiba Aquilion CT Systems

Description Aquilion Systems

Number of slices 64, 32, 16, 4

Detector coverage (z-axis), mm 32

Number of detectors (z-axis) 64

Minimum slice width, mm 0.5

Minimum rotation time, sec 0.5; 0.4, 0.35 optional

Generator power, kW 60; 72 optional

Large focal spot, mm 1.6 × 1.6

Small focal spot, mm 0.9 × 0.8

X-ray tube heat storage, MHU 7.5

X-ray tube cooling rate, kHU/min 1,386


Weight limit, kg (lb) 200 (440)

Precision of table movement, mm ±0.25


Weight limit, kg (lb) 280 (615)

Precision of table movement, mm ±0.25

Minimum height of patient table, cm (in) 30 (12)



Choosing a System

What You Need to Know When Interpreting CT Product Specifications

As a supplement to the findings from this month’s Evalua-tion of CT scanners, we provide this guide for readers who

desire a more general discussion of the factors that should

be considered when purchasing a CT scanner. By examin-

ing and considering the following discussion in addition to

reviewing our Evaluation findings, you can gain the per-

spectives necessary to select a unit that we did not evaluate

to ensure that it meets the needs of the clinical environ-

ment(s) for which it is intended.

A significant challenge for buyers is the fact that—even

though manufacturers follow international standards when

specifying CT performance—different companies’ specifi-

cations are not necessarily stated in the same terms. There-

fore, buyers often need to obtain further information and

conduct additional analysis.

The following factors are relevant regardless of the

number of slices chosen.

X-ray DoseThe radiation hazards of CT have only recently been fully

recognized. Dose-modulation techniques are now standard

and are of comparable effectiveness among the evaluated

systems. However, the dose required for suitable image

quality may not be comparable among the systems.

An example of the complexity of comparing doses is

the question of how dose is reported. All manufacturers

routinely report volume CT dose index (CTDI vol) values in

their specifications. These values are normalized with re-

spect to mAs. Yet there is no reason to expect that the

same mAs will be used by different CT systems for the

same exam, so directly comparing the CTDIvol values will

not yield meaningful information.

To illustrate this point, the CTDIvol values taken from

manufacturers’ specifications are reported in the table on

this page. Comparing the dose requires that we also knowtypical mAs values used by each system. (Unfortunately,

now that automatic dose control is standard, typical values

are hard to establish. The values we report here are esti-

mated from manufacturer literature and discussions we

have had with the manufacturers.) Multiplying the CTDI vol

by the typical effective mAs, then dividing by 100, yields

comparative CTDI values (bottom row of the table); ob-

serve that the lowest-dose system is not the one with the

lowest CTDIvol. Therefore, CTDIvol cannot be used tocompare devices. Instead, potential buyers should seek the

typical mAs values employed by existing users.

The next technological step in dose reduction is to fur-

ther reduce the dose during specific studies—cardiac ex-

ams, for example. Some manufacturers are now installing

systems that incorporate these more task-specific tech-

niques. Early experience with these systems has demon-

strated that further dose savings are possible. However,

there is usually some degree of tradeoff between dose re-

duction and the diagnostic efficacy of the images. So com-

paring the dose savings possible on different systems will

require an in-depth understanding of the technologies

involved.

X-ray ProductionThe power of a system’s x-ray generation (the output of

the x-ray tube and generator, measured in kW) seems to be

an easy specification to compare and is often used as such.

The power directly affects the maximum tube current that

is available (greater tube currents enable larger patients to

be scanned with shorter rotation times). Nevertheless, a

100 kW system is not twice as effective as a 50 kW sys-

tem. One reason is that, because of noise considerations,doubling the tube current increases the image quality by

only a factor of 1.4. A second reason is that the dose per

mAs is not a fixed quantity. As the CTDI values in the ta-

ble below demonstrate, some systems output 1.7 times the

dose for the same mAs. In some cases, therefore, the same

image quality can be achieved with less mAs. So generator

power specifications should not be compared in isolation.

Other factors—in particular, the typical power and mAs

needed for obese patients—should also be compared.


Comparison of ManufacturerCTDI Data


CTDIvol, body,

mGy

8.5 5.6 6.7 9.4

Typical body

mAs

140 250 150 150

Comparative

CTDI, mGy

11.9 14.0 10.05 14.1



Image Processing

Image reconstruction takes considerably longer than image

acquisition. While the fastest scanner can generate almost

200 images per second, the fastest reconstruction rate is 20

images per second. So even with the fastest computers, a

10-second scan can take almost two minutes to reconstruct.

Our measurements showed that a system’s overall scan

time—that is, the acquisition and processing times com-

bined—has little correlation with the specified reconstruc-

tion rate. Some systems start to process while the scan is

continuing, while others wait until the scan is complete.

What’s more, the maximum specified reconstruction rate

is highly dependent on the scan and reconstruction param-

eters (e.g., pitch, slice thickness, increment, reconstruction

filter). So it is very difficult to compare reconstruction rate

specifications. Buyers should ask to time typical clinical

cases.

Workflow andClinical Applications

All the images produced by a CT scanner must be viewed

and interpreted by a physician, so physicians must have the

tools to manage and display large data volumes. General-

purpose PACS workstations do not provide such tools,

however, meaning that more specialized workstations are

necessary. The possible choices include using a networked

workstation from the CT manufacturer, using standard

workstations connected to the CT scanner via a Web-based

application, and using a third-party workstation.

Each CT and workstation manufacturer has a different

approach to how to fit the CT data into the workflow. It is

not yet clear whether there is an optimum approach. The

use of remote general-purpose computers (thin client) ac-cessing a central processing computer (server) is becoming

more common. This provides a more cost-effective way to

share expensive resources and also allows physicians to

more easily access the advanced tools.

Each of the available solutions offers similar 3-D re-

construction and viewing functionality. Features such as

bone removal, vessel analysis, lung nodule measurement,

brain perfusion measurement, and colonography are avail-

able as options from every vendor. Differences among

systems include more specific features such as com-

puter-aided detection, stent planning, bone densitometry,

body perfusion measurement, pacemaker planning, and

dental imaging. Therefore, you should select the appropri-

ate 3-D processing based on your specific technical and

clinical needs.

Make sure you clearly understand the strengths and

limitations of each manufacturer’s approach and how it

fits your situation and requirements. Factors that will af-

fect your selection include your physicians’ preferences,

diagnostic workstations you already have, your network

bandwidth, the specialized software tools available from

the manufacturers, and the layout of your facility. ◆

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64-slice ct scanners evaluation

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