applications of t1rho

8/11/2019 Applications of T1rho

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Purpose

Determine T1values over time in patients who

have undergone intramedullary nailing to

improve post operation imaging.

Focus:

Patella, Femur and Tibia


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T1Imaging

T1or T1rhoutilizes components of T1and T2

RF pulses prevent spin from relaxing (T1) yet T2decay is still occurring

Mock T2

Results in a crisp and cleaner image than T2

Images fluidity similar to T2yet retains clarity.


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Post-Operative Patients

Loss occurs due to the loss of proteoglycan molecules which hold water molecules.

Retains fluidity of joint

Due to age, strain, etc.

T1imaging creates values which show intensity of proteoglycan

Healthy cartilage has lower T1values in seconds

Unhealthy cartilage has higher T1values in seconds

More Information: The effects of acute loading on T1rho and T2

relaxation times of tibiofemoral articular cartilage; UCSF Dept. Radiology


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Processing

Data collected from various clinical scans in

2012 processed via MATLAB.

Images created and overlay of cartilage area.

Image points are taken at various stages of post

op recovery

12 mos. is the final data point.

Utilizing this data, we can create averages.


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Data and Analysis

6 months Post-Op3 months Post-Op 6 months Post-Op

Patient 3 Patient 6Patient 4

Patellar

Femoral


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Analysis and Observations

Average T1 values were compiled in excel to create an understanding of how this

surgery affects T1values.

Patient 3

(6 Months)

Patient 4 (2

weeks)

Patient 4

(3 Months)

Patient 6

(6 Months)

46.13738571 68.0464642 63.38019462 37.13534848

T1values are not exact as possible based off of objective vs. subjective

data.

Hindrance from titanium and stainless steel implants in tibia is the

main source of discrepancy.

Unfortunately there are gaps within data

Patient mishaps or still required time for more Post-Op scans


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Conclusion

Current post- op identification is primarily limited to

Blood Tests

X-Rays and Radiographs.

The use of T1can be used in the definitive mapping of cartilage can assist in understanding anatomy of

cartilage and fluidity of joints after operation has occurred.

Development of these imaging techniques with magnetic resonance can allow physicians to

Provide early diagnosis of cartilage complications

Provide effective preventative measures and treatment for patients who have undergone

intramedullary nailing.


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Conclusion of My Experiences

Basics of Magnetic Resonance

Science and Mathematics

Procedures

7T and 9.4T

Preservation (Wax slicing)

Animal Handling

Professional Research Procedures


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Acknowledgements

Mentors: Guided the process of projects, presentations, etc.

Kevin

Sid

Damodar

Teachers: Provided complex knowledge of the basics of MROrganizers: Assigned projects and created classes

Shelly

Susan

Special Thanks to Dr. Reddy for allowing me tolearn under his directorship at the CMROI.


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Using a Mathematical Model to Determine T2

Relaxivity with Glucose as a Contrast Agent

Garimall S., Rajkumar S., DAquillaK.,

Reddy R. Ph.D


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Relaxivity: Concept

Relaxivity (r1and r2)in MRI refers to the

ability of any compound or element to

increase the relaxation rates (T1& T2) of

surrounding bulk protons.

Units are mM-1* sec-1

The relaxivity effect of a particular compound is

determined by its molecular structure and kineticbehavior.


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Relaxivity: Applications

Compounds with free electrons can impact

the relaxivity of bulk water protons quite

dramatically.

This allows the use of MRI contrast agents, like

Gadolinium (Gd) which allow for higher image

contrast.

Useful for tumor detection.


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Glucose as a contrast agent

Warburg Effect: Otto Heinrich Warburg

observed that tumor cells use glycolysis as

the predominant mode of energy production.

It follows that if differences in in vivoglucose

uptake and metabolism could be observed, tumor

detection would be possible.

Therefore glucose could be used as a contrastagent.


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Glucose vs. Gadolinium

Gadolinium is a superior contrast agent, but

Glucose offers some advantages, if an

acceptable image contrast can be achieved.

Glucose is endogenous to the human body, and

can be introduced in large physiological quantities

orally, intravenously, etc.

Cost effective, readily available.

Better tolerated by certain patients.

E.g. renal failure


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Evaluating Relaxivity (r2)

It is possible to evaluate the r2of a givencompound using this formula:

r2= 1/T2* 1000

(for a given concentration and temperature)where T2(ms) is the spin-spin relaxation constant

This formula requires the lengthy process of

generating a curve from multiple echo timepoints.

SI = S0e-TE/T2


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Evaluating Relaxivity (r2)

To save time and create a more efficient

process to determine r2 , it may be possible to

use a formula:

[-ln(Sexp/Sbaseline)/TE] = r2

Where:

Sexp/Sbaseline represents the signal intensity (SI) of

a given glucose sample at some echo time (TE)divided by the SI of a control sample without

glucose.


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Relaxivity Measurements

Five samples of glucose (0, 1, 2, 5, 10 mM) in

PBS (pH = 7), where 0 mM acted as the

baseline.

A standard T2 FLASHmapping sequence was

performed using the small in-house RF coil:

TE taken from 0-200 ms at 20 ms intervals.

SHOT TR = 8000 ms

T2map created of each sample.


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T2 Maps with 2% Agarose Samples0mM 1mM

2mM 5mM

10mM

Images showed good

fitting at R2= 0.95


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-0.500

0.000

0.500

1.000

1.500

2.000

2.500

3.000

3.500

4.000

0 50 100 150 200 250

Relaxivity (1/mM*s)

TE (ms)

Relaxivity vs. TE by concentration

10mm

5mm

2mm

1mm

Sample(mM)

r2

1 0.265

2 0.110

5 0.894

10 1.26


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0

200

400

600

800

1000

1200

1400

1600

1800

0 50 100 150 200 250

Signal Intensity

TE (ms)

Signal Intensity vs. TE by concentration

10mm

5mm

2mm

1mm

0mm

Expon. (10mm)

Expon. (5mm)

Expon. (2mm)

Expon. (1mm)

Expon. (0mm)

Concentration

Glucose Sample

(mM)

T2 (ms) by curve

fitting

r2

0 1754 0

1 1351 0.17

2 1515 0.09

5 990 0.44

10 794 0.69


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T2 decreases substantially as the glucoseconcentration is increased.

The advantage of using an agarose phantom is

that in theory, the change in T2 could only becaused by glucose.

Relaxivity of the first two time points (TE) is

unusually high, but levels out at later pointsfor all samples.

Repeat measurements are needed.

Observations & Key Points

applications of t1rho

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