PROF. DR. PINAR BALCIPROF. DR. PINAR BALCI

Dokuz Eylül University Dokuz Eylül University School of MedicineSchool of Medicine

Department of RadiologyDepartment of Radiology 

COPD is currently the 12th leading cause of disability in the world and is predicted to be 5th by the year 2020

The annual cost of morbidity and early mortality due to COPD is high

Smoking is the most important environmental risk factor

Prognosis varies individually

Emphysema + small airway disease

CT Why ? Worldwide accessibility of CT scanning is

available

Acquisition of lung images equivalent to anatomic evaluation non invasively

CT images themselves are densitometry maps of the lung

*Any change in lung leads to image changes via dansitometry

LimitationsLimitations

Disagreements on the best method to analyze the lung parenchyma

No definitive study using airway wall algorithms

Exposure of subjects to ionizing radiation

Use of improperly calibrated CT scanners

Target of assesment

Emphysema

Small airway disease

Rate and conribution of each pathology still unknown

Target of assesment

Emphysema

Regional distribution

Measurement of air-trapping in Small airway disease

Directly measuring the airway wall

VOLUME X-RAY ATTENUATION (EVALUATİON OF DENSITOMETRY)

HISTORY OF QCT

Gould first used QCT in lung *Modal CT attenuation value and the value of the fifth

percentile of the lung * This QCT indices correlated well with amorphometric

index derived from pathologic sections of the lung Subsequently, Müller used the "density mask" program

available on GE CT scanners in the late 1980s to quantify the amount of lung tissue that measured less than –910 HU

There is good correlation with both anatomic measures

in QCT and pulmonary function measures of emphysema

Able to measure low density regions by means of histogram analyzis in evaluation of total capacity of lung

In evaluation of residual volume or functional residual capacity identifies regions corresponding air entrapment.

Detection of emphyzema is direct measurement of lung remodelling in COPD

Detection of air entrapment is equivalent of indirect measurement of small air ways.

OVERLAPPİNG...?

No universally acceptable QCT method in COPD

2001 and 2008 workshops : Recomendations for COPD researchers

Newell JD Jr, Hogg JC, Snider GL. Report of a workshop: quantitative computed tomography scanning in longitudinal studies of emphysema. Eur Respir J. 2004 May;23(5):769-75.

Coxson HO. Proc Am Thorac Soc 2008 (5) ;874–877

TECHNICAL CONSIDERATIONS .1 CT : MDCT CT phantoms: Lung, water, soft tissue and bone

simulations made of inorganic materials Image acquisition parameters: For

optimisation of image quality with minimal radiation exposure

CT scanner make and model, CT scanner calibration using CT phantoms, image acquisition parameters, image reconstruction

parameters, lung volume at acquisition, intravenous contrast

media, quantitative image analysis method(s), CT radiation dose, CT data handling, and CT image processing

TECHNICAL CONSIDERATIONS .2 Lung volume in acquisition of images maximum inspiratory effort Optional: Respiratory gating; expiratory or paired

inspiratory/ expiratory images IV contrast media should not be

administered Optimal HU thresholds -950 HU 1-mm sections -910 HU 5-7 mm sections Window settings (WW 1000 HU, WL -700 HU) Radiation dose low dose technics CT data management CT data post-processing

TECHNICAL CONSIDERATIONS .3

Standard Quantitative Methodology Density mask Histogram analysis (lowest 15th percentile)

Mean lung density (volumetric evaluation)

Miscellaneous Techniques Minimum-intensity and maximum-intensity

projection images (MinIP and MIP)

In assesment of frequency distribution or histogram of lung densities, although the lowest 5th percentile reflects parenchimal density better and well-correlated with respiratory function tests

Hayhurst MD. Lancet 1984;2:320–322. Gould GA. Am Rev Respir Dis 1988; 137:380. Heremans A. Chest 1992; 102:805.

2008 the Alpha-1 Foundation sponsored a workshop resulted in recommendations in using lowest 15th percentile point of lung density

Visual assesment CT images: The simpliest assesment *Normal, 25% lung involvement by emphysema,

between 25% and 50% , between 50% and 75%, or greater than 75% involvement, with the total score expressed as percentage of total lung at that level

In general, visual inspection has yielded good correlations between CT and pathological measures of the extent and severity in all but the mildest cases

Visual assessment may lead to an overestimation of the extent of disease.Accuracy of CT densitometry is higher

As an alternate to routine visual inspection: Minimum-intensity projection (MinIP) is more sensitive (%62- %81)

Spouge D, Mayo JR, Cardoso W, et al.J Comput Assist Tomogr 1993;17:710–713 Gevenois PA, Yernault JC. Eur Respir J 1995;8:843–848 Remy-Jardin M, Remy J, Gosselin B, et al. Radiology 1996;200:665–671

Density mask It would be possible to disthinguish lung

regions (voxel) lower than certain threshold by means of this method

 Inspiratory and Expiratory Scanning Several controversies Inspiratory /paired inspiratory-expiratory

imaging Measurements of lung attenuation obtained at inspiration

and visual score better reflect abnormal results of pulmonary function tests in patients with less severe chronic obstructive pulmonary disease than do measurements obtained at expiration

Measurements of lung attenuation obtained at expiration better reflect pulmonary function abnormalities in patients with severe chronic obstructive pulmonary disease.

Akira M. AJR 2009;192:262-277

Assessment of Airway Wall Not standardized CT scanner with a minimum of 64 detectors The first and Obvious limitation is the resolution of the CT scanner *Pixel size 0.5 mm *The airways that are responsible for airflow limitation

are below the resolution of the CT scanner Three-dimensional algorithms are still insufficient There are now many airways to asses Parameters affecting assesment ?

There are three basic steps in the image processing

The first step is to load a large three-dimensional CT image dataset of the lungs on a specific patient

The next step is to use the image processing software to extract the lungs from the rest of the cervical, thoracic, and upper abdominal anatomy, a process referred to as image segmentation.

This image segmentation process is best accomplished with semiautomatic or fully automatic methods

The third step is to analyze the lung image data using histogram-type statistical methods.More advanced texture processing can be done as a fourth step if required

The next step in the image processing of emphysema is to look

at the distribution and types of emphysema present. There are

reports of successfully quantitating the cranio-caudal distribution of emphysema in the lungs

HRCT is of particular value in the diagnosis of emphysema when other diseases are suspected clinically

Preoperative and postoperative evaluation of emphysema

* Bullectomy * Lung Transplantation * Lung Volume Reduction Surgery

Phenotyping of Chronic Obstructive Pulmonary Disease in diagnosis and follow up

The association between emphysema and lung cancer has been recently re-examined in the context of low-dose lung cancer screening with conflicting results

Bullectomy It’s correlated CT quantification of bullae

volume with improvement in respiratory function and showed good correlation between the size of bullae and the probability of improved postoperative lung function

Mineo TC. J Thorac Cardiovasc Surg. 2007 Dec;134(6):1491-7

Lung Volume Reduction Surgery QCT is the most successful method of

reflecting morphologic alterations, severity and extention of emphysema

Bae KT. Radiology 1997;1997:705–714Becker. Am J Respir Crit Care Med 1998;157:1593–1599.Gierada DS.Radiology 1997;205:235–242.Gierada DS Chest 2000;117:991–998

Lung Volume Reduction Surgery QCT is the most successful method in

identification of lung volume to be removed, preoperatively

Gilbert S. . Acad Radiol 2006;13:1379–1386

Lung Volume Reduction Surgery Patient with large upper lobe lesions

respond better to LVRS than patients with small uniformly distributed disease

LVRS is more successful in cases dominant findings peripherally with respect to cases showing remarkable findings centrally

Coxson HO. Thorax 2003;58:510–514.Nakano Y. Am J Respir Crit Care Med 2001;164:2195–

2199

Recommendations from workshop 2008. 1

Quantitative CT scanning will provide useful data concerning lung structure that is responsible for changes in lung function that define COPD

These structural data are extremely important in understanding both pathogenesis and the effect of therapeutic interventions

Either the threshold cutoff analyzis or the percentile point analyzis provides useful information about the extent of emphysema

the volume measurements are strongly recommended not only for correction of the density data but for studies that require information about lung or lober volume changes

Alpha-1 Foundation workshop

Recommendations from workshop 2008. 2

There is no strict recommendation for airway analysis

The X-ray dose should be kept as low as possible in all studies

The CT scanner must be treated just like all measuring devices, and be properly calibrated and used without changing the features of the measuring device . A simple change in the X-ray dose or the reconstruction algorithm for the images have a great potential producing huge changes in the extent of emphysema being measured

Alpha-1 Foundation workshop