Shalabh Chandra

General utilities of multislice tomography in the cardiac field.

Objects: To show all cardiac evaluations multislice computed tomography (MSCT) can perform. Methods: MSCTs were performed on an MSCT scanner (Mx8000; Philips Medical Systems) with enhanced contrast acquisition. The reconstructed images were sent to a workstation for multiplanar reconstruction, volume rendering, and 3-D reconstruction. A total of 140 patients were studied with MSCT and conventional angiography (CA) to assess coronary artery stenosis. 30 of these patients were also evaluated by intravascular ultrasound (IVUS) for plaque characterization. A group of 20 patients were studied with MSCT, gated single-photon emission computed tomography (SPECT), and echocardiography for myocardial perfusion test and volumetric analysis. Results: The results of MSCT versus CA showed a sensitivity of 79.2% and a specificity of 93.7%, whereas for MSCT versus IVUS the sensitivity was 84.4% and the specificity 91.6%. A total of 156 plaques were detected by both methods. 105 (67%) were soft, 14 (24%) were fibrous and 37 (9%) were calcified. In the evaluation of myocardial perfusion, the cardiac software showed a sensitivity of 55% and a specificity of 80%. However, general evaluation disclosed a sensitivity of 88.5% and a specificity of 96.4%. The volumetric analysis showed a good correlation between MSCT and echocardiography for end-systolic volume (ESV), rS = 0.874, and end-diastolic volume (EDV), rS = 0.828. There was also a good correlation for the evaluation of the left ventricular anatomy: septal wall rS = 0.96, posterior wall rS = 0.81, and diameter of left ventricle rS = 0.69. Conclusion: Nowadays, MSCT allows different cardiologic evaluations with the same acquisition as that for the coronary arteries. These data show a general view of the patient providing information that is obtained by the hand of multiple cardiologic methods such as DA, IVUS, gated SPECT, and echocardiography.Methoden: Die MSCT wurde mit einem Mx8000 (Philips Medical Systems) nach Kontrastmittelgabe durchgeführt. Die rekonstruierten Bilder wurden an eine Workstation zur multiplanaren Rekonstruktion, Volumenrendering und 3-D-Rekonstruktion weitergeleitet. Insgesamt untersuchten wir 140 Patienten mittels MSCT und konventioneller Angiographie (Angio), um die Abschätzung von Koronarstenosen zu evaluieren. 30 dieser Patienten wurden zusätzlich mittels intravaskulärem Ultraschall (IVUS) zur Plaque-Charakterisierung untersucht. 20 Patienten hatten zusätzlich auch eine EKG-gesteuerte Single-Photon-Emissions-Computertomographie (SPECT) sowie eine Echokardiographie zur Beurteilung der Myokardperfusion und zur volumetrischen Analyse. Ergebnisse: Die Ergebnisse für den Vergleich von Angio mit MSCT ergaben eine Sensitivität von 79,2 % und eine Spezifität von 93,7 %. Im Vergleich zum IVUS fand sich für das MSCT eine Sensitiviät von 84,4 % bei einer Spezifität von 91,6%. 156 Plaques wurden von beiden Methoden erkannt, hiervon waren 105 (67%) weich, 14 (24%) fibrös und 37 (9%) kalzifiziert. Bei der Beurteilung der Myokardperfusion ergab sich für das MSCT eine Sensitivität von 55% bei einer Spezifität von 80%. Bei weiterer Analyse zeigte sich eine Senstivität von 88,5% und eine Spezifität von 96,4%. Die volumetrische Analyse zeigte eine gute Korrelation zwischen MSCT und Echokardiographie hinsichtlich der end-systolischen Volumina (ESV), r = 0,874 und enddiastolischen Volumina (EDV), r = 0,828. Hinsichtlich der Beurteilung der linksventrikulären Anatomie ergab sich ebenfalls eine gute Korrelation: Septum r = 0,96, posteriore Wand r = 0,81, LV-Durchmesser r = 0,69. Schlussfolgerung: das MSCT erlaubt heute eine differenzierte kardiologische Abklärung einschließlich der Koronaranatomie. Das MSCT liefert Informationen, die sonst nur mit mehreren Methoden wie IVUS, EKG-gesteuertes SPECT und Echokardiographie erhalten werden können.

Automatic vessel extraction and abdominal aortic stent planning in multislice CT

The abdominal aorta is the most common site for an aneurysm, which may lead to hemorrhage and death, to develop. The aim of this study was to develop a semi-automated method to de-lineate the vessels and detect the center-line of these vessels to make measurements necessary for stent design from multi-detector computed tomograms. We developed a robust method of tracking the aortic vessel tree with branches from a user selected seed point along the vessel path using scale space approaches, central transformation measures, vessel direction findings, iterative corrections and a priori information in determining the vessel branches. Fifteen patients were scanned with contrast on Mx8000 CT scanner (Philips Medical Systems), with a 3.2 mm thickness, 1.5 mm slice spacing, and a stack of 512x512x320 volume data sets were reconstructed. The algorithm required an initial user input to locate the vessel seen in axial CT slice. Next, the automated image processing took approximately two minutes to compute the centerline and borders of the aortic vessel tree. The results between the manually and automatically generated vessel diameters were compared and statistics were computed. We observed our algorithm was consistent (less than 0.01 S.D) and similar (less than 0.1 S.D) to manual results.

CT perfusion: comparison of gamma-variate fit and deconvolution

The purpose of this paper is to present results of a study comparing CT brain perfusion image calculated using the maximum slope and deconvolution method on data from 32 patients. The 32 patients were organized into two groups. One group was obtained using a 4cc/sec contrast injection rate and 10 sec injection period; the other group was obtained using a 6cc/sec injection rate and 7 sec injection period. All clinical data were analyzed using both the maximum slope and deconvolution methods. Perfusion maps computed from the two methods were reviewed by radiologists. The contrast enhanced CT data were noisy, especially in the white matter area. Our results showed that, for both methods, perfusion maps from 4cc/sec injection were noisier than those using a 6cc/sec injection. However, both 4cc/sec and 6cc/sec produced useful diagnostic images. Our qualitative side-by-side studies also showed that perfusion images from the maximum slope and deconvolution are both clinically useful and substantially equivalent.

Multislice CT brain image registration for perfusion studies

During the last several years perfusion CT techniques have been developed as an effective technique for clinically evaluating cerebral hemodynamics. Perfusion CT techniques are capable of measurings functional parameters such as tissue perfusion, blood flow, blood volume, and mean transit time and are commonly used to evaluate stroke patients. However, the quality of functional images of the brain frequently suffers from patient head motion. Because the time window for an effective treatment of stroke patient is narrow, a fast motion correction is required. The purpose of the paper is to present a fast and accurate registration technique for motion correction of multi-slice CT and to demonstrate the effects of the registration on perfusion calculation.