Caudad to cranial versus cranial to caudad CT scanning of the thorax: a comparison of two protocols

Pittman, Carla (2006) Caudad to cranial versus cranial to caudad CT scanning of the thorax: a comparison of two protocols. Masters thesis, Memorial University of Newfoundland.

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Abstract

Purpose: The current study compares artifact (motion at the lung bases and beam hardening from the superior vena cava and subclavian vein), clarity of vessels (hilar vessels, great vessels and aorta) and clarity of the nodal systems (stations 2R,2L,4R,5,6 and hilar) in the caudad to cranial and cranial to caudad direction when CT scanning the thorax. The purpose was to determine if one direction was associated with less artifact. -- Methods: 100 consecutive consenting patients were randomized into either cranial to caudad or caudad to cranial CT scanning of the thorax using block randomization. The images were interpreted independently by two radiologists who were blind to the direction for the scan. Images were analyzed using a 5 point Likert scale for artifact (motion, superior vena cava, subclavian vein), clarity of the vasculature structures (hilar vessels, great vessels, aorta), clarity of the nodal stations (2R, 2L, 4R, 5,6,hilar) and overall impression. Each scan was assessed on two separate occasions by the radiologists. Inter and intra observer correlations were measured with the Spearman Rank Coefficient. The Wilcoxin Rank Sum test was used to compare the direction of scanning. -- Results: Intra-observer correlations were strong ranging form 0.616-0.902 for Radiologist 1 and 0.537-0.902 for Radiologist 2. The inter-observer correlations were also good with Spearman Rank Coefficients values ranging from 0.102-0.793. The caudad to cranial direction of CT scanning was significantly better than cranial to caudad direction with respect to total artifact (motion+ superior vena cava+ subclavian vein), however, there was no statistically detectable difference in motion artifact. Clarity of the vasculature was deemed better by one radiologist in the caudad to cranial direction but not the other. Lymph node clarity in the upper thorax was felt to be better visualized with caudad to cranial scans versus cranial to caudad imaging, however, hilar lymph nodes and lymph nodes in the lower mediastinum showed not statistical difference. The quality of the overall images was significantly better. -- Conclusion: The caudad to cranial direction of CT scanning is significantly better with less beam hardening artifact and improved image quality, allowing better assessment of the great vessels and select nodal stations.

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