Electronic colon cleansing (ECC) is an emerging technique developed to segment the colon lumen from a patient’s abdominal computed tomography colonograghy (CTC) images. However, the residue stool and fluid tagged by contrast materials as well as mixed tissue distribution with partial volume (PV) effect impose several challenges for ECC, resulting in incomplete and over-complete cleansings. To address the PV effect, this work investigated an improved maximum a posteriori expectation-maximization (MAP-EM) image segmentation algorithm which simultaneously estimates tissue mixture percentages within each image voxel and statistical model parameters for the tissue distribution. Given the segmented tissue mixture information beyond the image voxel level, not only the PV effect has been satisfactorily addressed as a particular case of tissue mixture problem, but incomplete and over-complete ECC causes could also be maximally avoided. For clinical application to CTC that involves several issues transferring from theoretical analysis to practical validation, an innovative initialization procedure and refined estimation strategy were proposed to build an ECC pipeline based on the MAP-EM segmentation. The pipeline was evaluated based on 52 patient CTC studies, downloaded from the website of the Virtual Colonoscopy Screening Resource Center, by two radiologists. A noticeable improvement over our previous ECC pipeline was documented. Several typical cases were also presented to show visually the improved performance of the presented ECC pipeline.
A 57-year-old-male presented for whole-body PET with CT for restaging of lung cancer. Besides revealing postradiation changes, we noticed an unusual pattern of FDG uptake in the myocardium, with prominent metabolic uptake involving 4 chambers of the heart. Later that day, the patient was referred to the emergency department for increased heart rate, but otherwise asymptomatic. CT angiography was performed, which showed scattered filling defects in bilateral pulmonary arteries consistent with pulmonary embolism. The finding of prominent FDG uptake involving all cardiac chambers in this patient is likely related to heart strain caused by acute pulmonary embolism.
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