Pitfalls in diagnosing colon cancer on abdominal CT.

AIM: To assess the frequency of undetected colon cancer on conventional abdominal CT and to evaluate the imaging features that are characteristic of those cancers. MATERIALS AND METHODS: The present study included consecutive patients diagnosed with colorectal cancer at colonoscopy (2006-2015) who also underwent abdominal computed tomography (CT) performed for various reasons within a year prior to the colonoscopy. The frequency of undetected lesions was evaluated for the original CT interpretations ("original readers"). Two radiologists ("study readers"), blinded to the tumour location, independently performed interpretations oriented for colon cancer detection. The study readers analysed the imaging features of detected tumours (tumour shape, length, maximal wall thickness, free fluid, fat stranding, vascular engorgement, stenosis, and lymphadenopathy). Imaging features of the cancers undetected by the original readers were evaluated. RESULTS: The study included 127 patients. The original readers' frequency of undetected cancer was 25/127 (19.7%). Each study reader could not identify the cancer in 8/127 (6.3%) patients. Imaging features associated with undetected cancers by the original readers included the absence of fat stranding (p=0.007, p=0.003), absence of vascular engorgement (p<0.0001, p<0.0001) and absence of lymphadenopathy (p=0.005, p=0.004). Undetected tumours were shorter than those detected (original reader: 33.2±11.9 versus 51.4±18.2 mm; study reader: 32.5±9.6 versus 61.3±23.4 mm; p<0.001). CONCLUSION: Colon cancer is undetected in 20% of abdominal CT examinations in patients subsequently proven to have colon cancer at colonoscopy. The absence of fat stranding, vascular engorgement, or lymphadenopathy, and an average tumour length of 3.3 cm are contributing factors for failure of detection. Radiologists' training should emphasis these findings as it may improve cancer detection, and clinicians should be aware of the limitations of abdominal CT.

Utilizing mitochondrial events as biomarkers for imaging apoptosis.

Cells undergoing apoptosis show a plethora of time-dependent changes. The available tools for imaging apoptosis in live cells rely either on the detection of the activity of caspases, or on the visualization of exposure of phosphatidyl serine in the outer leaflet of the cell membrane. We report here a novel method for the detection of mitochondrial events during apoptosis, namely translocation of Bax to mitochondria and release of cytochrome c (Cyt c) using bimolecular fluorescence complementation. Expression of split yellow fluorescent protein (YFP) fragments fused to Bax and Cyt c, resulted in robust induction of YFP fluorescence at the mitochondria of apoptotic cells with very low background. In vivo expression of split YFP protein fragments in liver hepatocytes and intra-vital imaging of subcutaneous tumor showed elevated YFP fluorescence upon apoptosis induction. Thus, YFP complementation could be applied for high-throughput screening and in vivo molecular imaging of mitochondrial events during apoptosis.