Diagnostic Ability of Diffusion-weighted Magnetic Resonance Imaging to Discriminate Ampullary eoplasms: A Preliminary Study of 15 Cases

We assessed the diagnostic capability of diffusion-weighted magnetic resonance imaging (DWI) to predict the histological diagnosis of ampullary lesions to resolve the diagnostic uncertainty of endoscopic biopsy for ampullary neoplasms. From January 2009 to August 2011, we performed DWI using b values of 0 and 1000s/mm2 for 15 patients with a histological diagnosis of ampullary lesion (adenocarcinoma, n = 8; adenoma, n = 4; hyperplasia, n = 3). We compared the signal intensities (determined by comparing signal intensities of ampullary lesions and rating them as markedly hyperintense, hyperintense, or hypo-to-isointense relative to the duodenal wall) and the apparent diffusion coefficient (ADC, × 10-3 mm2/s) values of the ampullary lesions on DWI among the three groups based on the histological diagnosis. Values are expressed as median (range). The cancer-group lesions showed a significantly higher signal intensity than either adenoma or hyperplasia (markedly hyperintense/hyperintense/hypo-to-isointense; adenocarcinoma, 7/1/0; adenoma, 0/4/0; hyperplasia, 0/0/3; P < 0.005). The ADC values were significantly lower in adenocarcinoma at 1.46 (0.83-1.63) than in either adenoma at 2.14 (1.92-2.37) or hyperplasia at 2.06 (1.88-2.53) (P < 0.005). In addition, the ADC values in the malignant group (adenocarcinoma) were significantly lower than those in the benign groups (adenoma and hyperplasia) (P < 0.001). The findings suggested that DWI could contribute significantly to accurate preprocedural diagnosis of ampullary lesions

Survey of Period Variations of Superhumps in SU UMa-Type Dwarf Novae

We systematically surveyed period variations of superhumps in SU UMa-type dwarf novae based on newly obtained data and past publications. In many systems, the evolution of superhump period are found to be composed of three distinct stages: early evolutionary stage with a longer superhump period, middle stage with systematically varying periods, final stage with a shorter, stable superhump period. During the middle stage, many systems with superhump periods less than 0.08 d show positive period derivatives. Contrary to the earlier claim, we found no clear evidence for variation of period derivatives between superoutburst of the same object. We present an interpretation that the lengthening of the superhump period is a result of outward propagation of the eccentricity wave and is limited by the radius near the tidal truncation. We interpret that late stage superhumps are rejuvenized excitation of 3:1 resonance when the superhumps in the outer disk is effectively quenched. Many of WZ Sge-type dwarf novae showed long-enduring superhumps during the post-superoutburst stage having periods longer than those during the main superoutburst. The period derivatives in WZ Sge-type dwarf novae are found to be strongly correlated with the fractional superhump excess, or consequently, mass ratio. WZ Sge-type dwarf novae with a long-lasting rebrightening or with multiple rebrightenings tend to have smaller period derivatives and are excellent candidate for the systems around or after the period minimum of evolution of cataclysmic variables (abridged).Comment: 239 pages, 225 figures, PASJ accepte

A Case of Liver Metastasis from Small Intestinal Gastrointestinal Stromal Tumor 25 Years after Surgery including Autopsy Findings

Gastrointestinal stromal tumor (GIST) is the most common mesenchymal tumor in the digestive tract. Recurrences may occur even after radical resection; however, recurrence later than 10 years after surgery is rare. We report a case of GIST with recurrence of liver metastasis 25 years after surgery. A 56-year-old man complained of sudden epigastric pain and was transferred to the emergency department. He had undergone partial resection of the small intestine for leiomyosarcoma 25 years previously. Abdominal computed tomography showed multiple liver tumors with massive hemorrhage. Ultrasound-guided percutaneous biopsy was performed for the 15-mm hepatic tumor in segment 2. Pathological findings revealed proliferation of spindle-shaped atypical cells, and immunostaining for c-kit and CD34 was both positive; the patient was therefore diagnosed with GIST. He then underwent chemotherapy for 7 years but died of multiple organ failure due to GIST. Autopsy revealed GIST occupying the entire liver with peritoneal dissemination, and minute lung metastases that could not be identified by CT were also detected. This case is interesting in considering the recurrence of GIST, and we will report it together with the literature review