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Background and purpose: Delivery of high precision radiotherapy lymph node boosts requires detailed information on the interfraction positional variation of individual lymph nodes. In this study we characterized interfraction positional shifts of suspected malignant lymph nodes for rectal cancer patients receiving long course radiotherapy. Furthermore, we investigated parameters which could affect the magnitude of the position variation. Materials and Methods: Fourteen patients from a prospective clinical imaging study with a total of 61 suspected malignant lymph nodes in the mesorectum, presacral, and lateral regions, were included. The primary gross tumor volume (GTVp) and all suspected malignant lymph nodes were delineated on six magnetic resonance imaging scans per patient. Positional variation was calculated as systematic and random errors, based on shifts of center-of-mass, and estimated relative to either bony structures or the GTVp using a hierarchical linear mixed model. Results: Depending on location and direction, systematic and random variations (relative to bony structures) were within 0.6-2.8 mm and 0.6-2.9 mm, respectively. Systematic and random variations increased when evaluating position relative to GTVp (median increase of 0.6 mm and 0.5 mm, respectively). Correlations with scan time-point and relative bladder volume were found in some directions. Conclusions: Using linear mixed modeling, we estimated systematic and random positional variation for suspected malignant lymph nodes in rectal cancer patients treated with long course radiotherapy. Statistically significant correlations of the magnitude of the lymph node shifts were found related to scan time-point and relative bladder volume.
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PURPOSE: Primary acute intestinal ischaemia (AII) is an abdominal catastrophe caused by intravascular obstruction of blood supply. It is difficult to diagnose. Computerized tomography (CT) scan is the modality of choice for diagnostic evaluation. Majority of previous studies have evaluated CT findings in patients where AII was suspected. However, unveiling the unique radiological findings also in not initially suspected AII patients, might lead to the timely management of AII patients, and is the aim of this study. METHODS: In a single-center, retrospective case-control study, preoperative radiological findings from abdominal CT scans in 48 patients with primary AII were compared with 80 non-ischemic controls. Radiological findings were analyzed using multivariable logistical regression with adjustment for age and gender and reported as odds ratios (OR) with 95% confidence intervals (CI) and p values. RESULTS: Thirty-nine (81%) cases with AII were referred to an abdominal CT scan without a specific clinical suspicion of AII. Three main radiological categories (intestinal wall pathology [OR 7.4, CI 2.3-24.0, p value < 0.001], gastrointestinal vessel pathology [OR 19.3, CI 4.6-80.5, p value < 0.001) and intestinal diameter [OR 4.7, CI 1.6-13.4, p value 0.004]) were significantly different in AII patients. Subgroup analysis implied that pneumatosis intestinalis, increased contrast enhancement in the bowel wall, inferior mesenteric artery arteriosclerosis and colonic contraction were predictors of AII. CONCLUSION: Radiological changes within the intestinal wall, luminal diameter and gastrointestinal vessels are independent predictors of AII. Awareness of these radiological findings, therefore, plays a central role in patients with an indistinct clinical picture in early recognition and treatment of a life-threatening AII. TRIAL REGISTRATION NUMBER: NCT04361110 (April 24, 2020), retrospectively registered.