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summary Objectives: Radiation induced cranial nerve palsy (RICNP) involving the lower cranial nerves (CNs) is a serious complication of head and neck radiotherapy (RT). Recommendations for delineating the lower CNs on RT planning studies do not exist. The aim of the current study is to develop a standardized methodology for contouring CNs IX–XII, which would help in establishing RT limiting doses for organs at risk (OAR). Methods: Using anatomic texts, radiologic data, and guidance from experts in head and neck anatomy, we developed step-by-step instructions for delineating CNs IX–XII on computed tomography (CT) imaging. These structures were then contoured on five consecutive patients who underwent definitive RT for locally-advanced head and neck cancer (LAHNC). RT doses delivered to the lower CNs were calculated. Results: We successfully developed a contouring atlas for CNs IX–XII. The median total dose to the planning target volume (PTV) was 70 Gy (range: 66–70 Gy). The median CN (IX–XI) and (XII) volumes were 10 c.c (range: 8–12 c.c) and 8 c.c (range: 7–10 c.c), respectively. The median V50, V60, V66, and V70 of the CN (IX–XI) and (XII) volumes were (85, 77, 71, 65) and (88, 80, 74, 64) respectively. The median maximal dose to the CN (IX–XI) and (XII) were 72 Gy (range: 66–77) and 71 Gy (range: 64–78), respectively. Conclusions: We have generated simple instructions for delineating the lower CNs on RT planning imaging. Further analyses to explore the relationship between lower CN dosing and the risk of RICNP are recommended in order to establish limiting doses for these OARs.

The risk of invasive colorectal cancer in colorectal polyps correlates with lesion size. Our purpose was to define the most accurate methods for measuring polyp size at CT colonography (CTC) using three models of workstations and multiple observers.Six reviewers measured 24 unique polyps of known size (5, 7, 10, and 12 mm), shape (sessile, flat, and pedunculated), and location (straight or curved bowel segment) using CTC data sets obtained at two doses (5 mAs and 65 mAs) and a previously described colonic phantom model. Reviewers measured the largest diameter of polyps on three proprietary workstations. Each polyp was measured with lung and soft-tissue windows on axial, 2D multiplanar reconstruction (MPR), and 3D images.There were significant differences among measurements obtained at various settings within each workstation (p0.0001). Measurements on 2D images were more accurate with lung window than with soft-tissue window settings (p0.0001). For the 65-mAs data set, the most accurate measurements were obtained in analysis of axial images with lung window, 2D MPR images with lung window, and 3D tissue cube images for Wizard, Advantage, and Vitrea workstations, respectively, without significant differences in accuracy among techniques (0.11p0.59). The mean absolute error values for these optimal settings were 0.48 mm, 0.61 mm, and 0.76 mm, respectively, for the three workstations. Within the ultralow-dose 5-mAs data set the best methods for Wizard, Advantage, and Vitrea were axial with lung window, 2D MPR with lung window, and 2D MPR with lung window, respectively. Use of nearly all measurement methods, except for the Vitrea 3D tissue cube and the Wizard 2D MPR with lung window, resulted in undermeasurement of the true size of the polyps.Use of CTC computer workstations facilitates accurate polyp measurement. For routine CTC examinations, polyps should be measured with lung window settings on 2D axial or MPR images (Wizard and Advantage) or 3D images (Vitrea). When these optimal methods are used, these three commercial workstations do not differ significantly in acquisition of accurate polyp measurements at routine dose settings.

Rationale and objectives Multiple trials have documented wide interobserver variability between radiologists interpreting computed tomography colonography (CTC) exams. We sought to determine if nonradiologists could learn to interpret intraluminal findings at CTC with a high degree of sensitivity to determine if they could play a role as second readers in interpreting CTC exams. Materials and methods Seven nonradiologists (five medical students, two radiologic technologists) undertook self-directed CTC training using a teaching file of 50 cases; thereafter, each reader blindly interpreted 50 cases with colonoscopic correlation (30 positive, 20 negative). Results were compared with a previously studied cohort of radiologists. The two technologists additionally repeated the exam after 6 weeks of clinical experience. Results The sensitivity of nonradiologists for small (5–9 mm) polyps, large (>9 mm) lesions, and cancers was similar to that of radiologists (0.45 versus 0.63, 0.74 versus 0.71, and 0.80 versus 0.88, respectively). After 6 weeks of clinical experience as second readers, the accuracy of one technologist significantly improved (from 74% to 90%, P = .008), whereas accuracy of the other tended toward improvement (from 74% to 86%%, P = .25). Nonradiologists detected, on average, 6/36 additional polyps (17%) missed by any radiologist, and the sensitivity of 5/7 nonradiologists was significantly greater than at least one of the radiologists (P = .05). Conclusion Nonradiologists can perform similarly to radiologists in interpreting intraluminal findings at CTC, with nonradiologist performance improving even after experience with more than 100 cases. Skilled nonradiologists may play a vital role as a second reader of intraluminal findings or by performing quality control of examinations before patient dismissal.

2Department of Radiology, Mayo Clinic Rochester, Mayo East 2-B, 200 First St. SW, Rochester, MN 55905. Address correspondence to J. G. Fletcher. T colonography, or virtual colonoscopy, is now routinely used as a full structural examination of the colorectum following incomplete endoscopy [1] and in patients with elevated risk for complications during endoscopy or with aversion to endoscopy. CT colonography has demonstrated performance on par with optical colonoscopy in the screening of asymptomatic patients for adenomatous polyps in some hands [2] and has performed superiorly compared with nonendoscopic alternatives [3]. Optimal colonic inflation is essential to a high-quality CT colonography examination. Given the speed of image acquisition and reconstruction of MDCT scanners, patients must tolerate maximum inflation for only a few seconds, as opposed to endoscopy and barium enema, in which the colon remains inflated for much longer periods of time. Nevertheless, colonic insufflation is known to result in perforation, ranging from approximately 0.004–0.01% of cases for double contrast barium enema [4, 5] to 0.07–0.19% of cases for colonoscopy [6, 7]. To date, thousands of patients have undergone CT colonography without complications. Two cases of colonic perforation at CT have recently been reported in patients with known colonic disease [8, 9]. We report a case of perforation following CT colonography in a patient without known colonic disease.

Objective: To determine small bowel distention, scanning time, and side effects of commercially available oral contrast agents used in cross-sectional enterography. Methods: Ten healthy volunteers ingested 2000 mL of water, methylcellulose, polyethylene glycol (PEG), or 1350 mL of low-concentration barium (LCB) followed by 500 mL water on different days. Magnetic resonance imaging occurred every 10 minutes from 30 to 90 minutes after ingestion. Small bowel distention was compared between time points and agents. Volunteers ranked side effects, drinking difficulty, and preference. Results: By quantitative assessment, PEG and LCB distended small bowel loops better than water and methylcellulose (P < 0.0001). Time to optimal distention of the terminal ileum was from 51 to 72 minutes. Water and methylcellulose had the fewest side effects. Water was the most preferred contrast and PEG the least. Conclusions: Polyethylene glycol and LCB distend small bowel better than water and methylcellulose. Polyethylene glycol was the most difficult to drink and least preferred agent.

The purpose of this study was to evaluate the accuracy and precision of polyp measurements obtained with an automated tool in a colon phantom containing polyps of multiple sizes, morphologic types, and locations.A colon phantom was scanned at 12, 25, 50, and 100 mA with standard CT colonographic acquisition parameters. Four reviewers using manual 2D methods and an automated polyp measurement tool measured 24 polyps of varying sizes and morphologic types, some at a haustral fold tip and some not at a fold tip. The accuracy (difference from true value) of manual and automated methods was compared across polyp sizes, morphologic types, locations, and doses. Precision (closeness of different measures) was compared for intraobserver and interobserver measurements.The accuracy of automated polyp measurement was dependent on morphologic type (por = 0.02), size (for three of four reviewers, por = 0.05), and location of polyps with respect to haustral folds (two of four reviewers, por = 0.01). For two of four reviewers, automated measures were less accurate for 5-mm polyps, flat polyps, and polyps at the tips of folds (por = 0.04). Intraobserver precision was high, two automated measurements being within 0.1 mm of each other 82-93% of the time. Interobserver precision values for automated measures were more similar 85% of the time (82/96; p0.001).Accuracy of automated polyp measurements depends on polyp size, morphologic type, and location. When using an automated tool, radiologists should visually inspect automated polyp measurements, particularly for small and flat polyps and those located on folds, because manual measurements may be more accurate in this setting. Automated polyp measurements are more precise than manual measurements.

Computed tomographic (CT) enterography combines the improved spatial and temporal resolution of multi-detector row CT with large volumes of ingested neutral enteric contrast material to permit visualization of the small bowel wall and lumen. Adequate luminal distention can usually be achieved with oral hyperhydration, thereby obviating nasoenteric intubation and making CT enterography a useful, well-tolerated study for the evaluation of diseases affecting the mucosa and bowel wall. Unlike routine CT, which has been used to detect the extraenteric complications of Crohn disease such as fistula and abscess, CT enterography clearly depicts the small bowel inflammation associated with Crohn disease by displaying mural hyperenhancement, stratification, and thickening; engorged vasa recta; and perienteric inflammatory changes. As a result, CT enterography is becoming the first-line modality for the evaluation of suspected inflammatory bowel disease. CT enterography has also become an important alternative to traditional fluoroscopy in the assessment of other small bowel disorders such as celiac sprue and small bowel neoplasms.