Bovine arch and carotid artery atherosclerosis: are they related?

OBJECTIVES: The prevalence of the "bovine" arch in the population is known (8-25%). However, its prevalence in patients with significant carotid atherosclerosis has never been investigated. Altered flow patterns or turbulence that may occur in these patients may play a causative role in the development of atherosclerotic lesions. The primary purpose of this study was to retrospectively compare the prevalence of aortic arch variants in patients with and without significant carotid artery atherosclerosis, as we hypothesize that carotid atherosclerosis may be more prevalent in patients with a bovine arch due to hemodynamic alterations. A secondary objective was to review radiologist reporting of arch anatomy. METHODS: Single-center, retrospective, case-control study in which 79 patients with hemodynamically significant carotid artery atherosclerosis who underwent computed tomography angiography, magnetic resonance angiography, or unenhanced computed tomography (CT) imaging including the aortic arch were identified. These patients were then compared with 95 randomly selected controls without carotid atherosclerosis that underwent similar imaging during the same time period. Images were independently reviewed by two blinded radiologists, who assessed arch anatomy as normal, bovine, or other variant. The original radiology reports were reviewed for reporting of arch anatomy. RESULTS: In controls, 70% had normal arch anatomy, and 24% had a bovine arch. Among patients with significant carotid disease, these numbers were 70% and 20%, respectively. There was no statistically significant difference between incidence of arch variants in subjects with and without carotid artery atherosclerosis (P=.97). There was good interreader agreement. Among patients with aortic arch anomalies, 20% of the original radiology reports did not mention arch anatomy. CONCLUSIONS: In our experience, percentage of bovine arch anomalies in patients with significant carotid atherosclerosis is not significantly different from those without disease. Clinicians should be aware of the high prevalence of arch anomalies, which can impact endovascular approach and management, and radiologists should be aware of the clinical importance of reporting such variants.

Variability of gross tumor volume delineation in head-and-neck cancer using PET/CT fusion, Part II: the impact of a contouring protocol.

The purpose of this study was to assess the efficacy of a gross tumor volume (GTV) contouring protocol on interobserver variability between 4 physicians in positron emission therapy/computed tomography (PET/CT) treatment planning of head-and-neck cancer. A GTV contouring protocol for PET/CT treatment planning was developed utilizing 4 stages: Preliminary contouring on CT alone, determination of appropriate PET windowing, accurate image registration, and modification of CT contouring with correctly formatted PET/CT display and rules for modality disagreement. Two neuroradiologists and 2 radiation oncologists (designated as A, B, C, and D, respectively) were given a tutorial of PET/CT coregistered imaging individualized to their skill level, which included a step-by-step explanation of the protocol with clinical examples. Opportunities for questions and hands-on practice were given. The physicians were asked to re-contour 16 head-and-neck patients from Part I on PET/CT fusion imaging. Differences in volume magnitude were analyzed for statistical significance by analysis of variance (ANOVA) and paired t-tests (alpha<0.05). Volume overlap was analyzed for statistical significance using Wilcoxon signed-rank tests (alpha<0.05). Volume overlap increased significantly from Part I to Part II (p<0.05). One previously significant difference between physicians disappeared with the protocol in place. The mean fusion volume of Physician C, however, remained significantly larger than that of Physician D (p<0.01). This result is unchanged from Part I. The multidisciplinary contouring protocol significantly improved the coincidence of GTVs contoured by multiple physicians. The magnitudes of the volumes showed marginal improvement in consistency. Developing an institutional contouring protocol for PET/CT treatment planning is highly recommended to reduce interobserver variability.

Variability of gross tumor volume delineation in head-and-neck cancer using CT and PET/CT fusion.

PURPOSE: To assess the need for gross tumor volume (GTV) delineation protocols in head-and-neck cancer (HNC) treatment planning by use of positron emission tomography (PET)/computed tomography (CT) fusion imaging. Assessment will consist of interobserver and intermodality variation analysis. METHODS AND MATERIALS: Sixteen HNC patients were accrued for the study. Four physicians (2 neuroradiologists and 2 radiation oncologists) contoured GTV on 16 patients. Physicians were asked to contour GTV on the basis of the CT alone, and then on PET/CT fusion. Statistical analysis included analysis of variance for interobserver variability and Student's paired sample t test for intermodality and interdisciplinary variability. A Boolean pairwise analysis was included to measure degree of overlap. RESULTS: Near-significant variation occurred across physicians' CT volumes (p = 0.09) and significant variation occurred across physicians' PET/CT volumes (p = 0.0002). The Boolean comparison correlates with statistical findings. One radiation oncologist's PET/CT fusion volumes were significantly larger than his CT volumes (p < 0.01). Conversely, the other radiation oncologist's CT volumes tended to be larger than his fusion volumes (p = 0.06). No significant interdisciplinary variation was seen. Significant disagreement occurred between radiation oncologists. CONCLUSION: Significant differences in GTV delineation were found between multiple observers contouring on PET/CT fusion. The need for delineation protocol has been confirmed.