Interobserver variation in tumor delineation of liver metastases using Magnetic Resonance Imaging.

Background and purpose: Magnetic Resonance Imaging (MRI) guided stereotactic body radiotherapy (SBRT) of liver metastases is an upcoming high-precision non-invasive treatment. Interobserver variation (IOV) in tumor delineation, however, remains a relevant uncertainty for planning target volume (PTV) margins. The aims of this study were to quantify IOV in MRI-based delineation of the gross tumor volume (GTV) of liver metastases and to detect patient-specific factors influencing IOV. Materials and methods: A total of 22 patients with liver metastases from three primary tumor origins were selected (colorectal(8), breast(6), lung(8)). Delineation guidelines and planning MRI-scans were provided to eight radiation oncologists who delineated all GTVs. All delineations were centrally peer reviewed to identify outliers not meeting the guidelines. Analyses were performed both in- and excluding outliers. IOV was quantified as the standard deviation (SD) of the perpendicular distance of each observer's delineation towards the median delineation. The correlation of IOV with shape regularity, tumor origin and volume was determined. Results: Including all delineations, average IOV was 1.6 mm (range 0.6-3.3 mm). From 160 delineations, in total fourteen single delineations were marked as outliers after peer review. After excluding outliers, the average IOV was 1.3 mm (range 0.6-2.3 mm). There was no significant correlation between IOV and tumor origin or volume. However, there was a significant correlation between IOV and regularity (Spearman's ρs = -0.66; p = 0.002). Conclusion: MRI-based IOV in tumor delineation of liver metastases was 1.3-1.6 mm, from which PTV margins for IOV can be calculated. Tumor regularity and IOV were significantly correlated, potentially allowing for patient-specific margin calculation.

[Radiological abnormalities and long-term IUD use: think of actinomycosis]. / Intra-abdominale massa's en een intra-uterien device.

BACKGROUND: A rare cause of nonspecific, chronic abdominal pain is actinomycosis. Extensive disease can cause chronic peritonitis mimicking malignancy. CASE DESCRIPTION: A 59-year-old women presented with aspecific chronic abdominal pain, after 23 years of IUD use. Imaging showed two solid masses in the abdomen suggestive of malignant disease. Additional diagnostic procedures did not prove malignancy and biopsies showed chronic inflammation. In the absence of proof of malignancy and with regard to the long-term IUD use, actinomycosis was considered. A Pap smear showed Actinomyces 5 years earlier. Antibiotic treatment was instituted and remission of the intra-abdominal masses was seen after six months of treatment. CONCLUSION: Consider actinomycosis in a patient presenting with abdominal pain and (long-term) IUD use. Diagnosis is challenging and frequently impossible to confirm before treatment. This diagnosis should be considered after thorough workup for other diseases, especially malignancy. After such analysis, starting antibiotic therapy could prevent secondary complications and invasive procedures.