Variations of ITSS-Morphology and their Relationship to Location and Tumor Volume in Patients with Glioblastoma.

BACKGROUND: Susceptibility weighted imaging and assessment of intratumoral susceptibility signal (ITSS) morphology is used to identify high-grade glioma (HGG) in patients with suspected brain neoplasm. PURPOSE: The aim of this study was to outline variations in ITSS-morphology and their relationship to location as well as volume of the lesion in patients with glioblastoma (GB). MATERIALS AND METHODS: Contrast-enhanced SWI (CE-SWI) images of 40 patients with histologically confirmed GB were analyzed retrospectively with particular attention to ITSS-morphology dividing all lesions into two groups. Considering the location of the lesion within brain parenchyma, lesions with and without involvement of the subventricular zone (SVZ+/SVZ-) were discerned. Additionally, the contrast-enhancing tumor volume was evaluated. Statistical analysis was based on a classification analysis resulting in a classification rule (tree) as well as Mann-Whitney-U test. RESULTS: The distribution of ITSS-scores showed differences between the SVZ+ and SVZ- groups. While SVZ-GB showed only fine-linear or dot-like ITSS, in SVZ+ GB the ITSS-morphology changed with the tumor volume, that is, in larger tumors dense and conglomerated ITSS were the predominant finding. CONCLUSION: Our findings indicate that ITSS-morphology is not a random phenomenon. Location of GB, as well as tumor volume, appear to be factors contributing to ITSS morphology.

Radiation exposure in perfusion CT of the brain.

OBJECTIVE: This study aimed to show the simulation of the radiation exposure of the brain during perfusion measurements multi-detector-CT. MATERIAL AND METHODS: The effective dose and different organ doses were measured with thermoluminescent dosimeters in an Alderson-Rando phantom and compared with the data of a simulation program (CT-Expo V1.6) for varying scan protocols with different tube voltages (in kilovolts) and constant parameters for tube current (270 mAs), scan length (28.8 mm), scan time (40 seconds), slice thickness (24 × 1.2 mm), and number of scans (40) for multi-detector-CT perfusion measurements of the brain. RESULTS: The thermoluminescent dosimeter measurements yielded effective doses of 3.8 mSv (80 kV), 8.6 mSv (100 kV), 14.1 mSv (120 kV), and 22.2 mSv (140 kV). These values were in line with the data from the simulation program CT-Expo V1.6. The organ doses varied between 97 and 556 mGy (brain), 10.7 and 80.9 mGy (eye lens), 9.6 and 46 mGy (bone marrow), 1.2 and 6.7 mGy (thyroid gland), and 4.1 to 22.3 mGy (skin). The maximum local skin dose ranged from 355 mGy (80 kV) to 1855 mGy (140 kV) in the directly exposed part of the skin. CONCLUSIONS: The radiation exposure during perfusion measurements of the brain is strongly dependent on the tube voltage and can vary widely even if the other exposure parameters remain constant. Maximum organ doses up to 556 mGy (brain) can be measured. Even if we never reached local organ doses that can cause a direct radiation injury, the review of the tube voltages implemented by the vendor is mandatory beside the limitation of the scanned area by clinical examination and the reduction of the number of scans. Simulation programs are a valuable tool for dose measurements.

Benefits of contrast-enhanced SWI in patients with glioblastoma multiforme.

INTRODUCTION: SWI can help to identify high-grade gliomas (HGG). The objective of this study was to analyse SWI and CE-SWI characteristics, i.e. the relationship between contrast-induced phase shifts (CIPS) and intratumoral susceptibility signals (ITSS) and their association with tumour volume in patients with glioblastoma multiforme (GBM). MATERIALS AND METHODS: MRI studies of 29 patients were performed to evaluate distinct susceptibility signals comparing SWI and CE-SWI characteristics. The relationship between these susceptibility signals and CE-T1w tumour volume was analysed by using Spearman's rank correlation coefficient and Kruskal-Wallis-test. Tumour biopsies of different susceptibility signals were performed in one patient. RESULTS: Comparison of SWI and CE-SWI demonstrated different susceptibility signals. Susceptibility signals visible on SWI images are consistent with ITSS; those only seen on CE-SWI were identified as CIPS. Correlation with CE-T1w tumour volume revealed that CIPS were especially present in small or medium-sized GBM (Spearman's rho r = 0.843, P < 0.001). Histology identified the area with CIPS as the tumour invasion zone, while the area with ITSS represented micro-haemorrhage, highly pathological vessels and necrosis. CONCLUSION: CE-SWI adds information to the evaluation of GBM before therapy. It might have the potential to non-invasively identify the tumour invasion zone as demonstrated by biopsies in one case. KEY POINTS: • MRI is used to help differentiate between low- and high-grade gliomas. • Contrast-enhanced susceptibility-weighted MRI (CE-SWI) helps to identify patients with glioblastoma multiforme. • CE-SWI delineates the susceptibility signal (CIPS and ITSS) more than the native SWI. • CE-SWI might have the potential to non-invasively identify the tumour invasion zone.

The value of dual-energy CTA for control of surgically clipped aneurysms.

OBJECTIVE: Comparison of image quality in DE-CTA with and without automatic head bone removal (BR) versus CTA with 16-detectors as a tool in postoperative evaluation of patients after neurosurgical clipping. METHODS: In this study 30 aneurysms that had undergone neurosurgical clipping were included: 18 with DE-CTA and 12 with conventional CTA. The images were further processed using the volume rendering technique (VRT) and BR. Two experienced neuroradiologists reviewed the images regarding the severity of artefacts surrounding the clip, visibility of the vessels and remnant necks. The results were compared with DSA images, if performed. RESULTS: Significantly fewer disturbances by artefacts were observed in DE-CTA versus CTA in a 16-row system. Visibility of the surrounding vessels was satisfying in both techniques and there were comparable results with DSA with only one exception. All images produced with 140 kV provided fewer artefacts than those with 80 kV. CONCLUSION: DE-CTA provides better image quality with fewer disturbances by clip artefact, a satisfying evaluation of remnant aneurysm necks and the surrounding vessels. As this method is easily performed and readily accessible with fast image post-processing using BR it provides an opportunity to avoid invasive DSA in the evaluation of suspected aneurysm rests.