Search

Purpose: To estimate feasible dose reduction to reliably measure ventricular width in adults with hydrocephalus in follow-up cranial computed tomography (CCT) using a custom-made phantom., Materials and Methods: A gelatine-filled adult calvarium with embedded central fibers of two carrots representing the lateral ventricles was used as a phantom. The phantom was scanned 11 times with two CT scanners (LightSpeed Ultra, GE and Somatom Sensation, Siemens), using tube currents of 380/400, 350, 300, 250, 200, 150 and 100 mA, and tube voltages of 140, 120, 100 and 80 kV. The width of the carrots was measured at four sites in consensus decision of two principle investigators blinded to the scan parameters. Values measured at 380/400 mA and 140 kV served as a reference for the width of the ventricles. Measurements received 1 point if they did not differ more than 0.5 mm from the reference values. A maximum score of 4 could be achieved., Results: The relationship between the correct width measurement of the carrots (lateral ventricles) and the radiation dose can be described by a quadratic regression function. Pixel noise increases and accuracy of measurements decreases with a lower radiation dose. Starting from a tube current of 380/400 mA and a tube voltage of 140 kV, the dose can be reduced by 76 % for LightSpeed Ultra and by 80 % for Somatom Sensation provided that a margin of error of 37.5 % (score = 2.5) for correct width measurement of the carrots is accepted., Conclusion: Lowering the radiation dose by up to 48 % for LightSpeed Ultra and by 52 % for Somatom Sensation, compared to the standard protocol (120 kV and 400 mA) still allowed reliable measurements of ventricular widths in this model., Key Points: • There is a quadratic relationship between correct width measurements of lateral ventricles and radiation dose in CT. • Reduction of radiation dose results in increased pixel noise and increased error for correct ventricle width measurement. • Due to a considerable attenuation difference between cerebrospinal fluid and brain parenchyma, a dose reduction for the determination of ventricular size in CT seems feasible and should be performed., (© Georg Thieme Verlag KG Stuttgart · New York.)

Purpose: Pseudoprogression (PP) during adjuvant treatment of glioblastoma (GBM) is frequent and is a clinically and radiologically challenging problem. While there are several reports of the frequency of PP in GBM cohorts including mainly patients with primary GBM, there are few data on the incidence of PP in patients with secondary glioblastomas (sGBM). Therefore, the goal of this study was to evaluate the frequency of PP in sGBM., Methods and Materials: We retrospectively evaluated the incidence of PP in adult patients with sGBM treated with chemoradiation therapy (CRTx) using temozolomide (TMZ) and sought to assess if there was an association between PP and MGMT promoter methylation status, IDH mutations status, or 1p/19q codeletion. The definition of PP according to the Response Assessment in Neuro-Oncology Working Group was used., Results: None of the evaluable 15 sGBM patients in our series demonstrated a PP. Of the 9 sGBM patients who received concomitant CRTx with TMZ, 6 patients had the methylated MGMT promoter, and 6 patients had IDH mutations. There also was no PP identified in sGBM patients who received sequential CRTx, irrespective of MGMT or IDH status. The median time of follow-up was 3.4 years after diagnosis of an sGBM, and the median overall survival was 18.2 months (range, 14.3-45.2 months). Three of 15 patients had previously received radiation therapy for their World Health Organization low-grade 2 glioma, while none of them had received chemotherapy at that stage., Conclusions: Based on this small series of sGBM patients treated with CRTx (concomitantly or sequentially) the frequency of PP appears to be very low in sGBM, even in those patients with methylated MGMT promoter or IDH mutations. Our results highlight the differences between primary glioblastomas and sGBM in particular as they relate to PP., (Copyright © 2013 Elsevier Inc. All rights reserved.)