Benign external hydrocephalus: a review, with emphasis on management

Benign external hydrocephalus in infants, characterized by macrocephaly and typical neuroimaging findings, is considered as a self-limiting condition and is therefore rarely treated. This review concerns all aspects of this condition: etiology, neuroimaging, symptoms and clinical findings, treatment, and outcome, with emphasis on management. The review is based on a systematic search in the Pubmed and Web of Science databases. The search covered various forms of hydrocephalus, extracerebral fluid, and macrocephaly. Studies reporting small children with idiopathic external hydrocephalus were included, mostly focusing on the studies reporting a long-term outcome. A total of 147 studies are included, the majority however with a limited methodological quality. Several theories regarding pathophysiology and various symptoms, signs, and clinical findings underscore the heterogeneity of the condition. Neuroimaging is important in the differentiation between external hydrocephalus and similar conditions. A transient delay of psychomotor development is commonly seen during childhood. A long-term outcome is scarcely reported, and the results are varying. Although most children with external hydrocephalus seem to do well both initially and in the long term, a substantial number of patients show temporary or permanent psychomotor delay. To verify that this truly is a benign condition, we suggest that future research on external hydrocephalus should focus on the long-term effects of surgical treatment as opposed to conservative management

Internal Auditory Canal Tumor as an Incidental Finding on a Choline PET/CT Scan in a Prostate Cancer Patient

An 84-year-old man with a history of prostate cancer, treated with radiotherapy, presented with an increase in PSA levels. F-choline PET/CT showed foci of increased choline uptake in L4 and L5 vertebrae, suggestive of bone metastases and another focus in the right cerebellopontine angle. A brain MRI revealed a focus of intense contrast enhancement in the same region, consistent with an acoustic neuroma

Prospective PET image quality gain calculation method by optimizing detector parameters

Background Lutetium-based scintillators with highperformance electronics introduced time-of-flight (TOF) reconstruction in the clinical setting. Let G′ be the total signal to noise ratio gain in a reconstructed image using the TOF kernel compared with conventional reconstruction modes. G′ is then the product of G1 gain arising from the reconstruction process itself and (n.1) other gain factors (G2, G3,...Gn) arising from the inherent properties of the detector. Methods We calculated G2 and G3 gains resulting from the optimization of the coincidence and energy window width for prompts and singles, respectively. Both quantitative and image-based validated Monte Carlo models of Lu2SiO5 (LSO) TOF-permitting and Bi4Ge3O12 (BGO) TOFnonpermitting detectors were used for the calculations. Results G2 and G3 values were 1.05 and 1.08 for the BGO detector and G3 was 1.07 for the LSO. A value of almost unity for G2 of the LSO detector indicated a nonsignificant optimization by altering the energy window setting. G′ was found to be ~1.4 times higher for the TOF-permitting detector after reconstruction and optimization of the coincidence and energy windows. Conclusion The method described could potentially predict image noise variations by altering detector acquisition parameters. It could also further contribute toward a long-lasting debate related to cost-efficiency issues of TOF scanners versus the non-TOF ones. Some vendors re-engage nowadays to non-TOF product line designs in an effort to reduce crystal costs. Therefore, exploring the limits of image quality gain by altering the parameters of these detectors remains a topical issue. © 2015 Wolters Kluwer Health, Inc. All rights reserved

Evaluation of the performance of 18F-fluorothymidine positron emission tomography/computed tomography (18F-FLT-PET/CT) in metastatic brain lesions

18F-fluorothymidine (18F-FLT) is a radiolabeled thymidine analog that has been reported to help monitor tumor proliferation and has been studied in primary brain tumors; however, knowledge about 18F-FLT positron emission tomography/computed tomography (PET/CT) in metastatic brain lesions is limited. The purpose of this study is to evaluate the performance of 18F-FLT-PET/CT in metastatic brain lesions. A total of 20 PET/CT examinations (33 lesions) were included in the study. Semiquantitative analysis was performed: standard uptake value (SUV) with the utilization of SUVmax, tumor-to-background ratio (T/B), SUVpeak, SUV1cm3, SUV0.5cm3, SUV50%, SUV75%, PV50% (volume × SUV50%), and PV75% (volume × SUV75%) were calculated. Sensitivity, specificity, and accuracy for each parameter were calculated. Optimal cutoff values for each parameter were obtained. Using a receiver operating characteristic (ROC) curve analysis, the optimal cutoff values of SUVmax, T/B, and SUVpeak for discriminating active from non-active lesions were found to be 0.615, 4.21, and 0.425, respectively. In an ROC curve analysis, the area under the curve (AUC) is higher for SUVmax (p-value 0.017) compared to the rest of the parameters, while using optimal cutoff T/B shows the highest sensitivity and accuracy. PVs (proliferation × volumes) did not show any significance in discriminating positive from negative lesions. 18F-FLT-PET/CT can detect active metastatic brain lesions and may be used as a complementary tool. Further investigation should be performed. © 2019 by the authors

The impact of FDG-PET/CT on the management of breast cancer patients with elevated tumor markers and negative or equivocal conventional imaging modalities

Objective: To evaluate the clinical impact of fluorodeoxyglucose (FDG)-PET/computed tomography (CT) scan on restaging breast cancer patients with rising tumor markers and negative or equivocal findings in conventional imaging studies. Methods: We studied 46 patients with breast cancer of an average age of 57.6 years (ranging from 38 to 68 years). All patients were referred for an FDG-PET/CT scan because of elevated tumor markers, without any other obvious clinical or laboratory sign of relapse. Conventional imaging study results were either negative (29 out of 46 patients) or inconclusive (17 out of 46 patients). All patients underwent a whole-body FDG-PET/CT scan in a combined PET/CT. The findings were confirmed by a follow-up at least 9 months later, and when it was possible, final diagnosis was obtained by histopathology. Results: In 34 out of 46 patients, an FDG-PET/CT scan showed sites of increased metabolic activity, indicating active disease. In 23 out of 46 patients, the therapeutic approach and further clinical management were affected. The FDG-PET/CT scan was true-positive in 33 patients, false-positive in one patient, false-negative in five patients, and true-negative in seven patients. On the basis of our results in this population, an FDG-PET/CT scan had a sensitivity of 86.8%, a specificity of 87.5%, and an accuracy of 86.9%. The positive predictive value was 97.1% and the negative predictive value was 58.3%. Clinical management was affected in 50% of these patients. Conclusions: The FDG-PET/CT scan plays an important role in restaging breast cancer patients with rising tumor markers and negative or equivocal findings in conventional imaging techniques, with a consequent significant clinical impact on further management in these patients. © 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins

PET Counting Response Variability Depending on Tumor Location, Activity, and Patient Obesity: A Feasibility Study of Solitary Pulmonary Nodule Using Monte Carlo

We aim to investigate the counting response variations of positron emission tomography (PET) scanners with different detector configurations in the presence of solitary pulmonary nodule (SPN). Using experimentally validated Monte Carlo simulations, the counting performance of four different scanner models with varying tumor activity, location, and patient obesity is represented using a noise equivalent count rate (NECR). NECR is a well-established quantitative metric which has positive correlation with clinically perceived image quality. The combined effect of tumor displacement and increased activity shows a linear ascending trend for NECR with slope ranges of (12.5-18.2)∗10-3 (kBq/cm3)-1 for three-ring (3R) scanners and (15.3-21.5)∗10-3 (kBq/cm3)-1 for four-ring (4R). The trend for the combined effect of tumor displacement and patient obesity is exponential decay with 3R configurations weakly dependent on the patient obesity if the tumor is located at the center of the field of view with exponent's range of (6.6-33.8)∗10-2cm-1. The dependence is stronger for 4R scanners (9.6-38.5)∗10-2cm-1. The analysis indicates that quantitative PET data from the same SPN patient possibly examined in different time points (e.g., during staging or for the evaluation of treatment response) are affected by the different detector configurations and need to be normalized with patient weight, activity, and tumor location to reduce unwanted bias of the diagnosis. This paper provides also with a proof of concept for the ability of properly tuned simulations to provide additional insights into the counting response variability especially in tumor types where often borderline decisions have to be made regarding their characterization. © 1982-2012 IEEE

On the accuracy of a mutual information algorithm for PET-MR image registration

Image registration has been increasingly used in radiation diagnosis and treatment planning as a means of information integration from different imaging modalities (e.g. MRI, PET, CT). Especially for brain lesions, accurate 3D registration and fusion of MR and PET images can provide comprehensive information about the patient under study by relating functional information from PET images to the detailed anatomical information available in MR images. However, direct PET-MR image fusion in soft tissue is complicated mainly due to the lack of conspicuous anatomical features in PET images. This study describes the implementation and validation of a mutual information registration algorithm for this purpose. Ten patients with brain lesions underwent MR and PET/CT scanning. MR-PET registration was performed a) based on the well validated MR-CT registration technique and copying the transformation to the PET images derived from the PET/CT scan (MR/PET/CT registration method) and b) directly from the MR and PET images without taking into account the CT images (MR/PET registration method). In order to check the registration accuracy of the MR/PET method, the lesion (target) was contoured in the PET images and it was transferred to the MR images using both the above methods. The MR/PET/CT method served as the gold standard for target contouring. Target contours derived by the MR/PET method were compared with the gold standard target contours for each patient and the deviation between the two contours was used to estimate the accuracy of the PET-MR registration method. This deviation was less than 3 mm (i.e. comparable to the imaging voxel of the PET/CT scanning) for 9/10 of the cases studied. Results show that the mutual information algorithm used is able to perform the PET-MR registration reliably and accurately. © 2009 IOP Publishing Ltd and SISSA