Distinguishing Brain Metastasis Progression From Radiation Effects After Stereotactic Radiosurgery Using Longitudinal GRASP Dynamic Contrast-Enhanced MRI.

BACKGROUND: Differentiating brain metastasis progression from radiation effects or radiation necrosis (RN) remains challenging. Golden-angle radial sparse parallel (GRASP) dynamic contrast-enhanced MRI provides high spatial and temporal resolution to analyze tissue enhancement, which may differ between tumor progression (TP) and RN. OBJECTIVE: To investigate the utility of longitudinal GRASP MRI in distinguishing TP from RN after gamma knife stereotactic radiosurgery (SRS). METHODS: We retrospectively evaluated 48 patients with brain metastasis managed with SRS at our institution from 2013 to 2020 who had GRASP MRI before and at least once after SRS. TP (n = 16) was pathologically confirmed. RN (n = 16) was diagnosed on either resected tissue without evidence of tumor or on lesion resolution on follow-up. As a reference, we included a separate group of patients with non-small-cell lung cancer that showed favorable response with tumor control and without RN on subsequent imaging (n = 16). Mean contrast washin and washout slopes normalized to the superior sagittal sinus were compared between groups. Receiver operating characteristic analysis was performed to determine diagnostic performance. RESULTS: After SRS, progression showed a significantly steeper washin slope than RN on all 3 follow-up scans (scan 1: 0.29 ± 0.16 vs 0.18 ± 0.08, P = .021; scan 2: 0.35 ± 0.19 vs 0.18 ± 0.09, P = .004; scan 3: 0.32 ± 0.12 vs 0.17 ± 0.07, P = .002). No significant differences were found in the post-SRS washout slope. Post-SRS washin slope differentiated progression and RN with an area under the curve (AUC) of 0.74, a sensitivity of 75%, and a specificity of 69% on scan 1; an AUC of 0.85, a sensitivity of 92%, and a specificity of 69% on scan 2; and an AUC of 0.87, a sensitivity of 63%, and a specificity of 100% on scan 3. CONCLUSION: Longitudinal GRASP MRI may help to differentiate metastasis progression from RN.

18F-FDG PET-CT postoperative changes after maxillectomy: Findings and pitfalls in interpretation.

OBJECTIVE: We investigated the findings and pitfalls of FDG-PET/CT scanning after maxillectomy with reconstruction/rehabilitation procedures, in patients with head and neck malignancies treated during nine years at one tertiary medical centre. METHODS: Fourteen patients (10 males), aged 22-84 years, underwent 17 reconstruction/rehabilitation maxillectomy surgeries and 35 PET/CT scans. Postoperative PET/CT findings were correlated with clinical and imaging follow-up. RESULTS: Increased FDG uptake, mean SUVmax 2.4 ± 1.4 (range 0.3-4.3), was observed at the postoperative bed following 12 of 17 surgeries (71%; 10 obturators, two mesh reconstructions). Following the remaining 5/17 surgeries (three with a fat flap and two without any reconstructions), abnormal FDG uptake was not observed at the postoperative bed.CT features of postoperative sites included: non-homogeneous mixed iso/hyperdense structures (hollow or filled) with multiple surrounding and/or inside air bubbles ("sponge appearance") and mucosal thickening along the postoperative bed wall (in all cases with obturator implants); rich fat density material in reconstructions with a fat flap and in closures without reconstruction, and radiopaque elongated structures in mesh reconstructions.No correlation was found of the mean SUVmax in initial scans, with the time from the surgery date (10 ± 6 months; r=0.04, P=0.90), or with the mean SUVmax in final scans (at 25± 17 months, P=0.17). CONCLUSIONS:: Increased FDG uptake, together with corresponding non-specific CT features, may persist for a prolonged period after surgery with obturators and mesh implantations, mimicking malignancy or infection. Awareness of variations in postoperative PET-CT appearance can help avoid false interpretations and redundant invasive procedures.

Widespread cortical dyslamination in epilepsy patients with malformations of cortical development.

PURPOSE: Recent research in epilepsy patients confirms our understanding of epilepsy as a network disorder with widespread cortical compromise. Here, we aimed to investigate the neocortical laminar architecture in patients with focal cortical dysplasia (FCD) and periventricular nodular heterotopia (PNH) using clinically feasible 3 T MRI. METHODS: Eighteen epilepsy patients (FCD and PNH groups; n = 9 each) and age-matched healthy controls (n = 9) underwent T1 relaxation 3 T MRI, from which component probability T1 maps were utilized to extract sub-voxel composition of 6 T1 cortical layers. Seventy-eight cortical areas of the automated anatomical labeling atlas were divided into 1000 equal-volume sub-areas for better detection of cortical abnormalities, and logistic regressions were performed to compare FCD/PNH patients with healthy controls with the T1 layers composing each sub-area as regressors. Statistical significance (p < 0.05) was determined by a likelihood-ratio test with correction for false discovery rate using Benjamini-Hochberg method. RESULTS: Widespread cortical abnormalities were observed in the patient groups. Out of 1000 sub-areas, 291 and 256 bilateral hemispheric cortical sub-areas were found to predict FCD and PNH, respectively. For each of these sub-areas, we were able to identify the T1 layer, which contributed the most to the prediction. CONCLUSION: Our results reveal widespread cortical abnormalities in epilepsy patients with FCD and PNH, which may have a role in epileptogenesis, and likely related to recent studies showing widespread structural (e.g., cortical thinning) and diffusion abnormalities in various human epilepsy populations. Our study provides quantitative information of cortical laminar architecture in epilepsy patients that can be further targeted for study in functional and neuropathological studies.

State of the Art: Machine Learning Applications in Glioma Imaging.

OBJECTIVE: Machine learning has recently gained considerable attention because of promising results for a wide range of radiology applications. Here we review recent work using machine learning in brain tumor imaging, specifically segmentation and MRI radiomics of gliomas. CONCLUSION: We discuss available resources, state-of-the-art segmentation methods, and machine learning radiomics for glioma. We highlight the challenges of these techniques as well as the future potential in clinical diagnostics, prognostics, and decision making.

Fat necrosis after abdominal surgery: A pitfall in interpretation of FDG-PET/CT.

OBJECTIVE: We describe FDG-PET/CT findings of postoperative fat necrosis in patients following abdominal surgery, and evaluate their changes in size and FDG uptake over time. METHODS: FDG-PET/CT scans from January 2007-January 2016 containing the term 'fat necrosis' were reviewed. Lesions meeting radiological criteria of fat necrosis in patients with prior abdominal surgery were included. RESULTS: Forty-four patients, 30 males, mean age 68.4 ± 11.0 years. Surgeries: laparotomy (n=37; 84.1 %), laparoscopy (n=3; 6.8 %), unknown (n=4; 9.1 %). CTs of all lesions included hyperdense well-defined rims surrounding a heterogeneous fatty core. Sites: peritoneum (n=34; 77 %), omental fat (n=19; 43 %), subcutaneous fat (n=8; 18 %), retroperitoneum (n=2; 5 %). Mean lesion long axis: 33.6±24.9 mm (range: 13.0-140.0). Mean SUVmax: 2.6±1.1 (range: 0.6-5.1). On serial CTs (n=34), lesions decreased in size (p=0.022). Serial FDG-PET/CT (n=24) showed no significant change in FDG-avidity (p=0.110). Mean SUVmax did not correlate with time from surgery (p=0.558) or lesion size (p=0.259). CONCLUSION: Postsurgical fat necrosis demonstrated characteristic CT features and may demonstrate increased FDG uptake. However, follow-up of subsequent imaging scans showed no increases in size or FDG-avidity. Awareness of this entity is important to avoid misinterpretation of findings as recurrent cancer. KEY POINTS: • Postsurgical fat necrosis may mimic cancer in FDG-PET/CT. • Follow-up of fat necrosis showed no increase in FDG intensity. • CT follow-up showed a decrease in lesion size. • FDG uptake did not correlate with time lapsed from surgery.

Incorporation of relative cerebral blood flow into CT perfusion maps reduces false 'at risk' penumbra.

PURPOSE: The region defined as 'at risk' penumbra by current CT perfusion (CTP) maps is largely overestimated. We aimed to quantitate the portion of true 'at risk' tissue within CTP penumbra and to determine the parameter and threshold that would optimally distinguish it from false 'at risk' tissue, that is, benign oligaemia. METHODS: Among acute stroke patients evaluated by multimodal CT (NCCT/CTA/CTP) we identified those that had not undergone endovascular/thrombolytic treatment and had follow-up NCCT. Maps of absolute and relative CBF, CBV, MTT, TTP and Tmax as well as summary maps depicting infarcted and penumbral regions were generated using the Intellispace Portal (Philips Healthcare, Best, Netherlands). Follow-up CT was automatically co-registered to the CTP scan and the final infarct region was manually outlined. Perfusion parameters were systematically analysed - the parameter that resulted in the highest true-negative-rate (ie, proportion of benign oligaemia correctly identified) at a fixed, clinically relevant false-negative-rate (ie, proportion of 'missed' infarct) of 15%, was chosen as optimal. It was then re-applied to the CTP data to produce corrected perfusion maps. RESULTS: Forty seven acute stroke patients met selection criteria. Average portion of infarcted tissue within CTP penumbra was 15%±2.2%. Relative CBF at a threshold of 0.65 yielded the highest average true-negative-rate (48%), enabling reduction of the false 'at risk' penumbral region by ~half. CONCLUSIONS: Applying a relative CBF threshold on relative MTT-based CTP maps can significantly reduce false 'at risk' penumbra. This step may help to avoid unnecessary endovascular interventions.

The Role of Liver Segment-to-Spleen Volume Ratio in the Staging of Hepatic Fibrosis in Patients with Hepatitis C Virus Infection.

BACKGROUND: Accurate assessment of liver fibrosis is crucial for the management of patients with hepatitis C virus (HCV) infection. OBJECTIVES: To evaluate the performance of liver segment-to-spleen volume ratio in predicting the severity of liver fibrosis. METHODS: Sixty-four consecutive HCV patients were enrolled in this retrospective study. All patients underwent contrast-enhanced computed tomography (CT) and were divided into three groups based on their hepatic fibrosis stage evaluated by shear-wave elastography (SWE): non-advanced (F0-F1, n=29), advanced (F2, n=19) and severe fibrosis (F3-F4, n=16). Using semi-automated liver segmentation software, we calculated the following liver segments and spleen volumes for each participant: total liver volume (TLV), caudate lobe (CV), left lateral segment (LLV), left medial segment (LMV), right lobe (RV) and spleen (SV), a well as their ratios: CV/SV, RV/SV, LLV/SV, LMV/SV and TLV/SV. RESULTS: RV/SV was found to discriminate between patients with non-advanced and advanced fibrosis (P = 0.001), whereas SV, CV, RV, TLV/SV, LMV/SV and RV/SV discriminated between patients with advanced and severe fibrosis (P < 0.05). RV/SV ≤ 3.6 and RV ≤ 2.9 were identified as the best cutoff values to differentiate non-advanced from advanced fibrosis and advanced from severe fibrosis with sensitivities of 72.2% and 92.7%, specificities of 72.7% and 77.8%, and with an area under the receiver operating characteristic (ROC) curve of 0.797 and 0.847, respectively (P ≤ 0.002). CONCLUSIONS: RV/SV may be used for the assessment and monitoring of liver fibrosis in HCV patients prior to the administration of antiviral therapy, considering SWE as the reference method.

Unrecognized renal insufficiency and chemotherapy-associated adverse effects among breast cancer patients.

Several studies have shown that more than half of cancer patients have unrecognized renal insufficiency (RI), which is a reduced glomerular filtration rate (GFR) with normal serum creatinine. The aim of this study was to determine whether unrecognized RI is associated with an increased risk for chemotherapy-associated adverse effects in breast cancer patients treated with combined doxorubicin and cyclophosphamide treatment. GFR was estimated for 95 breast cancer patients from January 2005 to August 2009 using the Cockcroft-Gault formula. Unrecognized RI was defined as GFR less than 75 ml/min/1.73 m and the patients were grouped according to their estimated GFR. Logistic regression models were used to assess the effect of GFR on clinical outcomes. In total, 49 (52%) patients experienced at least one of the following chemotherapy-associated adverse effects during the course of treatment: an episode of neutropenic fever with hospital admission, a delay in chemotherapy treatment for a medical reason, a need for dose adjustment because of toxicity of the chemotherapeutic drugs, and the need for use of granulocyte colony-stimulating factor. The incidence of these adverse effects occurred more frequently in patients with GFR less than 75 compared with patients with GFR at least 75 (64 vs. 42%, odds ratio 5.29, 95% confidence interval 2.10-13.33) and remained statistically significant after adjustment for age, BMI, and initial doses of chemotherapeutic drugs (odds ratio 3.56, 95% confidence interval 1.08-11.67). Neutropenic fever, dose delay, and dose adjustment as separate outcomes occurred more frequently in the GFR less than 75 group but lost statistical significance after adjustment. Our results demonstrate that unrecognized RI is associated with an increased risk for chemotherapy-associated adverse events in this patient population. Further prospective studies are required to determine whether a dose reduction in patients with unrecognized RI reduces adverse effects without adversely affecting the benefit of treatment.

Percutaneous embolization of an incidentally diagnosed pulmonary aneurysm in a scleroderma patient.

A 59-year-old female with history of progressive scleroderma and pulmonary fibrosis was referred for biopsy of a pulmonary nodule that was discovered on computed-tomography (CT) chest surveillance, not present on prior CT- scan. Imaging was suspicious for granuloma, malignancy or aneurysm. CT- Angiography (CTA), performed immediately before the procedure, did not show enhancement of the mass, followed by placement of coaxial-needle into the mass. Suspicion of aneurysm was again raised and repeat CTA demonstrated contrast filling of the aneurysm. With the coaxial-needle in the aneurysm, embolization of the sac was performed using microfibrillar collagen, followed by confirmation of containment and thrombosis with CT.