Validation of a methylation-based signature for subventricular zone involvement in glioblastoma.

PURPOSE: Glioblastomas (GBM) with subventricular zone (SVZ) contact have previously been associated with a specific epigenetic fingerprint. We aim to validate a reported bulk methylation signature to determine SVZ contact. METHODS: Methylation array analysis was performed on IDHwt GBM patients treated at our institution. The v11b4 classifier was used to ensure the inclusion of only receptor tyrosine kinase (RTK) I, II, and mesenchymal (MES) subtypes. Methylation-based assignment (SVZM ±) was performed using hierarchical cluster analysis. Magnetic resonance imaging (MRI) (T1ce) was independently reviewed for SVZ contact by three experienced readers. RESULTS: Sixty-five of 70 samples were classified as RTK I, II, and MES. Full T1ce MRI-based rater consensus was observed in 54 cases, which were retained for further analysis. Epigenetic SVZM classification and SVZ were strongly associated (OR: 15.0, p = 0.003). Thirteen of fourteen differential CpGs were located in the previously described differentially methylated LRBA/MAB21L2 locus. SVZ + tumors were linked to shorter OS (hazard ratio (HR): 3.80, p = 0.02) than SVZM + at earlier time points (time-dependency of SVZM, p < 0.05). Considering the SVZ consensus as the ground truth, SVZM classification yields a sensitivity of 96.6%, specificity of 36.0%, positive predictive value (PPV) of 63.6%, and negative predictive value (NPV) of 90.0%. CONCLUSION: Herein, we validated the specific epigenetic signature in GBM in the vicinity of the SVZ and highlighted the importance of methylation of a part of the LRBA/MAB21L2 gene locus. Whether SVZM can replace MRI-based SVZ assignment as a prognostic and diagnostic tool will require prospective studies of large, homogeneous cohorts.

Diffuse paediatric-type high-grade glioma, H3-wildtype and IDH-wildtype: case series of a new entity.

Diffuse paediatric-type high-grade glioma, H3-wildtype and IDH-wildtype (pHGG) is a rare and aggressive brain tumor characterized by a specific DNA methylation profile. It was recently introduced in the 5th World Health Organization classification of central nervous system tumors of 2021. Clinical data on this tumor is scarce. This is a case series, which presents the first clinical experience with this entity. We compiled a retrospective case series on pHGG patients treated between 2015 and 2022 at our institution. Data collected include patients' clinical course, surgical procedure, histopathology, genome-wide DNA methylation analysis, imaging and adjuvant therapy. Eight pHGG were identified, ranging in age from 8 to 71 years. On MRI tumors presented with an unspecific intensity profile, T1w hypo- to isointense and T2w hyperintense, with inhomogeneous contrast enhancement, often with rim enhancement. Three patients died of the disease, with overall survival of 19, 28 and 30 months. Four patients were alive at the time of the last follow-up, 4, 5, 6 and 79 months after the initial surgery. One patient was lost to follow-up. Findings indicate that pHGG prevalence might be underestimated in the elderly population.

Spectral Computed Tomography-Derived Iodine Content and Tumor Response in the Follow-Up of Neuroendocrine Tumors-A Single-Center Experience.

Spectral computed tomography (SCT) allows iodine content (IC) calculation for characterization of hypervascularized neoplasms and thus might help in the staging of neuroendocrine tumors (NETs). This single-center prospective study analyzed the association between SCT-derived IC and tumor response in the follow-up of metastasized NETs. Twenty-six patients with a median age of 70 years (range 51-85) with histologically proven NETs and a total of 78 lesions underwent SCT for staging. Because NETS are rare, no primary NET types were excluded. Lesions and intralesional hotspots were measured in virtual images and iodine maps. Tumor response was classified as progressive or nonprogressive at study endpoint. Generalized estimating equations served to estimate associations between IC and tumor response, additionally stratified by lesion location. Most commonly affected sites were the lymph nodes, liver, pancreas, and bones. Median time between SCT and endpoint was 64 weeks (range 5-260). Despite statistical imprecision in the estimate, patients with higher IC in lymphonodular metastases had lower odds for disease progression (adjusted OR = 0.21, 95% CI: 0.02-2.02). Opposite tendencies were observed in hepatic and pancreatic metastases in unadjusted analyses, which vanished after adjusting for therapy and primary tumor grade.

MR Imaging Volumetric Response after Yttrium-90 Radioembolization for Colorectal Liver Metastases: Predictability at Baseline and Correlation with Survival.

PURPOSE: To prove the utility of magnetic resonance (MR) imaging response as a surrogate end point of treatment efficacy and survival after yttrium-90 transarterial radioembolization (TARE) for colorectal liver metastases (CRLMs), and to investigate whether outcomes can be predicted at baseline using MR imaging or clinical variables. MATERIALS AND METHODS: A total of 50 (135) patients with TARE for CRLMs between August 2008 and January 2020 and peri-interventional MR imaging within defined timeframes were included for tumor segmentation. Pretreatment and posttreatment target tumor volumes were measured according to the volumetric Response Evaluation Criteria In Solid Tumors (vRECIST) and the quantitative European Association for the Study of the Liver (qEASL) criteria. Cox regression models were used to analyze the impact of MR morphologic response, vascularity at baseline, and clinical variables on patient survival. Logistic regression analyses were used to evaluate the predictors of MR morphologic response at baseline. RESULTS: The median survival was 337 days (95% confidence interval [CI], 243-431). As opposed to the vRECIST, the application of the qEASL criteria 3 months after the treatment allowed for a significant (P < .05) separation of the survival curves for partial response, stable disease, and progressive disease with a median survival of 412 days (95% CI, 57-767) in responders. High tumor burden and technetium-99m lung shunt significantly decreased the probability of survival. MR morphologic response was not predictable at baseline using imaging or clinical data. CONCLUSIONS: MR response according to the qEASL criteria outperformed the vRECIST in measuring the biologic impact of TARE and predicting patient survival. Baseline contrast enhancement did not predict MR response to treatment, which may reflect elevated dose requirements in tumors with a high proportion of viable tumor volume.

Yttrium-90 radioembolization for unresectable hepatocellular carcinoma: predictive modeling strategies to anticipate tumor response and improve patient selection.

OBJECTIVES: This study aims to better characterize potential responders of Y-90-radioembolization at baseline through analysis of clinical variables and contrast enhanced (CE) MRI tumor volumetry in order to adjust therapeutic regimens early on and to improve treatment outcomes. METHODS: Fifty-eight HCC patients who underwent Y-90-radioembolization at our center between 10/2008 and 02/2017 were retrospectively included. Pre- and post-treatment target lesion volumes were measured as total tumor volume (TTV) and enhancing tumor volume (ETV). Survival analysis was performed with Cox regression models to evaluate 65% ETV reduction as surrogate endpoint for treatment efficacy. Univariable and multivariable logistic regression analyses were used to evaluate the combination of baseline clinical variables and tumor volumetry as predictors of ≥ 65% ETV reduction. RESULTS: Mean patients' age was 66 (SD 8.7) years, and 12 were female (21%). Sixty-seven percent of patients suffered from liver cirrhosis. Median survival was 11 months. A threshold of ≥ 65% in ETV reduction allowed for a significant (p = 0.04) separation of the survival curves with a median survival of 11 months in non-responders and 17 months in responders. Administered activity per tumor volume did predict neither survival nor ETV reduction. A baseline ETV/TTV ratio greater than 50% was the most important predictor of arterial devascularization (odds ratio 6.3) in a statistically significant (p = 0.001) multivariable logistic regression model. The effect size was strong with a Cohen's f of 0.89. CONCLUSION: We present a novel approach to identify promising candidates for Y-90 radioembolization at pre-treatment baseline MRI using tumor volumetry and clinical baseline variables. KEY POINTS: • A decrease of 65% enhancing tumor volume (ETV) on follow-up imaging 2-3 months after Y-90 radioembolization of HCC enables the early prediction of significantly improved median overall survival (11 months vs. 17 months, p = 0.04). • Said decrease in vascularization is predictable at baseline: an ETV greater than 50% is the most important variable in a multivariable logistic regression model that predicts responders at a high level of significance (p = 0.001) with an area under the curve of 87%.

High-grade astrocytoma with piloid features (HGAP): the Charité experience with a new central nervous system tumor entity.

PURPOSE: High-grade astrocytoma with piloid features (HGAP) is a recently described brain tumor entity defined by a specific DNA methylation profile. HGAP has been proposed to be integrated in the upcoming World Health Organization classification of central nervous system tumors expected in 2021. In this series, we present the first single-center experience with this new entity. METHODS: During 2017 and 2020, six HGAP were identified. Clinical course, surgical procedure, histopathology, genome-wide DNA methylation analysis, imaging, and adjuvant therapy were collected. RESULTS: Tumors were localized in the brain stem (n = 1), cerebellar peduncle (n = 1), diencephalon (n = 1), mesencephalon (n = 1), cerebrum (n = 1) and the thoracic spinal cord (n = 2). The lesions typically presented as T1w hypo- to isointense and T2w hyperintense with inhomogeneous contrast enhancement on MRI. All patients underwent initial surgical intervention. Three patients received adjuvant radiochemotherapy, and one patient adjuvant radiotherapy alone. Four patients died of disease, with an overall survival of 1.8, 9.1, 14.8 and 18.1 months. One patient was alive at the time of last follow-up, 14.6 months after surgery, and one patient was lost to follow-up. Apart from one tumor, the lesions did not present with high grade histology, however patients showed poor clinical outcomes. CONCLUSIONS: Here, we provide detailed clinical, neuroradiological, histological, and molecular pathological information which might aid in clinical decision making until larger case series are published. With the exception of one case, the tumors did not present with high-grade histology but patients still showed short intervals between diagnosis and tumor progression or death even after extensive multimodal therapy.

Decreased Medical Care During the COVID-19 Pandemic - A Comprehensive Analysis of Radiological Examinations.

OBJECTIVES: As a cross-section discipline within the hospital infrastructure, radiological departments might be able to provide important information regarding the impact of the COVID-19 pandemic on healthcare. The goal of this study was to quantify changes in medical care during the first wave of the pandemic using radiological examinations as a comprehensive surrogate marker and to determine potential future workload. METHODS: A retrospective analysis of all radiological examinations during the first wave of the pandemic was performed. The number of examinations was compared to time-matched control periods. Furthermore, an in-depth analysis of radiological examinations attributed to various medical specialties was conducted and postponed examinations were extrapolated to calculate additional workload in the near future. RESULTS: A total of 596,760 examinations were analyzed. Overall case volumes decreased by an average of 41 % during the shutdown compared to the control period. The most affected radiological modalities were sonography (-54 %), X-ray (-47 %) followed by MRI (-42 %). The most affected medical specialty was trauma and orthopedics (-60 % case volume) followed by general surgery (-49 %). Examination numbers increased during the post-shutdown period leading to a predicted additional workload of up to 22 %. CONCLUSION: This study shows a marked decrease in radiological examinations in total and among several core medical specialties, indicating a significant reduction in medical care during the first COVID-19 shutdown. KEY POINTS: · Number of radiological examinations decreased by 41 % during the first wave of the COVID-19 pandemic.. · Several core medical specialties were heavily affected with a reduction of case volumes up to 60 %.. · When extrapolating postponed examinations to the near future, the overall workload for radiological departments might increase up to 22 %.. CITATION FORMAT: · Fleckenstein FN, Maleitzke T, Böning G et al. Decreased Medical Care During the COVID-19 Pandemic - A Comprehensive Analysis of Radiological Examinations. Fortschr Röntgenstr 2021; 193: 937 - 946.

Neuroimaging Findings in Conjunction with Severe COVID-19.

PURPOSE: COVID-19 has a variable, but well-described course. However, some patients additionally present with neurological symptoms. Recent studies also show a broad range of neuroimaging features. The purpose of this study was to perform a snapshot analysis to approximate the frequency and types of neuroimaging findings on CT and MRI scans in a large cohort of SARS-CoV-2-positive patients in a level I COVID-19 center, both in general and in critically ill patients. MATERIALS AND METHODS: We retrospectively analyzed brain CT and MRI scans of 34 hospitalized COVID-19 patients at our level I COVID-19 center between March 15 and April 24 with regard to pathological neuroimaging findings. In addition, clinical parameters such as neurological symptoms, comorbidities, and type of ventilation therapy were also documented. A descriptive statistical analysis was performed. RESULTS: Pathological findings were detected in 38.2 % of patients in the study cohort. Based on the weekly institutional SARS-CoV-2 report of all positively tested patients in our clinic at the time of data collection, neuroimaging findings could be found in 6 % of all patients (34/565). The most common findings were microbleeds (20.6 %) and signs of hypoxic brain injury (11.8 %). Furthermore, cortical subarachnoid hemorrhage, typical and atypical cerebral hematomas, ischemic strokes, and generalized brain edema were documented. All neuroimaging findings occurred in patients who were either intubated or treated by ECMO. CONCLUSION: Based on the analysis of this large cohort of SARS-CoV-2-positive patients, pathological neuroimaging findings seem to be relatively rare in general but do occur in a substantial proportion of patients with severe COVID-19 disease needing intubation or ECMO. KEY POINTS: · Neuroimaging findings appear to be relatively rare in SARS-CoV-2 positive patients.. · Pathological findings occur mainly in critically ill COVID-19 patients.. · Frequent findings include hemorrhagic, ischemic and hypoxic changes.. · Critically ill COVID-19 patients should receive neuroimaging with a low threshold.. CITATION FORMAT: · Büttner L, Bauknecht HC, Fleckenstein FN et al. Neuroimaging Findings in Conjunction with Severe COVID-19. Fortschr Röntgenstr 2021; 193: 822 - 829.

Detectability of foreign body materials using X-ray, computed tomography and magnetic resonance imaging: A phantom study.

PURPOSE: To evaluate the effectiveness of plain radiography (X-ray. XR), computed tomography (CT) and magnetic resonance imaging (MR) in visualising commonly seen foreign bodies. A special focus was put on objects relevant to head and neck surgery. METHOD: Thirty-four commonly encountered objects of different compositions including wood, plastic, and glass were embedded in a gelatin gel phantom and imaged using XR, CT and MR. The success rates of radiologists in detecting and correctly identifying the foreign objects were evaluated. Subjective visibility was rated on a 4-point Likert scale. Objective visibility was analysed using region of interest-based contrast for CT. RESULTS: Sensitivity in foreign bodies detection was highest in MR (97.1 %) followed by CT (86.0 %) and x-ray (61.8 %). Success rates for the correct identification of the objects and material types were highest in MR (33.3 % and 39.2 %, respectively) followed by CT (25.5 % for both) and XR (16.7 % and 15.7 %). Overall, subjective visibility was rated higher in CT and MR imaging ("good visibility"), as compared to XR ("poor visibility"). Interreader agreement was high across modalities (Kendall's W = 0.935, 0.834 and 0.794 for XR, MR and CT, respectively). CONCLUSIONS: Detection and identification of non-ferromagnetic objects was most successful in MR followed by CT imaging in this experimental setup.

Molecular characterization of CNS paragangliomas identifies cauda equina paragangliomas as a distinct tumor entity.

Paragangliomas/pheochromocytomas are rare neuroendocrine tumors that arise from the adrenal gland or ganglia at various sites throughout the body. They display a remarkable diversity of driver alterations and are associated with germline mutations in up to 40% of the cases. Comprehensive molecular profiling of abdomino-thoracic paragangliomas revealed four molecularly defined and clinically relevant subtypes. Paragangliomas of the cauda equina region are considered to belong to one of the defined molecular subtypes, but a systematic molecular analysis has not yet been performed. In this study, we analyzed genome-wide DNA methylation profiles of 57 cauda equina paragangliomas and show that these tumors are epigenetically distinct from non-spinal paragangliomas and other tumors. In contrast to paragangliomas of other sites, chromosomal imbalances are widely lacking in cauda equina paragangliomas. Furthermore, RNA and DNA exome sequencing revealed that frequent genetic alterations found in non-spinal paragangliomas-including the prognostically relevant SDH mutations-are absent in cauda equina paragangliomas. Histologically, cauda equina paragangliomas show frequently gangliocytic differentiation and strong immunoreactivity to pan-cytokeratin and cytokeratin 18, which is not common in paragangliomas of other sites. None of our cases had a familial paraganglioma syndrome. Tumors rarely recurred (9%) or presented with multiple lesions within the spinal compartment (7%), but did not metastasize outside the CNS. In summary, we show that cauda equina paragangliomas represent a distinct, sporadic tumor entity defined by a unique clinical and morpho-molecular profile.

Improvement of image quality and diagnostic confidence using Smart MAR - a projection-based CT protocol in patients with orthopedic metallic implants in hip, spine, and shoulder.

BACKGROUND: In computed tomography (CT) scans, artifacts caused by metallic orthopedic implants still hamper the visualization of important, periprosthetic tissues. Smart MAR metal artifact reduction tool is a promising three-stage, projection-based, post-processing algorithm. PURPOSE: To determine whether the Smart MAR tool improves subjective and objective image quality and diagnostic confidence in patients with orthopedic implants of the hip, spine, and shoulder. MATERIAL AND METHODS: Seventy-two patients with orthopedic screws, hip/shoulder replacement, or spine spondylodesis were included. CT scans were performed on a single-source multislice CT scanner, raw data were post-processed using Smart MAR. Image quality was evaluated both quantitatively (ROI-based) and qualitatively (rater-based) and compared to iterative reconstructions (ASIR V). As comparative standard for artificial prosthetic breaks or loosening, follow-up examinations were used. RESULTS: Smart MAR reconstructions of the hip (n = 23), spine (n = 26), and shoulder (n = 23) showed a significantly reduced attenuation and noise of regions adjacent to metallic implants (P<0.002). Subjective image quality (P<0.005, shoulder P = 0.038/P = 0.046) and overall diagnostic confidence were higher in Smart MAR (all regions P<0.002). Signal-to-noise ratio (SNR; P = 0.72/P = 0.96) was not improved. Compared to standard ASIR V new, artificial metal extinctions (up to 50%) or periprosthetic hem lines (48%-73%) were introduced by Smart MAR. CONCLUSION: Smart MAR improved image quality of the hip, spine, and shoulder CT scans resulting in higher diagnostic confidence in evaluation of periprosthetic soft tissues. As shown for spine implants, it should be used with caution and as a complementary tool for evaluation of periprosthetic loosening or integrity of metal implant, as in many cases it introduced new artifacts.

Does Hepatic Steatosis Influence the Detection Rate of Metastases in the Hepatobiliary Phase of Gadoxetic Acid-Enhanced MRI?

The aim of this exploratory study was to evaluate the influence of hepatic steatosis on the detection rate of metastases in gadoxetic acid-enhanced liver magnetic resonance imaging (MRI). A total of 50 patients who underwent gadoxetic acid-enhanced MRI (unenhanced T1w in- and opposed-phase, T2w fat sat, unenhanced 3D-T1w fat sat and 3-phase dynamic contrast-enhanced (uDP), 3D-T1w fat sat hepatobiliary phase (HP)) were retrospectively included. Two blinded observers (O1/O2) independently assessed the images to determine the detection rate in uDP and HP. The hepatic signal fat fraction (HSFF) was determined as the relative signal intensity reduction in liver parenchyma from in- to opposed-phase images. A total of 451 liver metastases were detected (O1/O2, n = 447/411). O1/O2 detected 10.9%/9.3% of lesions exclusively in uDP and 20.2%/15.5% exclusively in HP. Lesions detected exclusively in uDP were significantly associated with a larger HSFF (area under curve (AUC) of receiver operating characteristic (ROC) analysis, 0.93; p < 0.001; cutoff, 41.5%). The exclusively HP-positive lesions were significantly associated with a smaller diameter (ROC-AUC, 0.82; p < 0.001; cutoff, 5 mm) and a smaller HSFF (ROC-AUC, 0.61; p < 0.001; cutoff, 13.3%). Gadoxetic acid imaging has the advantage of detecting small occult metastatic liver lesions in the HP. However, using non-optimized standard fat-saturated 3D-T1w protocols, severe steatosis (HSFF > 30%) is a potential pitfall for the detection of metastases in HP.

Comparing HCC arterial tumour vascularisation on baseline imaging and after lipiodol cTACE: how do estimations of enhancing tumour volumes differ on contrast-enhanced MR and CT?

OBJECTIVES: In this study, pre-treatment target lesion vascularisation in either contrast-enhanced (CE) CT or MRI and post-treatment lipiodol deposition in native CT scans were compared in HCC patients who underwent their first cTACE treatment. We analysed the impact of stratification according to cTACE selectivity on these correlations. METHODS: Seventy-eight HCC patients who underwent their first cTACE procedure were retrospectively included. Pre-treatment tumour vascularisation in arterial contrast phase and post-treatment lipiodol deposition in native CT scans were evaluated using the qEASL (quantitative tumour enhancement) method. Correlations were analysed using scatter plots, the Pearson correlation coefficient (PCC) and linear regression analysis. Subgroup analysis was performed according to lobar, segmental and subsegmental execution of cTACE. RESULTS: Arterial tumour volumes in both baseline CE CT (R2 = 0.83) and CE MR (R2 = 0.82) highly correlated with lipiodol deposition after cTACE. The regression coefficient between lipiodol deposition and enhancing tumour volume was 1.39 for CT and 0.33 for MR respectively, resulting in a ratio of 4.24. After stratification according to selectivity of cTACE, the regression coefficient was 0.94 (R2 = 1) for lobar execution, 1.38 (R2 = 0.96) for segmental execution and 1.88 (R2 = 0.89) for subsegmental execution in the CE CT group. CONCLUSIONS: Volumetric lipiodol deposition can be used as a reference to compare different imaging modalities in detecting vital tumour volumes. That approach proved CE MRI to be more sensitive than CE CT. Selectivity of cTACE significantly impacts the respective regression coefficients which allows for an innovative approach to the assessment of technical success after cTACE with a multitude of possible applications. KEY POINTS: • Lipiodol deposition after cTACE highly correlates with pre-treatment tumour vascularisation and can be used as a reference to compare different imaging modalities in detecting vital tumour volumes. • Lipiodol deposition also correlates with the selectivity of cTACE and can therefore be used to quantify the technical success of the intervention.

Metallic dental artifact reduction in computed tomography (Smart MAR): Improvement of image quality and diagnostic confidence in patients with suspected head and neck pathology and oral implants.

PURPOSE: We determined whether the Smart MAR metal artifact reduction tool - a three-stage, projection-based, post processing algorithm - improves subjective and objective image quality and diagnostic confidence in patients with dental artifacts and suspected head and neck pathology compared to standard adaptive statistical iterative reconstructions (ASIR V) alone. METHOD: The study included 100 consecutive patients with nonremovable oral implants or dental fillings and suspected oropharyngeal cancer or abscess. CT raw data of a single-source multislice CT scanner were postprocessed using ASIR V alone and with additional Smart MAR reconstruction. Image quality of baseline ASIR V and Smart MAR-based reconstruction series was compared both quantitatively (5 regions of interest, ROIs) and qualitatively (two independent raters). RESULTS: Additional Smart MAR reconstruction significantly seems to improve both attenuation and noise adjacent to implants and in more distant areas (all p < 0.001) compared to standard ASIR V reconstructions alone. Signal-to-noise ratio (SNR; p = 0.001) and contrast-to-noise ratio were improved significantly (CNR; p = 0.001). Smart MAR improved visualization of tumor/abscess (detected in 36 of 100 patients, 36%) and representative oropharyngeal tissue (p < 0.001). In 8 of 36 patients (22%), tumor was only detected in Smart MAR series. Mean total DLP was 506.8mGy*cm; average CTDIvol was 5.5 mGy. CONCLUSIONS: The supplementary use of the Smart MAR post-processing tool seems to significantly improve both subjective and objective image quality as well as diagnostic confidence and lesion detection in CT of the head and neck. In 22% of cases, the tumor was detected only in Smart MAR reconstructed images.

Tumour response in non-small-cell lung cancer patients treated with chemoradiotherapy - Can spectral CT predict recurrence?

INTRODUCTION: Tumour response in lung cancer treatment is monitored by measuring lesion size in computed tomography (CT). Spectral CT (SCT) offers additional information on tumour tissue besides morphology. We evaluated SCT iodine content (IC) and performed spectral slope analysis to assess the response of non-small-cell lung cancer (NSCLC) to chemoradiotherapy (CRT). METHODS: Eighty-three patients with advanced NSCLC treated by CRT prospectively underwent single-phase, contrast-enhanced SCT. Evaluation of all patients included treatment response (RECIST 1.1), quantitative measurements as well as SCT IC determination and spectral slope analysis in NSCLC primaries. Measurements were performed at the maximum cross-diameter of tumours and in areas with high iodine values (hotspot analysis). Iodine difference (ΔIC) was calculated. Secondary outcome parameters were IC and spectral slopes in mediastinal lymph nodes (n = 61). RESULTS: Twenty-four patients (29%) showed complete remission after CRT. Thirty-four patients (41%) had stable disease (SDSCT ) or partial regression (PRSCT ). Progressive disease (PDSCT ) was seen in 25 patients (30%). Hotspot analysis showed significantly higher iodine values in PDSCT than in SDSCT /PRSCT (P < 0.001). Ten patients (12%) with initially stable disease in SCT showed progressive disease during follow-up for up to 18 months (PDFU ). These patients also had significantly higher hotspot iodine values and ΔIC in the initial scan compared to patients with SD throughout the follow-up period (SDFU ) (29%) (P < 0.001). Enlarged lymph nodes showed significantly lower iodine content and a lower spectral slope pitch than normal-sized nodes (P = 0.003 to 0.029). CONCLUSION: Spectral CT-derived iodine content of NSCLC following CRT may help in predicting recurrence. Hotspot analysis and iodine heterogeneity allow the identification of residual vascularisation as an indicator of vital tumour tissue, indicating that IC might be a suitable imaging biomarker for predicting tumour progression. Iodine content and spectral slope analysis might also help in identifying metastatic lymph nodes.

Spectral CT in patients with acute thoracoabdominal bleeding-a safe technique to improve diagnostic confidence and reduce dose?

Computed tomography (CT) protocols for the detection of bleeding sources often include unenhanced CT series to distinguish contrast agent extravasation from calcification. This study evaluates whether virtual non-contrast images (VNC) can safely replace real non-contrast images (RNC) in the search for acute thoracoabdominal bleeding and whether monoenergetic imaging can improve the detection of the bleeding source.The 32 patients with active bleeding in spectral CT angiography (SCT) were retrospectively analyzed. RNC and SCT series were acquired including VNC and monoenergetic images at 40, 70, and 140 keV. CT numbers were measured in regions of interest (ROIs) in different organs and in the bleeding jet for quantitative image analysis (contrast-to-noise ratios [CNR] and signal-to-noise ratio [SNR]). Additionally, 2 radiologists rated detectability of the bleeding source in the different CT series. Wilcoxon rank test for related samples was used.VNC series suppressed iodine sufficiently but not completely (CT number of aorta: RNC: 33.3±12.3, VNC: 44.8 ±â€Š9.5, P = .01; bleeding jet: RNC: 43.1 ±â€Š16.9, VNC: 56.3 ±â€Š16.7, P = .02). VNC showed significantly higher signal-to-noise ratios than RNC for all regions investigated. Contrast-to-noise ratios in the bleeding jet were significantly higher in 40 keV images than in standard 140 keV images. The 40 keV images were also assigned the best subjective ratings for bleeding source detection.VNC can safely replace RNC in a CT protocol used to search for bleeding sources, thereby reducing radiation exposure by 30%. Low-keV series may enhance diagnostic confidence in the detection of bleeding sources.

Clinical routine use of virtual monochromatic datasets based on spectral CT in patients with hypervascularized abdominal tumors - evaluation of effectiveness and efficiency.

BACKGROUND: Virtual monochromatic images (VMI) generated using spectral computed tomography (CT) are promising recently available tools to improve diagnostic performance in oncologic patients. PURPOSE: To investigate if virtual monochromatic datasets are suitable for clinical routine use in patients with hypervascularized abdominal tumors. MATERIAL AND METHODS: A total of 41 patients with hypervascularized hepatocellular carcinoma (HCC), renal cell carcinoma (RCC), or neuroendocrine tumors (NET) were enrolled in the study; 451 CT series were analyzed. In an intra-individual study design, virtual monochromatic datasets of the arterial phase of each scan were computed. Image quality was assessed objectively by determining signal-to-noise ratio (SNR) and contrast-to-noise ratios (CNR) and subjectively by using five-point Likert-scales. The volume CT dose index (CTDIvol) was taken from each radiation dose report. The increase in reading time was estimated from the increase in the number of images. RESULTS: Intra-individual comparison of the spectral mode in the arterial phase with the portal venous phase revealed no significant increase in the applied dose. SNR, CNRtumor-to-liver , and CNRtumor-to-muscle were significantly increased by lowering virtual monochromatic energy. Subjective image quality scores revealed an increase of contrast in low energy datasets, resulting in significantly higher diagnostic confidence, but an increased image noise at low energies. While diagnostic confidence improved, taking all datasets into account resulted in a significantly longer estimated reading time. CONCLUSION: In clinical practice, the use of low energy VMI improved diagnostic confidence without a significant increase in dose. The main disadvantage is a decrease in efficiency due to longer reading times.

Tailored CT angiography in follow-up after endovascular aneurysm repair (EVAR): combined dose reduction techniques.

Background Endovascular aneurysm repair (EVAR) requires lifelong surveillance by computed tomography angiography (CTA). This is attended by a substantial accumulation of radiation exposure. Iterative reconstruction (IR) has been introduced to approach dose reduction. Purpose To evaluate adaptive statistical iterative reconstruction (ASIR) at different levels of tube voltage concerning image quality and dose reduction potential in follow-up post EVAR. Material and Methods One hundred CTAs in 67 patients with EVAR were examined using five protocols: protocol A (n = 40) as biphasic standard using filtered back projection (FBP) at 120 kV; protocols B (n = 40), C (n = 10), and D1 (n = 5) biphasic using ASIR at 120, 100, and 80 kV, respectively; and protocol D2 (n = 5) with a monophasic splitbolus ASIR protocol at 80 kV. Image quality was assessed quantitatively and qualitatively. Applied doses were determined. Results Applied doses in ASIR protocols were significantly lower than FBP standard (up to 75%). Compared to protocol A, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) (e.g. arterial CNR intra-/extra-stent lumen: A = 35.4 ± 13.5, B = 34.2 ± 10.0, C = 29.6 ± 6.8, D1 = 32.1 ± 6.3, D2 = 40.8 ± 23.1) in protocol B were equal and in protocols C and D equal to partially inferior, however not decisive for diagnostic quality. Subjective image quality ratings in all protocols were good to excellent without impairments of diagnostic confidence (A-D2: 5), with high inter-rater agreement (60-100%). Conclusion ASIR contributes to significant dose reduction without decisive impairments of image quality and diagnostic confidence. We recommend an adapted follow-up introducing ASIR and combined low-kV in the long-term surveillance after EVAR.