Improved visualization of hepatic tumors in magnetic resonance-guided thermoablation using T1-inversion-recovery imaging with variable inversion time.

OBJECTIVES: In magnetic resonance (MR)-guided interventions, visualization of hepatic lesions may be difficult using standard unenhanced T1-weighted gradient-echo volume-interpolated breath-hold (VIBE) sequence due to low contrast. Inversion recovery (IR) imaging may have the potential to improve visualization without the necessity to apply contrast agent. METHODS: Forty-four patients (mean age 64 years, female 33%) scheduled for MR-guided thermoablation due to liver malignancies (hepatocellular carcinoma or metastases) were prospectively included in this study between March 2020 and April 2022. Fifty-one liver lesions were intra-procedurally characterized before treatment. Unenhanced T1-VIBE was acquired as part of the standard imaging protocol. Additionally, T1-modified look-locker images were acquired with eight different inversion times (TI) between 148 and 1743 ms. Lesion-to-liver contrast (LLC) was compared between T1-VIBE and IR images for each TI. T1 relaxation times for liver lesions and liver parenchyma were calculated. RESULTS: Mean LLC in T1-VIBE sequence was 0.3 ± 0.1. In IR images, LLC was highest at TI 228 ms (1.04 ± 1.1) and significantly higher compared to T1-VIBE (p < 0.001). In subgroup analysis, lesions of colorectal carcinoma showed the highest LLC at 228 ms (1.14 ± 1.4), and hepatocellular carcinoma showed the highest LLC at 548 ms (1.06 ± 1.16). T1-relaxation times in liver lesions were higher compared to the adjacent liver parenchyma (1184 ± 456 vs. 654 ± 96 ms, p < 0.001). CONCLUSIONS: IR imaging is promising to provide improved visualization during unenhanced MR-guided liver interventions compared to standard T1-VIBE sequence when using specific TI. Low TI between 150 and 230 ms yields the highest contrast between liver parenchyma and malignant liver lesions. CLINICAL RELEVANCE STATEMENT: Improved visualization of hepatic lesions during MR-guided percutaneous interventions using inversion recovery imaging without the necessity to apply contrast agent. KEY POINTS: • Inversion recovery imaging is promising to provide improved visualization of liver lesions in unenhanced MRI. • Planning and guidance during MR-guided interventions in the liver can be performed with greater confidence without necessity to apply contrast agent. • Low TI between 150 and 230 ms yields the highest contrast between liver parenchyma and malignant liver lesions.

Comparative analysis of buffalo, local and continental cattle carcasses with the European Union classification system in Greece.

The carcasses produced in Greece from Greek Buffalo, indigenous and local crossbred cattle were evaluated using the European Union (EU) bovine classification system and compared with carcasses of continental breeds reared in the country. The main carcass production (67.8%) came from animals born in Greece with a relatively low percentage from local breeds (17%). The lightest carcass weight was found in Greek Brachyceros [145.2 ± 2.3 kg (males); 146.0 ± 3.1 kg (females)], while among locals the Greek Blonde rendered the heaviest carcass weights [303.2 ± 2.9 kg (males); 265.3 ± 3.5 kg (females)]. Muscle conformation scoring was the lowest in Buffalo [4.1 ± 0.1 (males); 4.9 ± 0.0 (females)] and the highest for males of Charolais and Blonde d'Aquitaine (11.2 ± 0.0 and 10.7 ± 0.0, respectively). The meat-purposed breeds produced carcasses of higher quality than dual-purposed, local breeds and dairy Holstein-Friesian. With the discriminant analysis, the correct classification of carcasses varied from 53.4% (males) to 47.8% (females) with high assignment percentage of Greek Buffalo males (81.6%), Simmental males (80.7%) and Holstein-Friesian females (98.5%).

MRI-guided percutaneous thermoablation as first-line treatment of recurrent hepatic malignancies following hepatic resection: single center long-term experience.

PURPOSE: Hepatic recurrence of liver malignancies is a leading problem in patients after liver resection with curative intention. Thermoablation is a promising treatment approach for patients after hepatic resection, especially in liver-limited conditions. This study aimed to investigate safety, survival, and local tumor control rates of MRI-guided percutaneous thermoablation of recurrent hepatic malignancies following hepatic resection. MATERIAL AND METHODS: Data from patients with primary or secondary hepatic malignancies treated between 2004 and 2018 with MRI-guided percutaneous thermoablation of hepatic recurrence after prior hepatic resection were retrospectively analyzed. Disease-free survival and overall survival rates were calculated using the Kaplan-Meier method. RESULTS: A total of 57 patients with hepatic recurrence (mean tumor size = 18.9 ± 9.1 mm) of colorectal cancer liver metastases (n = 27), hepatocellular carcinoma (n = 17), intrahepatic recurrence of cholangiocellular carcinoma (n = 9), or other primary malignant tumor entities (n = 4) were treated once or several times with MR-guided percutaneous radiofrequency (n = 52) or microwave ablation (n = 5) (range: 1-4 times). Disease progression occurred due to local recurrence at the ablation site in nine patients (15.8%), non-local hepatic recurrence in 33 patients (57.9%), and distant malignancy in 18 patients (31.6%). The median overall survival for the total cohort was 40 months and 49 months for the colorectal cancer group, with a 5-year overall survival rate of 40.7 and 42.5%, respectively. The median disease-free survival was 10 months for both the total cohort and the colorectal cancer group with a 5-year disease-free survival rate of 15.1 and 14.8%, respectively. The mean follow-up time was 39.6 ± 35.7 months. CONCLUSION: MR-guided thermoablation is an effective and safe approach in the treatment of hepatic recurrences in liver-limited conditions and can achieve long-term survival.

Treatment outcome after radiochemotherapy in anal cancer patients staged with 18F-FDG-PET-CT.

BACKGROUND: Anal cancer (AC) is a malignancy with increasing incidence and commonly treated with radiochemotherapy. Positron-emission tomography-computed tomography (PET/CT) has been shown to improve treatment outcome in various oncological diseases, however, for AC long-term outcome data is sparse. The aim of the present study is therefore to report outcomes in our cohort of PET/CT staged AC patients treated with radiochemotherapy. METHODS: Patients with AC who were treated with radiochemotherapy in curative intent were included in this retrospective study if a PET/CT scan was performed pre-therapeutically. Information from PET/CT was considered for nodal and primary target volume definition. Radiotherapy dose to the primary tumor was 50-66 Gy and concomitant chemotherapy included 5-fluorouracil and mitomycin-C. The uptake of 18F-fluorodeoxyglucose (FDG) was quantified using 50%-isocontour volumes of interests (VOIs) and measuring the standardized uptake value (SUV) and the metabolic tumor volume (MTV).18F-FDG uptake was correlated with baseline clinical parameters and long-term oncological outcome. Survival estimates were determined according to Kaplan-Meier. RESULTS: A total of 60 patients were included in this study. Estimates for three-year overall survival (OS) and disease free survival (DFS) were 94.5% and 80%. Five patients developed local (n = 2) or locoregional and local (n = 3) failure. Baseline PET/CT related parameters correlated with primary tumor stage, nodal stage and tumor grading. DFS was independent of T-stage, N-stage and baseline 18F-FDG-uptake. CONCLUSION: In this cohort of PET/CT staged AC patients, excellent outcomes for DFS were seen. PET-based markers of tumor burden correlate with local stage of AC, however, are not of prognostic relevance for disease-free survival.

68Ga-PSMA-PET/CT-directed IGRT/SBRT for oligometastases of recurrent prostate cancer after initial surgery.

Background: We evaluated efficacy and toxicity of 68Ga-PSMA-Positron Emission Tomography/Computed Tomography (PET/CT)-directed stereotactic body radiotherapy and image-guided radiotherapy (SBRT/IGRT) for oligometastases of prostate cancer recurrences after previous surgery.Methods: Nineteen patients were analyzed within a prospective PET-registry study (064/2013BO1) and retrospectively analyzed (807/2017BO2) fulfilling the following inclusion criteria: biochemical recurrence after radical prostatectomy, ≤five 68Ga-PSMA-PET/CT positive lesions. Biochemical control was evaluated with EORTC (European Organization for Research and Treatment of Cancer)- and Phenix-definitions. Toxicity was scored according to CTCAE-criteria v. 4.03.Results: A total of 38 oligometastases (19 patients, 2 with re-treatment) were treated with SBRT/IGRT from October 2014 to July 2017. 68Ga-PSMA-PET/CT-positive lesions were detected on average 39 months (5-139) after prostatectomy (pT2b-3b pN0-1 cM0). Mean PSA (Prostate-specific antigen)-level at time of imaging reached 2.2 ng/mL (range 0.2-10.1). PET/CT-positive lesions were treated with different fractionation schedules reaching biological equivalent doses (BED) of 116.7-230.0 Gy. Concomitant androgen deprivation therapy (ADT) was given in seven patients. After a median follow-up of 17 months (4-42) all patients were alive. Estimated 1-year PSA- control (n = 19) reached 80.8% (Phenix) and 67.5% (EORTC). A PSA-decline (≥50%) was detected in 16/19 patients after radiotherapy. Higher graded G3+-acute toxicity did not occur. Temporary late G3-proctitis was detected in one patient.Conclusions: Reaching of nadir ≤0.1 or 0.2 ng/mL was associated by improved DMFS (distant metastases free survival) and could serve as a surrogate endpoint for RT of oligometastases after initial prostatectomy. Short term effects of 68Ga-PSMA-PET/CT-based ablative radiotherapy for oligometastases demonstrated an acceptable toxicity profile and favorable biochemical response.

[Influence of immunomodulators on urological imaging]. / Einfluss von Immunmodulatoren auf die urologische Bildgebung.

BACKGROUND: Immune checkpoint inhibitors (ICI) have led to great advances in the therapy of metastatic renal cell and urothelial carcinoma. Currently ICI are approved for the first-line therapy of cisplatin-unfit patients (Atezolizumab, Pembrolizumab) and second-line therapy in patients with metastasized urothelial cancer (Atezolizumab, Nivolumab, Pembrolizumab). For the therapy of metastasized RCC, Nivolumab is approved as a second-line therapy and in combination with the CTLA­4 antibody Ipilimumab as a first-line therapy. OBJECTIVES: What does the optimized radiological follow-up and therapy response assessment for ICI, which differ in their pathways from common chemotherapeutics and anti-angiogenetic drugs, look like? What strategies are needed to meet the upcoming challenges concerning interpretation of the acquired images? METHODS: A systematic literature search was carried out for urothelial and renal cell carcinoma. RESULTS: Immune-related response criteria have been introduced to better characterize the imaging changes occurring under ICI, as monitoring response to immunotherapy still relies on RECIST. CONCLUSIONS: To properly identify and predict response after treatment with ICI, additional studies with long-term follow-ups are needed. Because of the growing use of ICI, radiologists and urologist should be familiar with common imaging findings (such as pseudo progress) under immunotherapy to correctly interpret these findings in daily routine.

[Active surveillance in prostate cancer]. / Active Surveillance beim Prostatakarzinom.

Prostate cancer remains among the most commonly diagnosed malignancies worldwide in men. In patients with low-risk prostate cancer, the risk of metastasis and mortality is very low; therefore, a tumor surveillance strategy can be used. In patients undergoing active surveillance, curative active therapy is postponed without compromising opportunities for cure until there is evidence of progression or the patient desires active therapy. The aim of active surveillance in prostate cancer patients is to minimize treatment-related toxicity without impairing patient survival. To maintain patients under active surveillance, the following criteria should be met: prostate-specific antigen (PSA) ≤10 ng/ml, Gleason score ≤6, cT1 or cT2a, ≤2 biopsy cores with <50% cancer involvement of every positive core. Follow-up in active surveillance patients is based on repeat biopsy, serial PSA measurements, and digital rectal examination.

Precision of T2 TSE MRI-CT-image fusions based on gold fiducials and repetitive T2 TSE MRI-MRI-fusions for adaptive IGRT of prostate cancer by using phantom and patient data.

INTRODUCTION: To increase precision of radiation treatment (RT) delivery in prostate cancer, MRI-based RT as well as the use of fiducials like gold markers (GMs) have shown promising results. Their combined use is currently under investigation in clinical trials. Here, we aimed to evaluate a workflow of image registration based on GMs between CT and MRI as well as weekly MRI-MRI adaption based on T2 TSE sequence. MATERIAL AND METHODS: A gel-phantom with two inserted GMs was scanned with CT and three different MR-scanners of 1.5 and 3 T (T2 TSE and T1 VIBE-Dixon, isotropic, voxel size 2 × 2 × 2 mm). After image fusion, deviations for fiducial and gel match were measured and artifacts were evaluated. Additionally, CT-MRI-match deviations and MRI-MRI-match deviations of 10 Patients from the M-basePro study using GMs were assessed. RESULTS: GMs were visible in all imaging modalities. The outer gel contours were matched with <1 mm deviation, contour volumes varied between 0 and 1%. The deviations of the GMs were less than 2 mm in any direction of MRI/CT. Shifts of peripherally or centrally located GMs were randomly distributed. The average MRI-CT-match precision of 10 patients with GMs was 1.9 mm (range 1.1-3.1 mm). CONCLUSIONS: Match inaccuracies for GMs between reference CT and voxel-isotropic T2-TSE sequences are small. Spatial deviations of CT- and MR-contoured fiducials were less than 2 mm, i.e., below SLT of the applied modalities. In patients, the average CT-MRI-match precision for GMs was 1.9 mm supporting their use in MR-guided high precision RT.

Frequency-selective non-linear blending for the computed tomography diagnosis of acute gangrenous cholecystitis: Pilot retrospective evaluation.

PURPOSE: To compare the diagnostic performance of frequency-selective non-linear blending and conventional linear blending contrast-enhanced CT for the diagnosis of acute (AC) and gangrenous (GC) cholecystitis. MATERIALS AND METHODS: Following local ethics committee approval for retrospective data analysis, a database search derived 39 patients (26 men, mean age 67.8 ±â€¯14.6 years) with clinical signs of acute cholecystitis, contrast enhanced CT (CECT) evaluation, cholecystectomy, and pathological examination of the resected specimen. The interval between CECT and surgery was 4.7 ±â€¯4.1 days. Pathological gross examination was used to categorize the cases into AC and GC. Subsequently, two radiologists categorized the CECT studies in a blinded and independent fashion into AC and GC, during two different reading sessions using linear blending and frequency-selective non-linear blending CECT. RESULTS: Histologic analysis diagnosed 31/39 (79.4%) cases of GC and 8/39 (20.6%) cases of AC. Image interpretation of linear blending CECT resulted in classification of 7/39 (17.9%) patients as GC and 32/39 (82.1%) as AC, whereas image interpretation of frequency-selective non-linear blending CECT resulted in classification of 29/39 (74.3%) patients as GC and 10/39 (25.7%) as AC. Sensitivity/specificity/PPV/NPV for detection of GC were 22.6%/100%/100%/25% with linear blending CECT and 80.6%/50%/86.2%/40% with frequency-selective non-linear blending CECT, respectively. Based on the histopathologic diagnosis frequency-selective non-linear blending had a significant improvement (p > 0.0001) in the diagnostic accuracy of gangrenous cholecystitis compared with linear blending. CONCLUSION: Frequency-selective non-linear blending post-processing increases the diagnostic accuracy of gangrenous cholecystitis owing to improved visualization of absence of focal enhancement and mural ulcerations.

A machine-learning framework for automatic reference-free quality assessment in MRI.

Magnetic resonance (MR) imaging offers a wide variety of imaging techniques. A large amount of data is created per examination which needs to be checked for sufficient quality in order to derive a meaningful diagnosis. This is a manual process and therefore time- and cost-intensive. Any imaging artifacts originating from scanner hardware, signal processing or induced by the patient may reduce the image quality and complicate the diagnosis or any image post-processing. Therefore, the assessment or the ensurance of sufficient image quality in an automated manner is of high interest. Usually no reference image is available or difficult to define. Therefore, classical reference-based approaches are not applicable. Model observers mimicking the human observers (HO) can assist in this task. Thus, we propose a new machine-learning-based reference-free MR image quality assessment framework which is trained on HO-derived labels to assess MR image quality immediately after each acquisition. We include the concept of active learning and present an efficient blinded reading platform to reduce the effort in the HO labeling procedure. Derived image features and the applied classifiers (support-vector-machine, deep neural network) are investigated for a cohort of 250 patients. The MR image quality assessment framework can achieve a high test accuracy of 93.7% for estimating quality classes on a 5-point Likert-scale. The proposed MR image quality assessment framework is able to provide an accurate and efficient quality estimation which can be used as a prospective quality assurance including automatic acquisition adaptation or guided MR scanner operation, and/or as a retrospective quality assessment including support of diagnostic decisions or quality control in cohort studies.

Discriminatory CT-textural features in splenic infiltration of lymphoma versus splenomegaly in liver cirrhosis versus normal spleens in controls and evaluation of their role for longitudinal lymphoma monitoring.

PURPOSE: To find CT-texture analysis (CTTA) features for the discrimination of splenomegaly due to diffuse lymphoma involvement and liver cirrhosis versus normal-sized spleens in controls and to assess their potential role for longitudinal lymphoma monitoring. MATERIAL AND METHODS: We had retrospectively identified 74 subjects with diffuse splenic involvement due to lymphoma (n = 29) and liver cirrhosis (n = 30), and healthy controls (n = 15), who underwent contrast-enhanced abdominal CT between August 2013 and October 2017. CTTA evaluation included heterogeneity, intensity, average, deviation, skewness, entropy of co-occurrence, number non-uniformity (NGLDM) and entropy NGLDM. A greater than 50% reduction of spleen volume after chemotherapy was considered proof for splenic involvement. RESULTS: There were significant differences of splenic CTTA-values before and after treatment of patients with lymphoma, including mean of entropy(p < .001), uniformity of average(p < .001), uniformity of deviation(p = .002) and entropy of skewness(p < .001). Significant differences of splenic CTTA-values in subjects with lymphoma vs. healthy controls were found for mean intensity(p < .001), mean average(p < .001), and entropy of deviation(p < .001). No significant differences in splenic CTTA-values were found in subjects with lymphoma that reached complete remission vs. controls. Splenic CTTA values mean intensity(p = .002) and mean average(p = .004) were significantly different between subjects with untreated lymphoma and subjects with liver cirrhosis. At end-of-treatment all lymphomas reached complete remission. Entropy/uniformity of heterogeneity(p < .001), mean intensity(p = .007), mean average (p = .007), uniformity of average(p = .008) and mean/entropy/uniformity of skewness(p = .001) measured at this time differed significantly from baseline. CONCLUSIONS: CTTA features in subjects with splenomegaly due to lymphoma and liver cirrhosis differ significantly from those of healthy controls and can be also used for monitoring lymphoma treatment. Quantitative CTTA features may increase the accuracy of diagnosing causes of splenomegaly.

Chest CT texture analysis for response assessment in systemic sclerosis.

PURPOSE: To evaluate the role of CT-textural features for monitoring lung involvement in subjects with systemic sclerosis(SSc) undergoing autologous stem cell transplantation(SCT) by comparison with semi-quantitative chest-CT, pulmonary function tests(PFT) and clinical parameters (modified Rodnan skin score[mRSS]). METHODS: In a retrospective single centre analysis, we identified 23 consecutive subjects(11male) with SSc between 07/2005 and 11/2016 that underwent chest CTs before, 6 and 12 months post-SCT. Response to therapy was defined at 6 months after transplantation as stabilisation or improvement in FVC > 10% and DLCOSB > 10%. CT-texture analysis(CTTA) including mean, entropy and uniformity were calculated. RESULTS: PFT classified the subjects into responders(18/23;78%) and non-responders(5/23;22%). mRSS improved in responders from 28.46 ±â€¯9.53 to 15.70 ±â€¯10.07 6 months after auto-SCT(p = .001) whereas in non-responders no significant improvement was registered. Fibrosis score increased significantly(mean2.33 ±â€¯1.23 vs.1.41 ±â€¯0.78; p = .005) in non-responders after 6 and 12months. Significant lower mean intensity and entropy of skewness and higher uniformity of skewness was found in responders vs. non-responders at baseline. Significant changes in CTTA-parameters were found in both responders and non-responders at 6months and only in responders also at 12months post-SCT. CONCLUSIONS: Changes in CT-textural features after SCT are associated with visual CT evaluation of SSc-related lung abnormalities, but complementary provide information about therapy-induced, structural pulmonary changes.

Combined PET/MRI: Global Warming-Summary Report of the 6th International Workshop on PET/MRI, March 27-29, 2017, Tübingen, Germany.

The 6th annual meeting to address key issues in positron emission tomography (PET)/magnetic resonance imaging (MRI) was held again in Tübingen, Germany, from March 27 to 29, 2017. Over three days of invited plenary lectures, round table discussions and dialogue board deliberations, participants critically assessed the current state of PET/MRI, both clinically and as a research tool, and attempted to chart future directions. The meeting addressed the use of PET/MRI and workflows in oncology, neurosciences, infection, inflammation and chronic pain syndromes, as well as deeper discussions about how best to characterise the tumour microenvironment, optimise the complementary information available from PET and MRI, and how advanced data mining and bioinformatics, as well as information from liquid biomarkers (circulating tumour cells and nucleic acids) and pathology, can be integrated to give a more complete characterisation of disease phenotype. Some issues that have dominated previous meetings, such as the accuracy of MR-based attenuation correction (AC) of the PET scan, were finally put to rest as having been adequately addressed for the majority of clinical situations. Likewise, the ability to standardise PET systems for use in multicentre trials was confirmed, thus removing a perceived barrier to larger clinical imaging trials. The meeting openly questioned whether PET/MRI should, in all cases, be used as a whole-body imaging modality or whether in many circumstances it would best be employed to give an in-depth study of previously identified disease in a single organ or region. The meeting concluded that there is still much work to be done in the integration of data from different fields and in developing a common language for all stakeholders involved. In addition, the participants advocated joint training and education for individuals who engage in routine PET/MRI. It was agreed that PET/MRI can enhance our understanding of normal and disrupted biology, and we are in a position to describe the in vivo nature of disease processes, metabolism, evolution of cancer and the monitoring of response to pharmacological interventions and therapies. As such, PET/MRI is a key to advancing medicine and patient care.

Experimental characterization of the biaxial mechanical properties of porcine gastric tissue.

Health problems related to the stomach are among the most important sources of morbidity in industrialized countries. There is evidence that mechanics may play an important role in various such pathologies. However, so far experimental data characterizing the mechanical properties of gastric tissue remain scarce, which significantly limits our understanding of the mechanics of the stomach. To help close this gap, we performed biaxial mechanical tests of porcine gastric tissue patches. Our experiments reveal a considerable anisotropy and different mechanical properties in the three major regions of the stomach (fundus, corpus, antrum). Moreover, they demonstrate that the mechanical properties of the gastric wall and the physiological function of the different regions of the stomach are closely related. This finding suggests that further examination of the mechanics of the gastric wall may indeed be a promising avenue of research towards a better understanding of the organic causes of frequent health problems related to the stomach.

Preoperative breast MR Imaging in patients with primary breast cancer has the potential to decrease the rate of repeated surgeries.

PURPOSE: The impact of preoperative MRI on re-excisions and mastectomy rate is discussed controversially in the literature. Aim of this study was to evaluate the effect of preoperative breast MRI on the surgical procedure and rate of repeated surgeries. MATERIAL AND METHODS: A total of 991 consecutive patients in the years 2009 and 2010 with 1036 primary breast cancers were retrospectively analyzed. Sixty percent (599 patients with 626 cancers) received preoperative breast MRI. Planned surgical procedures before and after MRI and numbers of repeated surgeries in patients with (MR+ ) and without preoperative MRI (MR-) were compared. RESULTS: The result of preoperative MRI changed the surgical procedure in 25% (157/626) of the cases. In 81% (127/157), MRI was beneficial for the patients, as otherwise occult carcinomas were removed (n=122) or further biopsy could be prevented (n=5). Mastectomy rates did not differ between MR+ and MR- group (39% vs. 39%). On multiple regression analysis, the MR+ group had a lower chance for repeated surgery (p<0.05). CONCLUSION: Preoperative MRI could lower the chance for repeated surgery in patients with primary breast cancer. The rate of mastectomy did not differ between patients undergoing preoperative MRI and those who did not.

Repeated surgeries in invasive lobular breast cancer with preoperative MRI: Role of additional carcinoma in situ and background parenchymal enhancement.

OBJECTIVES: Analysing the influence of additional carcinoma in situ (CIS) and background parenchymal enhancement (BPE) in preoperative MRI on repeated surgeries in patients with invasive lobular carcinoma (ILC) of the breast. METHODS: Retrospective analysis of 106 patients (mean age 58.6±9.9years) with 108 ILC. Preoperative tumour size as assessed by MRI, mammography and sonography was recorded and compared to histopathology. In contrast-enhanced MRI, the degree of BPE was categorised by two readers. The influence of additionally detected CIS and BPE on the rate of repeated surgeries was analysed. RESULTS: Additional CIS was present in 45.4% of the cases (49/108). The degree of BPE was minimal or mild in 80% of the cases and moderate or marked in 20% of the cases. In 17 cases (15.7%) at least one repeated surgery was performed. In n=15 of these cases, repeated surgery was performed after BCT (n=9 re-excisions, n=6 conversions to mastectomy), in n=2 cases after initial mastectomy. The initial surgical procedure (p=0.008) and additional CIS (p=0.046) significantly influenced the rate of repeated surgeries, while tumour size, patient age and BPE did not (p=ns). CONCLUSIONS: Additional CIS was associated with a higher rate of repeated surgeries, whereas BPE had no influence.

Low-Dose Volume-Perfusion CT of the Brain: Effects of Radiation Dose Reduction on Performance of Perfusion CT Algorithms.

PURPOSE: We aimed to compare different computed tomography (CT) perfusion post-processing algorithms regarding image quality of perfusion maps from low-dose volume perfusion CT (VPCT) and their diagnostic performance regarding the detection of ischemic brain lesions. METHODS AND MATERIALS: We included VPCT data of 21 patients with acute stroke (onset < 6h), which were acquired at 80 kV and 180 mAs. Low-dose VPCT datasets with 72 mAs (40 % of original dose) were generated using realistic low-dose simulation. Perfusion maps (cerebral blood volume (CBV); cerebral blood flow (CBF) from original and low-dose datasets were generated using two different commercially available post-processing methods: deconvolution-based method (DC) and maximum slope algorithm (MS). The resulting DC and MS perfusion maps were compared regarding perfusion values, signal-to-noise ratio (SNR) as well as image quality and diagnostic accuracy as rated by two blinded neuroradiologists. RESULTS: Quantitative perfusion parameters highly correlated for both algorithms and both dose levels (r ≥ 0.613, p < 0.001). Regarding SNR levels and image quality of the CBV maps, no significant differences between DC and MS were found (p ≥ 0.683). Low-dose MS CBF maps yielded significantly higher SNR levels (p < 0.001) and quality scores (p = 0.014) than those of DC. Low-dose CBF and CBV maps from both DC and MS yielded high sensitivity and specificity for the detection of ischemic lesions (sensitivity ≥ 0.82, specificity ≥ 0.90). CONCLUSION: Our results indicate that both methods produce diagnostically sufficient perfusion maps from simulated low-dose VPCT. However, MS produced CBF maps with significantly higher image quality and SNR than DC, indicating that MS might be more suitable for low-dose VPCT imaging.