Marker-less online MR-guided stereotactic body radiotherapy of liver metastases at a 1.5 T MR-Linac - Feasibility, workflow data and patient acceptance.

INTRODUCTION: Stereotactic body radiotherapy (SBRT) is an established ablative treatment for liver tumors with excellent local control rates. Magnetic resonance imaging guided radiotherapy (MRgRT) provides superior soft tissue contrast and may therefore facilitate a marker-less liver SBRT workflow. The goal of the present study was to investigate feasibility, workflow parameters, toxicity and patient acceptance of MRgSBRT on a 1.5 T MR-Linac. METHODS: Ten consecutive patients with liver metastases treated on a 1.5 T MR-Linac were included in this prospective trial. Tumor delineation was performed on four-dimensional computed tomography scans and both exhale triggered and free-breathing T2 MRI scans from the MR-Linac. An internal target volume based approach was applied. Organ at risk constraints were based on the UKSABR guidelines (Version 6.1). Patient acceptance regarding device specific aspects was assessed and toxicity was scored according to the common toxicity criteria of adverse events, version 5. RESULTS: Nine of ten tumors were clearly visible on the 1.5 T MR-Linac. No patient had fiducial markers placed for treatment. All patients were treated with three or five fractions. Median dose to 98% of the gross tumor volume was 38.5 Gy. The median time from "patient identity check" until "beam-off" was 31 min. Median beam on time was 9.6 min. Online MRgRT was well accepted in general and no treatment had to be interrupted on patient request. No event of symptomatic radiation induced liver disease was observed after a median follow-up of ten month (range 3-17 months). CONCLUSION: Our early experience suggests that online 1.5 T MRgSBRT of liver metastases represents a promising new non-invasive marker-free treatment modality based on high image quality, clinically reasonable in-room times and high patient acceptance. Further studies are necessary to assess clinical outcome, to validate advanced motion management and to explore the benefit of online response adaptive liver SBRT.

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.

Bronchial Artery Embolization in Hemoptysis: 10-Year Survival and Recurrence-Free Survival in Benign and Malignant Etiologies - A Retrospective Study.

Purpose: The aim of the study was to evaluate safety, effectiveness, recurrence rate and 10-year survival after bronchial artery embolization (BAE) in benign and malignant etiologies. Methods: The retrospective study includes 100 BAE procedures in 88 patients. Underlying disease was classified as benign (n = 67) and malignant (n = 21) etiologies. Immediate bleeding control and procedure safety were evaluated in all patients. In 51 (58 %) patients, follow-up data with a median follow-up time of 1015 days (range, 494 to 3727 days) were acquired to assess overall survival, time-to-recurrence of bleeding and recurrence-free survival, using Kaplan-Maier estimates to compare differences between both subgroups. Results: Immediate bleeding control was achieved after 96/100 procedures (96 %), with a minor complication rate of 5.0 %. No major complications occurred. The overall survival was 74 % after 1 year and 59 % after 5 years and 10 years. There was a significant difference in survival between the malignant and benign groups (p < 0.0001). Survival was 90 %, 80 % and 76 % at 1 year, 3 years and 10 years, respectively, in the benign group and 18 % and 0 % at 1 year and 3 years, respectively in the malignant group. The median time to recurrence of bleeding and recurrence-free survival were 239 days and 94 % after 1 year and 87 % after 10 years in the benign group, compared to 66 days and 34 % after 1 year and 0 % after 3 years in the malignant group (p = 0.0107). Conclusion: BAE is a safe and highly effective treatment option in hemoptysis. However, the recurrence rate and survival are highly dependent on the underlying disease. Key Points: • BAE is a safe and highly effective treatment option in hemoptysis.• Recurrence rate and survival are strongly dependent on the underlying disease with significantly impaired results in patients with malignant diseases. • Coil embolization is an effective BAE treatment method. Nevertheless, it should be mentioned, that reinterventions can be impeded, if embolization is performed in the proximal part of bronchial arteries. Citation Format: • Syha R, Benz T, Hetzel J et al. Bronchial Artery Embolization in Hemoptysis: 10-Year Survival and Recurrence-Free Survival in Benign and Malignant Etiologies - A Retrospective Study. Fortschr Röntgenstr 2016; 188: 1061 - 1066.

MR Image Reconstruction Using a Combination of Compressed Sensing and Partial Fourier Acquisition: ESPReSSo.

A Cartesian subsampling scheme is proposed incorporating the idea of PF acquisition and variable-density Poisson Disc (vdPD) subsampling by redistributing the sampling space onto a smaller region aiming to increase k-space sampling density for a given acceleration factor. Especially the normally sparse sampled high-frequency components benefit from this sampling redistribution, leading to improved edge delineation. The prospective subsampled and compacted k-space can be reconstructed by a seamless combination of a CS-algorithm with a Hermitian symmetry constraint accounting for the missing part of the k-space. This subsampling and reconstruction scheme is called Compressed Sensing Partial Subsampling (ESPReSSo) and was tested on in-vivo abdominal MRI datasets. Different reconstruction methods and regularizations are investigated and analyzed via global (intensity-based) and local (region-of-interest and line evaluation) image metrics, to conclude a clinical feasible setup. Results substantiate that ESPReSSo can provide improved edge delineation and regional homogeneity for multidimensional and multi-coil MRI datasets and is therefore useful in applications depending on well-defined tissue boundaries, such as image registration and segmentation or detection of small lesions in clinical diagnostics.

[Simultaneous whole-body PET-MRI in pediatric oncology : More than just reducing radiation?]. / Simultane Ganzkörper-PET-MRT in der pädiatrischen Onkologie : Mehr als nur Strahlenersparnis?

Diagnostic imaging plays an essential role in pediatric oncology with regard to diagnosis, therapy-planning, and the follow-up of solid tumors. The current imaging standard in pediatric oncology includes a variety of radiological and nuclear medicine imaging modalities depending on the specific tumor entity. The introduction of combined simultaneous positron emission tomography (PET) and magnetic resonance imaging (MRI) has opened up new diagnostic options in pediatric oncology. This novel modality combines the excellent anatomical accuracy of MRI with the metabolic information of PET. In initial clinical studies, the technical feasibility and possible diagnostic advantages of combined PET-MRI have been in comparison with alternative imaging techniques. It was shown that a reduction in radiation exposure of up to 70 % is achievable compared with PET-CT. Furthermore, it has been shown that the number of imaging studies necessary can be markedly reduced using combined PET-MRI. Owing to its limited availability, combined PET-MRI is currently not used as a routine procedure. However, this new modality has the potential to become the imaging reference standard in pediatric oncology in the future. This review article summarizes the central aspects of pediatric oncological PET-MRI based on existing literature. Typical pediatric oncological PET-MRI cases are also presented.

Pediatric Oncologic Imaging: A Key Application of Combined PET/MRI.

UNLABELLED: Pediatric imaging has been identified as a key application of combined whole-body PET/MRI. First studies have revealed the clinical feasibility and possible advantages of PET/MRI over PET/CT and MRI. Besides a significant reduction in radiation exposure of about 50 - 75 %, combined whole-body PET/MRI offers the diagnostic advantage of the multiparametric characterization of pathophysiologic processes and helps reduce the number of necessary imaging studies. However, very few studies focusing on pediatric PET/MRI have been published to date. Additional studies are necessary in order to fully appreciate the clinical impact of this novel method. This review article shall summarize the existing literature concerning pediatric PET/MRI and give insight into the practical experience derived from over 160 pediatric PET/MRI examinations that were performed in Tübingen. KEY POINTS: •Combined PET/MR is a promising imaging modality in pediatric oncology. •Using combined PET/MRI, diagnostic radiation exposure of pediatric patients and the number of necessary imaging studies can be reduced. •Further clinical studies are necessary in order to define specific indications for combined PET/MRI in pediatric radiology.

Prostate cancer gene 3 (PCA3) is of additional predictive value in patients with PI-RADS grade III (intermediate) lesions in the MR-guided re-biopsy setting for prostate cancer.

PURPOSE: Multiparametric magnetic resonance imaging (mpMRI) improves diagnostic accuracy in re-biopsies of men with prostate cancer (PC) suspicion, but predictive value is limited despite the use of the new Prostate Imaging Reporting and Data System (PI-RADS). Prognostic value of the PC-specific biomarker prostate cancer gene 3 (PCA3) added to the PI-RADS score was evaluated. METHODS: The study was a retrospective analysis of the institutional database for men with MR-guided biopsy (MR-GB) for suspicious lesion in mpMRI and who had an additional pre-MR-GB PCA3 testing for ongoing PC suspicion. All men had ≥ 1 negative ultrasound GB. Lesions were retrospectively scored by PI-RADS in three MRI sequences (T2w, DCE, and DWI). PCA3 was analyzed with cutoffs of 25 and 35. The prognostic value of mpMRI and PCA3 and the additional value of both were explored. RESULTS: Tumor detection rate (49 men, mean PSA 10 ng/ml, lesion size 40 mm(2)) was 45 % (22/49 patients). In the subgroup of PI-RADS IV°, 17/17 patients had PC; in PI-RADS III° (intermediate) 5/15 had PC, and all 5 had a PCA3 > 35. PCA3 > 35 had no additional prognostic value in the whole cohort. Out of the 10/15 PC negative patients (PI-RADS III°), PCA3 was < 35 in 6. The inclusion of PCA3 value in PI-RADS III° patients improved predictive accuracy to 91.8 %. CONCLUSION: MpMRI and subsequent grading to PI-RADS significantly improves PC detection in the re-biopsy setting. The diagnostic uncertainty in the PI-RADS intermediate group can be ameliorated by the addition of PCA3 cutoff of 35 to avoid potential unnecessary biopsies.

MR-based in vivo follow-up study of Achilles tendon volume and hydration state after ankle-loading activity.

The purpose of this study was to evaluate temporal alterations of the Achilles tendon volume and hydration state after cross-country-running. Achilles tendons of six untrained participants were examined on a 3T MR-scanner before running, immediately afterwards, and in the following 24, 48, and 72 h. Using a 3D-UTE sequence, caudal (CA) and cranial (CR) mid-portion tendon areas were examined with off-resonance saturation ratios (OSR) and T2* relaxation times. Tendon volume was measured with a self-written Matlab-based automated contour detection algorithm (AVAT) in submillimeter T2-weighted MR images. A significant influence of running in caudal (P = 0.017) and cranial OSR values (P = 0.001), tendon volume (P = 0.024), and cranial T2* measurements (P = 0.046), but not in caudal T2* values (P = 0.298) were found. In detail, mean individual OSR and tendon volume measurements demonstrated a similar but inverted course in their values after exercise: initially, OSR values increased after running (and tendon volume decreased), while subsequently a decrease of OSR values (with an increase of tendon volume) could be observed. OSR and tendon volume measurements are able to detect a physiological response of tendons to a mechanical stimulus. After a transient decrease of free water in the Achilles tendon, an increase with a maximum free water content 48 h after ankle loading and a tendency toward normalization after 72 h was found.

[Multiparametric imaging with simultaneous MRI/PET: Methodological aspects and possible clinical applications]. / Multiparametrische Bildgebung mittels simultaner MR/PET: Methodische Aspekte und klinische Anwendungsmöglichkeiten.

BACKGROUND: Combined MRI/PET enables the acquisition of a variety of imaging parameters during one examination, including anatomical and functional information such as perfusion, diffusion, and metabolism. OBJECTIVE: The present article summarizes these methods and their applications in multiparametric imaging via MRI/PET. RESULTS: Numerous studies have shown that the combination of these parameters can improve diagnostic accuracy for many applications, including the imaging of oncological, neurological, and inflammatory conditions. Because of the amount and the complexity of the acquired multiparametric data, there is a need for advanced analysis tools, such as methods of parameter selection and data classification. DISCUSSION: Currently, the clinical application of this process still has limitations. On the one hand, software for the fast calculation and standardized evaluation of the imaging data acquired is still lacking. On the other hand, there are deficiencies when comparing the results because of a lack of standardization of the assessment and diagnostic procedure.

Noninfectious Generalized Bronchiolitis in the Setting of Allogeneic Stem Cell Transplantation: A Potential Mimic of Lower Respiratory Tract Infection.

RATIONALE AND OBJECTIVES: To describe a little-known therapy-related small-airway phenomenon presumably caused by mucosal irritation in patients undergoing allogeneic stem cell transplantation (allo-SCT). MATERIALS AND METHODS: Retrospective database search at our institution identified 739 hematologic patients who underwent chemotherapy + allo-SCT between September 2004 and March 2014. After infectious pulmonary complications were excluded, 75 patients (female = 24; male = 51; median age = 47 years) with signs of generalized bronchiolitis (GB) on chest high-resolution computed tomography were identified. Computed tomography (CT) was performed proximate to chemotherapy onset; 92% had follow-up CT (mean, 1.9 weeks). The presence of centrilobular nodules, bronchial wall thickening (BWT), tree-in-bud (distributed diffuse vs. focal), ground-glass opacity, airspace opacification, luminal impactions, and air trapping was correlated with occurrence and duration of oral mucositis and therapy characteristics. Intensity of tree-in-bud and centrilobular nodules was graded absent (grade = 0), moderate (grade = 1), or marked (grade = 2). RESULTS: Overall incidence of GB among allo-SCT patients was 10.14%. GB was diagnosed at the time point of transplantation with a mean duration of CT findings of 4 weeks (±2.7). Tree-in-bud (17% [grade 2] and 83% [grade 1]) and BWT were present in 100% of the patients. Centrilobular nodules diffusely distributed were found in 45.5% of patients (20% [grade 2], 24% [grade 1], and 56% [none]). Air trapping and mosaic pattern were found in 13% and 16% of the patients, respectively. Resolution of GB was spontaneous. GB and its severity correlated with the temporal course and grade of oral mucositis; frequency and degree were not significantly influenced by the chemotherapy regimen. The incidence of GB in high-resolution computed tomography was statistically and significantly higher in patients with oral mucositis (P < 0.035). CONCLUSIONS: GB is frequent during chemotherapy for allo-SCT and is characterized by an even distribution of tree-in-bud, BWT, centrilobular nodules, mild clinical symptoms, and spontaneous resolution.

Comparison of chest-CT findings of Influenza virus-associated pneumonia in immunocompetent vs. immunocompromised patients.

PURPOSE: To retrospectively compare CT-patterns of pulmonary infiltration caused by different Influenza virus types and subtypes in immunocompetent and immunocompromised patients for possible discrimination. MATERIALS AND METHODS: Retrospective database search at our institution yielded 237 patients who were tested positive for Influenza virus type A or type B by bronchoalveolar lavage between January 2009 and April 2014. Fifty-six of these patients (female 26; male 30; median age 55.8 y, range 17-86 y; SD ± 14.4 y) underwent chest-HRCT due to a more severe clinical course of pulmonary infection. We registered all CT-findings compatible with pulmonary infection classifying them as airway predominant (tree-in-bud, centrilobular nodules, bronchial wall thickening ± peribronchial ground-glass opacity and consolidation) vs. interstitial-parenchymal predominant (bilateral, symmetrical GGO, consolidation, crazy paving and/or interlobular septal thickening). Twenty-six patients (46.4%) had follow-up CT-studies (0.78 mean, SD ± 5.8 scans). RESULTS: Thirty-six patients were immunocompromised (group I) whereas 20 patients were immunocompetent (group II). An airway-centric pattern of infection was found in 15 patients (group I) and 14 patients (group II) whereas an interstitial-parenchymal predominant pattern was found in 14 patients (group I) and 2 patients (group II). Eleven patients had a mixed pattern with no clear assignment to one group. At FU, 12 patients from group I and 3 from group II showed transitional infiltration patterns: in 10 patients from interstitial-parenchymal into airway predominant pattern and in five patients from airway predominant into interstitial-parenchymal. No significant differences in the pattern of pulmonary infection were found between different types and subtypes of Influenza viruses. CONCLUSION: Patterns of pulmonary infiltration caused by Influenza viruses do not significantly differ between immunocompetent and immunocompromised patients or between different types and subtypes of Influenza virus. One possible explanation for this could be the temporarily interchangeable character of pulmonary infiltration in this infection.

Assessment of relapse in patients with peritoneal carcinomatosis after cytoreductive surgery and hyperthermic intraperitoneal chemotherapy using F-18-FDG-PET/CT.

PURPOSE: In patients with peritoneal carcinomatosis (PC), cytoreductive surgery combined with hyperthermic intraperitoneal chemotherapy (HIPEC) is an evolving therapeutic approach with curative intention. The differentiation between posttherapeutic findings after HIPEC and relapse of PC is challenging. We evaluated the diagnostic value of F-18-FDG-PET/CT in patients with relapse of PC after HIPEC. MATERIALS AND METHODS: 36 patients with recurring PC after HIPEC were examined on a whole-body PET/CT system (44 examinations). The examination included 3 D F-18-FDG-PET and contrast-enhanced CT. Images were assessed by two experienced readers regarding the presence and the extent of PC using the peritoneal carcinomatosis index (PCI). Imaging results were correlated with surgical findings or follow-up. RESULTS: Relapse was suspected in 40 of 44 examinations. Relapse was missed by F-18-FDG PET/CT in 4 patients and significantly underestimated in 8 patients. The diagnostic accuracy for the detection of PC on a patient basis was 91 %, the sensitivity was 91 % and the positive predictive value was 100 %. The mean PCI was 11.4 ±â€Š11.9 for PET/CT, 8.4 ±â€Š10.3 for CT and 16.6 ±â€Š15.0 in the case of surgical exploration. The extent of PC was underestimated by PET/CT and even more by CT alone (p < 0.05). CONCLUSION: The diagnostic value of F-18-FDG PET/CT after cytoreductive surgery and HIPEC in the detection of recurring PC is superior to contrast-enhanced CT. However, the quantification of the extent of PC is limited due to post-therapeutic tissue alterations. KEY POINTS: • Imaging of recurrent PC after HIPEC is challenging due to posttherapeutic tissue alterations.• The extent of recurrent PC after HIPEC is systematically underestimated by F-18-FDG PET/CT.• F-18-FDG PET/CT provides improved sensitivity for recurrent PC compared to contrast-enhanced CT.• The correlation of the extent of recurrent PC depicted by F-18-FDG PET/CT and surgical exploration is better than that of contrast-enhanced CT and surgical exploration.

[Multiparametric imaging with simultaneous MR/PET. Methodological aspects and possible clinical applications]. / Multiparametrische Bildgebung mittels simultaner MR/PET. Methodische Aspekte und Möglichkeiten der klinischen Anwendungen.

Combined magnetic resonance imaging-positron emission tomography (MR/PET) enables acquisition of a variety of imaging parameters during a single examination including anatomical as well as functional information, such as perfusion, diffusion and metabolism. Numerous studies have shown that the combination of these parameters can improve the diagnostic accuracy for many applications especially in oncological imaging. Due to the amount and the complexity of the acquired multiparametric data there is a need for advanced analytical tools, such as methods of parameter selection and data classification. The present article summarizes these methods and their applications in multiparametric imaging via MR/PET.