Julian Kirchner

Evaluation of PET and MR datasets in integrated 18F-FDG PET/MRI: A comparison of different MR sequences for whole-body restaging of breast cancer patients

OBJECTIVES To investigate the diagnostic value of different MR sequences and 18F-FDG PET data for whole-body restaging of breast cancer patients utilizing PET/MRI. METHODS A total of 36 patients with suspected tumor recurrence of breast cancer based on clinical follow-up or abnormal findings in follow-up examinations (e.g. CT, MRI) were prospectively enrolled in this study. All patients underwent a PET/CT and subsequently an additional PET/MR scan. Two readers were instructed to identify the occurrence of a tumor relapse in subsequent MR and PET/MR readings, utilizing different MR sequence constellations for each session. The diagnostic confidence for the determination of a malignant or benign lesion was qualitatively rated (3-point ordinal scale) for each lesion in the different reading sessions and the lesion conspicuity (4-point ordinal scale) for the three different MR sequences was additionally evaluated. RESULTS Tumor recurrence was present in 25/36 (69%) patients. All three PET/MRI readings showed a significantly higher accuracy as well as higher confidence levels for the detection of recurrent breast cancer lesions when compared to MRI alone (p<0.05). Furthermore, all three PET/MR sequence constellations showed comparable diagnostic accuracy for the identification of a breast cancer recurrence (p>0.05), yet the highest confidence levels were obtained, when all three MR sequences were used for image interpretation. Moreover, contrast-enhanced T1-weighted VIBE imaging showed significantly higher values for the delineation of malignant and benign lesions when compared to T2w HASTE and diffusion-weighted imaging. CONCLUSION Integrated PET/MRI provides superior restaging of breast cancer patients over MRI alone. Facing the need for appropriate and efficient whole-body PET/MR protocols, our results show the feasibility of fast and morphologically adequate PET/MR protocols. However, considering an equivalent accuracy for the detection of breast cancer recurrences in the three PET/MR readings, the application of contrast-agent and the inclusion of DWI in the study protocol seems to be debatable.

Whole-body staging of female patients with recurrent pelvic malignancies: Ultra-fast 18F-FDG PET/MRI compared to 18F-FDG PET/CT and CT

Objectives To evaluate the diagnostic feasibility of an ultra-fast 18F-FDG PET/MRI protocol, including T2-w and contrast-enhanced T1-w imaging as well as metabolic assessment (PET) in comparison to 18F-FDG PET/CT and CT for whole-body staging of female patients with suspected recurrence of pelvic malignancies. Methods 43 female patients with suspected tumor recurrence were included in this study. Suspicion was based on clinical follow-up and abnormal findings on imaging follow-up. All patients underwent a PET/CT and a subsequent PET/MRI examination. Two readers were asked to evaluate ultra-fast PET/MRI, PET/CT as well as CT datasets of PET/CT separately for suspect lesions regarding lesion count, lesion localization and lesion characterization. Statistical analyses were performed both, on a per-patient and a per-lesion basis. Results Tumor relapse was present in 38 of the 43 patients. Based on CT readings 25/38 tumor relapses were correctly identified. PET/CT enabled correct identification of 37/38 patients, PET/MRI correctly identified 36 of the 38 patients with recurrent cancer. On a lesion-based analysis PET/MRI enabled the correct detection of more lesions, comprising a lesion-based sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of 50%, 58%, 76%, 31%, and 53% for CT, 97%, 83%, 93%, 94%, and 92% for PET/CT and 98%, 83%, 94%, 94%, and 94% for PET/MRI, respectively. Mean scan duration of ultra-fast PET/MRI, PET/CT and whole-body CT amounted to 18.5 ± 1 minutes, 18.2 ± 1 minutes and 3.5 minutes, respectively. Conclusion Ultra-fast PET/MRI provides equivalent diagnostic performance and examination time when compared to PET/CT and superior diagnostic performance to CT in restaging female patients suspected to have recurrent pelvic cancer.

18F-FDG PET/MRI in patients suffering from lymphoma: how much MRI information is really needed?

ObjectivesTo evaluate and compare the diagnostic potential of different reading protocols, entailing non-enhanced/contrast-enhanced and diffusion-weighted 18F-FDG PET/MR imaging for lesion detection and determination of the tumor stage in lymphoma patients.MethodsA total of 101 18F-FDG PET/MRI datasets including a (1) transverse T2-w HASTE and 18F-FDG PET (PET/MRI1), (2) with an additional contrast enhanced VIBE (PET/MRI2), and (3) with additional diffusion-weighted imaging (PET/MRI3) were evaluated. Scans were performed for initial staging, restaging during treatment, or at the end of treatment and under surveillance with suspicion for tumor relapse. In all datasets lymphoma manifestations as well as tumor stage in analogy to the revised criteria of the Ann Arbor staging system were determined. Furthermore, potential changes in therapy compared to the reference standard were evaluated. Hitherto performed PET/CT and all available follow-up and prior examinations as well as histopathology served as reference standard.ResultsPET/MRI1 correctly identified 53/55 patients with active lymphoma and 190/205 lesions. Respective values were 55/55, 202/205 for PET/MRI2 and 55/55, 205/205 for PET/MRI3. PET/MRI1 determined correct tumor stage in 88 out of 101 examinations, and corresponding results for PET/MRI2 were 95 out of 101 and 96 out of 101 in PET/MRI3. Relating to the reference standard changes in treatment would occur in 11% based on PET/MRI1, in 6% based on PET/MRI2, and in 3% based on PET/MRI3.ConclusionsThe additional application of contrast-enhanced and diffusion-weighted imaging to 18F-FDG PET/MRI resulted in higher diagnostic competence, particularly for initial staging and correct classification of the disease extent with potential impact on patient and therapy management.

Imaging children suffering from lymphoma: an evaluation of different 18F-FDG PET/MRI protocols compared to whole-body DW-MRI

ObjectivesThe objectives of this study were to evaluate and compare the diagnostic potential of different PET/MRI reading protocols, entailing non-enhanced / contrast-enhanced and diffusion-weighted 18F–FDG PET/MR imaging and whole-body diffusion-weighted MRI for lesion detection and determination of the tumor stage in pediatric lymphoma patients.MethodsA total of 28 18F–FDG PET/MRI datasets were included for analysis of four different reading protocols: (1) PET/MRI utilizing sole unenhanced T2w and T1w imaging, (2) PET/MRI utilizing additional contrast enhanced sequences, (3) PET/MR imaging utilizing unenhanced, contrast enhanced and DW imaging or (4) WB-DW-MRI. Statistical analyses were performed on a per-patient and a per-lesion basis. Follow-up and prior examinations as well as histopathology served as reference standards.ResultsPET/MRI correctly identified all 17 examinations with active lymphoma disease, while WB-DW-MRI correctly identified 15/17 examinations. Sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy were 96%, 96.5%, 97%, 95%, and 96% for PET/MRI1; 97%, 96.5%, 97%, 96.5%, and 97% for PET/MRI2; 97%, 96.5%, 97%, 96.5%, and 97% for PET/MRI3 and 77%, 96%, 96%, 78.5% and 86% for MRI-DWI.Conclusion18F–FDG PET/MRI is superior to WB-DW-MRI in staging pediatric lymphoma patients. Neither application of contrast media nor DWI leads to a noticeable improvement of the diagnostic accuracy of PET/MRI. Thus, unenhanced PET/MRI may play a crucial role for the diagnostic work-up of pediatric lymphoma patients in the future.

Evaluation of Practical Interpretation Hurdles in 68Ga-PSMA PET/CT in 55 Patients: Physiological Tracer Distribution and Incidental Tracer Uptake

Purpose To investigate the physiologic 68Ga-PSMA distribution and evaluate focal or diffuse radiotracer uptake in nonprostate cancer malignancies and in incidental findings. Methods 68Ga-PSMA PET/CT scans in 55 men performed for prostate cancer (49) or renal cell carcinoma (6) staging were analyzed retrospectively. Two radiologists evaluated the datasets in 2 reading sessions. First, physiological 68Ga-PSMA uptake was evaluated. Second, scans were analyzed for incidental uptake. SUVmax and SUVmean were recorded. Other imaging modalities, histopathology, or clinical follow-up served as standard of reference. Results Homogenous 68Ga-PSMA uptake of the lacrimal glands (SUVmax, 15.7 ± 7.2), parotid glands (SUVmax, 24.4 ± 8.1), submandibular glands (SUVmax, 26.7 ± 7.1), vocal cords (SUVmax, 8.4 ± 3), Waldeyer ring (SUVmax, 10.4 ± 4.3), liver (SUVmax, 8.2 ± 2.5), spleen (SUVmax, 10.9 ± 3.9), kidneys (SUVmax, 66.4 ± 25.4), and pars descendens duodeni (SUVmax, 17.6 ± 8.9) was observed in all patients. In 65% and 36%, respectively, homogenous 68Ga-PSMA uptake of the colon descendens (SUVmax, 10.6 ± 9.2) and the rectum (SUVmax, 3.7 ± 1.1) was found. Approximately 22% exhibited a 68Ga-PSMA uptake of the thyroid (SUVmax, 4.5 ± 1.2), and 21% exhibited a 68Ga-PSMA uptake of the knee’s synovia (SUVmax, 2.9 ± 0.2). Furthermore, 68Ga-PSMA uptake was found in 1 patient because of fibrous dysplasia of the right os ilium (SUVmax, 7.7). Conclusions Physiologic distribution of 68Ga-PSMA comprises uptake in lacrimal and salivary glands, vocal cords, Waldeyer ring, liver, spleen, and kidneys as well as various parts of the intestine. Moreover, nonspecific tracer uptake is regularly found in the thyroid and the synovia of the knee. Incidental 68Ga-PSMA uptake can occasionally reveal nonprostate cancer–associated remodeling processes, such as fibrous dysplasia.

Dual-phase hybrid 18F-Fluoride Positron emission tomography/MRI in ankylosing spondylitis: Investigating the link between MRI bone changes, regional hyperaemia and increased osteoblastic activity

Focal 18F‐Fluoride uptake on blood‐pool phase PET represents regional hyperaemia, while it indicates osteoblastic activity on mineralization phase PET. This study investigates the link between regional hyperaemia and osteoblastic activity in inflammatory and chronic lesions of ankylosing spondylitis (AS) of the sacroiliac joints (SIJ) using dual‐phase 18F‐Fluoride PET/MRI.

11C–MET PET/MRI for detection of recurrent glioma

IntroductionRadiological assessment of brain tumors is widely based on the Radiology Assessment of Neuro-Oncology (RANO) criteria that consider non-specific T1 and T2 weighted images. Limitation of the RANO criteria is that they do not include metabolic imaging techniques that have been reported to be helpful to differentiate treatment related changes from true tumor progression. In the current study, we assessed if the combined use of MRI and PET with hybrid 11C–MET PET/MRI can improve diagnostic accuracy and diagnostic confidence of the readers to differentiate treatment related changes from true progression in recurrent glioma.MethodsFifty consecutive patients with histopathologically proven glioma were prospectively enrolled for a hybrid 11C–MET PET/MRI to differentiate recurrent glioma from treatment induced changes. Sole MRI data were analyzed based on RANO. Sole PET data and in a third evaluation hybrid 11C–MET-PET/MRI data were assessed for metabolic respectively metabolic and morphologic glioma recurrence. Diagnostic performance and diagnostic confidence of the reader were calculated for the different modalities, and the McNemar test and Mann-Whitney U Test were applied for statistical analysis.ResultsHybrid 11C–MET PET/MRI was successfully performed in all 50 patients. Glioma recurrence was diagnosed in 35 of the 50 patients (70%). Sensitivity and specificity were calculated for MRI (86.11% and 71.43%), for 11C–MET PET (96.77% and 73.68%), and for hybrid 11C–MET-PET/MRI (97.14% and 93.33%). For diagnostic accuracy hybrid 11C–MET-PET/MRI (96%) showed significantly higher values than MRI alone (82%), whereas no significant difference was found for 11C–MET PET (88%). Furthermore, by rating on a five-point Likert scale significantly higher scores were found for diagnostic confidence when comparing 11C–MET PET/MRI (4.26 ± 0,777) to either PET alone (3.44 ± 0.705) or MRI alone (3.56 ± 0.733).ConclusionThis feasibility study showed that hybrid PET/MRI might strengthen RANO classification by adding metabolic information to conventional MRI information. Future studies should evaluate the clinical utility of the combined use of 11C–MET PET/MRI in larger patient cohorts.

Current Utilization and Acceptance of Multiparametric MRI in the Diagnosis of Prostate Cancer. A Regional Survey

PURPOSE  To assess the current regional acceptance, valuation, and clinical role of multiparametric MRI (mp-MRI) in prostate cancer diagnostics by patients and physicians. MATERIALS AND METHODS  Of 482 distributed standardized questionnaires, 328 patient and 31 physician questionnaires (urological and general practitioners in and around Düsseldorf) were analyzed over a period of 11 months. Questions were asked concerning general knowledge about prostate cancer, current diagnostic procedures, and knowledge about mp-MRI and MRI-guided biopsy. RESULTS  70 % of the patients regarded accurate and exact diagnostics of prostate carcinomas as very important and 68 % considered MP-MRI a useful technique. 28 % of the patients with elevated PSA levels and negative transrectal ultrasound-guided biopsy (TRUS-GB) received MP-MRI as a secondary diagnostic. More than half of the patients estimated their overall knowledge about prostate cancer mediocre or worse and wished for more information about MR diagnostics. The majority of physicians (55 %) ordered MP-MRI studies of the prostate and 68 % saw their basic role in secondary diagnostics. CONCLUSION  In this regional assessment mp-MRI of the prostate was considered useful by patients and practitioners. Currently, there still is a considerable discrepancy between recommended and the actual number of conducted MP-MRI studies, particularly in patients after previous negative TRUS-GB, although practitioners already see the benefit in this patient collective. Even though the use of prostate MRI is frequently more established than suggested in the current German S3-guideline, its full potential has not yet been exploited. More comprehensive information about the applications and diagnostic benefits of prostate MRI is needed and desired among patients and physicians. KEY POINTS   · The use of prostate MRI is frequently more established than suggested in the current German S3-guideline (12/2016). · The full potential of mp-MRI of the prostate has not been exploited. · More information about the clinical benefit and potential of prostate MRI is necessary and desired by patients and clinicians. CITATION FORMAT · Ullrich T, Schimmöller L, Oymanns M et al. Current Utilization and Acceptance of Multiparametric MRI in the Diagnosis of Prostate Cancer. A Regional Survey. Fortschr Röntgenstr 2018; 190: 419 - 426.

18 F-FDG PET/MR imaging in patients with suspected liver lesions: Value of liver-specific contrast agent Gadobenate dimeglumine

Objectives To evaluate the added value of the application of the liver-specific contrast phase of Gadobenate dimeglumine (Gd-BOPTA) for detection and characterization of liver lesions in 18F-FDG PET/MRI. Methods 41 patients with histologically confirmed solid tumors and known / suspected liver metastases or not classifiable lesions in 18F-FDG PET/CT were included in this study. All patients underwent a subsequent Gd-BOPTA enhanced 18F-FDG PET/MRI examination. MRI without liver-specific contrast phase (MRI1), MRI with liver-specific contrast phase (MRI2), 18F-FDG PET/MRI without liver-specific contrast phase (PET/MRI1) and with liver-specific contrast phase (PET/MRI2) were separately evaluated for suspect lesions regarding lesion dignity, characterization, conspicuity and confidence. Results PET/MRI datasets enabled correct identification of 18/18 patients with malignant lesions; MRI datasets correctly identified 17/18 patients. On a lesion-based analysis PET/MRI2 provided highest accuracy for differentiation of lesions into malignant and benign lesions of 98% and 100%. Respective values were 95% and 100% for PET/MRI1, 93% and 96% for MRI2 and 91% and 93% for MRI1. Statistically significant higher diagnostic confidence was found for PET/MRI2 and MRI2 datasets compared to PET/MRI1 and MRI1, respectively (p < 0.001). Conclusion The application of the liver-specific contrast phase in 18F-FDG PET/MRI further increases the diagnostic accuracy and diagnostic confidence for correct assessment of benign and malignant liver lesions.

Response assessment of bevacizumab therapy in GBM with integrated 11C-MET-PET/MRI: a feasibility study

BackgroundThe objective of this study was to evaluate the potential of integrated 11C-MET PET/MR for response assessment of relapsed glioblastoma (GBM) receiving bevacizumab treatment.MethodsEleven consecutive patients with relapsed GBM were enrolled for an integrated 11C-MET PET/MRI at baseline and at follow-up. Treatment response for MRI was evaluated according to Response Assessment in Neuro-oncology (RANO) criteria and integrated 11C-MET PET was assessed by the T/N ratio.ResultsMRI showed no patient with complete response (CR), six of 11 patients with PR, four of 11 patients with SD, and one of 11 patients with progressive disease (PD). PET revealed metabolic response in five of the six patients with partial response (PR) and in two of the four patients with stable disease (SD), whereas metabolic non-response was detected in one of the six patients with PR, in two of the four patients with SD, and in the one patient with PD. Morphological imaging was predictive for PFS and OS when response was defined as CR, PR, SD, and non-response as PD. Metabolic imaging was predictive when using T/N ratio reduction of >25 as discriminator. Based on the morphologic and metabolic findings of this study a proposal for applying integrated PET/MRI for treatment response in relapsed GBM was developed, which was significantly predictive for PFS and OS (P = 0.010 respectively 0,029, log).ConclusionsThis study demonstrates the potential of integrated 11C-MET-PET/MRI for response assessment of GBM and the utility of combined assessment of morphologic and metabolic information with the proposal for assessing relapsed GBM.