Heinz Peter Schlemmer

Simultaneous MR/PET Imaging of the Human Brain: Feasibility Study

The purpose of this study was to apply a magnetic resonance (MR) imaging-compatible positron emission tomographic (PET) detector technology for simultaneous MR/PET imaging of the human brain and skull base. The PET detector ring consists of lutetium oxyorthosilicate (LSO) scintillation crystals in combination with avalanche photodiodes (APDs) mounted in a clinical 3-T MR imager with use of the birdcage transmit/receive head coil. Following phantom studies, two patients were simultaneously examined by using fluorine 18 fluorodeoxyglucose (FDG) PET and MR imaging and spectroscopy. MR/PET data enabled accurate coregistration of morphologic and multifunctional information. Simultaneous MR/PET imaging is feasible in humans, opening up new possibilities for the emerging field of molecular imaging.

Gadolinium Retention in the Dentate Nucleus and Globus Pallidus Is Dependent on the Class of Contrast Agent

PURPOSE To compare changes in signal intensity (SI) ratios of the dentate nucleus (DN) and the globus pallidus (GP) to those of other structures on unenhanced T1-weighted magnetic resonance (MR) images between linear and macrocyclic gadolinium-based contrast agents (GBCAs). MATERIALS AND METHODS The study was approved by the ethical committee of the University of Heidelberg (reference no. S-324/2014). Owing to the retrospective character of the study, the ethical committee did not require any written informed consent. Two groups of 50 patients who underwent at least six consecutive MR imaging examinations with the exclusive use of either a linear GBCA (gadopentetate dimeglumine) or a macrocyclic GBCA (gadoterate meglumine) were analyzed retrospectively. The difference in mean SI ratios of DN to pons and GP to thalamus on unenhanced T1-weighted images from the last and first examinations was calculated. One-sample and independent-sample t tests were used to assess the difference in SI ratios for both groups, and regression analysis was performed to account for potential confounders. RESULTS The SI ratio difference in the linear group was greater than 0 (mean DN difference ± standard deviation, 0.0407 ± 0.0398 [P < .001]; GP, 0.0287 ± 0.0275 [P < .001]) and significantly larger (DN, P < .001 and standardized difference of 1.16; GP, P < .001 and standardized difference of 0.81) than that in the macrocyclic group, which did not differ from 0 (DN, 0.0016 ± 0.0266 [P = .680]; GP, 0.0031 ± 0.0354 [P = .538]). The SI ratio difference between the last and first examinations for the DN remained significantly different between the two groups in the regression analysis (P < .001). CONCLUSION This study indicates that an SI increase in the DN and GP on T1-weighted images is caused by serial application of the linear GBCA gadopentetate dimeglumine but not by the macrocyclic GBCA gadoterate meglumine. Clinical implications of this observation remain unclear.

Magnetic resonance imaging of the body trunk using a single-slab, 3-dimensional, T2-weighted turbo-spin-echo sequence with high sampling efficiency (SPACE) for high spatial resolution imaging: Initial clinical experiences

Purpose:The authors conducted a clinical evaluation of single-slab, 3-dimensional, T2-weighted turbo-spin-echo (TSE) with high sampling efficiency (SPACE) for high isotropic body imaging with large field-of-view (FoV). Materials and Methods:Fifty patients were examined in clinical routine with SPACE (regions of interest: pelvis n = 30, lower spine n = 12, upper spine n = 6, extremities n = 4) at 1.5 T. For achieving a high sampling efficiency, parallel imaging, high turbofactor, and magnetization restore pulses were used. In contrast to a conventional TSE imaging technique with constant flip angle refocusing, the refocusing pulse train of the SPACE sequence consists of variable flip angle radiofrequency pulses along the echo train. Results:Signal-to-noise ratio and contrast-to-noise ratio of SPACE images were of sufficient diagnostic value. The possibility of image reconstruction in multiple planes was of clinical relevance in all cases and simplified data analysis. Conclusion:The achievement of 3-dimensional, T2-weighted TSE magnetic resonance imaging with isotropic and high spatial resolution and interactive 3-dimensional visualization essentially improve the diagnostic potential of magnetic resonance imaging.

A Novel Stereotactic Prostate Biopsy System Integrating Pre-Interventional Magnetic Resonance Imaging and Live Ultrasound Fusion

PURPOSE We developed an effective way to precisely diagnose prostate cancer using a novel prostate biopsy system that integrates pre-interventional magnetic resonance imaging with peri-interventional ultrasound for perineal navigated prostate biopsy. MATERIALS AND METHODS A total of 106 men with findings suspicious for prostate cancer (median age 66 years, prostate specific antigen 8.0 ng/ml and prostate volume 47 ml) underwent multiparametric 3 Tesla magnetic resonance imaging. Suspicious lesions were marked and data were transferred to the novel biopsy system. Using a custom-made biplane transrectal ultrasound probe mounted on a stepper we gathered 3-dimensional ultrasound data and fused them with magnetic resonance imaging data. As a result, suspicious magnetic resonance imaging lesions were superimposed over the transrectal ultrasound data. Three-dimensional biopsy planning was done, including systematic biopsies. Perineal biopsies were taken under live ultrasound guidance and the precise site of each biopsy was documented in 3 dimensions. We evaluated feasibility, safety and cancer detection. RESULTS Prostate cancer was detected in 63 of 106 patients (59.4%). Magnetic resonance imaging findings correlated positively with histopathology in 71 of 103 patients (68.9%). In magnetic resonance imaging lesions marked as highly suspicious, the detection rate was 95.8% (23 of 24 cases). Lesion targeted cores had a significantly higher positivity rate than nontargeted cores. The procedural targeting error of the first 2,461 biopsy cores was 1.7 mm. Regarding adverse effects, 2 patients experienced urinary retention and 1 had a perineal hematoma. Urinary tract infections did not develop. CONCLUSIONS Perineal stereotactic prostate biopsies guided by the combination of magnetic resonance imaging and ultrasound enable effective examination of suspicious magnetic resonance imaging lesions. Each biopsy core taken is documented accurately for its location in 3 dimensions, enabling magnetic resonance imaging validation and tailored treatment planning. The morbidity of the procedure was minimal.

Can pre-operative contrast-enhanced dynamic MR imaging for prostate cancer predict microvessel density in prostatectomy specimens?

The aim of this study was to correlate quantitative dynamic contrast-enhanced MRI (DCE MRI) parameters with microvessel density (MVD) in prostate carcinoma. Twenty-eight patients with biopsy-proven prostate carcinoma were examined by endorectal MRI including multiplanar T2- and T1-weighted spin-echo and dynamic T1-weighted turbo-FLASH MRI during and after intravenous Gd-DTPA administration. Microvessels were stained on surgical specimens using a CD31 monoclonal antibody. The MVD was quantified in hot spots by counting (MVC) and determining the area fraction by morphometry (MVAF). The DCE MRI data were analyzed using an open pharmacokinetic two-compartment model. In corresponding anatomic locations the time shift (Δt) between the beginning of signal enhancement of cancer and adjacent normal prostatic tissue, the degree of contrast enhancement and the contrast exchange rate constant (k21) were calculated. The MVC and MVAF were elevated in carcinoma (p<0.001 and p=0.002, respectively) and correlated to k21 (r=0.62, p<0.001 and r=0.80, p<0.001, respectively). k21-values of carcinoma were significantly higher compared with normal peripheral but not central zone tissue. Δt was longer in high compared with low-grade tumors (p=0.025). The DCE MRI can provide important information about individual MVD in prostate cancer, which may be helpful for guiding biopsy and assessing individual prognosis.

Critical Evaluation of Magnetic Resonance Imaging Targeted, Transrectal Ultrasound Guided Transperineal Fusion Biopsy for Detection of Prostate Cancer

PURPOSE Diagnosis and precise risk stratification of prostate cancer is essential for individualized treatment decisions. Magnetic resonance imaging/transrectal ultrasound fusion has shown encouraging results for detecting clinically significant prostate cancer. We critically evaluated magnetic resonance imaging targeted, transrectal ultrasound guided transperineal fusion biopsy in routine clinical practice. MATERIALS AND METHODS Included in this prospective study were 347 consecutive patients with findings suspicious for prostate cancer. Median age was 65 years (range 42 to 84) and mean prostate specific antigen was 9.85 ng/ml (range 0.5 to 104). Of the men 49% previously underwent transrectal ultrasound guided biopsies, which were negative, and 51% underwent primary biopsy. In all patients 3 Tesla multiparametric magnetic resonance imaging was done. Systematic stereotactic prostate biopsies plus magnetic resonance imaging targeted, transrectal ultrasound guided biopsies were performed in those with abnormalities on magnetic resonance imaging. Imaging data and biopsy results were analyzed. A self-designed questionnaire was sent to all men on further clinical history and biopsy adverse effects. RESULTS Of 347 patients biopsy samples of 200 (58%) showed prostate cancer and 73.5% of biopsy proven prostate cancer were clinically relevant according to National Comprehensive Cancer Network (NCCN) criteria. On multiparametric magnetic resonance imaging 104 men had findings highly suspicious for prostate cancer. The tumor detection rate was 82.6% (86 of 104 men) with a Gleason score of 7 or greater in 72%. Overall targeted cores detected significantly more cancer than systematic biopsies (30% vs 8.2%). Of 94 patients without cancer suspicious lesions on magnetic resonance imaging 11 (11.7%) were diagnosed with intermediate risk disease. Regarding adverse effects, 152 of 300 patients (50.6%) reported mild hematuria, 26% had temporary erectile dysfunction and 2.6% needed short-term catheterization after biopsy. Nonseptic febrile urinary tract infections developed in 3 patients (1%). CONCLUSIONS Magnetic resonance imaging targeted, transrectal ultrasound guided transperineal fusion biopsy provides high detection of clinically significant tumors. Since multiparametric magnetic resonance imaging still has some limitations, systematic biopsies should currently not be omitted. The morbidity of the transperineal saturation approach is reasonable and mainly self-limiting.

Comparative Analysis of Transperineal Template Saturation Prostate Biopsy Versus Magnetic Resonance Imaging Targeted Biopsy with Magnetic Resonance Imaging-Ultrasound Fusion Guidance

PURPOSE Multiparametric magnetic resonance imaging and magnetic resonance imaging targeted biopsy may improve the detection of clinically significant prostate cancer. However, standardized prospective evaluation is limited. MATERIALS AND METHODS A total of 294 consecutive men with suspicion of prostate cancer (186 primary, 108 repeat biopsies) enrolled in 2013 underwent 3T multiparametric magnetic resonance imaging (T2-weighted, diffusion weighted, dynamic contrast enhanced) without endorectal coil and systematic transperineal cores (median 24) independently of magnetic resonance imaging suspicion and magnetic resonance imaging targeted cores with software registration (median 4). The highest Gleason score from each biopsy method was compared. McNemars tests were used to evaluate detection rates. Predictors of Gleason score 7 or greater disease were assessed using logistic regression. RESULTS Overall 150 cancers and 86 Gleason score 7 or greater cancers were diagnosed. Systematic, transperineal biopsy missed 18 Gleason score 7 or greater tumors (20.9%) while targeted biopsy did not detect 11 (12.8%). Targeted biopsy of PI-RADS 2-5 alone overlooked 43.8% of Gleason score 6 tumors. McNemars tests for detection of Gleason score 7 or greater cancers in both modalities were not statistically significant but showed a trend of superiority for targeted primary biopsies (p=0.08). Sampling efficiency was in favor of magnetic resonance imaging targeted prostate biopsy with 46.0% of targeted biopsy vs 7.5% of systematic, transperineal biopsy cores detecting Gleason score 7 or greater cancers. To diagnose 1 Gleason score 7 or greater cancer, 3.4 targeted and 7.4 systematic biopsies were needed. Limiting biopsy to men with PI-RADS 3-5 would have missed 17 Gleason score 7 or greater tumors (19.8%), demonstrating limited magnetic resonance imaging sensitivity. PI-RADS scores, digital rectal examination findings and prostate specific antigen greater than 20 ng/ml were predictors of Gleason score 7 or greater disease. CONCLUSIONS Compared to systematic, transperineal biopsy as a reference test, magnetic resonance imaging targeted biopsy alone detected as many Gleason score 7 or greater tumors while simultaneously mitigating the detection of lower grade disease. The gold standard for cancer detection in primary biopsy is a combination of systematic and targeted cores.

Fast whole-body assessment of metastatic disease using a novel magnetic resonance imaging system: initial experiences.

Objective:The objective of this study was to investigate the clinical use of a novel whole-body magnetic resonance imaging (MRI) system for comprehensive assessment of tumor spread in clinical routine. Material and Methods:Sixty-five patients with different tumors with known metastatic disease and 6 healthy volunteers were included. High-resolution MRI from head to toe was performed using multiple phased-array surface coil elements, 24 independent receiver channels, and an integrated parallel acquisition technique (iPAT). A total room time of less than 60 minutes was required. Whole-body MRI and conventional spiral computed tomography (CT) were independently evaluated and compared in terms of feasibility, location/number of detected metastases, and therapeutic relevance. Results:Whole-body MRI was successfully performed in 68 of 71 subjects. Compared with CT, more metastases were detected by MRI in 11 of 63 patients (17%), particularly in brain, liver, spleen, lymph nodes, bone marrow, muscle, and subcutaneous fat tissue. According to these findings, therapy had to be modified in 6 of 63 patients (10%). Conclusions:High-resolution whole-body MRI is feasible in clinical routine within 1 single examination and offers great potential for fast assessment of individual tumor spread and total tumor burden.

High-Signal Intensity in the Dentate Nucleus and Globus Pallidus on Unenhanced T1-Weighted Images: Evaluation of the Macrocyclic Gadolinium-Based Contrast Agent Gadobutrol.

ObjectiveThe aim of this study was to compare changes in the signal intensity (SI) ratio of the dentate nucleus (DN) to the pons, DN to cerebrospinal fluid (CSF), and globus pallidus (GP) to thalamus on unenhanced T1-weighted magnetic resonance imaging (MRI) scans after serial injections of the macrocyclic gadolinium-based contrast agent gadobutrol. Materials and MethodsThirty patients who had received at least 5 MRI examinations (plus an additional last MRI for reference) with the exclusive use of gadobutrol, resulting in a total cumulative dose of 54.1 ± 30.4 mL gadobutrol, were analyzed retrospectively. Signal intensity ratio differences were calculated for DN-to-pons, DN-to-CSF, and GP-to-thalamus ratios by subtracting the SI ratio at the first MRI from the SI ratio at the last MRI scan. One-sample t tests were employed to examine if they differed from 0. Regression and correlational analyses were performed to examine whether the SI ratio differences were predicted by a number of control variables. ResultsSignal intensity ratio differences did not differ significantly from 0, neither for the DN-to-pons ratio (−0.0035 ± 0.0476, P = 0.69), the DN-to-CSF ratio (−0.0539 ± 0.3217, P = 0.37), nor the GP-to-thalamus ratio (−0.0020 ± 0.0211, P = 0.60). None of the control variables predicted changes in SI ratios. ConclusionsIn contrast to a recently published study, we did not find signal increases in the DN or in the GP after serial injections of gadobutrol, even though the total dose applied here was considerably larger than in the respective study. This finding adds further support to the hypothesis that the molecular structure of a gadolinium-based contrast agent as either macrocyclic or linear is a crucial factor for its potential to cause gadolinium deposition in the brain. Future studies should further assess this hypothesis by additional animal investigations as well as histopathological and clinical correlation studies.

Histological verification of 11C-choline-positron emission/computed tomography-positive lymph nodes in patients with biochemical failure after treatment for localized prostate cancer.

To evaluate the potential of 11C‐choline‐positron emission tomography (PET)/computed tomography (CT) for planning surgery in patients with prostate cancer and prostate‐specific antigen (PSA) relapse after treatment with curative intent.