Current Value of Biparametric Prostate MRI with Machine-Learning or Deep-Learning in the Detection, Grading, and Characterization of Prostate Cancer: A Systematic Review.

Prostate cancer detection with magnetic resonance imaging is based on a standardized MRI-protocol according to the PI-RADS guidelines including morphologic imaging, diffusion weighted imaging, and perfusion. To facilitate data acquisition and analysis the contrast-enhanced perfusion is often omitted resulting in a biparametric prostate MRI protocol. The intention of this review is to analyze the current value of biparametric prostate MRI in combination with methods of machine-learning and deep learning in the detection, grading, and characterization of prostate cancer; if available a direct comparison with human radiologist performance was performed. PubMed was systematically queried and 29 appropriate studies were identified and retrieved. The data show that detection of clinically significant prostate cancer and differentiation of prostate cancer from non-cancerous tissue using machine-learning and deep learning is feasible with promising results. Some techniques of machine-learning and deep-learning currently seem to be equally good as human radiologists in terms of classification of single lesion according to the PIRADS score.

Magnetic resonance imaging reveals distinct bone marrow patterns in indolent and advanced systemic mastocytosis.

Systemic mastocytosis (SM) is broadly subcategorized according to mast cell (MC) burden and organ involvement into indolent (ISM), smoldering (SSM), and advanced SM (AdvSM). However, the pattern and extent of bone involvement remains controversial. In this institutional review board (IRB)-approved study, 115 patients with different forms of SM (ISM (n = 37, 32%), SSM (n = 9, 8%), and AdvSM (n = 69, 60%)) underwent a whole-body magnetic resonance imaging including sagittal and coronal T1 and turbo inversion recovery magnitude (TIRM) sequences of the spine. The evaluation included the pattern and extent of pathologic bone marrow (BM) signals in the spine and extremities, osteolytic lesions, and vertebral fractures. A pathologic BM pattern was observed in 4/37 (11%), 8/9 (89%), and 66/69 (96%); affection of the appendicular skeleton in 3/37 (8%), 8/9 (89%), and 67/69 (97%); and vertebral fractures in 7/37 (19%), 0/9, and 13/69 (19%) patients with ISM, SSM, and AdvSM, respectively. In AdvSM, pathologic BM pattern included activated (62%), diffuse sclerotic (25%), and small-spotted BM (9%), respectively. Only activated/sclerotic BM was associated with significantly higher MC burden, organ damage, and inferior median survival (2.9 years, p = 0.04). Vertebral fractures resembled classical multi-segmental osteoporotic fractures in ISM but not in AdvSM in which they were only found in activated/sclerotic BM. Only one patient with AdvSM had a focal osteolytic lesion in the femur. Activated/sclerotic BM changes of the spine and affection of the appendicular skeleton are indicative for SSM or AdvSM. Osteolytic lesions, which are very rare, and osteoporotic fractures are ineligible for the diagnosis of AdvSM.

Gadobutrol in Renally Impaired Patients: Results of the GRIP Study.

OBJECTIVE: The aim of this study was to assess the potential risk of gadobutrol-enhanced magnetic resonance imaging (MRI) in patients with moderate to severe renal impairment for the development of nephrogenic systemic fibrosis (NSF). MATERIALS AND METHODS: We performed a prospective, international, multicenter, open-label study in 55 centers. Patients with moderate to severe renal impairment scheduled for any gadobutrol-enhanced MRI were included. All patients received a single intravenous bolus injection of gadobutrol at a dose of 0.1 mmol/kg body weight. The primary target variable was the number of patients who develop NSF within a 2-year follow-up period. RESULTS: A total of 908 patients were enrolled, including 586 with moderate and 284 with severe renal impairment who are at highest risk for developing NSF. The mean time since renal disease diagnosis was 1.83 and 5.49 years in the moderate and severe renal impairment cohort, respectively. Overall, 184 patients (20.3%) underwent further contrast-enhanced MRI with other gadolinium-based contrast agents within the 2-year follow-up. No patient developed symptoms conclusive of NSF. CONCLUSIONS: No safety concerns with gadobutrol in patients with moderate to severe renal impairment were identified. There were no NSF cases.

Can Ferumoxytol be Used as a Contrast Agent to Differentiate Between Acute and Chronic Inflammatory Kidney Disease?: Feasibility Study in a Rat Model.

OBJECTIVES: Ferumoxytol, an intravenous iron supplement, can be used in off-label mode as a contrast agent in magnetic resonance imaging. The aim of this study was to assess whether ferumoxytol can be used as a marker of inflammation in animal models of acute and chronic inflammatory kidney diseases. MATERIAL AND METHODS: The institutional animal care committee approved this study. A total of 18 rats were examined: 6 healthy Sprague Dawley rats as a control group; 6 rats with polycystic kidney disease (PKD) as a model for chronic inflammatory disease; Thy-1, an antibody triggering glomerulonephritis, was injected in 6 rats as a model for acute inflammation. Each rat was examined directly before and 24 hours after intravenous administration of ferumoxytol at a dose of 30 mg Fe/kg body weight. T2* times of renal tissue were approximated using a multiecho sequence. Changes in relative T2* times and T2 signal intensity after ferumoxytol injection were calculated. RESULTS: Statistically significant differences between the 3 groups were found: the T2* times of both, Thy-1 and PKD rats were statistically significant different compared with the control group (T2* time ratio after/before: Thy-1, 0.21; PKD, 0.19, control, 0.28; P = 0.002). The highest T2 signal loss in the renal cortex was observed in the Thy-1 rats (T2 signal intensity ratio after/before: Thy-1, 0.49; PKD, 0.79; control, 0.78; P = 0.0005). CONCLUSIONS: Ferumoxytol-enhanced magnetic resonance imaging allows detection and differentiation of acute and chronic inflammatory kidney disease based on different patterns of parenchymal ferumoxytol depositions. Ferumoxytol thus might help to differentiate between different types of inflammation in various kidney diseases.

Fast inner-volume imaging of the lumbar spine with a spatially focused excitation using a 3D-TSE sequence.

RATIONALE AND OBJECTIVES: The purpose of this study was to evaluate the feasibility and technical quality of a zoomed three-dimensional (3D) turbo spin-echo (TSE) sampling perfection with application optimized contrasts using different flip-angle evolutions (SPACE) sequence of the lumbar spine. MATERIALS AND METHODS: In this prospective feasibility study, nine volunteers underwent a 3-T magnetic resonance examination of the lumbar spine including 1) a conventional 3D T2-weighted (T2w) SPACE sequence with generalized autocalibrating partially parallel acquisition technique acceleration factor 2 and 2) a zoomed 3D T2w SPACE sequence with a reduced field of view (reduction factor 2). Images were evaluated with regard to image sharpness, signal homogeneity, and the presence of artifacts by two experienced radiologists. For quantitative analysis, signal-to-noise ratio (SNR) values were calculated. RESULTS: Image sharpness of anatomic structures was statistically significantly greater with zoomed SPACE (P < .0001), whereas the signal homogeneity was statistically significantly greater with conventional SPACE (cSPACE; P = .0003). There were no statistically significant differences in extent of artifacts. Acquisition times were 8:20 minutes for cSPACE and 6:30 minutes for zoomed SPACE. Readers 1 and 2 selected zSPACE as the preferred sequence in five of nine cases. In two of nine cases, both sequences were rated as equally preferred by both the readers. SNR values were statistically significantly greater with cSPACE. CONCLUSIONS: In comparison to a cSPACE sequences, zoomed SPACE imaging of the lumbar spine provides sharper images in conjunction with a 25% reduction in acquisition time.

CAIPIRINHA-Dixon-TWIST (CDT)-volume-interpolated breath-hold examination (VIBE) for dynamic liver imaging: comparison of gadoterate meglumine, gadobutrol and gadoxetic acid.

PURPOSE: CAIPIRINHA-Dixon-TWIST (CDT)-VIBE is a robust method for abdominal magnetic resonance imaging providing both high spatial and high temporal resolution. The purpose of this study was to examine the influence of different gadolinium based contrast agents (GBCA) on image quality (IQ) with CDT-VIBE. MATERIALS AND METHODS: In this IRB-approved, retrospective, inter-individual comparison study, 86 patients scanned at 3T were included. Within 28s, 14 high-resolution 3D datasets were acquired using CDT-VIBE. 37 patients received 0.1mmol/kg gadoterate meglumine, 28 patients 0.1mmol/kg gadobutrol, and 19 patients 0.1mL/kg gadoxetic acid. Two blinded, board-certified radiologists assessed the image quality on a 5 point scale, as well as the number of hepatic arterial dominant (HAD) phases. RESULTS: Regardless of the GBCA utilized, CDT-VIBE resulted in good IQ in terms of best IQ achieved among all 14 datasets (gadobutrol 4.3, gadoterate meglumine 3.9, gadoxetic acid 3.7). With respect to worst IQ, the three groups showed statistically significant differences with gadobutrol receiving the highest rating (3.6) and gadoxetic acid the lowest (2.4) (gadoterate meglumine 3.0; 0.0014

Zoomed EPI-DWI of the head and neck with two-dimensional, spatially-selective radiofrequency excitation pulses.

OBJECTIVES: To evaluate the feasibility of zoomed diffusion-weighted EPI (z-EPI) in the head and neck in a healthy volunteer population and to compare to conventional single-shot EPI (c-EPI). MATERIAL AND METHODS: Nine volunteers were included in this prospective, IRB-approved study. Examinations were performed on a 3 T-MR system equipped with a two-channel, fully-dynamic parallel transmit array. The acquired sequences consisted of a T2w-TSE, a c-EPI, and two z-EPI acquisitions. For quantitative assessment of distortion artefacts, DW images were fused with T2-TSE images. Misregistration of DW images with T2-TSE images was assessed in the cervical spine. For qualitative assessment, two readers ranked c-EPI and z-EPI sequences in terms of susceptibility artefacts, image blur, and overall imaging preference. ADC values of several anatomical regions were calculated and compared between sequences. RESULTS: Mean maximum distortion with the c-EPI was 5.9 mm ± 1.6 mm versus 2.4 mm ± 1 mm (p < 0.05) with z-EPI. Both readers found more blur and susceptibility artefacts in every case with c-EPI. No statistically significant differences in calculated ADC values were observed. CONCLUSION: z-EPI of the head and neck leads to substantial image quality improvements relative to c-EPI due to a reduction in susceptibility artefacts and image blur. KEY POINTS: • Zoomed DWI is feasible in the head and neck. • Image quality improves substantially with zoomed DWI of the neck. • Zoomed DWI exhibits markedly reduced susceptibility artefacts.

Enhancement characteristics and impact on image quality of two gadolinium chelates at equimolar doses for time-resolved 3-Tesla MR-angiography of the calf station.

PURPOSE: To compare enhancement characteristics and image quality of two macrocyclic gadolinium chelates, gadoterate meglumine and gadobutrol, in low-dose, time-resolved MRA of the calf station. MATERIALS AND METHODS: 100 consecutive patients with peripheral arterial disease (stages II-IV) were retrospectively analysed. Fifty patients were included in each group - 32 men and 18 women for gadobutrol (mean age 67 years) and 34 men, 16 women for gadoterate meglumine (mean age 64 years). 0.03 mmol/kg bw of either gadobutrol or gadoterate meglumine was injected. Gadobutrol was diluted 1 ∶ 1 with normal saline (0.9% NaCl) to provide similar injection volume and bolus geometry compared to the undiluted 0.5 M dose of gadoterate meglumine. Signal-to-noise-ratio (SNR), contrast-to-noise-ratio (CNR) and image quality were analysed and compared between the two groups. RESULTS: Mean SNR ranged from 83.0 ± 46.7 (peroneal artery) to 96.4 ± 64.5 (anterior tibial artery) for gadobutrol, and from 37.6 ± 13.8 (peroneal artery) to 45.3 ± 16.4 (anterior tibial artery) for the gadoterate meglumine group (p<0.0001). CNR values ranged from 30.1 ± 20.1 (peroneal artery) to 37.6 ± 26.0 (anterior tibial artery) for gadobutrol and from 14.9 ± 8.0 (peroneal artery) to 18.6 ± 16.4 (anterior tibial artery) for gadoterate meglumine (p<0.0001). No significant difference in image quality was found except for the peroneal arteries (p = 0.006 and p = 0.04). Interreader agreement was excellent (kappa 0.87-0.93). CONCLUSION: The significantly better enhancement as assessed by SNR and CNR provided by gadobutrol compared to gadoterate meglumine does not translate into substantial differences in image quality in an equimolar, low-dose, time-resolved MRA protocol of the calves.

Assessment of acute intestinal graft versus host disease by abdominal magnetic resonance imaging at 3 Tesla.

OBJECTIVES: After allogeneic stem cell transplantation (SCT), a reliable diagnosis of acute graft versus host disease (aGvHD) is essential for an early and successful treatment. It is the aim of this analysis to assess intestinal aGvHD by magnetic resonance imaging (MRI). METHODS: Prior to allogeneic SCT, 64 consecutive patients underwent abdominal MRI examination on a 3 T MR system, including axial and coronal T2w sequences and a three-dimensional dynamic T1w, contrast enhanced sequence. After SCT, 20 patients with suspected aGvHD received a second MRI as well as an endoscopic examination. RESULTS: Nine patients suffered from histologically proven intestinal aGvHD. In eleven patients intestinal aGvHD was excluded. In all aGvHD patients typical MRI findings with long-segment bowel wall thickening--always involving the terminal ileum--with profound submucosal oedema, were detected. The bowel wall was significantly thickened in patients with intestinal aGvHD. Bowel contrast enhancement spared the submucosa while demonstrating strong mucosal hyperemia. CONCLUSIONS: In intestinal aGvHD, a characteristic MR-appearance can be detected. This MRI pattern might facilitate an early and non-invasive diagnosis of intestinal aGvHD. MRI might thus be used as a sensitive tool to rule out or support the clinical diagnosis of aGvHD. KEY POINTS: • Acute intestinal graft versus host disease (aGvHD) can be assessed by MRI. • The aGvHD of the bowel demonstrates a characteristic MR imaging pattern. • Bowel wall shows extensive long-segment wall thickening with profound submucosal oedema. • Terminal ileum seems invariably affected; other bowel segments show variable involvement. • Colonoscopy in suspected aGvHD should include inspection of terminal ileum.

Zoomed EPI-DWI of the pancreas using two-dimensional spatially-selective radiofrequency excitation pulses.

BACKGROUND: Implementation of DWI in the abdomen is challenging due to artifacts, particularly those arising from differences in tissue susceptibility. Two-dimensional, spatially-selective radiofrequency (RF) excitation pulses for single-shot echo-planar imaging (EPI) combined with a reduction in the FOV in the phase-encoding direction (i.e. zooming) leads to a decreased number of k-space acquisition lines, significantly shortening the EPI echo train and potentially susceptibility artifacts. PURPOSE: To assess the feasibility and image quality of a zoomed diffusion-weighted EPI (z-EPI) sequence in MR imaging of the pancreas. The approach is compared to conventional single-shot EPI (c-EPI). MATERIAL AND METHODS: 23 patients who had undergone an MRI study of the abdomen were included in this retrospective study. Examinations were performed on a 3T whole-body MR system (Magnetom Skyra, Siemens) equipped with a two-channel fully dynamic parallel transmit array (TimTX TrueShape, Siemens). The acquired sequences consisted of a conventional EPI DWI of the abdomen and a zoomed EPI DWI of the pancreas. For z-EPI, the standard sinc excitation was replaced with a two-dimensional spatially-selective RF pulse using an echo-planar transmit trajectory. Images were evaluated with regard to image blur, respiratory motion artifacts, diagnostic confidence, delineation of the pancreas, and overall scan preference. Additionally ADC values of the pancreatic head, body, and tail were calculated and compared between sequences. RESULTS: The pancreas was better delineated in every case (23/23) with z-EPI versus c-EPI. In every case (23/23), both readers preferred z-EPI overall to c-EPI. With z-EPI there was statistically significantly less image blur (p<0.0001) and respiratory motion artifact compared to c-EPI (p<0.0001). Diagnostic confidence was statistically significantly better with z-EPI (p<0.0001). No statistically significant differences in calculated ADC values were observed between the two sequences. CONCLUSION: Zoomed diffusion-weighted EPI leads to substantial image quality improvements with reduction of susceptibility artifacts in pancreatic DWI.

Do depressed patients without activation of the hypothalamus-pituitary-adrenal (HPA) system have metabolic disturbances?

This study compared features of the metabolic syndrome between healthy controls and depressed patients without activation of the hypothalamus-pituitary-adrenal (HPA) system. After exclusion of non-suppressors to 1mg dexamethasone, we included 20 depressed inpatients and 34 healthy controls in the analyses. We assessed HPA system activity (diurnal saliva cortisol profile, cortisol excretion), normetanephrine excretion as well as fasting glucose, lipid profile and blood pressure. With regard to body composition, we measured waist circumference as well as visceral fat and adrenal volume by magnetic resonance (MR) imaging. Five depressed patients (25%) and five healthy controls (15%) fulfilled the criteria of the metabolic syndrome according NCEP-ATP-III. Depression was significantly related with fasting glucose and negatively associated with mean blood pressure (BP) and, by trend, with low HDL-cholesterol. We conclude that depressed patients may have modest metabolic disturbances even in the complete absence of activation of stress-responsive systems. Hence some metabolic disturbances in depressed patients may not be explicable by HPA activation. Additional factors are required to mediate the link between affective and metabolic disorders.

Nonenhanced ECG-gated quiescent-interval single shot MRA: image quality and stenosis assessment at 3 tesla compared with contrast-enhanced MRA and digital subtraction angiography.

PURPOSE: To evaluate the diagnostic accuracy of a nonenhanced electrocardiograph-gated quiescent-interval single shot MR-angiography (QISS-MRA) at 3 Tesla with contrast-enhanced MRA (CE-MRA) and digital subtraction angiography (DSA) serving as reference standard. MATERIALS AND METHODS: Following institutional review board approval, 16 consecutive patients with peripheral arterial disease underwent a combined peripheral MRA protocol consisting of a large field-of-view QISS-MRA, continuous table movement MRA, and an additional time-resolved MRA of the calves. DSA correlation was available in eight patients. Image quality and degree of stenosis was assessed. Sensitivity and specificity of QISS-MRA was evaluated with CE-MRA and DSA serving as the standards of reference and compared using the Fisher exact test. RESULTS: With the exception of the calf station, image quality with QISS-MRA was rated statistically significantly less than that of CE-MRA (P < 0.05, P = 0.17, and P = 0.6, respectively). A greater percentage of segments were not accessible with QISS-MRA (19.5-20.1%) in comparison to CE-MRA (10.9%). Relative to DSA, sensitivity for QISS-MRA was high (100% versus 91.2% for CE-MRA, P = 0.24) in the evaluated segments; however, specificity (76.5%) was substantially less than that of CE-MRA (94.6%, P = 0.003). CONCLUSION: Overall image quality and specificity of QISS-MRA at 3T are diminished relative to CE-MRA. However, when image quality is adequate, QISS-MRA has high sensitivity and, thus, has potential use in patients with contraindications to gadolinium.

Clinical application of 3D VIBECAIPI-DIXON for non-enhanced imaging of the pancreas compared to a standard 2D fat-saturated FLASH.

PURPOSE: To compare a fast 3D VIBE sequence with Dixon fat saturation and CAIPIRINHA acceleration techniques (3D VIBE(CAIPI-DIXON)) to a standard 2D FLASH sequence with spectral fat saturation and conventional GRAPPA acceleration technique (2D Flash(GRAPPA-fs)) for non-enhanced imaging of the pancreas. METHODS AND MATERIALS: In this retrospective, institutional review board-approved intra-individual comparison study, 29 patients (7 female, 22 male; mean age 60.4 ± 20.9 years) examined on a 48-channel 3.0-T MR system (MAGNETOM Skyra VD 13, Siemens Healthcare Sector, Germany) were included. 3D VIBE(CAIPI-DIXON) (TR/TE-3.95/2.5+1.27 ms; spatial resolution-1.2 × 1.2 × 3.0 mm(3); CAIPIRINHA 2 × 2 [1], acquisition time-0:12 min) and 2D Flash(GRAPPA-fs) (TR/TE-195/3.69 ms; 1.2 × 1.2 × 3.0 mm(3); GRAPPA 2, 3 × 0:21 min) sequences were performed in each subject in random order prior to the administration of an intravenous contrast agent. Two radiologists evaluated the images with regard to diagnostic preference. Semi-quantitative signal ratios were calculated for the pancreas versus the liver, spleen, muscle, and visceral fat. Inter-reader agreement was calculated using unweighted Cohen's kappa. Signal ratio results were analyzed using a univariate analysis of variance. Additional signal-to-noise (SNR) measurements were performed in a phantom. RESULTS: 3D VIBE(CAIPI-DIXON) was preferred in 72.4% (both readers) and 2D Flash(GRAPPA-fs) in 3.4%/6.9% (reader 1/2) of cases with a kappa value of 0.756. The main reasons for this preference were homogenous fat saturation with 3D VIBE(CAIPI-DIXON) and reduced motion artifacts due to a faster acquisition, leading to improved delineation of the pancreas. Signal ratios of pancreatic to fat signal for 3D VIBE(CAIPI-DIXON) (10.08 ± 3.48) and 2D Flash(GRAPPA-fs) (6.53 ± 3.07) were statistically different (P<.001). However, no additional statistically significant differences in signal ratios were identified (range: 0.73 ± 0.18 to 1.37 ± 0.40; .514

In vivo sodium (23Na) imaging of the human kidneys at 7 T: preliminary results.

OBJECTIVE: To evaluate the feasibility of in vivo (23)Na imaging of the corticomedullary (23)Na gradient and to measure (23)Na transverse relaxation times (T2*) in human kidneys. METHODS: In this prospective, IRB-approved study, eight healthy volunteers (4 female, 4 male; mean age 29.4 ± 3.6 years) were examined on a 7-T whole-body MR system using a (23)Na-only spine-array coil. For morphological (23)Na-MRI, a 3D gradient echo (GRE) sequence with a variable echo time scheme (vTE) was used. T2* times were calculated using a multiecho 3D vTE-GRE approach. (23)Na signal-to-noise ratios (SNR) were given on a pixel-by-pixel basis for a 20-mm section from the cortex in the direction of the medulla. T2* maps were calculated by fitting the (23)Na signal decay monoexponentially on a pixel-by-pixel basis, using least squares fit. RESULTS: Mean corticomedullary (23)Na-SNR increased from the cortex (32.2 ± 5.6) towards the medulla (85.7 ± 16.0). The SNR increase ranged interindividually from 57.2% to 66.3%. Mean (23)Na-T2* relaxation times differed statistically significantly (P < 0.001) between the cortex (17.9 ± 0.8 ms) and medulla (20.6 ± 1.0 ms). CONCLUSION: The aim of this study was to evaluate the feasibility of in vivo (23)Na MRI of the corticomedullary (23)Na gradient and to measure the (23)Na T2* relaxation times of human kidneys at 7 T. KEY POINTS: • High field MR offers new insights into renal anatomy and physiology. • (23) Na MRI of healthy human kidneys is feasible at ultra-high field. • Renal (23) Na concentration increases from the cortex in the medullary pyramid direction. • In vivo measurements of renal (23) Na-T2* times are demonstrated at 7.0 T.

3T renal (23)Na-MRI: effects of desmopressin in patients with central diabetes insipidus.

PURPOSE: The purpose of this prospective study was to assess physiologic changes in the renal corticomedullary (23)Na-concentration ([(23)Na]) gradient with (23)Na-MRI at 3.0T in patients with central diabetes insipidus (CDI) before and after intranasal administration of 20 µg desmopressin (DDAVP). METHODS AND MATERIALS: Four patients with CDI (all male, mean age 60.2 years) were included in this IRB-approved study. For (23)Na-imaging, a 3D density adapted, radial GRE-sequence (TE = 0.55 ms; TR = 120 ms; projections = 8,000; spatial resolution = 5 × 5 × 5 mm(3)) was used in combination with a dedicated (23)Na-coil and reference phantoms. The corticomedullary [(23)Na] gradient (in mmol/L/mm) was calculated pixel-by-pixel along a linear region-of-interest (ROI) spanning from the renal cortex in the direction of the medulla. Mean ± SDs of [(23)Na] were calculated for each patient as well as for the entire group. RESULTS: Mean [(23)Na] increased along the corticomedullary gradient from the cortex (pre-DDAVP 38.0 ± 6.3 mmol/L vs. post-DDAVP 30.7 ± 3.5 mmol/L) to the medulla (pre-DDAVP 71.6 ± 14.8 mmol/L vs. post-DDAVP 59.7 ± 10.8 mmol/L). The overall mean decrease of [(23)Na] after DDAVP administration was 17.1 ± 1.1 %. CONCLUSION: (23)Na-MRI with state-of-the-art techniques at 3T depicts the physiologic renal response to the administration of desmopressin in patients with central diabetes insipidus.

Value of diffusion-weighted MR imaging for the detection of nephritis.

PURPOSE: To evaluate diffusion-weighted MR imaging (DWI-MRI) for the detection and assessment of infectious renal disease. MATERIALS AND METHODS: Twenty-one patients with suspicious increased signal intensity of the kidneys on DWI sequences and corresponding ADC decrease were identified. Sixty patients without clinical signs of renal infection served as a control group. All patients were examined with the following sequences: EPI-DWI (0/400/800 s/mm(2)), T2w HASTE, and T1w VIBE after intravenous injection of Gd-chelate. Confirmation of renal infection was established on the basis of clinical criteria. T1w and T2w images were assessed and compared to DWI for the presence of altered signal, and the degree of the visibility of pathology was graded on an ordinal three-point scale. RESULTS: In all 21 patients with positive DWI findings a renal infection could be confirmed. T2w imaging and contrast-enhanced T1w imaging displayed obvious pathologic signal in 3/21 (14%) and 11/19 (58%) patients and slightly pathologic signal in 17/21 (81%) and 7/19 (37%), respectively. The median visibility score of 2 for the DWI and the T1w images was significantly higher than the score of 1 for the T2w imaging, P = 0.0001 (DWI versus T2w) and P = 0.078 (T1w versus T2w). CONCLUSION: DWI of the kidneys seems to be highly sensitive for the detection of infections within the kidney.

Impact of field strength and RF excitation on abdominal diffusion-weighted magnetic resonance imaging.

AIM: To retrospectively and prospectively compare diffusion-weighted (DW) images in the abdomen in a 1.5T system and 3.0T systems with and without two-channel functionality for B1 shimming. METHODS: DW images of the abdomen were obtained on 1.5T and 3.0T (with and without two-channel functionality for B1 shimming) scanners on 150 patients (retrospective study population) and 10 volunteers (prospective study population). Eight regions were selected for clinical significance or artifact susceptibility (at higher field strengths). Objective grading quantified signal-to-noise ratio (SNR), and subjective evaluation qualified image quality, ghosting artifacts, and diagnostic value. Statistical significance was calculated using χ(2) tests (categorical variables) and independent two-sided t tests or Mann-Whitney U tests (continuous variables). RESULTS: The 3.0T using dual-source parallel transmit (dpTX 3.0T) provided the significantly highest SNRs in nearly all regions. In regions susceptible to artifacts at higher field strengths (left lobe of liver, head of pancreas), the SNR was better or similar to the 1.5T system. Subjectively, both dpTX 3.0T and 1.5T systems provided higher image quality, diagnostic value, and less ghosting artifact (P < 0.01, most values) compared to the 3.0T system without dual-source parallel transmit (non-dpTX 3.0T). CONCLUSION: The dpTX 3.0T scanner provided the highest SNR. Its image quality, lack of ghosting, and diagnostic value were equal to or outperformed most currently used systems.

Impact of time-resolved MRA on diagnostic accuracy in patients with symptomatic peripheral artery disease of the calf station.

OBJECTIVE: The purpose of this article is to evaluate the added diagnostic accuracy of time-resolved MR angiography (MRA) of the calves compared with continuous-table-movement MRA in patients with symptomatic lower extremity peripheral artery disease (PAD) using digital subtraction angiography (DSA) correlation. MATERIALS AND METHODS: Eighty-four consecutive patients with symptomatic PAD underwent a low-dose 3-T MRA protocol, consisting of continuous-table-movement MRA, acquired from the diaphragm to the calves, and an additional time-resolved MRA of the calves; 0.1 mmol/kg body weight (bw) of contrast material was used (0.07 mmol/kg bw for continuous-table-movement MRA and 0.03 mmol/kg bw for time-resolved MRA). Two radiologists rated image quality on a 4-point scale and stenosis degree on a 3-point scale. An additional assessment determined the degree of venous contamination and whether time-resolved MRA improved diagnostic confidence. The accuracy of stenosis gradation with continuous-table-movement and time-resolved MRA was compared with that of DSA as a correlation. Overall diagnostic accuracy was calculated for continuous-table-movement and time-resolved MRA. RESULTS: Median image quality was rated as good for 578 vessel segments with continuous-table-movement MRA and as excellent for 565 vessel segments with time-resolved MRA. Interreader agreement was excellent (κ = 0.80-0.84). Venous contamination interfered with diagnosis in more than 60% of continuous-table-movement MRA examinations. The degree of stenosis was assessed for 340 vessel segments. The diagnostic accuracies (continuous-table-movement MRA/time-resolved MRA) combined for the readers were obtained for the tibioperoneal trunk (84%/93%), anterior tibial (69%/87%), posterior tibial (85%/91%), and peroneal (67%/81%) arteries. The addition of time-resolved MRA improved diagnostic confidence in 69% of examinations. CONCLUSION: The addition of time-resolved MRA at the calf station improves diagnostic accuracy over continuous-table-movement MRA alone in symptomatic patients with PAD.

Steady state vascular imaging with extracellular gadobutrol: evaluation of the additional diagnostic benefit in patients who have undergone a peripheral magnetic resonance angiography protocol.

BACKGROUND: To evaluate the feasibility and additional diagnostic benefit of a high-resolution steady state 3D-volume interpolated breath-hold exam (VIBE) sequence between a continuous table movement (CTM) MR angiography of the entire runoff vasculature and a time-resolved (TWIST) MRA of the calves. METHODS: In this retrospective IRB approved study 224 patients (72 women, 152 men, mean age 67.29 ± 13.9) were included who had undergone a low-dose MR angiographic protocol at 3T (Siemens TimTrio) after injection of 0.1 mmol/kg gadobutrol including a CTM MRA, a time-resolved MRA of the calf station and a steady state 3D VIBE sequence prior to the time-resolved MRA. One board-certified radiologist rated the image quality of the steady state VIBE sequences on an ordinal three point scale (excellent, good, poor) and analyzed the images for additional diagnostic findings of and beyond the vascular system in comparison to the CTM MRA and the time-resolved MRA. Descriptive statistics and demographic patient data were used for further evaluation. RESULTS: The image quality of the steady state imaging of the pelvis, upper and lower leg was excellent in up to 88%, 84% and 47%, respectively, while poor image quality was only detected in the upper (2%) and lower leg (6%). An additional diagnostic benefit was found in 44% of the patients overall. The most common relevant pathologies included inflammatory processes of the soft tissues (26%), thrombi (14%), abscesses (13%) and tumors (11%). In subgroups of patients above the age of 60, 65, 70, 75 and 80 years an additional pathology was found in 50% 33%, 44%, 65% and 58%, respectively. There was no significant difference in terms of additional findings between men and women (46% and 39%, p > 0.05) and inpatients and outpatients (42% and 45%, p > 0.05). CONCLUSION: Steady state imaging is also feasible with extracellular contrast agents with good image quality yielding additional diagnostic findings in up to 44% and above in patients older than 60 years of age irrespective of gender or patient status. Given the short acquisition time of 4 minutes this sequence could be added to all peripheral MRA exams.

Comparison of Dynamic and Liver-Specific Gadoxetic Acid Contrast-Enhanced MRI versus Apparent Diffusion Coefficients.

BACKGROUND: Hepatic lesions often present diagnostic connundrums with conventional MR techniques. Hepatobiliary phase contrast-enhanced imaging with gadoxetic acid can aid in the characterization of such lesions. However, quantitative measures describing late-phase enhancement must be assessed relative to their accuracy of hepatic lesion classification. PURPOSE: To compare quantitative parameters in gadoxetic acid contrast-enhanced dynamic and hepatobiliary phase imaging versus apparent diffusion coefficients in hepatic lesion characterization. MATERIAL AND METHODS: 57 patients with focal hepatic lesions on gadoxetic acid MR were included. Lesion enhancement at standard post-contrast time points and in the hepatobiliary phase (HB; 15 and 25 minutes post-contrast) was assessed via calculation of contrast (CR) and enhancement ratios (ER). Apparent diffusion coefficient (ADC) values were also obtained. Values for these parameters were compared among lesions and ROC analyses performed. RESULTS: HB enhancement was greatest with FNH and adenomas. HB ER parameters but not HB CR could distinguish HCC from benign entities (0.9 ER ROC AUC versus 0.5 CR ROC AUC). There was no statistically significant difference found between the 15 and 25 minutes HB time points in detection of any lesion (p>0.4). ADC values were statistically significantly higher with hemangiomas (p<0.05) without greater accuracy in lesion detection relative to HB phase parameters. CONCLUSION: Hepatobiliary phase gadoxetic acid contrast-enhanced MR characterizes focal hepatic lesions more accurately than ADC and conventional dynamic post-contrast time point enhancement parameters. ER values are generally superior to CR. No discernible benefit of 25 minute versus 15 minute delayed imaging is demonstrated.