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Purpose To evaluate vessel assessment in virtual monoenergetic images (VMI40keV) and virtual-non-contrast images (VNC) derived from venous phase spectral detector computed tomography (SDCT) acquisitions in comparison to arterial phase and true non-contrast (TNC) images. Methods Triphasic abdominal SDCT was performed in 25 patients including TNC, arterial and venous phase. VMI40keV and VNC were reconstructed from the venous phase and compared to conventional arterial-phase images (CIart), TNC and conventional venous-phase images (CIven). Vessel contrast and virtual contrast removal were analyzed with region-of-interest-based measurements and in a qualitative assessment. Results Quantitative analysis revealed no significant attenuation differences between TNC and VNC in arterial vessels (p-range 0.07–0.47) except for the renal artery (p = 0.011). For venous vessels, significant differences between TNC and VNC were found for all veins (p p = 0.26), yet these differences remained within a 10 HU range in most patients. No significant attenuation differences were found between CIart/VMI40keV in arterial vessels (p-range 0.06–0.86). Contrast-to-noise ratio provided by VMI40keV and CIart was equivalent for all arterial vessels assessed (p-range 0.14–0.91). Qualitatively, VMI40keV showed similar enhancement of abdominal and pelvic arteries as CIart and VNC were rated comparable to TNC. Conclusion Our study suggests that VNC and VMI40keV derived from single venous-phase SDCT offer comparable assessment of major abdominal vessels as provided by routine triphasic examinations, if no dynamic contrast information is required.

Objectives Comprehensive training in ultrasound (US) imaging during radiology residency is crucial if radiologists are expected to maintain a substantial role in this widely used imaging modality. This study aimed to evaluate the current curriculum of US training among radiology residency programs across the country via a nationwide survey. Methods A 28-question survey was distributed among all academic radiology departments in the United States and their radiology residents. The survey consisted of 4 sections: general demographic information, training information, clinical competency, and adequacy of training (perspective). The Student t test and 1-way analyses of variance were performed to assess statistical significance. Results Overall, 256 residents from 32 states completed the questionnaire. Only 114 (45%) residents reported having a dedicated rotation for performing US studies. Although 228 (89%) of trainees believed they received adequate experience for interpreting US studies, only 66 (26%) of them had the same belief about performing them. Only 116 (45%) of the residents were comfortable operating the US machines in their departments. Higher years of residency training, having a dedicated rotation for performing US studies, and having more than 10 hours per year of didactic lectures and/or more than 5 hours per year of case conferences dedicated to US had a positive impact on the residents' clinical competency and perspective (all P Conclusions Most radiology residents do not feel confident in performing US examinations by themselves. However, higher clinical competency was reported in the residents who had dedicated rotations for performing US studies and received more hours of US lectures and case conferences throughout their residency.

Objective The purpose of the study was to investigate the potential added value of 18F-FDG-PET/MRI (functional information derived from PET) over standard diagnostic liver MRI (excellent soft tissue characterization) in diagnosing and staging suspected primary hepatobiliary malignancies including extrahepatic cholangiocarcinoma (ECC), intrahepatic cholangiocellular carcinoma (ICC) and gallbladder cancer (GBCA). Methods Twenty consecutive patients with suspected hepatobiliary malignancy were included in this retrospective study. All patients underwent combined whole-body (WB) 18F-FDG-PET/MRI including contrast-enhanced MRI of the liver, contrast-enhanced WB-MRI and WB 18F-FDG-PET. Two experienced readers staged hepatobiliary disease using TNM criteria: first based on MRI alone and then based on combined 18F-FDG-PET/MRI. Subsequently, the impact of FDG-PET/MRI on clinical management compared to MRI alone was recorded. Histopathologic proof served as the reference standard. Results Hepatobiliary neoplasms were present in 16/20 patients (ECC n = 3, ICC n = 8, GBCA n = 5), two patients revealed benign disease, two were excluded. TNM staging with 18F-FDG-PET/MRI was identical to MRI alone in 11/18 (61.1 %) patients and correctly changed the stage in 4/18 (22.2 %), resulting in a change in management for 2/4 patients (11.1 %). 18F-FDG-PET/MRI was false-positive in 3/18 cases (16.7 %). Both MRI and 18F-FDG-PET/MRI were falsely positive in 1 case without malignancy. Conclusions A small incremental benefit of 18F-FDG-PET/MRI over standard MRI of the liver was observed. However, in some cases 18F-FDG-PET/MRI may lead to false-positive findings. Overall there is seemingly limited role of 18F-FDG-PET/MRI in patients with suspected hepatobiliary malignancy.

Background In abdominal imaging, contrast-enhanced computed tomography (CT) examinations are most commonly applied; however, unenhanced examinations are still needed for several clinical questions but require additional scanning and radiation exposure. Purpose To evaluate accuracy of virtual non-contrast (VNC) from arterial and venous phase spectral-detector CT (SDCT) scans compared to true-unenhanced (TNC) images for the evaluation of liver parenchyma and vessels. Material and Methods A total of 25 patients undergoing triphasic SDCT examinations were included. VNC was reconstructed from arterial and venous phases and compared to TNC images. Quantitative image analysis was performed by region of interest (ROI)-based assessment of mean and SD of attenuation (HU) in each liver segment, spleen, portal vein, common hepatic artery, and abdominal aorta. Subjectively, iodine subtraction and diagnostic assessment were rated on 5-point Likert scales. Results Attenuation and image noise measured in the liver from VNC were not significantly different from TNC (TNC: 54.6 ± 10.8 HU, VNC arterial phase: 55.7 ± 10.8 HU; VNC venous phase: 58.3 ± 10.0 HU; P > 0.05). VNC also showed accurate results regarding attenuation and image noise for spleen, portal vein, and abdominal aorta. Only iodine subtraction in the common hepatic artery in the arterial phase was insufficient which was confirmed by the subjective reading. Apart from that, subjective reading showed accurate iodine subtraction and comparable diagnostic assessment. Conclusion VNC from the arterial and venous phases were very similar to TNC yielding mostly negligible differences in attenuation, image noise, and diagnostic utility. Inadequate iodine subtraction occurred in hepatic arteries in the arterial phase.

Objectives: To evaluate the added value of spectral results derived from Spectral Detector CT (SDCT) to the characterization of renal cystic lesions (RCL). Methods: This retrospective study was approved by the local Institutional review board. 70 consecutive patients who underwent abdominopelvic SDCT and had at least one RCL were included. 84 RCL were categorized as simple, complex or neoplastic based on attenuation values on single-phase post-contrast images. Attenuation values were measured in each lesion on standard conventional CT images (stCI) and virtual monoenergetic images of 40keV and 100keV. A spectral curve slope was calculated and intra lesional iodine concentration (IC) was measured using iodine-density maps. Reference standard was established using histopathologic correlation, prior and follow-up imaging. Analysis of variance (ANOVA) was used to compare between the groups. Results: Mean attenuation values for benign simple and complex RCL differed significantly (42 ± 16 vs 8 ± 3 HU; p < 0.001). IC was almost identical in benign simple and complex RCL (0.23 ± 0.04 mg ml−1 vs 0.24 ± 0.04 mg ml−1), while IC in neoplastic RCL was significantly higher (2.10 ± 0.08 mg ml−1 ; p < 0.001). The mean spectral curve slope did not differ significantly between simple and complex RCL (0.30 ± 0.03 vs 0.33 ± 0.05) but was significantly higher in neoplastic RCL (2.60 ± 0.10; p < 0.001). Conclusions: Spectral results of SDCT are highly promising in distinguishing benign complex RCL from enhancing neoplastic RCL based on single-phase post-contrast imaging only. Advances in knowledge: SDCT can assist in differentiating between benign complex and neoplastic renal cystic lesions.

Small bowel (SB) diverticulosis is a rare disorder that may entail serious complications, including SB diverticulitis. Both are often missed in imaging. Magnetic resonance enterography/enteroclysis (MRE) is increasingly used to assess SB disease; awareness of the appearance of SB diverticulitis is essential to ensure appropriate management. Our aim was to systematically describe imaging characteristics of SB diverticulosis and diverticulitis in MRE. This retrospective, HIPAA-compliant study identified 186 patients with suspected SB diverticulosis/diverticulitis in medical databases of two tertiary medical centres between 2005 and 2011. Patients with surgically confirmed diagnoses of SB diverticulosis/diverticulitis were included. Two observers analyzed MR images for the presence, location, number, and size of diverticula, wall thickness, and mural and extramural patterns of inflammation. Seven patients were recruited. MRI analysis showed multiple diverticula in all (100 %). Diverticular size ranged from 0.5 to 6 cm. Prevalence of diverticula was higher in the proximal than the distal SB (jejunum 86 %, ileum 57 %, distal ileum43%). Diverticulitis occurred in 3/7 patients (43 %) showing asymmetric bowel wall thickening and focal mesenteric inflammation. SB diverticulitis demonstrates characteristic MRE imaging features to distinguish this rare disorder from more common diseases. Asymmetric, focal mesenteric and mural inflammation and presence of multiple diverticula are keys to diagnosis. • Small bowel diverticulosis and diverticulitis is rare and often missed in imaging • Acquired small bowel diverticula are variable in size and number • Small bowel diverticulitis demonstrates characteristic features on MR enterography/enteroclysis • A focal or segmental asymmetric small bowel inflammation should prompt the search for diverticula

Castleman disease (CD) is a rare lymphoproliferative disorder of unknown etiology that may occur anywhere in the lymphatic system. Imaging plays an important role in detecting and staging this disease. Positron Emission Tomography/Magnetic Resonance Imaging (PET/MRI) combines the metabolic information derived from nuclear medical imaging with the high soft tissue resolution from MRI. We review the features of CD in standard diagnostic imaging, analyze the specific imaging findings of CD in FDG-PET/MRI and discuss a potential benefit of PET/MRI based on the case of a 15-year-old female patient with retroperitoneal CD.

Purpose To evaluate the role of 3T-MRI–guided adaptive high-dose-rate (HDR) combined intracavitary and interstitial brachytherapy for cervical cancer using a novel intracavitary split-ring (ICSR) applicator adapter. Methods and Materials We retrospectively reviewed all HDR brachytherapy cases from 2013 to 2015 using an ICSR applicator. Initial optimization was performed using 3T multiparametric MRI (mpMRI) series with an applicator in place. The mpMRI series were discretionarily acquired before subsequent fractions for possible target adaptation. When necessary, interstitial needles (ISNs) were inserted through a novel ICSR adapter or freehand. Dosimetric parameters, clinical outcomes, and toxicities were compared between groups. Results Seventeen patients were included, with a mean followup of 32 months. An mpMRI series preceded each initial fraction and 52.9% of patients underwent ≥1 additional pretreatment mpMRI. Among these subsequent fractions, the high-risk clinical target volume was reduced in 80% vs. 41% without pretreatment mpMRI. Five patients had ISN placement (seven insertions) to improve extracervical target coverage. Mean D90 (Gy) per fraction to the high-risk clinical target volume and intermediate-risk clinical target volume with and without an ISN were 7.51 ± 1.07 vs. 6.14 ± 0.52 (p = 0.028) and 6.35 ± 0.75 vs. 5.21 ± 0.49 (p = 0.007), respectively. Mean fractional D2cc (Gy) for organs at risk was comparable. No Grades 3–4 toxicity was reported. Disease-free survival and local control for the ICSR-ISN and ICSR-alone groups were 29.8 months/80.0% and 31.2 months/83.3%, respectively. Conclusions The mpMRI acquisition with ICSR applicator in place immediately before HDR brachytherapy for cervical cancer guided successful adaptive treatment optimization and delivery. Our initial experience with a novel interstitial adapter for the split-ring applicator demonstrated excellent target coverage without compromising organs at risk, resulting in good local control and disease-free survival.

Introduction Positron emission tomography-magnetic resonance imaging (PET-MRI) is increasingly used in the clinical setting of oncologic malignancies. Comparing PET/computed tomography (CT) and PET-MR in oncologic diseases, an overall good to excellent correlation is reported by most published articles in this field. The individual value of PET-MR for distinct oncologic diseases in the abdomen, however, is still under investigation. This article (1) reviews the established role and value of PET and MRI as individual imaging modalities in the workup of certain oncologic diseases within the abdomen and (2) reports our initial experience in this field to provide a perspective of the potential future role and expected value of PET-MR in these clinical scenarios.

PET/MRI is a new hybrid modality which is increasingly being used in clinical settings, although both clinical evaluation and technical optimization are still an ongoing process. Initial experience with this new imaging device proves promising for oncologic applications. Other clinical indications in the field of cardiac imaging and neuroimaging are also being explored. This article aims to review the current status of PET/MRI and its value in oncologic applications, and summarizes our own preliminary experience in this field.

Background Tissue-specific gadolinium-based contrast agents such as Gd-BOPTA, Gd-EOB-DTPA are increasingly used for liver imaging. Despite the added value of the hepatobiliary phase a proper arterial phase is still critical, especially in patients with chronic liver diseases. So far, there are limited data in the literature about the effect of the injection speed of Gd-EOB-DTPA in liver and vessel enhancement. Purpose To evaluate the effect of injection rate on the enhancement of liver parenchyma and vasculature in Gd-EOB-DTPA-enhanced liver MRI. Material and Methods Eighty patients who underwent Gd-EOB-DTPA-enhanced liver MRI (1.5T multichannel MR-system) were retrospectively evaluated. We used a Care Bolus technique with an injection rate of 2 mL/s in group 1 ( n = 40) and a Care Bolus technique with an injection rate of 1 mL/s in group 2 ( n = 40) to determine the start of the arterial-dominant phase. Signal intensities were measured in vascular structures and liver parenchyma. Signal-to-noise-ratio (SNR), SNR increase (SNRi), and percentage enhancement (PE) were calculated and compared by a students t-test. Results The SNR, SNRi, and PE of the aorta in the arterial phase were significantly higher in group 2 in comparison to group 1 ( P = 0.007, P = 0.0043, and P < 0.001, respectively). There were no significant differences concerning the SNR, SNRi, or PE of the portal vein and the normal liver parenchyma between both groups at all time points. Conclusion The study shows that a lower injection rate of 1 mL/s enables a higher enhancement in the aorta in the arterial phase compared with Gd-EOB-DTPA-enhanced MRI with the more commonly used injection rate of 2 mL/s.

The aim of this study is to determine MRI characteristics which indicate liver metastases of neuroendocrine tumors (NET) rather than metastases of other origin (non-NET).Sixty-nine patients with histopathologically proven liver metastases from NET and 69 patients with known liver metastases of other origin underwent MRI of the liver using a 1.5 T MR-scanner. Two board certified radiologists assessed presence of fluid-fluid-levels, number and distribution pattern, signal intensity (SI) characteristics, lesion homogeneity, presence of central necrosis and intratumoral hemorrhage in T2w and T1w non-contrast imaging. A multivariate logistic regression analysis was performed to determine the independent association of image findings and occurrence of NET.Fluid-fluid-levels were identified in 19/69 of patients with NET-metastases, and in none of the patients in the control group (p0.0001). Hyperintense SI in T1w imaging, markedly hyperintense SI in T2w imaging, a disseminated distribution pattern and intratumoral hemorrhage were indicative of NET metastases (p0.05). After statistical adjustment for all significant MRI findings, fluid-fluid-levels (OR: 17.6, 95% CI: 1.9-166.5), strongly hyperintense SI in T2w (OR: 4.7, 95% CI: 1.8-12.7) and a disseminated distribution pattern (OR: 2.9, 95% CI: 1.1-7.4) were independent predictors for NET metastases.The presence of fluid-fluid-levels is highly indicative of NET liver metastases and can be used as an independent predictor to distinguish them from metastases of other origin.

To prospectively compare findings of magnetic resonance (MR) lymphangiography with those of lymphoscintigraphy, evaluate the pattern and delay of lymphatic drainage, compare typical findings, and investigate discrepancies between the techniques.This prospective study was performed according to the Declaration of Helsinki and was approved by the local ethics committee. Thirty consecutive patients with uni- or bilateral lymphedema and lymph vessel transplants of the lower extremities were examined with 3.0-T fat-saturated three-dimensional gradient-echo MR after gadopentetate dimeglumine injection. Results of all examinations were correlated with corresponding results of lymphoscintigraphy examinations. Results of both techniques were separately reviewed in consensus by a radiologist and a nuclear physician, who rated delay and pattern of drainage, number of enhancing levels, and quality of conspicuity of the depiction of lymph nodes and lymph vessels. Sensitivity and specificity were calculated by using combined results of both techniques and clinical presentation findings as reference standard. Correlation was calculated with weighted k coefficients.Weak lymphatic drainage at lymphoscintigraphy correlated with lymphangiectasia at MR lymphangiography (13 of 33 affected extremities). Lymph vessels were clearly visualized with MR lymphangiography (five of 24 affected extremities), while they were not detectable with lymphoscintigraphy. Depiction of inguinal lymph nodes was clearer with lymphoscintigraphy (five of 60 extremities). Correlation of both techniques was excellent for delay (κ=0.93) and pattern (κ=0.84) of drainage, good for depiction of lymph nodes (κ=0.67) and number of enhancing levels (κ=0.77), and moderate for depiction of lymph vessels (κ=0.50). Sensitivity and specificity for delay and pattern of drainage were concordant, whereas MR lymphangiography showed a higher sensitivity for lymph vessel abnormalities (100% vs 79%) and lower specificity for lymph node abnormalities (78% vs 100%).Imaging findings of MR lymphangiography and lymphoscintigraphy show a clear concordance. With lymphoscintigraphy, better visualization of inguinal lymph nodes was achieved, whereas with MR lymphangiography, better depiction of lymph vessels and morphologic features of lymph vessel abnormalities were achieved.

To clinically evaluate MRI of the knee using a highly resolved isotropic fat-saturated (fs) proton-density weighted 3D-TSE-sequence (SPACE) at 3T.Imaging was performed on a 3T-scanner (Magnetom TRIO). For technical evaluation, sagittally orientated SPACE-datasets (repetition-time [TR], 1200 milliseconds/[TE], 30 milliseconds/voxel-size, 0.5 mm3/acquisition time, 10:35 minutes) were acquired from the dominant knee of 10 healthy volunteers. In the 3 major anatomic planes, 0.5, 1, and 2 mm thick reconstructions were performed. Signal-to-noise (SNR), SNR-efficiency, contrast-to-noise (CNR) ratios, and anatomic detail visualization were compared with a state-of-the-art 2D-TSE-sequence in 3 imaging planes (TR, 3200 milliseconds/TE, 30 milliseconds/acquisition time, 12:34 minutes). Sixty patients with cartilage and meniscus pathologies were examined with these techniques. Patient SPACE-datasets were assessed in 1-mm thick reconstructions. Arthroscopical correlation was available for 18 patients. Lesion detection and diagnostic confidence were assessed by 2 radiologists independently. Statistical analysis was performed using 95% confidence intervals, Wilcoxon signed rank tests, and Weighted-kappa.SNR-efficiency of SPACE was 4 to 5 times higher than for 2D-TSE-sequences. SNR and CNR of 1-mm thick SPACE-reconstructions were comparable to 2D-TSE-sequences and provided superior visualization of small structures such as meniscal roots.Correlation with arthroscopy did not show significant differences between 2D- and 3D-sequences. One reader detected significantly more cartilage abnormalities with the 2D-TSE-sequence (131 vs. 151, P = 0.04), probably because of an unfamiliar fluid/cartilage contrast. Diagnostic confidence was significantly higher for meniscus abnormalities for SPACE for 1 reader. Intersequence-correlation was excellent (kappa = 0.82-0.92). Interreader-correlation was good to excellent (kappa = 0.71-0.80), intrareader-correlation was excellent (kappa = 0.90-0.92) for both sequences.Time-efficient 3D-TSE-imaging of the knee at 3T is feasible with adequate SNR and CNR and excellent anatomic detail visualization. Detection and visualization of meniscus and cartilage pathologies is comparable to standard 2D-TSE-sequences. 3D-TSE-sequences with consecutive multiplanar reconstruction may become a valuable component of future knee-MRI protocols.

Time-resolved pulmonary perfusion MRI requires both high temporal and spatial resolution, which can be achieved by using several nonconventional k-space acquisition techniques. The aim of this study is to compare the image quality of time-resolved 3D pulmonary perfusion MRI with different k-space acquisition techniques in healthy volunteers at 1.5 and 3 T.Ten healthy volunteers underwent contrast-enhanced time-resolved 3D pulmonary MRI on 1.5 and 3 T using the following k-space acquisition techniques: (a) generalized autocalibrating partial parallel acquisition (GRAPPA) with an internal acquisition of reference lines (IRS), (b) GRAPPA with a single "external" acquisition of reference lines (ERS) before the measurement, and (c) a combination of GRAPPA with an internal acquisition of reference lines and view sharing (VS). The spatial resolution was kept constant at both field strengths to exclusively evaluate the influences of the temporal resolution achieved with the different k-space sampling techniques on image quality. The temporal resolutions were 2.11 seconds IRS, 1.31 seconds ERS, and 1.07 VS at 1.5 T and 2.04 seconds IRS, 1.30 seconds ERS, and 1.19 seconds VS at 3 T.Image quality was rated by 2 independent radiologists with regard to signal intensity, perfusion homogeneity, artifacts (eg, wrap around, noise), and visualization of pulmonary vessels using a 3 point scale (1 = nondiagnostic, 2 = moderate, 3 = good). Furthermore, the signal-to-noise ratio in the lungs was assessed.At 1.5 T the lowest image quality (sum score: 154) was observed for the ERS technique and the highest quality for the VS technique (sum score: 201). In contrast, at 3 T images acquired with VS were hampered by strong artifacts and image quality was rated significantly inferior (sum score: 137) compared with IRS (sum score: 180) and ERS (sum score: 174). Comparing 1.5 and 3 T, in particular the overall rating of the IRS technique (sum score: 180) was very similar at both field strengths. At 1.5 T the peak signal-to-noise ratio of the ERS was significantly lower in comparison to the IRS and the VS technique (14.6 vs. 26.7 and 39.6 respectively, P0.004).Using the IRS sampling algorithm comparable image quality and SNR can be achieved at 1.5 and 3 T. At 1.5 T VS offers the best possible solution for the conflicting requirements between a further increased temporal resolution and image quality. In consequence the gain of increased scanning efficiency from advanced k[r]-space sampling acquisition techniques can be exploited for a further improvement of image quality of pulmonary perfusion MRI.

Dynamic susceptibility contrast MRI (DSC-MRI) is the current standard for the measurement of Cerebral Blood Flow (CBF) and Cerebral Blood Volume (CBV), but it is not suitable for the measurement of Extraction Flow (EF) and may not allow for absolute quantification. The objective of this study was to develop and evaluate a methodology to measure CBF, CBV, and EF from T1-weighted dynamic contrast-enhanced MRI (DCE-MRI). A two-compartment modeling approach was developed, which applies both to tissues with an intact and with a broken Blood-Brain-Barrier (BBB). The approach was evaluated using measurements in normal grey matter (GM) and white matter (WM) and in tumors of 15 patients. Accuracy and precision were estimated with simulations of normal brain tissue. All tumor and normal tissue curves were accurately fitted by the model. CBF (mL/100 mL/min) was 82 +/- 21 in GM and 23 +/- 14 in WM, CBV (mL/100 mL) was 2.6 +/- 0.8 in GM and 1.3 +/- 0.4 in WM. EF (mL/100 mL/min) was close to zero in GM (-0.009 +/- 0.05) and WM (-0.03 +/- 0.08). Simulations show an overlap between CBF values of WM and GM, which is eliminated when Contrast-to-Noise (CNR) is improved. The model provides a consistent description of tracer kinetics in all brain tissues, and an accurate assessment of perfusion and permeability in reference tissues. The measurement sequence requires optimization to improve CNR and the precision in the perfusion parameters. With this approach, DCE-MRI presents a promising alternative to DSC-MRI for quantitative bolus-tracking in the brain.

The appropriate staging of malignant tumors is increasingly important as new therapeutic strategies develop. Because metastatic involvement of the liver in extrahepatic malignant disease may significantly change therapeutic approach, it is important to rule out such involvement with high confidence. Moreover, the differentiation between incidental benign lesions, such as hemangioma, focal nodular hyperplasia (FNH), or adenoma, is of high interest. Magnetic resonance (MR) imaging has proved reliable for diagnostic work-up of the liver. Liver-specific contrast agents have been especially helpful in detecting and precisely characterizing focal liver lesions, but the use of these agents has been limited because it has not been possible to perform both proper vascular phase and liver-specific phase within a reasonable time frame and in a single examination after a single injection of contrast agent. However, the hepatobiliary contrast agent gadolinium-ethoxybenzyl (Gd-EOB)-DTPA now allows combined dynamic imaging and hepatocyte-specific imaging in one examination. Gd-EOB-DTPA can be injected as a bolus and shows the enhancement characteristics and vascularity of liver lesions. In the delayed phase, which is acquired most appropriately 20 min after injection, Gd-EOB-DTPA is taken up selectively by functioning hepatocytes. Thus, malignant liver lesions, e.g. metastases, are spared from contrast uptake of the surrounding liver parenchyma. These lesions are hypointense in contrast to the surrounding bright liver. We review the current literature and present a practical approach to Gd-EOB-enhanced MR imaging using imaging examples of patients with liver metastases.

We report our initial clinical experience from a pilot study to compare the diagnostic accuracy of hybrid PET/MRI with PET/CT in colorectal cancer and discuss potential PET/MRI workflow solutions for colorectal cancer. Patients underwent both FDG PET/CT and PET/MRI (Ingenuity TF PET/MRI, Philips Healthcare) for rectal cancer staging or colorectal cancer restaging. The PET acquisition of PET/MRI was similar to that of PET/CT whereas the MRI protocol was selected individually based on the patient’s medical history. One nuclear medicine physician reviewed the PET/CT studies and one radiologist reviewed the PET/MRI studies independently. The diagnostic accuracy of each modality was determined in consensus, using available medical records as a reference. Of the 12 patients enrolled, two were for initial staging and ten for restaging. The median scan delay between the two modalities was 60 min. The initial imaging was PET/CT in nine patients and PET/MRI in three patients. When PET/CT was performed first, the SUV values of the 16 FDG avid lesions were greater at PET/MRI than at PET/CT. In contrast, when PET/MRI was performed first, the SUV values of the seven FDG avid lesions were greater at PET/CT than at PET/MRI. PET/MRI provided more detailed T staging than PET/CT. On a per-patient basis, with both patient groups combined for the evaluation of N and M staging/restaging, the true positive rate was 5/7 (71%) for PET/CT and 6/7 (86%) for PET/MRI, and true negative rate was 5/5 (100%) for both modalities. On a per-lesion basis, PET/CT identified 26 of 29 (90%) tumor lesions that were correctly detected by PET/MRI. Our proposed workflow allows for comprehensive cancer staging including integrated local and whole-body assessment. Our initial experience shows a high diagnostic accuracy of PET/MRI in T staging of rectal cancer compared with PET/CT. In addition, PET/MRI shows at least comparable accuracy in N and M staging as well as restaging to PET/CT. However, the small sample size limits the generalizability of the results. It is expected that PET/MRI would yield higher diagnostic accuracy than PET/CT considering the high soft tissue contrast provided by MRI compared with CT, but larger studies are necessary to fully assess the benefit of PET/MRI in colorectal cancer.

Purpose To investigate the image quality and vessel depiction of renal MRA with integrated parallel imaging techniques (iPAT) using acceleration factors of 2 and 3. Materials and Methods In this prospective study renal MRA was performed on 14 and 12 patients with acceleration factors of 3 and 2, respectively. For the MRA a 3D-GRE sequence with an acquired spatial resolution of 0.9 × 0.8 × 1.0 mm3 was applied (TR/TE = 3.79 msec/1.39 msec, FOV = 400 mm × 320 mm, acquired matrix = 512 × 384, flip angle = 25°) on a 32-channel 1.5T MR scanner. The acquisition time was 26 seconds with iPAT 2, and 19 seconds with iPAT3. All parameters other than acquisition time and acceleration factor were kept constant. To assess the signal-to-noise ratio (SNR) we performed repetitive phantom measurements using iPAT 2 and 3. The images were rated by two radiologists in terms of noise, artifacts, and the quality of vessel depiction for the proximal, segmental, and subsegmental renal artery. A Mann-Whitney U-test and kappa-test were used for statistical analysis. Results SNR decreased significantly with iPAT 3 in the phantom measurements. The two readers found no difference in noise, but significantly fewer artifacts with iPAT 3. The depiction of segmental vessels was significantly better for both readers with iPAT 3, and the subsegmental vessels were rated significantly better by one reader. iPAT 3 also resulted in a better interreader agreement. Conclusion The use of iPAT 3 for renal MRA enables a better depiction of the distal parts of the renal artery. The decrease in SNR is not diagnostically impairing. J. Magn. Reson. Imaging 2006. © 2006 Wiley-Liss, Inc.

Objective: The objective of this study was to improve delineation of small and large bowel (SB, LB) anatomy and pathology with postoperative or complex multisegmental inflammatory changes using dual-contrast-technique (DCT) for magnetic resonance enteroclysis (MRE) with luminal contrast media of opposed signal characteristics. Materials and Methods: Sixty patients underwent MRE with iron oxide-based negative contrast in the SB. Thirty patients received additional rectal instillation of water for positive contrast (DCT). Two observers evaluated the degree of distention and the ease of identification of bowel anatomy and pathologies (none n = 22, stenosis n = 16, abscess n = 4, fistulae n = 5, postoperative changes and adhesions n = 13) using a 4-point scale. Mann-Whitney U-test and kappa statistics were applied. Results: LB and the terminal ileum were significantly better distended and identified with DCT (P ≤ 0.0001; P = 0.034). Interobserver agreement improved with DCT for all pathologies except for "prestenotic dilatation." Conclusions: Comprehensive MR imaging of SB and LB with DCT improves the identification of modified anatomy and most pathologies in inflammatory and postsurgical bowel.

The aim of this prospective, multireader trial was to investigate image quality and vascular delineation of cranial multislice CT angiography (MSCTA) to identify strengths and weaknesses of the method. Sixty consecutive patients underwent standardized cranial MSCTA. The mean estimated effective dose was 0.96±0.11 mSv. Three masked readers independently graded image quality parameters and vascular delineation on a 5-point scale. Vascular attenuation values and dose-length products were assessed quantitatively. Quantitative parameters were evaluated with a proportional odds regression model with bootstrapped standard errors to adjust the relevant standard errors for correlation within subjects and across readers. The non-parametric Wilcoxon sign-rank test was applied for quantitative measurements. Good to excellent ratings were observed regarding image quality parameters and vascular delineation. The delineation of veins was rated higher than that of arteries (OR 2.00). Smaller arterial segments were rated significantly less favorably than larger segments (OR up to 26.98). Moreover, the cavernous sinus, the C2 segment of the ICA and the communicating arteries demonstrated lower scores. Attenuation values were >240 HU and vessel-to-parenchyma ratios >7 in all vessels. Cranial MSCTA achieved high ratings regarding image quality and vascular delineation. Relative weaknesses were found in small arterial subsegments and in vessels in close topographical proximity to bone.

Meningeal carcinomatosis remains a challenging diagnosis to make, with both cerebrospinal fluid (CSF) analysis and radiological methods having a limited sensitivity. We aimed at describing a possible diagnostic sign of multislice CT angiography (MS-CTA) in the diagnosis of meningeal carcinomatosis. Upon retrospective analysis of MSCT angiographies of the brain, a conspicuous sign of the vessels of the interhemispheric fissure was noted in five patients. Cranial MSCT angiographies were performed with a standardized protocol (120 kV, 200 mA s, collimation of 4×1 mm, table feed per rotation 4 mm). We injected 120 ml of nonionic contrast medium as a bolus, and data acquisition was started after a fixed delay of 35 s. In order to elucidate the finding, correlation with clinical follow-up and/or CSF findings was performed for all patients. In five patients there was a blurring, an increased number, and a pathologic configuration of the vessels of the interhemispheric fissure. All five patients with this sign had clinical signs and symptoms of meningeal carcinomatosis. Three patients had positive CSF cytology, one further patient had follow-up spinal MRI 6 weeks later demonstrating meningeal carcinomatosis. One patient declined lumbar puncture. MS-CTA has the capacity to demonstrate a pathologic configuration of the vessels of the interhemispheric fissure in patients with meningeal carcinomatosis. This sign may serve as an indicator of meningeal carcinomatosis and should raise the suspicion of this disease entity.

Purpose To compare high-resolution T2-weigthed images of the liver with and without integrated parallel acquisition techniques (iPAT) using either breath-hold sequences in combination with prospective acquisition motion correction (PACE) or respiratory triggering. Materials and Methods Ten volunteers and 10 patients underwent each four different high-resolution fast spin echo (FSE) T2-weigthed sequences with 5 mm slice thickness and a full 320 matrix: a multi-breath-hold FSE sequence with and without iPAT and PACE and a respiratory-triggered FSE sequence with and without iPAT. Image quality was rated with a five-point scale by two independent readers. Signal intensity measurements were performed on a water phantom. Results The sequences with iPAT required a substantially shorter acquisition time without loss of image quality. Overall image quality was rated equal for all sequences by both readers. Image time for nine slices with iPAT was 13 seconds (19 seconds without iPAT) with multi-breath-hold and on average 4:00 minutes (7:02 minutes without iPAT) with respiratory triggering. Imaging with the PACE technique resulted in more correct positioning of the image stacks. Conclusion T2-weighted fast imaging with iPAT is feasible and results in high-quality images within a short acquisition time. Overall image quality is not negatively affected by iPAT. J. Magn. Reson. Imaging 2004;20:443–450. © 2004 Wiley-Liss, Inc.

Introduction Thehuman pelvis harbors a variety of organs and structures that can be at the origin of developing neoplasms. The clinical and diagnostic workup, the staging, and the appropriate treatment and disease follow-up of these neoplasms are diverse and complex anddependon the organ and tumor type, among other factors. Similarly, the individual diagnostic algorithms and the value of imaging in these algorithms vary between organs and tumor types. The possibility to directly access the target tissue and organ via percutaneous, transrectal, transvaginal, or transurethral approaches offers many options for the diagnosis and staging of the disease and may make one think that imaging is a less requested diagnostic tool. At the same time, a large variety of imaging modalities are nowadays available to assist in the diagnostic workup of oncologic diseases in general and in the diseases of the pelvis in particular. Although constantly improving imaging technology and newly developing imaging techniques are at the disposition of the clinician, oftentimes their diagnostic effect and evidence-based value seem underestimated or remain to be determined. Conversely, for many oncologic diseases of the pelvis, the value of imaging in diagnosing and staging is well established, documented, and accepted knowledge. Ultrasound (US) of the female pelvis, as an example, is a cost-effective and widely and readily available imaging tool, providing comprehensive information in most instances, despite being operator dependent. The endovaginal approach significantly improves its diagnostic performance. Computed tomography (CT) is the standard of care to assess the metastatic spread of disease for pelvic malignancies. To complement the diagnostic value of CT with functional

Purpose: The present study was performed to evaluate the utility of axial, coronal and sagittal multiplanar reformations (MPR) and maximum intensity projections (MIP) in the detection of pulmonary nodules as compared to axial standard reconstructions (SR). Materials and Methods: 103 patients with suspicion or evidence of pulmonary nodules underwent multidetector-row computed tomography (MDCT; Somatom plus 4 Volume Zoom, Siemens, Germany) of the chest in a single-breath-hold technique. The raw data were acquired with a collimation of 1 mm and a pitch of 6 and underwent reconstruction with 0.6mm increment. MPR and MIP in three planes [5 mm slice thickness (SL), 4 mm increment] were calculated from the raw data and compared to axial SR (5 mm SL). Three blinded observers evaluated the number, size and the quality of depiction of pulmonary nodules according to a 3-point confidence scale (1 = certain, 2 = probable , 3 = uncertain). Four patient groups were formed using the axial SR. Group 1 presenting no nodules, group 2 presenting probable nodules and group 3 presenting definitively lung nodules. Patients with more than 7 pulmonary nodules (group 4) were not included in the study. The 1 mm slice was used as the gold standard. Results: Inter-observer correlation was good at r=0.77. MIP were superior in the depiction of pulmonary nodules at a statistically significant level of p

Purpose: Assessment of 3 different rectal contrast agents (water, methylcellulose, ultrasound gel) for their suitability for colorectal imaging in multislice CT (MS-CT). Methods: 115 patients with colorectal diseases underwent MS-CT with varying, rectal contrast agents in a prospective study. Images were assessed by 2 independent CT-experienced radiologists. 6 criterias were evaluated, using a 5-point scale. Results: Methylcellulose (MC) proved to be significantly superior to ultrasound gel (US). Especially, differentiation of healthy and diseased bowel and bowel wall and lumen were aided, which was proven by quantitative analysis of attenuation values. Rectal distension is greater using MC or US than for water. More proximal parts of the colon could be better distended with water. The interobserver correlation was good (kappa 0.76). Conclusions: Rectal filling with MC significantly improves diagnostic confidence in colorectal examinations. Ease of administration and lack of problems suggest its use as a clinical routine tool.

Purpose: System-related complications in surgically implanted catheter-port systems (CPS) for intraarterial (i.a.) chemotherapy are well known. In most cases of complications, the treatment must be interrupted and the catheter-port system must be repaired surgically. We describe microinvasive interventional radiological procedures to correct some dysfunctions of CPS. Methods: Five patients with repetitive dysfunction of CPS were treated with interventional techniques. Two patients presented with perfusion impairment, one patient had a pseudoaneurysm of the hepatic artery, and two patients presented with catheter displacement. Radiological interventions included mechanical recanalization with a guidewire, vascular stenting, and correction of catheter dislocation with a gooseneck snare. Results: In all cases, correct function of the CPS was restored. No intervention-related complications occurred and surgery was avoided. Chemotherapy could be continued for a period of 4–10 months. Conclusion: For some system-related complications, minimally invasive radiological interventions can be used to restore the function of CPS for i.a. chemotherapy.

Fragestellung: Die perkutane interventionellradiologische und die chirurgische Implantation von venosen Port-Katheter-Systemen werden beschrieben und ihre Ergebnisse werden vergleichend gegenubergestellt. Methode: Bei 53 Patienten mit maligner Grunderkrankung wurde interventionell-radiologisch ein Port-Katheter-System in der V. subclavia zur zentralvenosen Chemotherapie implantiert. Technisches Vorgehen, Implantationsdauer, Funktionsdauer sowie die Komplikationsraten wurden mit Ergebnissen der chirurgischen Implantation verglichen. Ergebnisse: Die Implantation war in allen Fallen erfolgreich. Die mittlere Dauer der Masnahme betrug 36 min (20–55 min), die mittlere Funktionsdauer der Systeme 189 Tage (7–518 Tage). Die Funktionsrate betrug 92,5% bei einer Komplikationsrate von 15% (8/53). In 3 Fallen (5,7%) trat ein Pneumothorax auf, in 2 Fallen (3,8%) eine Infektion, in 2 weiteren Fallen eine Okklusion bzw. ein Katheterdefekt und in 1 Fall (1,8%) eine unkomplizierte Wunddehiszenz. Bei 12/53 Patienten (22,6%) wurde das Port-Katheter-System explantiert, davon in 4 Fallen (7,6%) komplikationsbedingt. Schlusfolgerungen: Die interventionell-radiologische Implantation von zentralvenosen Langzeit-Port-Katheter-Systemen ist in Technik und Komplikationsrate der chirurgischen Methode vergleichbar.

PURPOSE To compare softcopy and hardcopy reading of chest radiographs a software tool was designed for creating lesions with clearly defined size, location and contrast. METHOD An ROC study was performed using a set of chest radiographs with 300 simulated small nodules and linear details displayed on film and on a 1 K monitor. Six observers participated in the study. ROC curves were generated on the basis of 7200 decisions. RESULTS There was no significant difference in observer performance overall (AUC = Area under curve). Monitor: 0.84 +/- 0.08 vs. AUC, Film: 0.84 +/- 0.08). Slight, but not statistical significant differences were found in the detection of low-contrast lung nodules and of linear lung details. CONCLUSION Soft-copy reading using a high quality 1 K CRT display provides the same accuracy for the detection of subtle computer-simulated lesions as hardcopy reading. A software tool could be used for assigning optimal characteristics of CRT- and hardcopy displays using clearly defined lesions as a gold standard.

Evaluate the performance of PET/MRI at tissue interfaces with different attenuation values for detecting lymph node (LN) metastases and for accurately measuring maximum standardised uptake values (SUVmax) in lung cancer patients.Eleven patients underwent PET/CT and PET/MRI for staging, restaging or follow-up of suspected or known lung cancer. Four experienced readers determined the N stage of the patients for each imaging method in a randomised blinded way. Concerning metastases, SUVmax of FDG-avid LNs were measured in PET/CT and PET/MRI in all patients. A standard of reference was created with a fifth experienced independent reader in combination with a chart review. Results were analysed to determine interobserver agreement, SUVmax correlation between CT and MRI (three-segment model) attenuation correction and diagnostic performance of the two techniques.Overall interobserver agreement was high (κ = 0.86) for PET/CT and substantial (κ = 0.70) for PET/MRI. SUVmax showed strong positive correlation (Spearman's correlation coefficient = 0.93, P 0.001) between the two techniques. Diagnostic performance of PET/MRI was slightly inferior to that of PET/CT, without statistical significance (P 0.05).PET/MRI using three-segment model attenuation correction for LN staging in lung cancer shows a strong parallel to PET/CT in terms of SUVmax, interobserver agreement and diagnostic performance.•F18-FDG PET/MRI shows similar performance to F18-FDG PET/CT in lung cancer N staging. •PET/MRI has substantial interobserver agreement in N staging. •A three-segment model attenuation correction is reliable for assessing the mediastinum.

Purpose Comparison of radiation doses in pulsed and continuous fluoroscopy to quantify the dose reduction by pulsed fluoroscopy. Further, the applicability of pulsed fluoroscopy in clinical routine has been evaluated. Materials and methods In a human pelvic phantom, the radiation dose (skin entry dose in cGycm2) was measured at two pulses per second (pps), 3 pps, 6 pps, 12 pps and continuous fluoroscopy mode, respectively, using image-intensifier entries of 38 cm, 25 cm, and 17 cm. 300 examinations were carried out, and the results of the different fluoroscopy modes were registered. Results Dose reduction depends on the image-intensifier entry. Compared to the radiation dose in continuous fluoroscopy, with 12 pps fluoroscopy the radiation dose can be reduced at a minimum of 51%, with 6 pps fluoroscopy to 40%, with 3 pps fluoroscopy to 20%, and with 2 pps fluoroscopy to a minimum of 14.5%. Clinical routine has shown that 78% of all examinations can be performed with 2 or 3 pps fluoroscopy mode. In 12.7% of the cases pulsed fluoroscopy of diverse frequencies was used, in an additional 2% combined with continuous fluoroscopy. Exclusively, continuous fluoroscopy has been employed in 2% of the cases. Conclusions Using pulsed fluoroscopy, an 80% reduction of the radiation dose compared to continuous fluoroscopy is possible. About 96% of all examinations can be performed with pulsed fluoroscopy of different pulse rate and without using continuous fluoroscopy.

Purpose: The purpose of this study was to evaluate the feasibility of diffusion tensor imaging of the kidney at a field strength of 3T. We assessed fractional anisotropy (FA) and apparent diffusion coefficients (ADC) of various acquisition protocols and determined the reproducibility of these measurements. FA, ADC, signal-to-noise ratios (SNR), and contrast-to-noise ratios (CNR) were compared with those acquired at 1.5T. Material and Methods: Ten healthy volunteers were examined with a respiratory-triggered echo-planar imaging sequence (TR: 1800 ms, TE: 58 ms, b = 0, 300 s/mm 2 ) on a 3-Tesla whole-body MR scanner. Protocol variations included diffusion measurements during free-breathing, in 6 or 12 directions, and an additional b-value of 50 s/mm 2 . A breath-hold protocol was also integrated (TR: 820 ms, TE: 58 ms, b = 0, 300 s/mm 2 ). Measurements with 2 b-values and 6 diffusion directions were also acquired at 1.5 T. SNR was calculated with the difference-image method. Statistical analysis was performed with Wilcoxon signed-rank tests. Intrareader correlation was assessed with weighted kappa coefficients and reproducibility with the root-mean-square-average and the Bland-Altman-method. Results: At 3T, SNR of cortex and medulla and CNR of cortex/medulla were significantly higher than at 1.5T, leading to improved corticomedullary discrimination. There were no significant FA- and ADC differences with 2 b-values and 6 diffusion directions between measurements at 1.5T and 3T. FA of the medulla was significantly higher than that of the cortex in all measurements. Tractography visualized a typical radial diffusion direction in the medulla. Best image quality was achieved with a respiratory triggered protocol with 12 acquisition directions. Measurements with 3 b-values led to decreased ADCs. Acquisition in 12 directions resulted in decreased cortical FA. FA and ADC of breath-hold and free-breathing acquisitions were significantly higher than that of the respiratory-triggered protocol. Intrareader correlation ranged from kappa 0.60 to 0.96. Variance of the respiratory-triggered protocol was smaller than that of breath-hold and free-breathing protocols. Variance was highest for medullary FA in all protocols with reproducibility coefficients ranging from 0.36 to 0.46. Conclusion: Diffusion tensor imaging of the kidney at 3T is feasible and yields significantly higher SNR and CNR. FA and ADCs do not significantly differ from 1.5T. Number of b-values influences ADC-values. Acquisitions in 12 directions provide lower cortical FA-values. We recommend a respiratory-triggered protocol because of improved image quality and reproducibility.

Purpose: To retrospectively assess an improved quantitative methodology with separate assessment of perfusion and permeability for characterization of primary renal cell carcinoma (RCC) and monitoring antiangiogenic treatment. Materials and Methods: Fifteen RCC patients before surgery, 6 RCC patients before and after neoadjuvant antiangiogenic therapy, and 15 patients without renal disease underwent dynamic contrast-enhanced (DCE)-MRI of the kidney with integrated retrospective respiratory triggering and an individual arterial input function. Tracer kinetic analysis was performed with a two-compartment-filtration-model for the kidney data and a two-compartment-exchange-model for the tumor data, providing four independent parameters: the perfusion-parameters plasma flow (FP) and plasma volume (VP), and the permeability-parameters extraction flow (FE) and extravascular-extracellular volume (VE). Results: In tumors FP and FE were significantly lower than in normal kidneys. Tracer kinetic analysis displayed hemodynamic alteration caused by vessel infiltration or necrosis. Papillary RCC could be differentiated from clear-cell variants by a distinct perfusion pattern. In antiangiogenically treated RCC VE was not significantly decreased, while the perfusion parameters VP and FP were significantly diminished. Conclusion: DCE-MRI with integrated motion compensation enables evaluation of primary RCC and detects distinct perfusion patterns. Quantification with a two-compartment-exchange-model produces a separate perfusion- and permeability characterization and may become a diagnostic tool to monitor antiangiogenic treatment. J. Magn. Reson. Imaging 2010; 31: 490–501. © 2010 Wiley-Liss, Inc.

Abdominal imaging at 3.0 T has shown to be challenging because of a number of artifacts and effects related to the physics at higher field strength. For bowel imaging at 3.0 T, artifacts due to magnetic field inhomogeneities, standing waves, increased susceptibility, and greater chemical shift effects are of particular concern because they are likely to affect the assessment of relevant structures and counterbalance the benefits of higher signal-to-noise ratio. Regarding small- and large-bowel magnetic resonance imaging, the benefits of higher field strengths translate mainly in better contrast-to-noise ratio of contrast-enhanced T1-weighted gradient echo and T2-weighted imaging, whereas steady-state free precession sequences seem to suffer from serious degradation of image quality. The present article summarizes the technical challenges in bowel imaging at 3.0 T, provides an overview of performance compared with 1.5 T in small- and large-bowel diseases including the rectum, and revises the current literature.

The most important advantage of 3.0-T magnetic resonance (MR) imaging systems is their increased signal-to-noise ratio (SNR) compared with 1.5-T systems. The higher SNR can be used to shorten acquisition time, achieve higher spatial resolution, or a combination of the two, thereby improving image quality and clinical diagnosis. In fact, 3.0-T MR imaging systems have already proved superior to 1.5-T systems in neuroradiologic and musculoskeletal applications. In the abdomen, 3.0-T MR imaging is uniquely beneficial for techniques such as enhanced and nonenhanced hepatic imaging, diffusion-weighted imaging, angiography, MR pancreatography, and colonography. Admittedly, 3.0-T abdominal imaging has important technical limitations, such as standing wave artifact, chemical shift artifact, susceptibility artifact, and safety issues such as increased energy deposition within the patient's body. Furthermore, 3.0-T abdominal MR imaging is still in the early stages of development and requires substantial modifications of the pulse sequences and hardware components used for 1.5-T imaging. Nevertheless, the ability to obtain physiologic and functional information within reasonably short acquisition times with 3.0-T abdominal MR imaging bodies well for the future of this imaging technique.

Imaging of the arteries of the lower extremity is most often performed in patients who have known or suspected peripheral artery occlusive disease. Due to the recent advances in imaging modalities, the radiologic approach to the diagnosis of peripheral artery occlusive disease has changed substantially in the last few years. Recent technical developments such as the introduction of new image reconstruction algorithms and dedicated contrast agents have pushed the limits of MR angiography toward higher spatial resolution and image quality and have enabled time-resolved imaging. This article discusses various techniques of peripheral MR angiography, including step-by-step, hybrid, continuous table movement, and non–contrast-enhanced MR angiography.