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PURPOSE: To compare the accuracy of PET/MR imaging with that of FDG PET/CT and to determine the MR sequences necessary for the detection of liver metastasis using a trimodality PET/CT/MR set-up. METHODS: Included in this single-centre IRB-approved study were 55 patients (22 women, age 61 ± 11 years) with suspected liver metastases from gastrointestinal cancer. Imaging using a trimodality PET/CT/MR set-up (time-of-flight PET/CT and 3-T whole-body MR imager) comprised PET, low-dose CT, contrast-enhanced (CE) CT of the abdomen, and MR with T1-W/T2-W, diffusion-weighted (DWI), and dynamic CE imaging. Two readers evaluated the following image sets for liver metastasis: PET/CT (set A), PET/CECT (B), PET/MR including T1-W/T2-W (C), T1-W/T2-W with either DWI (D) or CE imaging (E), and a combination (F). The accuracy of each image set was determined by receiver-operating characteristic analysis using image set B as the standard of reference. RESULTS: Of 120 liver lesions in 21/55 patients (38 %), 79 (66 %) were considered malignant, and 63/79 (80 %) showed abnormal FDG uptake. Accuracies were 0.937 (95 % CI 89.5 - 97.9 %) for image set A, 1.00 (95 % CI 99.9 - 100.0 %) for set C, 0.998 (95 % CI 99.4 - 100.0 %) for set D, 0.997 (95 % CI 99.3 - 100.0 %) for set E, and 0.995 (95 % CI 99.0 - 100.0 %) for set F. Differences were significant for image sets D - F (P < 0.05) when including lesions without abnormal FDG uptake. As shown by follow-up imaging after 50 - 177 days, the use of image sets D and both sets E and F led to the detection of metastases in one and three patients, respectively, and further metastases in the contralateral lobe in two patients negative on PET/CECT (P = 0.06). CONCLUSION: PET/MR imaging with T1-W/T2-W sequences results in similar diagnostic accuracy for the detection of liver metastases to PET/CECT. To significantly improve the characterization of liver lesions, we recommend the use of dynamic CE imaging sequences. PET/MR imaging has a diagnostic impac

BACKGROUND: Hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) shows high potential for patients with oropharyngeal cancer. Dental implants can cause substantial artifacts in the oral cavity impairing diagnostic accuracy. Therefore, we evaluated new MRI sequences with multi-acquisition variable-resonance image combination (MAVRIC SL) in comparison to conventional high-bandwidth techniques and in a second step showed the effect of artifact size on MRI-based attenuation correction (AC) with a simulation study. METHODS: Twenty-five patients with dental implants prospectively underwent a trimodality PET/CT/MRI examination after informed consent was obtained under the approval of the local ethics committee. A conventional 3D gradient-echo sequence (LAVA-Flex) commonly used for MRI-based AC of PET (acquisition time of 14 s), a T1w fast spin-echo sequence with high bandwidth (acquisition time of 3.2 min), as well as MAVRIC SL sequence without and with increased phase acceleration (MAVRIC, acquisition time of 6 min; MAVRIC-fast, acquisition time of 3.5 min) were applied. The absolute and relative reduction of the signal void artifact was calculated for each implant and tested for statistical significance using the Wilcoxon signed-rank test. The effect of artifact size on PET AC was simulated in one case with a large tumor in the oral cavity. The relative difference of the maximum standardized uptake value (SUVmax) in the tumor was calculated for increasing artifact sizes centered over the second molar. RESULTS: The absolute reduction of signal void from LAVA-Flex sequences to the T1-weighted fast spin-echo (FSE) sequences was 416 mm(2) (range 4 to 2,010 mm(2)) to MAVRIC 481 mm(2) (range 12 to 2,288 mm(2)) and to MAVRIC-fast 486 mm(2) (range 39 to 2,209 mm(2)). The relative reduction in signal void was significantly improved for both MAVRIC and MAVRIC-fast compared to T1 FSE (-75%/-78% vs. -62%, p < 0.001 for both). The relative error for SUVmax was neg

PURPOSE: The purpose of this study was to evaluate the image quality and sensitivity of ultralow radiation dose single-energy computed tomography (CT) with tin filtration for spectral shaping and iterative reconstructions for the detection of pulmonary nodules in a phantom setting. METHODS: Single-energy CT was performed using third-generation dual-source CT (SOMATOM Force; 2 × 192 slices) at 70 kVp, 100 kVp with tin filtration (100Sn kVp), and 150Sn kV with tube current-time product adjustments resulting in standard dose (CT volume dose index, 3.1 mGy/effective dose, 1.3 mSv at a scan length of 30 cm), 1/10th dose level (0.3 mGy/0.13 mSv), and 1/20th dose level (0.15 mGy/0.06 mSv). An anthropomorphic chest phantom simulating an intermediate-sized adult with randomly distributed solid pulmonary nodules of various sizes (2-10 mm; attenuation, 75 HU at 120 kVp) was used. Images were reconstructed with advanced model-based iterative reconstruction (ADMIRE; strength levels 3 and 5) and were compared with those acquired with second-generation dual-source CT at 120 kVp (reconstructed with filtered back projection) and sinogram-affirmed iterative reconstruction (strength level 3) at the lowest possible dose at 120 kVp (CT volume dose index, 0.28 mGy). One blinded reader measured image noise, and 2 blinded, independent readers determined overall image quality on a 5-grade scale (1 = nondiagnostic to 5 = excellent) and marked nodule localization with confidence rates on a 5-grade scale (1 = unsure to 5 = high confidence). The constructional drawing of the phantom served as reference standard for calculation of sensitivity. Two patients were included, for proof of concept, who were scanned with the 100Sn kVp protocol at the 1/10th and 1/20th dose level. RESULTS: Image noise was highest in the images acquired with second-generation dual-source CT and reconstructed with filtered back projection. At both the 1/10th and 1/20th dose levels, image noise at a tube voltage of 100Sn k

OBJECTIVE: The objective of this study was to assess the discriminative power of dual-energy computed tomography (DECT) versus single-energy CT (SECT) to distinguish between ferromagnetic and non-ferromagnetic ballistic projectiles to improve safety regarding magnetic resonance (MR) imaging studies in patients with retained projectiles. MATERIALS AND METHODS: Twenty-seven ballistic projectiles including 25 bullets (diameter, 3-15 mm) and 2 shotgun pellets (2 mm each) were examined in an anthropomorphic chest phantom using 128-section dual-source CT. Data acquisition was performed with tube voltages set at 80, 100, 120, and 140 kV(p). Two readers independently assessed CT numbers of the projectile's core on images reconstructed with an extended CT scale. Dual-energy indices (DEIs) were calculated from both 80-/140-kV(p) and 100-/140-kV(p) pairs; receiver operating characteristics curves were fitted to assess ferromagnetic properties by means of CT numbers and DEI. RESULTS: Nine (33%) of the projectiles were ferromagnetic; 18 were nonferromagnetic (67%). Interreader and intrareader correlations of CT number measurements were excellent (intraclass correlation coefficients, >0.906; P < 0.001). The DEI calculated from both 80/140 and 100/140 kV(p) were significantly (P < 0.05) different between the ferromagnetic and non-ferromagnetic projectiles. The area under the curve (AUC) was 0.75 and 0.8 for the tube voltage pairs of 80/140 and 100/140 kV(p) (P < 0.05; 95% confidence interval, 0.57-0.94 and 0.62-0.97, respectively) to differentiate between the ferromagnetic and non-ferromagnetic ballistic projectiles; which increased to 0.83 and 0.85 when shotgun pellets were excluded from the analysis. The AUC for SECT was 0.69 and 0.73 (80 and 100 kV[p], respectively). CONCLUSIONS: Measurements of DECT combined with an extended CT scale allow for the discrimination of projectiles with non-ferromagnetic from those with ferromagnetic properties in an anthropomorphic chest phantom w

Purpose: Percutaneous transhepatic primary biliary stenting (PS) is an alternative to the widely used staged procedure (secondary biliary stenting, SS) for treating obstructive jaundice in cancer patients. To evaluate the efficacy and safety of PS and SS, a retrospective analysis was carried out. Materials and Methods: The percutaneous biliary stenting procedures performed between January 2000 and December 2007 at one hepatobiliary center were retrospectively analyzed, comparing the technical success rates, complications, and length of hospitalization of the two procedures. Of 61 patients (mean age 65.5 ± 13.1 years; range 31.1-92.7 years) suffering from obstructive jaundice caused by primary or metastatic tumors, 30 received PS and 31 received SS. The groups were comparable in the anatomical level of the obstruction, stent configuration, or the concurrent presence of cholangitis. Placement of metallic stents required one session for patients in the PS group and an average of 2.6 ± 1.1 sessions for patients in the SS group. Results: The overall technical success rate was 98.4% with 1 (1/61) failed approach to transcend the occlusion in the SS group. The rate of minor complications was 10% in the PS group and 6.5% in the SS group. The corresponding rates of major complications were 23.3% and 54.8%, respectively. SS patients had a higher rate of complications in general ( P < 0.05), as well as a higher rate of severe complications in particular ( P < 0.05). Procedural mortality was 0% for both the groups. The mean overall length of hospitalization was 7.7 ± 9.6 days for PS and 20.6 ± 19.6 days for SS ( P < 0.001). Conclusion: Primary percutaneous biliary stenting of malignant biliary obstructions is as efficacious and safer than a staged procedure with secondary stenting. By virtue of requiring shorter hospital stays, primary stenting is likely to be more cost-effective.

BACKGROUND: As the largest single lymphatic organ in the human body, the spleen is responsible for central immunological and haematological tasks. Therefore, the spleen can be subject to a wide range of pathologic disorders. Computed tomography (CT) represents the most widely applied cross-sectional abdominal imaging technique and is considered the imaging modality of choice for the evaluation of numerous abdominal pathological conditions. Hypodense splenic lesions are frequently encountered on abdominal CT images. Although most hypodense lesions of the spleen can be considered benign, some findings and clinical conditions warrant closer attention to the lesion. CT offers a number of morphological criteria that can be applied to differentiate hypodense lesions of the spleen, such as a the appearance of a lesion's borders, its attenuation, as well as the presence of calcifications or solid components. METHODS: This article reviews the most common splenic pathologies leading to hypodense appearances on CT images and illustrates the key CT imaging findings in the context of the clinical history of the patients. CONCLUSION: The key imaging findings of hypodense splenic lesions are presented in order to aid interpretation during routine evaluation of abdominal CT images. TEACHING POINTS: • Haemangiomas, congenital in origin, represent the most common benign lesions of the spleen. • Lymphoma represents the most common malignant tumour of the, usually secondarily involved, spleen. • Most hypodense splenic lesions on CT represent benign lesions that require no further work-up. • For correct interpretation, hypodense splenic lesions need to be evaluated in the clinical context.

Over the past years, the number of coronary computed tomography angiography (CTA) studies performed worldwide has been steadily increasing. Performing a coronary CTA study with appropriate protocols tailored to the individual patient and clinical question is mandatory to obtain an image quality that is diagnostic for the study purpose. This process can be considered the primary mainstay of each coronary CTA study. The secondary mainstay is represented by the correct analysis and interpretation of the acquired data, as well as reporting of the pertinent imaging findings to the referring physician. The latter process requires knowledge of the advantages and disadvantages of various post-processing methods. In addition, a standardized approach can be helpful to avoid false-positive and false-negative findings regarding the presence or absence of coronary artery disease. By implementing various radiation dose reduction techniques, care needs to be taken to keep the radiation dose of coronary CTA as low as reasonably achievable while maintaining the diagnostic capacity of the examination. This review describes a practical approach to the analysis and interpretation of coronary CTA data, including the standardized reporting of the relevant imaging findings to the referring physicians.