Assessment of hepatic function employing hepatocyte specific contrast agent concentrations to multifactorially evaluate fibrotic remodeling.

Background: Diffuse parenchymal liver diseases are contributing substantially to global morbidity and represent major causes of deaths worldwide. The aim of our study is to assess whether established hepatic fat and iron quantitation and relaxometry-based quantification of hepatocyte-specific contrast material as surrogate for liver function estimation allows to evaluate liver fibrosis. Methods: Retrospective consecutive study. Seventy-two healthy patients (mean age: 53 years) without known liver disease, 21 patients with temporary elevated liver enzymes (mean: 65 years) and 109 patients with biopsy proven liver fibrosis or cirrhosis (mean: 61 years), who underwent liver magnetic resonance imaging (MRI) with a hepatocyte-specific contrast agent [gadoxetate disodium, gadolinium ethoxybenzyl-diethylenetriaminepentaacetic acid (Gd-EOB-DTPA), 0.25 mmol/mL Primovist, Bayer AG, Leverkusen, Germany] at 1.5 T (n=133) and at 3 T (n=69), were included. Fibrosis was classified using the histopathological meta-analysis of histological data in viral hepatitis (METAVIR) and the clinical Child-Pugh scores. Gd-concentration were quantified using T1 map-based calculations. Gd-concentration mapping was performed by using a Look-Locker approach prior to and 912±159 s after intravenous administration of hepatocyte specific contrast agent. Additionally, parenchymal fat fraction, R2*, bilirubin, gender and age were defined as predicting factors. Diagnostic accuracy was calculated in a monoparametric (linear regression, predictor: Gd-concentration) and multiparametric model (predictors: age, bilirubin level, iron overload, liver fat fraction, Gd concentration in the left and right liver lobe). Results: Mean Gd-concentration in the liver parenchyma was significantly higher for healthy patients ([Gd] =0.51 µmol/L) than for those with liver fibrosis or cirrhosis ([Gd] =0.31 µmol/L; P<0.0001) and with acute liver disease ([Gd] =0.28 µmol/L), though there were no significant differences for the latter two groups. There was a significant moderate negative correlation for the mean Gd-concentration and the METAVIR score (ρ=-0.44, P<0.0001) as well as for the Child-Pugh stage (ρ=-0.35, P<0.0001). There was a significant strong correlation between the bilirubin concentration and the Gd-concentration (ρ=-0.61, P<0.0001). The diagnostic accuracy for the discrimination of healthy patients and patients with known fibrosis or cirrhosis was 0.74 (0.71/0.60 sensitivity/specificity) in a monoparametric and 0.76 (0.85/0.61 sensitivity/specificity) in a machine learning based multiparametric model. Conclusions: T1 mapping-based quantification of hepatic Gd-EOB-DTPA concentrations performed in a multiparametric model shows promising diagnostic accuracy for the detection of fibrotic changes. Liver biopsy might be replaced by imaging examinations.

Diagnostic Value of Computed Tomography Angiography in Suspected Acute Ischemic Stroke Patients With Respect to National Institutes of Health Stroke Scale Score.

OBJECTIVE: Noncontrast computed tomography (NCCT) plus computed tomography angiography (CTA) is the standard imaging modality for acute stroke. We investigated whether there is an additional diagnostic value of supra-aortic CTA in relation to National Institutes of Health Stroke Scale (NIHSS) and resultant effective radiation dose. METHODS: In this observational study, 788 patients with suspected acute stroke were included and divided into 3 NIHSS groups: group 1, NIHSS 0-2; group 2, NIHSS 3-5; and group 3, NIHSS ≥ 6.Computed tomography scans were assessed for findings of acute ischemic stroke and vascular pathologies in 3 regions. Final diagnosis was obtained from medical records. Effective radiation dose was calculated based on the dose-length product. RESULTS: Seven hundred forty-one patients were included. Group 1 had 484 patients, group 2 had 127 patients, and group 3 had 130 patients. Computed tomography diagnosis of acute ischemic stroke was made in 76 patients. In 37 patients, a diagnosis of acute stroke was made based on pathologic CTA findings in case of an unremarkable NCCT. Stroke occurrence was the lowest in groups 1 and 2, with 3.6% and 6.3%, respectively, compared with 12.7% in group 3. If both NCCT and CTA were positive, the patient was discharged with a stroke diagnosis. Male sex had the highest effect on the final stroke diagnosis. The mean effective radiation dose was 2.6 mSv. CONCLUSIONS: In female patients with NIHSS 0-2, additional CTA rarely contains relevant additional findings decisive for treatment decisions or overall patient outcomes; therefore, CTA in this patient group might yield less impactful findings, and the applied radiation dose could be lowered by approximately 35%.

Estimation of differential renal function on routine abdominal imaging employing compressed-sensed contrast-enhanced MR: a feasibility study referenced against dynamic renal scintigraphy in patients with deteriorating renal retention parameters.

PURPOSE: To assess whether high temporal/spatial resolution GRASP MRI acquired during routine clinical imaging can identify several degrees of renal function impairment referenced against renal dynamic scintigraphy. METHODS: This retrospective study consists of method development and method verification parts. During method development, patients subject to renal imaging using gadoterate meglumine and GRASP post-contrast MRI technique (TR/TE 3.3/1.6 ms; FoV320 × 320 mm; FA12°; Voxel1.1 × 1.1x2.5 mm) were matched into four equally-sized renal function groups (no-mild-moderate-severe impairment) according to their laboratory-determined estimated glomerular filtration rates (eGFR); 60|120 patients|kidneys were included. Regions-of-interest (ROIs) were placed on cortices, medullary pyramids and collecting systems of bilateral kidneys. Cortical perfusion, tubular concentration and collecting system excretion were determined as TimeCortex=Pyramid(sec), SlopeTubuli (sec-1), and TimeCollecting System (sec), respectively, and were measured by a combination of extraction of time intensity curves and respective quantitative parameters. For method verification, patients subject to GRASP MRI and renal dynamic scintigraphy (99mTc-MAG3, 100 MBq/patient) were matched into three renal function groups (no-mild/moderate-severe impairment). Split renal function parameters post 1.5-2.5 min as well as MAG3 TER were correlated with time intensity parameters retrieved using GRASP technique; 15|30 patients|kidneys were included. RESULTS: Method development showed differing values for TimeCortex=Pyramid(71|75|93|122 s), SlopeTubuli(2.6|2.1|1.3|0.5 s-1) and TimeCollecting System(90|111|129|139 s) for the four renal function groups with partial significant tendencies (several p-values < 0.001). In method verification, 29/30 kidneys (96.7%) were assigned to the correct renal function group. CONCLUSION: High temporal and spatial resolution GRASP MR imaging allows to identify several degrees of renal function impairment using routine clinical imaging with a high degree of accuracy.

Mid-term results of minimally invasive deltoid-split versus standard open deltopectoral approach for PHILOS™ (proximal humeral internal locking system) osteosynthesis in proximal humeral fractures.

PURPOSE: Only a few reports compare the mid- and long-term outcome of the minimally invasive deltoid split (MIDS) with the classic anterior deltopectoral (DP) approach for osteosynthesis in proximal humeral fractures. This study compared the mid-term functional and the radiological results in patients with proximal humeral fractures undergoing osteosynthesis with the proximal humeral internal locking system (PHILOS™). METHODS: All patients undergoing osteosynthesis between 2008 and 2015 were clinically and radiologically examined with a minimal follow-up period of 1 year. Functional outcomes were analyzed using the DASH- and Constant Shoulder Scores (CSS). Radiological results were analyzed using a newly developed score. RESULTS: Thirty-nine patients underwent PHILOS™ osteosynthesis with the MIDS and twenty-three with the DP approach. Follow-up time was 41 months in the MIDS group and 62 months in the DP group, respectively. The median CSS was similar with 79 points in the MIDS group and 82 points in the DP group (p = 0.17). The MIDS group showed a significant lower power measurement in the CSS. In four-part fractures, a substantially lower CSS in absolute numbers in the MIDS group was detected. The median DASH score was 26.7 points in the MIDS group and 25.8 points in the DP group (p = 0.48). There was no difference in the radiological score. More patients with partial avascular necrosis (AVN) were found in the MIDS group, most with three- and four-part fractures. However, this was not statistically significant. Morbidity was similar between groups. CONCLUSION: The results of the two surgical approaches are statistically comparable. Some differences such as a lower power measurement in the MIDS group, a higher partial AVN frequency and more plate removals are observed. In four-part fractures, the CSS was lower in the MIDS compared to the DP cohort. The MIDS technique might not be a solution for all fracture types, and the surgeon should be careful to analyze the morphology of the fracture before deciding upon the approach. Four-part fractures might be better treated with a DP approach.

The Cricothyroid Joint: A Practical Guide for Distinguishing Between Different Joint Types.

OBJECTIVE: Type A cricothyroid joint (CTJ) leads to a higher elongation of the vocal folds than Type B/C CTJ. Therefore, the determination for the CTJ type is important whether to perform a cricoid-thyroid approximation for a pitch elevation in transwomen with gender dysphoria. This study aimed to develop a tool for clinicians and radiologists for distinguishing between Type A (cricoid cartilage protuberance) and Type B/C (flat surface with/without cartilage of the cricoid) CTJs on high-resolution computed tomography (HRCT). STUDY DESIGN: This was a prospective study. METHODS: Analysis of 60 male HRCTs and 60 female HRCTs of the larynx/CTJs. Three-dimensional reconstruction of the laryngeal cartilages, based on visualization of the CTJ in HRCT scans. The intercartilaginous distances (nearest distance between the inner side of the Thyroid and outer side of the cricoid of the CTJ) were measured to compare different types of CTJs. RESULTS: In all HRCT scans, three-dimensional reconstructions of the CTJ were feasible. All Type A CTJs showed the typical cricoid cartilage protuberance (like a volcano) in biplanar images and three-dimensional reconstructions. All Type B/C CTJs showed a flat cricoid joint cartilage in biplanar images and three-dimensional reconstructions. The type distribution was Type A: 61% in male and female larynges; Type B/C: 39% in male and female larynges. The intercartilaginous distances were Type A: 0.71 mm [0.42-0.98] in male larynges and 0.75 mm [0.44-1.40] in female larynges; Type B/C: 1.13 mm [0.36-1.24] in male larynges and 1.32 mm [0.76-2.47] in female larynges. CONCLUSIONS: In HRCT scans, the Type A CTJ showed an intercartilaginous space less than 1 mm. In contrast, the Type B/C CTJ showed an intercartilaginous distance exceeded 1 mm.

How Age and Frequency Impact the Thyroid Cartilages of Professional Singers.

OBJECTIVES/HYPOTHESIS: Young professional singers can easily reach very high pitches. In contrast, older singers often complain that they have to exert substantially more laryngopharyngeal force to reach the same high pitch compared with their earlier years. Various factors such as the property changes of the mucosa and ossification that impact the singing apparatus were suggested as explanations in the literature. The aim of this study was to analyze thyroid deformation-and thereby stiffness indirectly-during singing as a potential reason for this phenomenon. STUDY DESIGN: Prospective study. METHODS/DESIGN: We examined 44 female professional singers. High-resolution computed tomography scans were performed during singing at the fundamental mean speaking frequency and the first and second octaves above it. Digital Imaging and Communications in Medicine scan data were rendered and visualized 3-dimensionally using MIMICS software. By superimposition of the different 3-dimensional images, different positions of the thyroid were visualized. The distance from the posterior border of the thyroid was measured in all the examinations. RESULTS: All laryngeal cartilages could be three-dimensionally visualized. The magnitude of the thyroidal deformation significantly depends on pitch and significantly correlates with age (r2 = 0.7, P < 0.001). CONCLUSIONS: The thyroid cartilage is flexible and its formability is especially important during singing. At higher pitches, the cartilage was more deformed. The larynx in older singers showed less thyroid cartilage deformation.

Computed tomography as primary postoperative follow-up after laparoscopic Roux-en-Y gastric bypass.

AIM: To evaluate upper abdominal computed tomography (CT) scan as primary follow-up after laparoscopic Roux-en-Y gastric bypass (LRYGB). METHODS: This prospective study was approved by the Ethical Committee of the State of Zurich, and informed consent was obtained from all patients. Sixty-one patients who underwent LRYGB received upper abdominal CT on postoperative day 1, with the following scan parameters: 0.6 mm collimation, 1.2 mm pitch, CareKV with reference 120 mAs and 120 kV, and 0.5 s rotation time. Diluted water-soluble radiographic contrast-medium (50 mL) was administered to achieve gastric pouch distension without movement of the patient. 3D images were evaluated to assess postoperative complications and the radiation dose received was analysed. RESULTS: From the 70 patients initially enrolled in the study, 9 were excluded from analysis upon the intraoperative decision to perform a sleeve gastrectomy and not a LRYGB. In all of the 61 patients who were included in the analysis, CT was feasible and there were no instances of aspiration or vomiting. In 7 patients, two upper abdominal scans were necessary as the pouch was not distended by contrast medium in the first acquisition. Radiologically, no leak and no relevant stenosis were found on the first postoperative day. These early postoperative CT findings were consistent with the findings at clinical follow-up 6 wk postoperatively, with no leaks, stenosis or obstructions being diagnosed. The average total dose length product in CT was 536.6 mGycm resulting in an average effective dose of 7.8 mSv. The most common surgical complication, superficial surgical site infections (n = 4), always occurred at the upper left trocar site, where the circular stapler had been introduced. CONCLUSION: Early LRYGB postoperative multislice spiral CT scan is feasible, with low morbidity, and provides more accurate anatomical information than standard upper gastrointestinal contrast study.

PD-1 Checkpoint Inhibitor Associated Autoimmune Encephalitis.

OBJECTIVE: To report first-hand narrative experience of autoimmune encephalitis and to briefly review currently available evidence of autoimmune encephalitis in cancer patients treated with immune checkpoint inhibitors. SETTING: A case study is presented on the management of a patient who developed autoimmune encephalitis during nivolumab monotherapy occurring after 28 weeks on anti-PD-1 monotherapy (nivolumab 3 mg/kg every 2 weeks) for non-small cell lung cancer. RESULTS: No substantial improvement was observed by antiepileptic treatment. After administration of 80 mg methylprednisolone, neurologic symptoms disappeared within 24 h and the patient fully recovered. CONCLUSIONS: Immune checkpoint inhibitor treatment can lead to autoimmune encephalitis. Clinical trial data indicate a frequency of autoimmune encephalitis of ≥0.1 to <1% with a higher probability during combined or sequential anti-CTLA-4/anti-PD-1 therapy than during anti-PD-1 or anti-PD-L1 monotherapy. Further collection of evidence and translational research is warranted.

3D analysis of the movements of the laryngeal cartilages during singing.

OBJECTIVE: The vocal range of untrained singers rarely exceeds one and a half octaves, but professional singers have a range of at least two and a half octaves. The aim of this study was to better understand the muscle and cartilage movements responsible for the control of vocal pitch in singing. STUDY DESIGN: Prospective study. METHODS: We recruited 49 female professional singers (25 sopranos and 24 altos) and analyzed laryngeal three-dimensional images derived from high-resolution computed tomography scans obtained at the mean speaking fundamental frequency (F0) and at one (F1) and two octaves (F2) above this pitch. RESULTS: From F0 to F1, the only observable movement was a backward cricoid tilting caused by the cricothyroid muscles (CTMs), leading to vocal fold stretching. Above F1, a medial rotation and inward rocking of the arytenoid cartilages was observed, caused by the lateral cricothyroid muscles (LCAMs) and leading to inferior displacement of the vocal process of the arytenoid cartilage, and thus to further vocal fold stretching. CONCLUSION: Trained singers achieve the first octave of pitch elevation by simple cricothyroid approximation. Further pitch elevation necessitates a complex movement of the arytenoids, first by CTM contraction and second by LCAM contraction. LEVEL OF EVIDENCE: 4. Laryngoscope, 127:1639-1643, 2017.

Three-dimensional Imaging of High-resolution Computer Tomography of Singers' Larynges-A Pilot Study.

OBJECTIVES/HYPOTHESIS: Biplanar imaging technique is not sufficient for an exact visualization and evaluation of the laryngeal biomechanics during speaking or singing. The aim of this pilot study was to test a 3D-visualization software MIMICS (Materialize Interactive Medical Image Control System, Materialize, Leuven, Belgium) for visualizing laryngeal cartilages and resonance space of living humans during singing based on high-resolution computed tomography (HRCT) and analyzing the biomechanics thereof. STUDY DESIGN: This is a prospective pilot study. METHODS: A total of 10 professional female singers (five sopranos and five altos) was scanned with HRCT in three singing positions fundamental frequency (ƒo), first octave (ƒo+1 8va) and second octave (ƒo+2 8va). RESULTS: All relevant laryngeal structures and resonance space could be 3D visualized. Superimposing the different HRCT scans showed an inward rotation and rocking of the arytenoid cartilages from ƒo+1 8va to ƒo+2 8va and a backward tilting of the cricoid cartilage from ƒo+1 8va to ƒo+2 8va. Moreover, we could demonstrate a vocal fold elongation of 13% from ƒo to ƒo+1 8va and an additional elongation from ƒo+1 8va to ƒo+2 8va of 10% in type A cricothyroid joints (CTJ) A and 4% in CTJ's type B/C. There were no significant differences between sopranos and altos in all parameters (length of the glottis, subglottic diameter, distance between anterior commissure and cervical spine, and CTJ distribution). CONCLUSIONS: This noninvasive 3D-visualization technique with MIMICS allows the anatomical structures and landmarks of the larynx to be analyzed. We believe that this pilot study will serve as a basis for further biomechanical studies on speakers' and singers' larynges.

Primary non-closure of mesenteric defects in laparoscopic Roux-en-Y gastric bypass: reoperations and intraoperative findings in 146 patients.

BACKGROUND: Internal hernias (IH) after laparoscopic Roux-en-Y gastric bypass (LRYGB) have been reported with an incidence of 11 %. IH can lead to bowel incarceration and potentially bowel necrosis. The aim of this study was to analyze reoperations and intraoperative findings in a cohort of patients with unclosed mesenteric defects. METHODS: From a prospective database of patients with LRYGB, we selected as primary cohort patients with non-closure of mesenteric defects and abdominal reoperation for analysis. The data included pre-, intra- and post-operative findings, computed tomogram results and laboratory test results. This group underwent a very very long limb LRYGB, at that time the institutional standard technique. Additionally, a more recently operated cohort with primary closure of mesenteric defects was also analyzed. RESULTS: We identified 146 patients with primary non-closure and reoperation, mean age of 43.8 years. The main indication for reoperation was unclear abdominal pain in 119 patients with 27 patients undergoing a reoperation for other reasons (weight regain, prophylactic surgical inspection of mesenteric defects). Median time and mean excess weight loss from RYGB to reoperation were 41.1 months and 62.7 %, respectively. The incidence of IH was 14.4 %, with all patients with an IH being symptomatic. Conversion rate from laparoscopic to open surgery was 5.5 %, mortality 0.7 % and morbidity 3.4 %. Thirty-one patients underwent a second re-look laparoscopy. Eleven patients had recurrent open mesenteric defects. Three hundred and sixteen patients who underwent primary closure of the mesenteric defects had a reoperation rate of 13.6 % and an IH rate of 0.6 %. CONCLUSION: The incidence of IH in patients without closure of mesenteric defects and reoperation is high and substantially higher compared to patients with primary closure of mesenteric defects. Patients with or without closure of mesenteric defects following LRYGB with acute, chronic or recurrent pain should be referred to a bariatric surgeon for diagnostic laparoscopy.

Serum creatinine measurements: evaluation of a questionnaire according to the ESUR guidelines.

BACKGROUND: The European Society of Urogenital Radiology (ESUR) propose measurements of serum creatinine levels in patients undergoing contrast-enhanced studies with a high probability of impaired renal function and therefore with a higher risk of CIN and NSF. PURPOSE: To determine whether the recommended questionnaire is able to select these patients. MATERIAL AND METHODS: Over a time period of 10 months the questionnaire was conducted in 1389 patients (725 women, 654 men) before contrast administration for computed tomography (CT) or magnetic resonance imaging (MRI) examination. Serum creatinine (SCr) measurements and calculation of estimated glomerular filtration rate (eGFR) values were performed when one or more answers were positive. Eighty-one patients were excluded due to incomplete data. Statistical evaluation of the questionnaire was done retrospectively. RESULTS: Four hundred and ninety-nine patients (38%) gave one or more positive answers to the questionnaire. Of these, 71 (14%) had an eGFR <60 mL/min/1.73 m(2), 31 (6%) had an eGFR <45 mL/min/1.73 m(2), and five (1%) had an eGFR <30 mL/min/1.73 m(2). Only the question concerning previous renal disease showed a significant correlation to an eGFR <60 mL/min/1.73 m(2) (P < 0.05) and <45 mL/min/1.73 m(2). Slight correlations with some other risk factors (renal disease, family history of renal disease, arterial hypertension with medication, analgetic medication with nephrotoxic drugs) were found for either a threshold of 60 or 45 mL/min/1.73 m(2). In addition, there was a positive correlation with patient age. CONCLUSION: We propose to reduce the questionnaire to a smaller number of risk factors and consider a point-of-care (POC) SCr measurement for all patients aged >70 years without a recent eGFR value while referred for CT. For MRI a SCr measurement is not mandatory while using medium and lowest risk contrast agents.

Choi response criteria for prediction of survival in patients with metastatic renal cell carcinoma treated with anti-angiogenic therapies.

OBJECTIVE: Anti-angiogenic drugs cause a reduction in tumour density (Choi criteria) first and then in size [Response Evaluation Criteria In Solid Tumours (RECIST)]. The prognostic significance of changes in tumour density in metastatic renal cell carcinoma (mRCC) is unknown and was assessed in this study. METHODS: The prognostic significance of partial response (PR) as opposed to non-response [stable disease (SD) + progressive (PD)] to anti-angiogenic therapy was assessed in patients with mRCC separately for both criteria using the log-rank test and Cox regression models. RESULTS: Both criteria were applied to 35 patients. The response was identical for all eight patients with PR and most patients with PD (10/12) when using the RECIST and Choi criteria. Adding tumour density information, 14 patients with SD were re-categorised as having PR (7), SD (4), and PD (3). Patients with PR (Choi) were progression free significantly longer [hazard ratio (HR) 0.24; 95 % CI 0.10-0.57; P = 0.001] and had better overall survival (HR 0.36; 95 % CI 0.15-0.89; P = 0.026) compared to patients with SD or PD. The predictive value of PR according to RECIST was not statistically significant. CONCLUSIONS: In mRCC, the Choi criteria separate prognostic groups better when compared with RECIST. This may allow early discrimination of patients benefiting from continued treatment.

Annular pancreas associated with duodenal carcinoma.

Annular pancreas (AP) is a rare congenital anomaly. Coexisting malignancy has been reported only in a few cases. We report what is, to the best of our knowledge, the first case in the English literature of duodenal adenocarcinoma in a patient with AP. In a 55-year old woman with duodenal outlet stenosis magnetic resonance cholangiopancreatography showed an aberrant pancreatic duct encircling the duodenum. Duodenojejunostomy was performed. Eight weeks later she presented with painless jaundice. Duodenopancreatectomy revealed a duodenal adenocarcinoma, surrounded by an incomplete AP. Thus, co-existent malignancy with AP can be present without obstructive jaundice and without being visible through preoperative diagnostics.

Assessment of intraoperative liver deformation during hepatic resection: prospective clinical study.

BACKGROUND: The implementation of intraoperative navigation in liver surgery is handicapped by intraoperative organ shift, tissue deformation, the absence of external landmarks, and anatomical differences in the vascular tree. To investigate the impact of surgical manipulation on the liver surface and intrahepatic structures, we conducted a prospective clinical trial. METHODS: Eleven consecutive patients [4 female and 7 male, median age = 67 years (range = 54-80)] with malignant liver disease [colorectal metastasis (n = 9) and hepatocellular cancer (n = 2)] underwent hepatic resection. Pre- and intraoperatively, all patients were studied by CT-based 3D imaging and assessed for the potential value of computer-assisted planning. The degree of liver deformation was demonstrated by comparing pre- and intraoperative imaging. RESULTS: Intraoperative CT imaging was successful in all patients. We found significant deformation of the liver. The deformation of the segmental structures is reflected by the observed variation of the displacements. There is no rigid alignment of the pre- and intraoperative organ positions due to overall deflection of the liver. Locally, a rigid alignment of the anatomical structure can be achieved with less than 0.5 cm discrepancy relative to a segmental unit of the liver. Changes in total liver volume range from -13 to +24%, with an average absolute difference of 7%. CONCLUSIONS: These findings are fundamental for further development and optimization of intraoperative navigation in liver surgery. In particular, these data will play an important role in developing automation of intraoperative continuous registration. This automation compensates for liver shift during surgery and permits real-time 3D visualization of navigation imaging.

Measuring aortic diameter with different MR techniques: comparison of three-dimensional (3D) navigated steady-state free-precession (SSFP), 3D contrast-enhanced magnetic resonance angiography (CE-MRA), 2D T2 black blood, and 2D cine SSFP.

PURPOSE: To compare nongated three-dimensional (3D) contrast-enhanced magnetic resonance angiography (CE-MRA) with 3D-navigated cardiac-gated steady-state free-precession bright blood (3D-nav SSFP) and noncontrast 2D techniques for ascending aorta dimension measurements. MATERIALS AND METHODS: Twenty-five clinical exams were reviewed to evaluate the ascending aorta at 1.5T using: breathhold cine bright blood (SSFP), cardiac-triggered T2 black blood (T2 BB), axial 3D-nav SSFP, and nongated 3D CE-MRA. Three radiologists independently measured aortic size at three specified locations for each sequence. Means, SDs, interobserver correlation, and vessel edge sharpness were statistically evaluated. RESULTS: Measurements were greatest for 3D-nav SSFP and 3D CE-MRA and smallest for T2 BB. There was no significant difference between 3D-nav SSFP and 3D CE-MRA (P = 0.43-0.86), but significance was observed comparing T2 BB to all sequences. Interobserver agreement was uniformly >0.9, with T2 BB best, followed closely by 3D-nav SSFP and 2D cine SSFP, and 3D CE-MRA being the worst. Edge sharpness was significantly poorer for 3D CE-MRA compared to the other sequences (P < 0.001). CONCLUSION: If diameter measurements are the main clinical concern, 3D-nav SSFP appears to be the best choice, as it has a sharp edge profile, is easy to acquire and postprocess, and shows very good interobserver correlation.

Peripheral moving-table contrast-enhanced magnetic resonance angiography (CE-MRA) using a prototype 18-channel peripheral vascular coil and scanning parameters optimized to the patient's individual hemodynamics.

PURPOSE: To demonstrate that with a priori determination of individual patient hemodynamics, peripheral contrast-enhanced magnetic resonance angiography (pCE-MRA) can be customized to maximize signal-to noise ratio (SNR) and avoid venous enhancement. MATERIALS AND METHODS: Using a 1.5T MRI scanner and prototype 18-channel peripheral vascular (PV) coil designed for highly accelerated parallel imaging, geometry (g)-factor maps were determined. SNR-maximized protocols considering the two-dimensional sensitivity encoding (2D SENSE) factor, TE, TR, bandwidth (BW), and flip angle (FA) were precalculated and stored. For each exam, a small aortic timing bolus was performed, followed by dynamic three-dimensional (3D)-MRA of the calf. Using this information, the aorta to pedal artery and calf arteriovenous transit times were measured. This enabled estimation of the maximum upper and middle station acquisition duration to allow lower station acquisition to begin prior to venous arrival. The appropriately succinct SNR-optimized protocol for each station was selected and moving-table pCE-MRA was performed using thigh venous compression and high-relaxivity contrast material. RESULTS: The protocol was successfully applied in 15 patients and all imaging demonstrated good SNR without diagnosis-hindering venous enhancement. CONCLUSION: By knowing each patient's venous enhancement kinetics, scan parameters can be optimized to utilize maximum possible acquisition time. Some time is added for the timing scans, but in return time-resolved calf CE-MRA, maximized SNR, and decreased risk of venous enhancement are gained.

Non-contrast-enhanced MR imaging of the renal arteries.

In this article, we focus on non-contrast magnetic resonance angiography techniques for evaluating renal artery imaging. Time-of-flight, phase contrast, steady-state free procession, and arterial spin labeling are discussed.