Assessment of the tibial slope is highly dependent on the type and accuracy of the preceding acquisition.

BACKGROUND: Precise measurement of the tibial slope (TS) is crucial for realignment surgery, ligament reconstruction, and arthroplasty. However, there is little consensus on the ideal assessment. It was hypothesized that the tibial slope changes according to the acquisition technique and both tibial length as well as femoral rotation serve as potential confounders. METHODS: 104 patients (37 women, 67 men; range 12-66 years) were retrospectively selected, of which all patients underwent a 1.5-Tesla MRI and either additional standard lateral radiographs (SLR, n = 52) or posterior stress radiographs (PSR, n = 52) of the index knee. Two blinded observers evaluated the medial tibial slope as the medial TS is primarily used in clinical practice. Additionally, the length of the diaphyseal axis and the extent of radiographic malrotation were measured. RESULTS: Mean TS on MRI was significantly lower compared to radiographs (4.2° ± 2.9° vs. 9.1° ± 3.6°; p < 0.0001). There was a significant correlation between MRI and PSR (p < 0.0001 with r = 0.7), but not with SLR (p = 0.93 with r = 0.24). Tibial length was a significant predictor for the difference between MRI and SLR (regression coefficient ß = - 0.03; p = 0.035), yet not between MRI and PSR (ß = - 0.003; p = 0.9). Femoral rotation proved to be a significant predictor for the agreement between both observers (PSR: ß = 0.14; p = 0.001 and SLR: ß = 0.08; p = 0.04). ICC indicated a high interrater agreement for the radiographic assessment (ICC ≥ 0.72). CONCLUSIONS: There is a substantial variance between MRI and radiographic measurement of the tibial slope. However, as MRI assessment is time-consuming and requires specialized software, instrumented radiographs might be an alternative. Due care has to be taken to ensure that radiographs contain a sufficient tibial length, and femoral rotation is avoided. STUDY DESIGN: Case series (diagnosis); Level of evidence, 4.

High tibial slope correlates with increased posterior tibial translation in healthy knees.

PURPOSE: Notwithstanding the importance of the tibial slope (TS) for anterior tibial translation, little information is available regarding the implications on posterior laxity, particularly in healthy subjects. It was hypothesized that increased TS is associated with decreased posterior tibial translation (PTT) in healthy knees. METHODS: A total of 124 stress radiographs of healthy knees were enrolled in this study. Tibial slope and the posterior tibial translation were evaluated using a Telos device with a 150-N force at 90° of knee flexion. Two blinded observers reviewed independently on two different occasions. RESULTS: One hundred and twenty-four patients [35 females and 89 males; 41 (range 18-75) years] were enrolled in this study, with a mean PTT of 2.8 mm (±1.9 mm; range 0-8 mm) and a mean TS of 8.6° (±2.6°; range 1°-14°). Pearson correlation showed a significant correlation between the PTT and TS in the overall patient cohort (P < 0.0001) with r = 0.76 and R 2 = 0.58. There was no statistical difference between female and male patients regarding the PTT or the TS. Subgrouping of the patient cohort (four groups with n = 31) according to their TS (groups I < 7°; II = 7°-8.5°; III = 9°-10.5°; IV ≥ 11°) revealed significant differences between each subgroup, respectively. Furthermore, there was a weak but significant correlation between age and PTT (P = 0.004, r = 0.26). CONCLUSION: In addition to the substantial variance in tibial slope and posterior laxity among healthy knees, high tibial slope significantly correlates with increased posterior tibial translation. Increasing age is further associated with a greater magnitude of posterior tibial translation. Consequently, knowledge of the tibial slope facilitates simple estimation of posterior knee laxity, which is mandatory for PCL reconstruction and knee arthroplasty.

Diagnostic performance of susceptibility-weighted magnetic resonance imaging for the assessment of sub-coracoacromial spurs causing subacromial impingement syndrome.

OBJECTIVES: To evaluate the potential of susceptibility-weighted-magnetic-resonance-imaging (SWMR) for the detection of sub-coracoacromial spurs in patients with clinically suspected subacromial impingement syndrome (SAIS), compared to standard MR-sequences and radiographs. METHODS: Forty-four patients with suspected SAIS were included. All patients underwent radiography, standard MRI of the shoulder and SWMR. Radiograph-based identification of sub-coracoacromial spurs served as goldstandard. Radiographs identified twenty-three spurs in twenty-three patients. Twenty-one patients without spur formation served as reference group. Detection rate, sensitivity/specificity and interobserver-agreements were calculated. Linear regression was applied to determine the relationship between size measurements on radiographs and MRI. RESULTS: Detection rates for spurs on standard MRI and SWMR were 47.8 % and 91.3 % compared to radiography (p<0.001). SWMR demonstrated a sensitivity of 97.7 % (CI=0.92-1) and a specificity of 91.3 % (CI=0.788-1) for the identification of spurs. Standard MR-sequences achieved a sensitivity of 47.8 % (CI=0.185-0.775) and a specificity of 80.8 % (CI=0.642-0.978). Size measurements between SWMR and radiography showed a good correlation (R2=0.75;p<0.0001), while overestimating lesion size (5.7±1.2 mm; 4.3±1.3 mm;p<0.0001). Interobserver-agreement for spurs was high on SWMR (R2=0.74;p<0.0001), but low on standard MRI (R2=0.24;p<0.0001). CONCLUSIONS: SWMR allows a reliable detection of sub-coracoacromial spur formation in patients with SAIS and is superior to standard MR-sequences using radiography as goldstandard. KEY POINTS: • SWMR has the potential to reliably identify sub-coracoacromial spurs without radiation exposure. • SWMR provides comparable detection rates to conventional radiography for sub-coracoacromial spur formation. • SWMR yields higher detection rates compared to standard-MR regarding sub-coracoacromial spur formation. • SWMR can be implemented in routine shoulder MRI protocols.

Segment-by-segment assessment of left ventricular myocardial affection in Anderson-Fabry disease by non-enhanced T1-mapping.

Background Anderson-Fabry disease (AFD) is an X-linked lysosomal enzyme disorder associated with an intracellular accumulation of sphingolipids, which shorten myocardial T1 relaxation times. Myocardial affection, however, varies between different segments. Purpose To evaluate the specific segmental distribution and degree of segmental affection in AFD patients. Material and Methods Twenty-five patients with AFD, 14 patients with hypertrophic cardiomyopathy (HCM), and 21 controls were included. A Modified Look-Locker Inversion Recovery sequence (MOLLI) was used for non-enhanced T1 mapping at 1.5 T in addition to standard cardiac imaging in 10-12 short axis views. T1 values were evaluated with a mixed model ANOVA and regression analysis to determine the best diagnostic cutoff values for T1 for each myocardial segment. Results Regression analysis showed the best diagnostic cutoff compared to controls in cardiac segments 1-4, 8-9, and 14. Mean differences between T1 for AFD versus HCM were greatest in segment 3, 4, and 9 (99 ms, 103 ms, 86 ms, respectively). Overall T1 times were 888 ± 70 ms and 903 ± 14 ms (AFD with and without LVH); 1014 ± 17 ms and 1001 ± 22 ms (HCM and controls, P < 0.05). Conclusion Myocardial segments are affected by a varying degree of T1 shortening in AFD patients. Segment-specific cutoff values allow the most specific detection and quantification of the extent of myocardial affection.

Diagnosis of Calcific Tendonitis of the Rotator Cuff by Using Susceptibility-weighted MR Imaging.

PURPOSE: To evaluate the diagnostic performance of susceptibility-weighted imaging (SWI) and standard shoulder joint magnetic resonance (MR) sequences in comparison to that of conventional radiography for the identification of calcifications in the rotator cuff in patients with calcific tendonitis. MATERIALS AND METHODS: The institutional review board approved this prospective study. Written informed consent was obtained from all subjects. Fifty-four patients clinically suspected of having calcific tendonitis of the rotator cuff were included. On radiographs (the standard of reference), 27 patients had positive calcification findings, and 27 did not. Standard MR sequences and SWI, including magnitude and phase imaging, were performed. The diameter of calcifications was measured to assess intermodality correlations. Sensitivity, specificity, and intra- and interobserver agreement were calculated. Phantom measurements were performed to assess the detection limit of SWI. RESULTS: Fifty-six calcifications were detected with radiography in 27 patients. Most (55 calcifications, 98%) could be identified as calcifications by using SWI. Standard T1- and T2-weighted sequences were used to identify 33 calcifications (59%). SWI yielded a sensitivity of 98% (95% confidence interval [CI]: 0.943, 1) and specificity of 96% (95% CI: 0.886, 1) for the identification of calcifications when compared with radiography. Standard rotator cuff MR sequences yielded a sensitivity of 59% (95% CI: 0.422, 0.758) and specificity of 67% (95% CI: 0.493, 0.847). Diameter measurements demonstrated a high correlation between SWI and radiography (R(2) = 0.90), with overestimation of lesion diameter at SWI (mean ± standard deviation for SWI, 7.6 mm ± 5.4; for radiography, 5.3 mm ± 5.1). SWI yielded higher interobserver agreement (R(2) = 0.99, P < .001; 95% CI: 0.989, 0.996) compared with standard MR sequences (R(2) = 0.67, P = .62; 95% CI: 0.703, 0.899). In phantom experiments, SWI and computed tomography were used to identify small calcifications that were missed at radiography. CONCLUSION: SWI enables the reliable detection of calcifications in the rotator cuff in patients with calcific tendonitis by using conventional radiography as a reference and offers better sensitivity and specificity than standard rotator cuff MR sequences.

Cardiovascular Magnetic Resonance Imaging in Patients with an Implantable Loop Recorder.

BACKGROUND: Implantable loop recorders (ILRs) allow continuous cardiac monitoring for 3-6 years and are a valuable tool for the investigation of syncopal episodes, palpitations, and atrial fibrillations as well as risk stratification after myocardial infarction. Although magnetic resonance imaging (MRI) in patients with ILRs has been shown to be safe, the impact of ILRs on cardiac MRI image quality has not been investigated yet. Thus, we tested the diagnostic value of cardiac MRI in patients with various types of ILRs. METHODS: Two patients with an ILR and a clinical indication to assess myocardial burden of scarring and fibrosis or stress-induced myocardial ischemia underwent cardiac MRI. Device interrogation was performed prior to, immediately after, and 3 months after cardiac MRI. RESULTS: The post-MRI follow-ups revealed no change in programmed ILR parameters, sensing fidelity, and battery parameters. However, ILRs caused significant, uninterpretable hyperintensity artifacts in cardiac MRI. CONCLUSIONS: Further clinical studies are warranted to investigate whether modified MRI techniques are helpful to eliminate imaging artifacts.

Positive Outcome After a Small-Caliber Gunshot Fracture of the Upper Cervical Spine without Neurovascular Damage.

BACKGROUND: Gunshot wounds to the cervical spine most frequently concur with serious injuries to the spinal cord and cervical vessels and often have a fatal outcome. CASE REPORT: We describe the case of a 35-year-old male with a complex fracture of the C2 vertebra body and a mandibular fracture after a penetration gunshot to the cervical spine. Computed tomography (CT) at admission revealed the exact extent of the fractures and the small caliber bullet lodged next to the C2 vertebra. In this rare and extremely lucky case no collateral vascular or neurological damage was detected. Eighteen months after surgical bullet removal and posterior C1-C3 fusion complete bone healing of the C2 vertebra was achieved and there were no secondary neurovascular deficits. CONCLUSIONS: Immediate surgical C1-C3 fixation resulted in an excellent outcome without secondary neurovascular deficits in this rare case of traumatic complex C2 vertebral fracture caused by a gunshot injury.

Implications of imaging criteria for the management and treatment of intraductal papillary mucinous neoplasms - benign versus malignant findings.

OBJECTIVES: Evaluation of computed tomography (CT) and magnetic resonance imaging (MRI) for differentiation of pancreatic intraductal papillary mucinous neoplasm (IPMN) subtypes based on objective imaging criteria. METHODS: Fifty-eight patients with 60 histologically confirmed IPMNs were included in this retrospective study. Eighty-three imaging studies (CT,n = 42; MRI,n = 41) were analysed by three independent blinded observers (O1-O3), using established imaging criteria to assess likelihood of malignancy (-5, very likely benign; 5, very likely malignant) and histological subtype (i.e., low-grade (LGD), moderate-grade (MGD), high-grade dysplasia (HGD), early invasive carcinoma (IPMC), solid carcinoma (CA) arising from IPMN). RESULTS: Forty-one benign (LGD IPMN,n = 20; MGD IPMN,n = 21) and 19 malignant (HGD IPMN,n = 3; IPMC,n = 6; solid CA,n = 10) IPMNs located in the main duct (n = 6), branch duct (n = 37), or both (n = 17) were evaluated. Overall accuracy of differentiation between benign and malignant IPMNs was 86/92 % (CT/MRI). Exclusion of overtly malignant cases (solid CA) resulted in overall accuracy of 83/90 % (CT/MRI). The presence of mural nodules and ductal lesion size ≥30 mm were significant indicators of malignancy (p = 0.02 and p < 0.001, respectively). CONCLUSIONS: Invasive IPMN can be identified with high confidence and sensitivity using CT and MRI. The diagnostic problem that remains is the accurate radiological differentiation of premalignant and non-invasive subtypes. KEY POINTS: • CT and MRI can differentiate benign from malignant forms of IPMN. • Identifying (pre)malignant histological IPMN subtypes by CT and MRI is difficult. • Overall, diagnostic performance with MRI was slightly (not significantly) superior to CT.

Gd-EOB enhanced MRI T1-weighted 3D-GRE with and without elevated flip angle modulation for threshold-based liver volume segmentation.

BACKGROUND: Despite novel software solutions, liver volume segmentation is still a time-consuming procedure and often requires further manual optimization. With the high signal intensity of the liver parenchyma in Gd-EOB enhanced magnetic resonance imaging (MRI), liver volume segmentation may be improved. PURPOSE: To evaluate the practicability of threshold-based segmentation of the liver volume using Gd-EOB-enhanced MRI including a customized three-dimensional (3D) sequence. MATERIAL AND METHODS: A total of 20 patients examined with Gd-EOB MRI (hepatobiliary phase T1-weighted (T1W) 3D sequence [VIBE]; flip angle [FA], 10° and 30°) were enrolled in this retrospective study. The datasets were independently processed by two blinded observers (O1 and O2) in two ways: manual (man) and threshold-based (thresh; study method) segmentation of the liver each followed by an optimization step (man+opt and thresh+opt; man+opt [FA10°] served as reference method). Resulting liver volumes and segmentation times were compared. A liver conversion factor was calculated in percent, describing the non-hepatocellular fraction of the total liver volume, i.e. bile ducts and vessels. RESULTS: Thresh+opt (FA10°) was significantly faster compared to the reference method leading to a median volume overestimation of 4%/8% (P < 0.001). Using thresh+opt (FA30°), segmentation was even faster (P < 0.001) and even reduced median volume deviation of 0%/2% (O1/O2; both P > 0.2). The liver conversion factor was found to be 10%. CONCLUSION: Threshold-based liver segmentation employing Gd-EOB-enhanced hepatobiliary phase standard T1W 3D sequence is accurate and time-saving. The performance of this approach can be further improved by increasing the FA.

MR guidance and thermometry of percutaneous laser disc decompression in open MRI: an initial clinical investigation.

OBJECTIVES: To assess the feasibility, safety and efficacy of real-time MR guidance and thermometry of percutaneous laser disc decompression (PLDD). METHODS: Twenty-four discs in 22 patients with chronic low-back and radicular pain were treated by PLDD using open 1.0-T magnetic-resonance imaging (MRI). A fluoroscopic proton-density-weighted turbo spin-echo (PDw TSE) sequence was used to position the laser fibre. Non-spoiled gradient-echo (GRE) sequences were employed for real-time thermal monitoring based on proton resonance frequency (PRF). Radicular pain was assessed over 6 months with a numerical rating scale (NRS). RESULTS: PLDD was technically successful in all cases, with adequate image quality for laser positioning. The PRF-based real-time temperature monitoring was found to be feasible in practice. After 6 months, 21 % reported complete remission of radicular pain, 63 % at least great pain relief and 74 % at least mild relief. We found a significant decrease in the NRS score between the pre-intervention and the 6-month follow-up assessment (P < 0.001). No major complications occurred; the single adverse event recorded, moderate motor impairment, resolved. CONCLUSIONS: Real-time MR guidance and PRF-based thermometry of PLDD in the lumbar spine under open 1.0-T MRI appears feasible, safe and effective and may pave the way to more precise operating procedures. KEY POINTS: • Percutaneous laser disc decompression (PLDD) is increasingly used instead of conventional surgery. • Open 1.0-T MRI with temperature mapping seems technically successful in monitoring PLDD. • Pain relief was at least 'great' in 64 % of patients. • No major complications occurred. • Open 1.0-T MRI appears a safe and effective option for patient-tailored PLDD.

Ankle laxity: stress investigation under MRI control.

OBJECTIVE: The purpose of this study was to examine the advantages of MRI-guided ankle stress examinations in the detection of chronic ankle instability. SUBJECTS AND METHODS: An MRI-compatible stress device was developed and tested for MRI safety. Bilateral MRI stress examinations were performed on 50 volunteers with and without clinically evident subjective instability of the ankle joints (72 subjective stable ankle joints in 37 subjects, 28 ankles in 15 subjects with chronic ankle instability). Both the inversion test and the anterior drawer test were performed under axial, coronal, 45° paraxial, and sagittal T2-weighted fast spin-echo image control. MR images were assessed for talar tilt, subtalar tilt, anterior talus translation, anterior calcaneus translation, medial talocalcaneal translation, and the diameters of the lateral ankle ligaments (anterior talofibular ligament, calcaneofibular ligament, and posterior talofibular ligament). RESULTS: The MRI stress device was found suitable and safe for use in the MRI environment. The talocrural and subtalar joints could be assessed simultaneously. Significant differences between groups A and B (p≤0.05) were found in talar tilt, subtalar tilt, anterior talus translation, anterior calcaneus translation, medial talocalcaneal translation, and decrease in diameters of calcaneofibular and posterior talofibular ligaments. Also found were sex differences in talar tilt, subtalar tilt, anterior talus translation, and diameters of the anterior talofibular, calcaneofibular, and posterior talofibular ligaments. Significant relations were found between talar tilt and anterior talus translation, subtalar tilt and anterior calcaneus translation, subtalar tilt and medial talocalcaneal translation, and between anterior calcaneus translation and medial talocalcaneal translation in groups A and B. CONCLUSION: Stress examination under MRI control has advantages in the assessment of mechanical ankle instability. Additional diagnostic and clinically relevant information is obtained through direct imaging of the ligaments and assessment of additional parameters of ankle laxity (subtalar tilt, anterior calcaneus translation, medial talocalcaneal translation). The main advantages are objective imaging and measurement of abnormal looseness of the lower ankle joint and its direct simultaneous comparison with the upper ankle joint.

Evaluation of a MR-quadrupole imaging coil for spinal interventions in a vertical 1.0 T MRI.

The in vivo pain treatment was successfully performed with the patient in a prone position. The PD-weighted TSE with echo time = 10 ms rendered contrast-to-noise-ratio values of 27 ± 10 for needle/fat, 1.6 ± 5 for needle/muscle, and 4 ± 4.7 for needle/nerve tissue. The mean diameter of the needle artifact was 1.2 ± 0.2 mm. In the T(1)-weighted gradient echo, the needle's artifact diameter was 6 ± 2 mm; the needle's contrast-to-noise ratio relative to muscle tissue was 4 ± 2, 7.6 ± 1.5 for needle/fat, and 5 ± 1 for needle/nerve tissue. With the PD-weighted TSE (echo time = 10 ms) and the T(1)-weighted gradient echo, the needle was imaged reliably throughout the intervention. The butterfly surface coil is feasible for the guidance of spinal interventions in a prone patient.

Wearable cardioverter-defibrillator: friend or foe in suspected myocarditis?

AIM: Wearable cardioverter defibrillator (WCD, LifeVest, and Zoll) therapy has become a useful tool to bridge a temporarily increased risk for sudden cardiac death. However, despite extensive use, there is a lack of evidence whether patients with myocarditis and impaired LVEF may benefit from treatment with a WCD. METHODS AND RESULTS: We conducted a single-centre retrospective observational study analysing patients with a WCD prescribed between September 2015 and April 2020 at our institution. In total, 135 patients were provided with a WCD, amongst these 76 patients (mean age 48.9 ± 13.7 years; 84.2% male) for clinically suspected myocarditis. Based on the results of the endomyocardial biopsy and, where available cardiac magnetic resonance imaging, 39 patients (51.3%) were diagnosed with myocarditis and impaired LVEF and 37 patients (48.7%) with dilated cardiomyopathy (DCM) without evidence of cardiac inflammation. The main immunohistopathological myocarditis subtype was lymphocytic myocarditis in 36 (92.3%) patients, and four patients (10.3%) of this group had an acute myocarditis. Three patients had cardiac sarcoidosis (7.7%). Ventricular tachycardia occurred in seven myocarditis (in total 41 VTs; 85.4% non-sustained) and one DCM patients (in total one non-sustained ventricular tachycardia). Calculated necessary WCD wearing time until ventricular tachycardia occurrence is 86.41 days in myocarditis compared with 6.46 years in DCM patients. CONCLUSIONS: Our data suggest that myocarditis patients may benefit from WCD therapy. However, as our study is not powered for outcome, further randomized studies powered for the outcome morbidity and mortality are necessary.

Intradiscal temperature monitoring using double gradient-echo pulse sequences at 1.0T.

PURPOSE: To validate an unspoiled gradient-recalled echo pulse sequence with dual echo acquisition as a means to increase temperature sensitivity while monitoring intradiscal laser ablation therapy. MATERIALS AND METHODS: Phantom experiments as well as in vitro thermal ablation simulations were performed in an open 1.0T magnetic resonance (MR) scanner. Three methods of noninvasive MR-thermometry based on the signal void decrease caused by T1-relaxation time increase (T1), the temperature-dependent proton resonance frequency (PRF) shift, and a combination of both methods with complex differences (CD) were compared. Temperature accuracy and reliability of temperature distribution were the main assessment criteria. RESULTS: The optimum temperature sensitivity was found using CD in phantom experiments. During in vitro experiments the PRF showed the smallest margin of error (T1: +/-1.64 degrees C, PRF: +/-1.23 degrees C, CD: +/-1.29 degrees C) and the best qualitative evaluation of temperature. CONCLUSION: Intradiscal temperature monitoring with an unspoiled dual-echo sequence is most accurate with PRF-thermometry in combination with the long echo time. Magnitude images with an initial short echo time permit high image detail of the heat-induced lesion.

Evaluation of thermometric monitoring for intradiscal laser ablation in an open 1.0 T MR scanner.

PURPOSE: The purpose of this study was to evaluate different methods of magnetic resonance thermometry (MRTh) for the monitoring of intradiscal laser ablation therapy in an open 1.0 Tesla magnetic resonance (MR) scanner. MATERIAL AND METHODS: MRTh methods based on the two endogenous MR temperature indicators of spin-lattice relaxation time T1 and water proton resonance frequency (PRF) shift were optimised and compared in vitro. For the latter, we measured the effective spin-spin relaxation times T2* in intervertebral discs of volunteers. Then we compared four gradient echo-based imaging techniques to monitor laser ablations in human disc specimens. Criteria of assessment were outline of anatomic detail, immunity against needle artefacts, signal-to-noise ratio (SNR) and accuracy of the calculated temperature. RESULTS: T2* decreased in an inverse and almost linear manner with the patients' age (r = 0.9) from 70 to 30 ms (mean of 49 ms). The optimum image quality (anatomic details, needle artefacts, SNR) and temperature accuracy (+/-1.09 degrees C for T1-based and +/-1.11 degrees C for PRF-based MRTh) was achieved with a non-spoiled gradient-echo sequence with an echo time of TE = 10 ms. CONCLUSION: Combination of anatomic and thermometric non-invasive monitoring of laser ablations in the lumbar spine is feasible. The temperature accuracy of the investigated T1- and PRF-based MRTh methods in vitro is high enough and promises to be reliable in vivo as well.

Recurrent osteoid osteoma: interstitial laser ablation under magnetic resonance imaging guidance.

Thermal ablation has become a therapy of choice in the treatment of osteoid osteomas. To date, computed tomography has been the standard imaging modality for minimally invasive treatment regimes. We report a case of a 46-year-old man with a recurrent osteoid osteoma in the right tibial head after CT-guided drill excision and repeat treatment with laser ablation under open high-field MRI guidance. We describe the steps of the interventional MRI procedure and discuss related innovative guidance and monitoring features, and potential benefits of MRI compared with CT-guided techniques. In conclusion, MR-guided laser ablation was proved to be safe and effective.

Passive navigation principle for orthopedic interventions with MR fluoroscopy.

INTRODUCTION: Of late, computer-assisted surgery has become a novel challenge for orthopedic surgeons. However, for orthopedic interventions magnetic resonance (MR) fluoroscopy is in its early stages of development. The authors have developed an innovative passive navigation concept, which is potentially applicable for many magnetic resonance image (MRI)-guided musculoskeletal interventions. With this method, no switching between different planes is required, since the cross-sectional modality of the MRI is used as a new navigation approach. MATERIALS AND METHODS: This method was mainly evaluated in retrograde drilling of artificial osteochondral lesions of the talus as an example of difficult navigation in drill placement due to poor visualization with X-ray and complex anatomy. To accomplish this objective, a passive navigation device was constructed and evaluated in nine cadaveric ankle joint specimens. Feasibility and accuracy of navigated drillings were evaluated. RESULTS: The interactive high-field MR fluoroscopy and the passive aiming device allow precise drilling of osteochondral lesions of the talus, despite the complex anatomy of the ankle. Drillings could be performed with an accuracy of 1.6 mm. The drilling guide was safe and easy to handle. CONCLUSION: The MR-assisted retrograde drilling of osteochondral lesions may enable precise and safe treatment without radiation exposure. This passive navigation technique for MR fluoroscopy is potentially applicable for many orthopedic interventions and may present an alternative to other navigation methods. Especially, the treatment of pediatric and adolescent patients may benefit from the typical MRI properties.

68Ga-PSMA-PET/CT for the evaluation of liver metastases in patients with prostate cancer.

BACKGROUND: The purpose of this study was to evaluate the imaging properties of hepatic metastases in 68Ga-PSMA positron emission tomography (PET) in patients with prostate cancer (PC). METHODS: 68Ga-PSMA-PET/CT scans of PC patients available in our database were evaluated retrospectively for liver metastases. Metastases were identified using 68Ga-PSMA-PET, CT, MRI and follow-up scans. Different parameters including, maximum standardized uptake values (SUVmax) of the healthy liver and liver metastases were assessed by two- and three-dimensional regions of interest (2D/3D ROI). RESULTS: One hundred three liver metastases in 18 of 739 PC patients were identified. In total, 80 PSMA-positive (77.7%) and 23 PSMA-negative (22.3%) metastases were identified. The mean SUVmax of PSMA-positive liver metastases was significantly higher than that of the normal liver tissue in both 2D and 3D ROI (p ≤ 0.05). The mean SUVmax of PSMA-positive metastases was 9.84 ± 4.94 in 2D ROI and 10.27 ± 5.28 in 3D ROI; the mean SUVmax of PSMA-negative metastases was 3.25 ± 1.81 in 2D ROI and 3.40 ± 1.78 in 3D ROI, and significantly lower than that of the normal liver tissue (p ≤ 0.05). A significant (p ≤ 0.05) correlation between SUVmax in PSMA-positive liver metastases and both size (ρSpearman = 0.57) of metastases and PSA serum level (ρSpearman = 0.60) was found. CONCLUSIONS: In 68Ga-PSMA-PET, the majority of liver metastases highly overexpress PSMA and is therefore directly detectable. For the analysis of PET images, it has to be taken into account that also a significant portion of metastases can only be detected indirectly, as these metastases are PSMA-negative.

Performance survey on a new standardized formula for oral signal suppression in MRCP.

BACKGROUND: Orally administered substances, which reduce image contamination by overlying gastrointestinal fluid signals, can be used to enhance the quality of MRCP images. Recently, a new standardized formula consisting of biological substances has become available. The objective of this study is to provide a first assessment of achievable MRCP image quality, taste and palatability of this new dedicated agent. METHODS: In January 2015 to May 2015 practicing radiologists in Germany, Austria and Switzerland were asked to evaluate image quality as well as taste and palatability when using the new agent (LumiVision®; b.e. imaging; Baden-Baden; Germany) in MRCP questionnaire. Both criteria were rated with a 6-point Likert scale ranging from "1" (best) to "6" (worst). RESULTS: A total 185 of 475 radiologic institutions (39%) submitted feedback on image quality, 187 (39%) on the taste/palatability. Assessments of image quality regarding presence of disturbing gastrointestinal fluid signal resulted in a median of 2. The majority of patients rated the subjective taste as very good (median of 1). No side effects of relevance were recorded. CONCLUSION: This large survey shows that the tested product is considered effective by radiologists regarding MRCP image quality. Patients' feedback on taste and palatability was very positive.