Novel Metal Artifact Reduction Techniques with Use of Slice-Encoding Metal Artifact Correction and View-Angle Tilting MR Imaging for Improved Visualization of Brain Tissue near Intracranial Aneurysm Clips.

PURPOSE: The MR image quality after intracranial aneurysm clipping is often impaired because of artifacts induced by metal implants. The purpose of the present study was to evaluate the benefit of a new WARP sequence with slice-encoding metal artifact correction (SEMAC) and view-angle tilting (VAT) MR imaging as novel artifact reduction techniques. MATERIALS AND METHODS: A new WARP TSE (a work-in-progress software package provided by Siemens Healthcare) sequence was implemented for cranial applications based on a turbo spin echo (TSE) sequence. T1- and T2-weighted images with standard and WARP TSE sequences were acquired from 6 patients with 11 clipping sites, and the images were compared based on artifact size and general image quality. RESULTS: T2- and T1-weighted WARP TSE sequences resulted in a highly significant reduction of metal artifacts compared with standard sequences (T2w- WARP TSE: 89.8 ± 1.4 %; T1w- WARP TSE: 84.9 ± 2.9 %; p < 0.001) without a substantial loss of image quality. CONCLUSION: The use of a new WARP TSE sequence after aneurysm clipping is highly beneficial for increasing the diagnostic MR image quality due to a striking reduction of metal artifacts.

[Classification of normal labral variants and labral injuries]. / Klassifikation von Normvarianten des Labrums und Labrumverletzungen.

The glenoid labrum is an important stabilizer of the glenohumeral joint. Labral injuries affect the stability of the shoulder joint to varying degrees depending on the localization, the extension and the structures involved. Because of the complex anatomy and the high variability of the glenoid labrum, in-depth knowledge concerning normal variations and labral injury patterns is required as well as high-resolution imaging with intra-articular contrast in order to discriminate anatomical variants from pathological findings. Therefore, magnetic resonance (MR) and alternatively computed tomography (CT) arthrography have become established as the imaging methods of choice. In this review MR arthrographic findings of normal labral variants and different labral injury patterns are portrayed.

High-resolution bone imaging for osteoporosis diagnostics and therapy monitoring using clinical MDCT and MRI.

Osteoporosis is classified as a public health problem due to its increased risk for fragility fractures. Osteoporotic fractures, in particular spine and hip fractures, are associated with a high morbidity and mortality, and generate immense financial cost. The World Health Organisation (WHO) based the diagnosis of osteoporosis on the measurement of bone mineral density (BMD) using dual-energy X-ray absorptiometry (DXA). However, BMD values of subjects with versus without osteoporotic fractures overlap. Furthermore, it was reported that the anti-fracture effects of drugs could be only partially explained by their effects on BMD. Bone strength reflects the integration of BMD and bone quality. The later can be partly determined by measurements of bone microstructure. Therefore, substantial research efforts have been undertaken to assess bone microstructure by using high-resolution imaging techniques, including high-resolution peripheral quantitative computed tomography (hr-pQCT), high-resolution multi-detector computed tomography (MDCT), and high-resolution magnetic resonance imaging (MRI). Clinical MDCT and MRI systems are broadly available and allow an adequate depiction of the bone microstructure at the clinically most important fracture sites, i.e. radius, spine and hip. Bone microstructure parameters and finite element models can be computed in high-resolution MDCT and MR images. These measurements improved the prediction of bone strength beyond the DXA-derived BMD and revealed pharmacotherapy effects, which are partly not captured by BMD. Therefore, high-resolution bone imaging using clinical MDCT and MRI may be beneficial for osteoporosis diagnostics and allow a highly sensitive monitoring of drug treatment, which plays an important role in the prevention of fragility fractures.

[Imaging of patellofemoral instability]. / Bildgebung der patellofemoralen Instabilität.

Patellofemoral instability remains a diagnostic and therapeutic challenge due to its multifactorial genesis. The purpose of imaging is to systematically analyze predisposing factors, such as trochlear dysplasia, patella alta, tibial tuberosity-trochlear groove (TT-TG) distance, rotational deformities of the lower limb and patellar tilt. In order to evaluate anatomical abnormalities with a sufficient diagnostic accuracy, standardized measurement methods and implementation of various imaging modalities are necessary.Diagnosis of acute and often overlooked lateral patellar dislocation can be established with magnetic resonance imaging (MRI) because of its characteristic patterns of injury. Damage to the medial patellofemoral ligament (MPFL) has a significance just as high as the predisposing risk factors in relation to the cause of chronic instability.

Irreversible muscle damage in bodybuilding due to long-term intramuscular oil injection.

Intramuscular oil injections generating slowly degrading oil-based depots represent a controversial subject in bodybuilding and fitness. However they seem to be commonly reported in a large number of non-medical reports, movies and application protocols for 'site-injections'. Surprisingly the impact of long-term (ab)use on the musculature as well as potential side-effects compromising health and sports ability are lacking in the medical literature. We present the case of a 40 year old male semi-professional bodybuilder with systemic infection and painful reddened swellings of the right upper arm forcing him to discontinue weightlifting. Over the last 8 years he daily self-injected sterilized sesame seed oil at numerous intramuscular locations for the purpose of massive muscle building. Whole body MRI showed more than 100 intramuscular rather than subcutaneous oil cysts and loss of normal muscle anatomy. 2-step septic surgery of the right upper arm revealed pus-filled cystic scar tissue with the near-complete absence of normal muscle. MRI 1 year later revealed the absence of relevant muscle regeneration. Persistent pain and inability to perform normal weight training were evident for at least 3 years post-surgery. This alarming finding indicating irreversible muscle mutilation may hopefully discourage people interested in bodybuilding and fitness from oil-injections. The impact of such chronic tissue stress on other diseases like malignancy remains to be determined.

[Femoral osteotomy for patellofemoral instability]. / Femorale Osteotomien bei patellofemoraler Instabilität.

Axis and torsion malalignment of the femur has been widely recognized as a primary reason for patellofemoral instability and pain. In this article we explain the current concepts of biomechanics and describe the radiological findings in computed tomography (CT) examination. We describe the technique of a biplanar varus and/or external rotation distal femoral osteotomy in detail. Existing clinical studies describe this technique as part of a multimodal treatment concept with good to excellent results. We present our current technique and clinical results.

Clinical and structural evaluation of arthroscopic double-row suture-bridge rotator cuff repair: early results of a novel technique.

PURPOSE: Assessment of repair integrity and clinical outcome after arthroscopic repair of rotator cuff tears in double-row suture-bridge technique with the use of a new knotless suture-anchor system. METHODS: The first treated 25 patients with arthroscopic rotator cuff repair in the suture-bridge technique using a novel knotless anchor and chain-link suture system were evaluated. Patients with isolated full-thickness supraspinatus tears were selected. They were followed clinically with functional scores (Constant score, ASES index), visual analog scale (VAS), and instrumentally with Isobex digital strength analyzer preoperatively, at 6 and 14 months postoperatively. The repair integrity was evaluated with MRI at an average of 14 months postoperatively. RESULTS: Significant improvement of pain, strength, range of motion, and functional scores occurred (P < 0.05). There was a re-tear rate of 20%. The subjective parameters (VAS and ASES Index) showed non-significant (n.s.) differences between the re-tear and intact repair groups, whereas the objective parameters (Constant score, muscle power and active ROM) showed significant differences between both groups (P < 0.05). CONCLUSION: The functional outcome has improved significantly with this new knotless anchor-chain system and was more superior in shoulders with intact repair, whereas the resulted repair integrity was not better than other types of double-row repair techniques mentioned in the recent literature. However, this early report of the novel technique may show limited power for comparison due to the relatively small sample size.

[Ultrasound-guided intraarticular injection for MR arthrography of the shoulder]. / Ultraschallgesteuerte intraartikuläre Kontrastmittelapplikation für die MR-Arthrografie der Schulter.

PURPOSE: To evaluate ultrasound guidance for intraarticular contrast injection via an anterolateral approach in comparison with fluoroscopic guidance. MATERIALS AND METHODS: Contrast agent injection was performed in 40 consecutive patients, 20 under sonographic guidance and 20 under fluoroscopic guidance. None of the patients had previous shoulder surgery. The procedure time was measured and the efficiency of joint distension, incidence of extravasation and intraarticular air on the consecutive MR arthrograms were assessed by three blinded radiologists with musculoskeletal radiology experience. Statistical analysis was performed using the Kruskal-Wallis test. RESULTS: Intraarticular contrast injection was successfully accomplished in all 40 patients. Subsequent MR arthrograms did not show any significant difference between sonographic and fluoroscopic guidance with respect to diagnostic quality, joint distension (p=0.6665), intraarticular air bubbles (p=0.1567) and occurrence of contrast extravasation (p=0.8565). The mean duration of ultrasound-guided injection was 7:30 min compared to a shorter procedure time of 4:15 min for fluoroscopic guidance. In both groups, no procedural complications were observed. CONCLUSION: Ultrasound-guided injection for MR arthrography of the shoulder via an anterolateral approach represents a simple, safe, and effective technique which yields comparable results to those of injection under fluoroscopic guidance, but is slightly more time-consuming.

[Persistent knee pain and palpable tumor in the popliteal fossa]. / Persistierende Knieschmerzen und palpabler Tumor in der Kniekehle.

The case of a female Patient with increasing pain and a palpable mass in the right popliteal fossa shows the spectrum of possible differential diagnoses for the radiologist. The diagnosis of a juxtaarticular myxoma made on the interpretation of conventional x-ray and magnetic resonance imaging was finally confirmed by biopsy.

Rotator cuff tears: assessment with MR arthrography in 275 patients with arthroscopic correlation.

We assessed the diagnostic performance of magnetic resonance (MR) arthrography in the diagnosis of articular-sided partial-thickness and full-thickness rotator cuff tears in a large symptomatic population. MR arthrograms obtained in 275 patients including a study group of 139 patients with rotator cuff tears proved by arthroscopy and a control group of 136 patients with arthroscopically intact rotator cuff tendons were reviewed in random order. MR imaging was performed on a 1.0 T system (Magnetom Expert, Siemens). MR arthrograms were analyzed by two radiologists in consensus for articular-sided partial-thickness and full-thickness tears of the supraspinatus, infraspinatus, and subscapularis tendons. At arthroscopy, 197 rotator cuff tears were diagnosed, including 105 partial-thickness (93 supraspinatus, nine infraspinatus, three subscapularis) and 92 full-thickness (43 supraspinatus, 20 infraspinatus, 29 subscapularis) tendon tears. For full-thickness tears, sensitivity, specificity, and accuracy were 96%, 99%, and 98%, respectively, and for partial tears 80%, 97%, and 95%, respectively. False negative and positive assessments in the diagnosis of articular-sided partial-thickness tears were predominantly [78% (35/45)] observed with small articular-sided (Ellman grade1) tendon tears. MR arthrography is highly accurate in the diagnosis of full-thickness rotator cuff tears and is accurate in the diagnosis of articular-sided partial-thickness tears. Limitations in the diagnosis of partial-thickness tears are mainly restricted to small articular-sided tears (Ellman grade 1) due to difficulties in differentiation between fiber tearing, tendinitis, synovitic changes, and superficial fraying at tendon margins.

[Magnetic resonance imaging of glenohumeral instability]. / Stellenwert der MR-Bildgebung bei der Diagnostik der Schulterinstabilität.

Conventional MR imaging and MR arthrography are established diagnostic imaging modalities for investigating shoulder instability. Since there are currently various surgical shoulder stabilization methods as well as conservative treatment strategies, the role of imaging is to provide diagnostic information to help determine the therapeutic approach. Whereas conventional MR imaging is usually sufficient for the evaluation of acute shoulder injuries due to the presence of a posttraumatic joint effusion, MR arthrography is the imaging modality of choice for chronic shoulder instability. Atraumatic and microtraumatic instability of the shoulder must be distinguished from traumatic instability since clinical findings and secondary or associated injuries differ from those of traumatic instability. Injuries of the IGHL-complex can be reliably diagnosed with MR arthrography. Traumatic anteroinferior luxation causes labroligamentous injuries at the glenoid insertion (Bankart-, Perthes-, ALPSA-, and non-classifiable chronic lesions) and injuries of the IGHL and its humeral insertion (HAGL-, BHAGL-, and floating AIGL-lesions). The type of injury and extent of degenerative changes or scarring that can be assessed with MR arthrography influence the therapeutic approach and in particular the decision between arthroscopic and open surgical methods of stabilization.

Comparison of multislice CT arthrography and MR arthrography for the detection of articular cartilage lesions of the elbow.

The objective of this study was to compare the value of multislice CT arthrography and MR arthrography in the assessment of cartilage lesions of the elbow joint. Twenty-six cadaveric elbow specimens were examined with the use of CT arthrography and MR arthrography prior to joint exploration and macroscopic inspection of articular cartilage. Findings at CT and MR arthrography were compared with macroscopic assessments in 104 cartilage areas. At macroscopic inspection, 45 cartilage lesions (six grade 2 lesions, 25 grade 3 lesions, 14 grade 4 lesions) and 59 areas of normal articular cartilage were observed. With macroscopic assessment as the gold standard CT and MR arthrography showed an overall sensitivity/specificity of 80/93% and 78/95% for the detection of cartilage lesions, respectively. Only two of six grade 2 lesions were detected by CT and MR arthrography. For the diagnosis of grade 3 and 4 lesions, the sensitivity/specificity was 87/94% with CT arthrography, and 85/95% with MR arthrography. In an experimental setting multislice CT arthrography and MR arthrography showed a similar performance in the detection of cartilage lesions. Both methods indicated limited value in the diagnosis of grade 2 articular cartilage lesions.

[MR imaging of variants of the superior labral-bicipital complex and SLAP lesions]. / Normvarianten des oberen Labrum-Bizepssehnen-Komplexes und differentialdiagnostische Kriterien von SLAP-Läsionen in der Magnetresonanztomographie.

In the detection of SLAP (superior labral anterior to posterior) lesions of the shoulder MR arthrography shows a significantly higher sensitivity compared with conventional MR techniques and therefore, represents the method of choice in diagnostic imaging of the superior labral-bicipital complex. On the basis of morphological criteria it mostly allows distinction of traumatic lesions and anatomic variants of the superior labrum and the biceps anchor as well as classification of detected SLAP lesions (types 1-4 according to Snyder). However, the differentiation of a SLAP type 2 lesion and a sublabral recess can be very difficult, even if all distinction criteria are considered.

Changes in calcaneal trabecular bone structure assessed with high-resolution MR imaging in patients with kidney transplantation.

The purpose of this study was to use high-resolution magnetic resonance (HR-MR) imaging to analyze the trabecular bone structure of the calcaneus in patients before and after renal transplantation and to compare this technique with bone mineral density (BMD) in predicting therapy-induced bone loss and osteoporotic fracture status. HR-MR imaging (voxel size: 0.195 x 0.195 x 1 mm) was performed at 1.5 T with an axial and sagittal orientation in 48 patients after transplantation, 12 patients before renal transplantation and 20 healthy controls. Structure measures analogous to standard histomorphometry and fractal dimension were determined in these images. BMD measurements of the lumbar spine and the proximal femur were obtained in the healthy female controls and the patients. Vertebral and peripheral fracture status were determined in all patients. The structural measures app.BV/TV, Tb.Sp, Tb.Th and Tb.N showed significant differences between controls and patients (p<0.05) while fractal dimension showed no significant differences. Neither the structural measures nor BMD showed significant differences between patients before and after transplantation. Correlations between time after transplantation versus structural measures and BMD were not significant. Differences between fracture and nonfracture patients were significant for the structural measures app.BV/TV, Tb.Sp and Tb.N (axial images) as well as for app.Tb.Th (sagittal images) and spine BMD (p<0.05) but not for hip BMD. Using odds ratios the strongest discriminators between patients with and without fractures were app. BV/TV, app.Tb.Sp (axial images) and app.Tb.Th (sagittal images), even after adjustment for age and BMD. Using receiver operating characteristic analysis the highest diagnostic performance was found for a combination of BMD and structural measures. In conclusion, our results indicate that structural measures obtained from HR-MR images may be used to characterize fracture incidence in kidney transplant patients; the best results, however, are obtained using a combination of BMD and structural measures.

[The texture-analysis of high-resolution computed tomograms as an additional procedure in osteoporosis diagnosis: in-vitro studies on vertebral segments]. / Strukturanalyse hochauflösender Computertomogramme als ergänzendes Verfahren in der Osteoporosediagnostik: in-vitro-Untersuchungen an Wirbelsäulensegmenten.

PURPOSE: The purpose of this study was to perform texture analysis of high-resolution CT images obtained from human vertebral specimens and to correlate these parameters with the biomechanical stability of the specimens. In addition, structure data were compared with bone mineral density (BMD) assessed by quantitative CT (QCT). MATERIAL AND METHODS: High-resolution CT images and standard QCT sections were obtained in 36 vertebral motion segments, each consisting of two vertebrae with intact ligaments and intervertebral disc. The trabecular structure in the CT images was assessed using three texture analysis techniques: Trabecular threshold area ratio (TTAR), fractal dimension without thresholding (OTS) and fractal dimension with thresholding (ITS). Finally, the maximum compressive strength (MCS) was determined using a biomechanical testing device. RESULTS: A correlation of r = 0.76 (p < 0.01) was obtained for TTAR versus MCS, of r = 0.83 (p < 0.01) for ITS versus MCS, and of r = 0.35 (p > 0.01) for OTS versus MCS, while r = 0.76 (p < 0.01) was found for BMD versus MCS. Best results were obtained by combining structure measures and BMD (r = 0.85, p < 0.01). CONCLUSIONS: This in vitro study showed a significant correlation between structure measures and biomechanical strength, which was comparable to BMD and strength. However, best correlations were obtained by combining both measures. Using both BMD and structure measures therefore may improve the prediction of biomechanically determined bone strength.

[Computer-assisted structure analysis of trabecular bone in the diagnosis of osteoporosis]. / Computergestützte Strukturanalyse des trabekulären Knochens in der Osteoporosediagnostik.

Osteoporosis is characterized by reduced bone mass and a deterioration of bone structure which results in an increased fracture risk. The purpose of this review is to evaluate structure analysis techniques in the diagnosis of osteoporosis. Several imaging techniques were applied to analyze trabecular bone, such as conventional radiography, high-resolution computed tomography (HR-CT) and high-resolution magnetic resonance imaging (HR-MRI). The best results were obtained using high-resolution tomographic techniques. The highest spatial resolutions in vivo were achieved using HR-MRI. These studies show that texture parameters and bone mineral density predict bone strength and osteoporotic fractures in a complementary fashion. Combining both techniques yields the best results in the diagnosis of osteoporosis.