Ansgar Rudisch

Metallic artifacts in magnetic resonance imaging of patients with spinal fusion. A comparison of implant materials and imaging sequences.

Study Design. Devices for spinal fusion were compared with respect to their influence on magnetic resonance images. In addition, different magnetic resonance pulse sequences were evaluated to elicit their susceptibility to imaging artifacts. Objectives. To determine the implants with the least imaging artifacts as a recommendation for the spine surgeon and to assess the best imaging strategy for the radiologist. Summary of Background Data. For patients who have had surgical spinal fusion with instrumentation, magnetic resonance imaging is the most favorable diagnostic method. Unfortunately, metallic implants lead to severe degradation of image quality. These artifacts depend on the material of the implant and on the choice of the pulse sequence. Methods. The fusion devices were mounted on a simple plastic phantom in various combinations and were imaged on 1.5‐T magnetic resonance units. Frequently used types of plates and screws made of titanium or steel in various alloys were examined on the phantom with routinely used pulse sequences. The results of these examinations were compared with those in patient studies involving the same implants as well as the same pulse sequences. Results. The least imaging artifacts were caused by titanium implants, especially when using shorter screws, wider screw placement, and thinner titanium plates. Nevertheless, there were distinct image distortions that could lead to erroneous image interpretation. The best images were acquired by spin echo (T1), turbo spin echo (T1, T2), and half Fourier single shot turbo spin echo (HASTE) sequences. Sequences containing any gradient echo components (gradient echo or turbo gradient and spin echo sequence or frequency‐selective fat saturation techniques) resulted in the highest amount of image degradation. Conclusion. By choosing appropriate spinal fusion devices as well as pulse sequences, postoperative magnetic resonance imaging examinations can give acceptable results, in spite of the presence of metallic implants.

Dynamic T1 mapping predicts outcome of chemoradiation therapy in primary rectal carcinoma: Sequence implementation and data analysis

To describe details about the implementation of a dynamic T1‐mapping technique and a simple data analysis strategy that can be used to predict therapy outcome in primary rectal carcinoma and to investigate the physiologic meaning of the obtained parameter.

Pathologic-sonographic correlation in temporomandibular joint pathology.

The accuracy of high-resolution ultrasonography (HR-US) in detecting disk displacement and condylar erosion of the temporomandibular joint (TMJ) was evaluated, using corresponding cryosections as a “gold standard”. HR-US of the TMJ was performed with a high frequency 12 MHz transducer on 30 preserved autopsy specimens. Succeeding sonography, the autopsy specimens were deep-frozen and cut in paracoronal planes corresponding to the sonographic images. HR-US diagnoses were compared with cryosectional findings in a blinded fashion. HR-US detected 19 (95%) of 20 instances of condylar erosion and 16 (73%) of 22 instances of disk displacement. There were one false-positive finding for condylar erosion and two false-positive findings for disk displacement. The accuracy of HR-US evaluating condylar erosion and disk displacement rated 93% and 73%, respectively. In conclusion, condylar erosion was reliably assessed by HR-US, but the evaluation of disk position was less accurate.

Structural Characteristics of Bilateral Temporomandibular Joint Disc Displacement Without Reduction and Osteoarthrosis Are Important Determinants of Horizontal Mandibular and Vertical Ramus Deficiency: A Magnetic Resonance Imaging Study

PURPOSE To estimate in patients with temporomandibular joint (TMJ) arthralgia whether magnetic resonance (MR) imaging findings of bilateral TMJ disc displacement without reduction (DDwoR) and/or osteoarthrosis (OA) are determinants of horizontal mandibular and vertical ramus deficiencies. PATIENTS AND METHODS Bilateral MR imaging of the TMJ was performed in 68 consecutive patients with TMJ arthralgia to identify those with bilateral TMJ DDwoR and/or OA. Linear and angular cephalometric measurements were performed to apply selected criteria of horizontal mandibular (gonion-menton [Go-Me] <73 mm and articulare-pogonion [Ar-Pog] <105 mm) and vertical ramus (articulare-gonion [Ar-Go] <45 mm) deficiencies. Logistic regression analysis was used to estimate the association between selected MR imaging and cephalometric parameters. RESULTS In the age- and gender-adjusted analysis, significant increases in the risk of horizontal mandibular (odds ratio, 7.5:1; P = .031) and vertical ramus (odds ratio, 9.5:1; P = .003) deficiencies occurred with bilateral DDwoR and OA. CONCLUSION In patients with TMJ arthralgia, the MR imaging parameters of DDwoR and OA seem important determinants of horizontal mandibular and vertical ramus deficiencies.

In-vivo visualisation of the anatomical structures related to the acupuncture points Dai mai and Shen mai by MRI: A single-case pilot study

BackgroundThe concept of acupuncture point localisation in Traditional Chinese Medicine (TCM) is based on millenary practical experience. Modern imaging methods such as PET, MRI and SPECT have been used primary for the investigation of the mechanisms of action of acupuncture. In this pilot single-case study we have evaluated the technical possibilities for in-vivo imaging of the anatomical relations of acupuncture points using state of the art MRI.MethodsPreliminary experiments relating to the quality of acupuncture needles under the setting of MRI were done both with stainless steel and gold needles. In a second step, in-vivo imaging was carried out. A licensed acupuncture practitioner (RM) chose two points belonging to the so-called extraordinary vessels. In 2 sequential, separate procedures, he inserted himself gold acupuncture needles using a neutral technique (known as Ping Bu Ping Xie) into the Dai mai and Shen mai points, i.e. gall bladder 26 and bladder 62. Imaging was done on a Siemens Magnetom Avanto MR scanner using a head array and body coil. Mainly T1-weighted imaging sequences, as routinely used for patient exams, were used to obtain multi-slice images.ResultsIn the preliminary experiments only acupuncture needles made of gold showed enough stability in order to be used for further imaging procedures. Using an onion and a banana as an object, further studies showed that the gold needles produced a void defect that corresponds to the tip of the inserted needle, while at the same time an artefactually increased diameter was observed. The in-vivo experiments showed that the Dai mai point was in relation to the abdominal internal oblique muscle. The Shen mai point artefact showed up close to the longus and brevis peroneal tendons at the fibular malleolus. Side effects related to heating or burning were not observed. Improved anatomical recognition was obtained using 3D-volume rendering techniques.ConclusionThrough an adequate choice of acupuncture material (gold needles) as well as of ideal MRI imaging sequences it has been possible to visualize the anatomical characteristics at the acupuncture points Dai mai and Shen mai in-vivo. At the selected sites the needles showed a relation to tendino-fascial and muscular structures. These anatomical structures fit well into the recently described WOMED concept of lateral tension in which these acupuncture points play a regulatory role.

Are temporomandibular joint disk displacements without reduction and osteoarthrosis important determinants of mandibular backward positioning and clockwise rotation

OBJECTIVE The aim of this study was to estimate whether, in patients with temporomandibular joint (TMJ) arthralgia, the magnetic resonanace imaging (MRI) findings of bilateral TMJ disk displacement without reduction (DDwoR) and/or osteoarthrosis (OA) are determinants of mandibular backward positioning and/or clockwise rotation. STUDY DESIGN Bilateral MRI of the TMJ was performed in 50 consecutive TMJ arthralgia patients to identify individuals with bilateral TMJ DDwoR and/or OA. Linear and angular cephalometric measurements were taken to apply selected criteria of mandibular backward positioning (FH to Na-Pog <84°, Na-A-Pog >5°, and SNB <75°) and clockwise rotation (FH to OP >13°, MP to FH >35°, and S-Gn to FH >64°). Logistic regression analysis was used to estimate the association between selected MRI and cephalometric parameters. RESULTS In the age- and gender-adjusted analyses, significant increases in risk of mandibular backward positioning and clockwise rotation occurred with bilateral DDwoR and OA (9.5:1; P = .040). CONCLUSION In patients with TMJ arthralgia the MRI parameters of DDwoR and OA seem to be important determinants of mandibular backward positioning and clockwise rotation.

Proof of concept: differential effects of Valsalva and straining maneuvers on the pelvic floor

OBJECTIVE To prove a basic physiological principle in healthy women, demonstrating different movement patterns of diaphragm, pelvic floor, and muscular wall surrounding the abdominal cavity during a Valsalva maneuver as opposed to a straining maneuver, by means of real-time dynamic magnetic resonance imaging (MRI). STUDY DESIGN The study was performed at Hochzirl Hospital, Austria and Department of Radiology, Medical University Innsbruck, Austria. Four healthy women underwent MRI measurements in a 1.5-T whole body MR-scanner. Coronal, sagittal, and axial slices were acquired simultaneously and a dynamic MRI sequence was used to assess cranio-caudal movements of the diaphragm and pelvic floor and of concomitant changes in anterolateral abdominal muscle thickness and abdominal diameter at the umbilical level. RESULTS Both the Valsalva maneuver and the straining maneuver began with deep inspiration and downward movement of the diaphragm. During the exertion phase of both maneuvers, abdominal muscle thickness increased and abdominal diameter decreased. During the Valsalva maneuver, the pelvic floor moved cranially parallel to the diaphragm, whereas during the straining maneuver, the pelvic floor was markedly displaced caudally. CONCLUSION The Valsalva maneuver reflects an expiratory pattern with diaphragm and pelvic floor elevation, whereas during straining the pelvic floor descends.

Association Between Missing Posterior Teeth and Occurrence of Temporomandibular Joint Condylar Erosion: A Cone Beam Computed Tomography Study

PURPOSE To determine a possible association between asymptomatic temporomandibular joint (TMJ) condylar erosion and the number of missing posterior teeth and their location, as well as the number of dental quadrants with missing posterior teeth. MATERIALS AND METHODS This case-control study involved 210 patients (male to female ratio = 98:112) aged 16-74 years, with 105 asymptomatic patients with TMJ condylar erosion and a control group of 105 patients without TMJ condylar erosion. Cone beam computed tomography images were evaluated to classify the severity of TMJ condylar erosion as grade 0 (absence of erosion), grade I (slight erosion), grade II (moderate erosion), or grade III (extensive erosion). RESULTS The number of missing posterior teeth (mean ± standard deviation [SD]; 2.7 ± 2.4 vs 0.7 ± 1.2) (P < .001), number of dental quadrants with missing posterior teeth (1.5 ± 1.3 vs 0.6 ± 0.9) (P < .001), and bilateral location of missing posterior teeth (41 ± 39.0 vs 10 ± 9.5) (P < .001) were all significantly higher in patients with erosion than in those without erosion. The condylar erosion grade was significantly associated with the number of missing posterior teeth (odds ratio [OR] = 1.24; P = .006), the number of dental quadrants with missing posterior teeth (OR = 1.36; P = .006), and the bilateral occurrence of missing posterior teeth (OR = 3.03; P = .002). CONCLUSION The findings from this study suggest a possible association between TMJ condylar erosion grades and the number of missing posterior teeth, the number of quadrants with missing posterior teeth, and the bilateral occurrence of missing posterior teeth.

Diagnosing extensor carpi ulnaris tendon dislocation with dynamic rotation MRI of the wrist

OBJECTIVE The purpose of this study was to retrospectively correlate the kinematic dynamic rotation MRI (DR-MRI) of the wrist for assessment of extensor carpi ulnaris (ECU) tendon subluxation and dislocation. MATERIAL AND METHODS The presence of an ECU tendon subluxation or dislocation on the DR-MRI report was correlated to findings of the surgical report. RESULTS DR-MRI findings showed an ECU subluxation in 12 cases and an ECU dislocation in 13 cases. Surgery showed an ECU subluxation in 13 cases and an ECU dislocation in 12 cases (ĸ = 0.92). CONCLUSION DR-MRI is a feasible method to visualize ECU tendon subluxation and dislocation.

Tunnel widening after ACL reconstruction with aperture screw fixation or all-inside reconstruction with suspensory cortical button fixation: Volumetric measurements on CT and MRI scans☆

BACKGROUND Tunnel widening after anterior cruciate ligament reconstruction (ACLR) is influenced by the surgical and fixation techniques used. Computed tomography (CT) is the most accurate image modality for assessing tunnel widening, but magnetic resonance imaging (MRI) might also be reliable for tunnel volume measurements. In the present study tunnel widening after ACLR using biodegradable interference screw fixation was compared with all-inside ACLR using button fixation, with tunnel volume changes being measured on CT and MRI scans. STUDY DESIGN Randomized controlled trial; Level of evidence, 2. METHODS Thirty-three patients were randomly assigned to hamstring ACLR using a biodegradable interference screw or all-inside cortical button fixation. CT and MRI scanning were done at the time of surgery and six months after. Tunnel volume changes were calculated and compared. RESULTS On CT, femoral tunnel volumes changed from the postoperative state (100%) to 119.8% with screw fixation and 143.2% with button fixation (P=0.023). The changes in tibial tunnel volumes were not significant (113.9% vs. 117.7%). The changes in bone tunnel volume measured on MRI were comparable with those on CT only for tunnels with interference screws. Tibial tunnels with button fixation were significantly underestimated on MRI scanning (P=0.018). CONCLUSIONS All-inside ACLR using cortical button fixation results in increased femoral tunnel widening in comparison with ACLR with biodegradable interference screw fixation. MRI represents a reliable imaging modality for future studies investigating tunnel widening with interference screw fixation.