Magnetic resonance imaging of the lumbar spine after epidural and nerve root injection therapy: evaluation of soft tissue changes.

OBJECTIVE: Magnetic resonance imaging (MRI) was performed to evaluate soft tissue changes after nerve root and epidural injections in lumbar spine in patients with radiculopathy. MATERIALS/METHODS: Patients underwent a multiple-shot injection protocol to nerve root/epidural space. The MRI protocol included T1-weighted, T2-weighted, STIR, and contrast-enhanced, fat-saturated T1-weighted sequences before and after treatment. RESULTS: In all treated patients, a diffuse wedge-shaped edema in paravertebral tissues with a slight contrast enhancement was seen. Two small hematomas in the paravertebral muscle were noted. No changes in the epidural space, the abscess, or a lipodystrophy in epidural/nerve root space occurred. CONCLUSION: Normal tissue changes after injection therapy of lumbar radiculopathy include wedge-shaped tissue edema at the injection level. In a minority of patients, small hematomas may occur.

Heating of non-ferromagnetic total hip endoprostheses during magnetic resonance imaging in an animal model.

To determine the heating effects of magnetic resonance imaging (MRI) on non-ferromagnetic total hip endoprostheses, hip endoprostheses were tested in vitro and in an ex vivo animal model. The MRI protocol on a 1.5 T scanner consisted of five sequences with a total duration of 23 min. The maximum heating of prosthetic material was 0.17 K in vitro and 0.90 K ex vivo; the maximum heating of bone surrounding tissue was 0.73 K ex vivo. Slight heating of the prostheses and the surrounding tissue was noted, which should not have any side effects in patients with titanium total hip endoprostheses.

Effective dose of CT- and fluoroscopy-guided perineural/epidural injections of the lumbar spine: a comparative study.

The objective of this study was to compare the effective radiation dose of perineural and epidural injections of the lumbar spine under computed tomography (CT) or fluoroscopic guidance with respect to dose-reduced protocols. We assessed the radiation dose with an Alderson Rando phantom at the lumbar segment L4/5 using 29 thermoluminescence dosimeters. Based on our clinical experience, 4-10 CT scans and 1-min fluoroscopy are appropriate. Effective doses were calculated for CT for a routine lumbar spine protocol and for maximum dose reduction; as well as for fluoroscopy in a continuous and a pulsed mode (3-15 pulses/s). Effective doses under CT guidance were 1.51 mSv for 4 scans and 3.53 mSv for 10 scans using a standard protocol and 0.22 mSv and 0.43 mSv for the low-dose protocol. In continuous mode, the effective doses ranged from 0.43 to 1.25 mSv for 1-3 min of fluoroscopy. Using 1 min of pulsed fluoroscopy, the effective dose was less than 0.1 mSv for 3 pulses/s. A consequent low-dose CT protocol reduces the effective dose compared to a standard lumbar spine protocol by more than 85%. The latter dose might be expected when applying about 1 min of continuous fluoroscopy for guidance. A pulsed mode further reduces the effective dose of fluoroscopy by 80-90%.

Imaging of infected total arthroplasty with Tc-99m-labeled antigranulocyte antibody Fab'fragments.

OBJECTIVE: The objective of this study was to evaluate the diagnostic accuracy of Tc-99m-labeled antigranulocyte antibody Fab' fragments in infected total arthroplasty. MATERIALS AND METHODS: A total of 38 immunoscintigrams were evaluated retrospectively with 15 to 25 mCi Tc-99m-labeled antigranulocyte antibody-Fab' fragments. The final diagnosis was assessed by articular puncture or intraoperative sampling. RESULTS: In the total hip replacement group the authors found 10 true positives, 7 true negatives, 8 false positives, and 1 false negative; and in the total knee replacement group they found 4 true positives, 8 true negatives, and no false positives or false negatives. They also found a sensitivity of 93%, a specificity of 65%, and a positive predictive accuracy of 63%. There was a negative predictive accuracy of 94%. CONCLUSION: The high negative predictive accuracy in the whole group suggests that the scan can be used to exclude infection in most cases. Negative results with a high clinical suspicion merits further investigation. A positive result will require further correlative imaging, especially for total knee replacement.

Lumbar disk herniation: correlation of histologic findings with marrow signal intensity changes in vertebral endplates at MR imaging.

PURPOSE: To compare findings at preoperative magnetic resonance (MR) imaging with data for tissue composition of herniated disks in patients after microsurgical removal of herniated material. MATERIALS AND METHODS: Fifty-one patients underwent MR imaging before microsurgical removal of extruded lumbar disk herniation material. Marrow signal intensity changes along the cartilaginous endplates were classified according to Modic types 1-3. Severity of changes was evaluated with respect to extension along the endplate in the anteroposterior diameter (0%, <33%, 33%-66%, >66%). The existence of a dorsal vertebral corner defect was evaluated in relation to the existence of hyaline cartilage in the disk extrusion material. RESULTS: Mean tissue composition of herniated material in all patients was 63% anulus fibrosus, 30% nucleus pulposus, and 8% cartilaginous endplate. Twenty-five of the 51 patients had hyaline cartilaginous material in the extrusion (range, 5%-50%). Patients without marrow signal intensity changes along the cartilaginous endplate showed significantly less cartilaginous material in the extruded disk (P =.023, Fisher exact test). Mean percentage hyaline cartilage in patients without changes was 2% +/- 4 (SD) (Modic type 1, 16% +/- 15; type 2, 10% +/- 12). When the changes extended 33% of the vertebral endplate, there was cartilaginous endplate material in the extruded disk (P =.006). Cartilage from the endplate was present in the extruded disk material in 40% (16 of 40) of patients without a vertebral corner defect and in 82% (nine of 11) of patients with a vertebral corner defect (P =.019). CONCLUSION: Avulsion-type disk herniation seems to be common, and vertebral endplate marrow signal intensity changes on MR images are indicative of cartilaginous material in the extruded disk herniation material.