MR imaging mapping of skeletal muscle denervation in entrapment and compressive neuropathies.

The diagnoses of entrapment and compressive neuropathies have been based on the findings from clinical examinations and electrophysiologic tests, such as electromyography and nerve conduction studies. The use of magnetic resonance (MR) imaging for the diagnosis of entrapment or compressive neuropathies is increasing because MR imaging is particularly useful for discerning potential causes and for identifying associated muscle denervation. However, it is sometimes difficult to localize nerve entrapment or demonstrate nerve compression lesions with MR imaging. Nevertheless, even in these cases, MR imaging may show denervation-associated changes in specific muscles innervated by the affected nerves. The analysis of denervated muscle distributions by using MR imaging, with a knowledge of nerve innervation patterns, would be helpful for determining the nerves involved and the levels of nerve entrapment or compression. In this context, the mapping of skeletal muscle denervation with MR imaging has a supplementary or even a primary role in the diagnosis of entrapment and compressive neuropathies.

Magnetic resonance imaging diagnoses of bone scan abnormalities in breast cancer patients.

OBJECTIVE: To investigate the type of MR imaging diagnosis that corresponded to spinal lesions detected on a bone scan according to the number of lesions in breast cancer patients. MATERIALS AND METHODS: We retrospectively reviewed spinal MR images of 134 patients with breast cancer whose bone scans showed one or more spinal hot uptakes. The patients were grouped according to the number of spinal lesions detected on the bone scan: one or two lesions versus multiple (more than two) lesions. By using MR imaging, we determined the etiology of the spinal lesions in terms of being either benign or malignant. If the lesions were benign, we further categorized them into several specific pathologies. RESULTS: Sixty-four (48%) of 134 patients had one or two spinal lesions as seen on a bone scan. On MR imaging, 45 (70%) of the 64 lesions had benign pathologies, whereas 19 lesions (30%) were malignant. The benign pathologies in the 45 patients included facet arthrosis in 20 patients (44%), discovertebral degeneration in 12 patients (27%), compression fractures in eight patients (18%), and Schmorl's nodes in five patients (11%). Seventy (52%) of 134 patients had multiple spinal lesions as seen on the bone scan, and MR imaging revealed multiple bone metastases in 67 patients (96%) and facet arthrosis in three patients (4%). CONCLUSION: One or two spinal lesions seen on a bone scan in breast cancer patients are more likely to be benign pathologies such as facet arthrosis, discovertebral degeneration, compression fracture or Schmorl's node on MR imaging.

Optimization of the contrast mixture ratio for simultaneous direct MR and CT arthrography: an in vitro study.

OBJECTIVE: This study was designed to determine the optimal mixture ratio of gadolinium and iodinated contrast agent for simultaneous direct MR arthrography and CT arthrography. MATERIALS AND METHODS: An in vitro study was performed utilizing mixtures of gadolinium at six different concentrations (0.625, 1.25, 2.5, 5.0, 10 and 20 mmol/L) and iodinated contrast agent at seven different concentrations (0, 12.5, 25, 37.5, 50, 75 and 92-99.9%). These mixtures were placed in tissue culture plates, and were then imaged with CT and MR (with T1-weighted sequences, proton-density sequences and T2-weighted sequences). CT numbers and signal intensities were measured. Pearson's correlation coefficients were used to assess the correlations between the gadolinium/iodinated contrast agent mixtures and the CT numbers/MR signal intensities. Scatter diagrams were plotted for all gadolinium/iodinated contrast agent combinations and two radiologists in consensus identified the mixtures that yielded the optimal CT numbers and MR signal intensities. RESULTS: The CT numbers showed significant correlation with iodinated contrast concentrations (r = 0.976, p < 0.001), whereas the signal intensities as measured on MR images showed a significant correlation with both gadolinium and iodinated contrast agent concentrations (r = -484 to -0.719, p < 0.001). A review of the CT and MR images, graphs, and scatter diagram of 42 combinations of the contrast agent showed that a concentration of 1.25 mmol/L gadolinium and 25% iodinated contrast agent was the best combination for simultaneous CT and MR imaging. CONCLUSION: A mixture of 1.25 mmol/L gadolinium and 25% iodinated contrast agent was found to be optimal for simultaneous direct MR arthrography and CT arthrography.

Metal artifact reduction by the alteration of technical factors in multidetector computed tomography: a 3-dimensional quantitative assessment.

OBJECTIVE: The purpose of this study was to examine the effects of computed tomographic (CT) parameters on metal artifact reduction in multidetector CT (MDCT) using a quantitative 3-dimensional (3D) measurement of the metal artifact volume. METHODS: A steel-based plate and screw were implanted in the femora of 3 porcine thigh specimens. The specimens were examined using 16-slice MDCT with 7 different combinations of acquisition parameters that consisted of kilovolt (peak) (kV[p]) and effective milliampere-seconds (mAs): 120 and 100; 120 and 300; 120 and 500; 120 and 1000; 140 and 100; 140 and 300; and 140 and 500 under a detector collimation of 0.75 mm and a beam pitch of 0.45. The axial image reconstructions were performed with 4 different settings: 0.75-, 1-, 2-, and 2-mm slice thickness reconstruction under an extended CT scale. At the levels of all 14 screws in the 3 femora, the metal artifact volumes in various combinations of acquisition and reconstruction settings were measured using personal computer-based 3D imaging software and were compared with each other. RESULTS: The presence of a metal artifact was significantly reduced by increasing the kilovoltage and by decreasing the reconstruction thickness (P < 0.05; 2-way analysis of variance test). Neither increasing the effective mAs nor applying extended CT scale reduced the presence of the metal artifact significantly (P = 0.599 and P = 0.474, respectively). Compared with the metal artifact volume at 120 kV(p) and 100 mAs and a 2-mm slice thickness as a reference setting, the metal artifact reduction rate was 22% by increasing kilovoltage to 140, whereas only 11% by increasing mAs to 1000. CONCLUSIONS: We could quantitatively measure the metal artifact volume in MDCT by using 3D imaging software. In practice, the results of our study indicate that increasing kilovoltage is more effective for metal artifact reduction than increasing the effective mAs.

"MR corner sign": value for predicting presence of ankylosing spondylitis.

OBJECTIVE: The purpose of this study was to evaluate the MRI features of the "MR corner sign" and to determine its diagnostic usefulness in ankylosing spondylitis. We reviewed the spinal MR images of 52 patients with ankylosing spondylitis and compared these images with those of 52 age- and sex-matched control subjects. CONCLUSION: The MR corner sign was defined as a triangular and sharply marginated corner abnormality in a vertebral body unassociated with osteophytes or Schmorl's node. MR corner lesions were significantly more common in the ankylosing spondylitis group than in the control group (Fisher's exact test, p < 0.001). The sensitivity, specificity, and positive and negative predictive values of the MR corner sign were 44%, 96%, 92%, and 63%, respectively. The most frequent feature of signal intensity was a Modic type II change (77%). In patients with ankylosing spondylitis, the MR corner sign was fre quently seen at the thoracolumbar junction, whereas degenerative corner lesions were commonly seen in the lower lumbar spine. When the MR corner sign is detected on spinal MR images in daily practice, it should not be overlooked because it suggests the possibility of ankylosing spondylitis, which should then be further evaluated.

Grading anterior cruciate ligament graft injury after ligament reconstruction surgery: diagnostic efficacy of oblique coronal MR imaging of the knee.

OBJECTIVE: The purpose of this study was to evaluate the diagnostic efficacy of using additional oblique coronal MRI of the knee for grading anterior cruciate ligament (ACL) graft injury after ligament reconstruction surgery. MATERIALS AND METHODS: We retrospectively reviewed 51 consecutive MR knee examinations of 48 patients who underwent both ACL reconstruction and follow-up arthroscopy. The MR examinations included the orthogonal axial, sagittal, coronal images and the oblique coronal T2-weighted images, which were oriented in parallel with the course of the femoral intercondylar roof. Two radiologists independently evaluated the status of the ACL grafts with using the routine knee MRI and then with adding the oblique coronal imaging. The severity of ACL graft injury was graded using a 3-point system from MR images as intact, partial tear or complete tear, and the results were compared with the arthroscopic results. Weighted kappa statistics were used to analyze the diagnostic accuracies of the knee MRI with and without the additional oblique coronal imaging. For each evaluation, the observers reported a confidence level for grading the ACL graft injuries in the two imaging groups. RESULTS: The weighted kappa values according to the routine knee MRI were 0.555 (reader 1) and 0.515 (reader 2). The inclusion of additional oblique coronal imaging increased the weighted kappa values to 0.666 (reader 1) and 0.611 (reader 2). The mean confidence levels by each reader were significantly higher (p < 0.01, paired t-test) with the additional oblique coronal imaging than by using the routine knee MRI alone. CONCLUSION: The additional use of oblique coronal MRI of the knee improves both the diagnostic accuracy and confidence for grading ACL graft injury.

Radiologic and pathologic findings of nonpalpable thyroid carcinomas detected by ultrasonography in a medical screening center.

OBJECTIVE: The purpose of this study was to investigate the ultrasonographic and pathologic findings of nonpalpable thyroid carcinomas and reliable guidelines for fine-needle aspiration (FNA). METHODS: Our study was approved by our Institutional Review Board, and written informed consent was waived. Between April 2004 and June 2006, screening ultrasonography was performed for 16,352 self-referred patients in the health care center. Among 1325 nonpalpable thyroid nodules in 1009 patients, pathologic results of FNA revealed 823 benign, 154 indeterminate, 198 nondiagnostic, and 150 malignant nodules. Fifty-eight malignant thyroid nodules (39 microcarcionomas and 19 carcinomas >1 cm, confirmed by both FNA and thyroidectomy) in 55 patients and 82 benign nodules (confirmed by both FNA and follow-up over 2 years) in 75 patients were included for the analysis. Three radiologists retrospectively analyzed the ultrasonographic features of these nonpalpable thyroid nodules for echogenicity, shape, margin, calcification, degree of cystic changes, and size. We compared the radiologic and pathologic findings between microcarcinomas and carcinomas larger than 1 cm for extra-capsular invasion, lymph node metastasis, bilaterality, and multicentricity using univariate analysis. RESULTS: Marked hypoechogenicity, an irregular shape, a taller-than-wide shape, a well-defined spiculated margin, microcalcification, and an entirely solid nature were significant predictors for malignancy (P < .05), whereas a cutoff value of 1 cm in the longest diameter was not significant (P = .184). However, extracapsular invasion (P = .024) and lymph node metastasis (P = .019) were observed more frequently in carcinomas larger than 1 cm (73.7% and 42.1%, respectively) than in microcarcinomas (38.5% and 12.8%). CONCLUSIONS: Ultrasonographic findings suggesting malignancy should be preferentially considered as indicators for FNA, regardless of size, in nonpalpable thyroid nodules. However, extracapsular invasion and lymph node metastasis are closely related to the size of the thyroid nodule.

Cervical interlaminar epidural steroid injection for neck pain and cervical radiculopathy: effect and prognostic factors.

OBJECTIVE: To verify the usefulness of a fluoroscopy guided cervical interlaminar epidural steroid injection (CIESI) in patients with neck pain and cervical radiculopathy and to evaluate outcome predictors. DESIGN: We retrospectively analyzed 91 patients from July 2004 to June 2005 in whom CIESI was initially performed for neck pain and cervical radiculopathy. Therapeutic effects were evaluated 2 weeks after the administration of CIESI, and CIESI effectiveness was graded using a five-point scale, namely, whether the pain had disappeared, was much improved, slightly improved, the same, or aggravated. We also used a visual analog scale (VAS) for the clinical evaluation. According to documentation and follow-up charts, we categorized treatments as effective or ineffective. Possible outcome predictors, namely, diagnosis (spinal stenosis vs herniated disc), primary symptoms (neck pain vs radiculopathy vs both), age, gender, and duration of pain (more or less than 6 months) were also analyzed. Fisher's exact test, the chi-square test, and multiple logistic regression analysis were used for the statistical analysis. PATIENTS: After their medical records had been reviewed, 76 patients were included in this study. Inclusion criteria were: the availability of a cross-sectional image, such as a CT scan or an MR image, and a follow-up record after injection. RESULTS AND CONCLUSIONS: The medical records of 76 patients (male:female = 41 : 35) of mean age 53.1 years (range 32 years to 82 years) were reviewed. Two weeks after injection, 55 patients (72.4%) had experienced effective pain relief. Patients with herniated discs had significantly better results than patients with spinal stenosis (86.1% vs 60.0%) (P < 0.05). Other non-significant predictors of an improved outcome included: a symptom duration of <6 months, a young age, and the presence of cervical radiculopathy. Multiple regression analysis showed that the only factor that was significantly associated with outcome was the cause of the pain, i.e., herniated disc or spinal stenosis. Fluoroscopy guided CIESI is a safe and effective means of treating patients with neck pain and cervical radiculopathy. The most important outcome predictor was cause of pain, and patients with herniated disc experienced better pain relief than those with spinal stenosis.

Transforaminal epidural steroid injection for lumbosacral radiculopathy: preganglionic versus conventional approach.

OBJECTIVE: The present study was undertaken to evaluate the effectiveness of transforaminal epidural steroid injection (TFESI) with using a preganglionic approach for treating lumbar radiculopathy when the nerve root compression was located at the level of the supra-adjacent intervertebral disc. MATERIALS AND METHODS: The medical records of the patients who received conventional TFESI at our department from June 2003 to May 2004 were retrospectively reviewed. TFESI was performed in a total of 13 cases at the level of the exiting nerve root, in which the nerve root compression was at the level of the supra-adjacent intervertebral disc (the conventional TFESI group). Since June 2004, we have performed TFESI with using a preganglionic approach at the level of the supra-adjacent intervertebral disc (for example, at the neural foramen of L4-5 for the L5 nerve root) if the nerve root compression was at the level of the supra-adjacent intervertebral disc. Using the inclusion criteria described above, 20 of these patients were also consecutively enrolled in our study (the preganglionic TFESI group). The treatment outcome was assessed using a 5-point patient satisfaction scale and by using a VAS (visual assessment scale). A successful outcome required a patient satisfaction scale score of 3 (very good) or 4 (excellent), and a reduction on the VAS score of > 50% two weeks after performing TFESI. Logistic regression analysis was also performed. RESULTS: Of the 13 patients in the conventional TFESI group, nine showed satisfactory improvement two weeks after TFESI (69.2%). However, in the preganglionic TFESI group, 18 of the 20 patients (90%) showed satisfactory improvement. The difference between the two approaches in terms of TFESI effectiveness was of borderline significance (p = 0.056; odds ratio: 10.483). CONCLUSION: We conclude that preganglionic TFESI has the better therapeutic effect on radiculopathy caused by nerve root compression at the level of the supra-adjacent disc than does conventional TFESI, and the difference between the two treatments had borderline statistical significance.

Osseous metastasis from renal cell carcinoma: "flow-void" sign at MR imaging.

PURPOSE: To characterize the appearance and determine the importance of the "flow-void" sign on magnetic resonance (MR) images of patients with osseous metastasis from renal cell carcinoma. MATERIALS AND METHODS: Three musculoskeletal radiologists retrospectively and independently reviewed the medical records of 16 patients who had undergone MR imaging and in whom 20 osseous metastatic lesions from renal cell carcinoma had been diagnosed on the basis of clinical and radiologic findings. They assessed the MR images for the presence and frequency of the flow-void sign--multiple dot-like or tubular structures with low signal intensity. They then compared these findings on MR images with the corresponding areas on available images obtained with radiography (n = 16), computed tomography (CT) (n = 6), and digital subtraction angiography (n = 3) and with the results of histopathologic analysis for the same patient group. They noted the location, diameter, and appearance of the lesion and the flow-void sign, as well as variations in signal intensity within the lesion and among lesions. Statistical analysis was performed to determine the level of interobserver agreement. RESULTS: Radiographic findings and the level of signal intensity on MR images were nonspecific for diagnosis of osseous metastasis from renal cell carcinoma. The flow-void sign was identified at the lesion core or margin with a mean frequency of 76.7% by the three observers (in 15, 16, and 15 of 20 lesions, by observers 1, 2, and 3, respectively). Most of these areas of low signal intensity were tubular structures of less than 3 mm in diameter; in three lesions, they measured 5-8 mm in diameter. In 14 lesions, these structures corresponded to dilated blood vessels or veins identifiable on CT images (six lesions) or digital subtraction angiographic images (four lesions) or at histopathologic analysis (four lesions). The flow-void sign on MR images corresponded to vessels depicted on the CT scans available for six lesions and on the angiographic images available for four lesions. CONCLUSION: Observation of the flow-void sign in lesions depicted on musculoskeletal MR images may prove helpful for diagnosing osseous metastasis from renal cell carcinoma and for treatment planning, especially in patients with occult or forgotten primary renal tumor.

A straightforward algorithm for the quantification of power Doppler signals.

RATIONALE AND OBJECTIVES: To document a simple algorithm that quantifies power Doppler signals by computer-based statistical image analysis. METHODS: Personal computer-based software was developed. Color pixels representing power Doppler signals were separated from the background gray pixels in power Doppler images converted in BMP format. To avoid misregistration during this segmentation, a threshold value is required to adequately distinguish between gray and color pixels. Equating the intensity of each color pixel to a Power Value (PV), a histogram of Power Values in power Doppler images was obtained. RESULTS: The software was designed to allow users to adjust two thresholds (Difference Threshold and Intensity Threshold) by observing the segmentation results in real time. The software calculates the following indexes within any region of interest as defined by the operator: mean PV, peak PV, standard deviation of PV, percentage power Doppler area, and integrated PV per unit area. CONCLUSIONS: Power Doppler signals can be objectively quantified using this straightforward algorithm. This simple and practical method can be applied to comparative or longitudinal studies upon vascularity or blood flow.