Faculty Bibliography

OBJECTIVE:The objective of our study was to investigate the use of PET in the detection of malignant peripheral nerve sheath tumors (MPNSTs) in patients with neurofibromatosis type 1 (NF1). MATERIALS AND METHODS/METHODS:Forty-five patients with NF1 who underwent whole-body PET for suspected MPNST based on clinical symptoms or radiologic examinations were retrospectively evaluated. Ten patients underwent additional carbon-11 (11C) methionine PET because of equivocal 18F-FDG PET findings or because of a discrepancy between the FDG PET and clinical findings. PET images were evaluated for the distribution and uptake pattern, and the standardized uptake values (SUVs) were obtained. Twenty-seven patients underwent biopsy or surgery of the detected lesions and 18 patients were followed up clinically and with repeat imaging studies. RESULTS:Fifty lesions were identified on FDG PET. There were eight false-positive results and one false-negative on FDG PET. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of FDG PET in detecting MPNSTs in patients with NF1 were 95%, 72%, 71%, 95%, and 82%, respectively. Using 11C methionine PET in combination with FDG PET reduced the number of false-positive results from eight to two, which increased the specificity from 72% to 91%. In five patients, 11C methionine FDG PET contributed additional information about nontarget lesions that influenced treatment planning. CONCLUSION/CONCLUSIONS:FDG PET is a sensitive technique in the detection of MPNSTs in patients with NF1. The addition of 11C methionine PET increases specificity in equivocal cases. PET may improve preoperative tumor staging by detecting metastases or second primary tumors, which often are present in patients with NF1.

OBJECTIVE:This study aimed to prospectively compare measurement precision of calf intramyocellular lipid (IMCL) quantification at 3.0 and 1.5 T using (1)H magnetic resonance spectroscopy ((1)H-MRS). MATERIALS AND METHODS/METHODS:We examined the soleus and tibialis anterior (TA) muscles of 15 male adults [21-48 years of age, body mass index (BMI)=21.9-38.0 kg/m(2)]. Each subject underwent 3.0- and 1.5-T single-voxel, short-echo-time, point-resolved (1)H-MRS both at baseline and at 31-day follow-up. The IMCL methylene peak (1.3 ppm) was scaled to unsuppressed water peak (4.7 ppm) using the LCModel routine. Full width at half maximum (FWHM) and signal-to-noise ratios (SNRs) of unsuppressed water peak were measured using jMRUI software. Measurement precision was tested by comparing interexamination coefficients of variation (CV) between different field strengths using Wilcoxon matched pairs signed rank test in all subjects. Overweight subjects (BMI>25 kg/m(2)) were analyzed separately to examine the benefits of 3.0-T acquisitions in subjects with increased adiposity. RESULTS:No significant difference between 3.0 and 1.5 T was noted in CVs for IMCL of soleus (P=.5). CVs of TA were significantly higher at 3.0 T (P=.02). SNR was significantly increased at 3.0 T for soleus (64%, P<.001) and TA (62%, P<.001) but was lower than the expected improvement of 100%. FWHM at 3.0 T was significantly increased for soleus (19%, P<.001) and TA (7%, P<.01). Separate analysis of overweight subjects showed no significant difference between 3.0- and 1.5-T CVs for IMCL of soleus (P=.8) and TA (P=.4). CONCLUSION/CONCLUSIONS:Using current technology, (1)H-MRS for IMCL at 3.0 T did not improve measurement precision, as compared with 1.5 T.

OBJECTIVE:The objectives of our study were to evaluate whether MRI findings of the sacroiliac joints are able to distinguish between active and inactive disease in patients with established ankylosing spondylitis and to determine whether these findings correlate with markers of clinical activity, disease duration, severity, and degree of radiographic damage. MATERIALS AND METHODS/METHODS:Eighteen patients with symptomatic moderate to severe ankylosing spondylitis were evaluated. MRI of the sacroiliac joint (1.5 T) was performed using fat-saturated T2-weighted, T1-weighted, STIR, and fat-saturated contrast-enhanced T1-weighted sequences. The sacroiliac joints were evaluated by two radiologists for enhancement, subchondral bone marrow edema, erosions, and subchondral fatty marrow infiltration. Findings on MRI were analyzed for correlation with multiple clinical characteristics and measures of disease activity, including radiographic scoring. RESULTS:In 17 patients, MRI showed abnormal findings of the sacroiliac joint. Ten patients showed active disease on MRI as measured by abnormal enhancement and subchondral bone marrow edema. Disease activity detected using MRI correlated in a positive fashion with only C-reactive protein (CRP) level. There was no correlation with the other measures of disease activity or with disease duration. In 14 patients, fatty subchondral bone marrow was detected on MRI. These changes were seen in patients with active and chronic disease and correlated with higher radiographic scores but not with disease duration or markers of disease activity. CONCLUSION/CONCLUSIONS:Contrast-enhanced MRI of the sacroiliac joint is sensitive in depicting sacroiliitis in patients with established ankylosing spondylitis. Subchondral edema and enhancement correlate with high CRP levels. Subchondral fatty bone marrow changes were seen in both active and chronic sacroiliitis and are correlated with higher radiographic scores; these changes may be a marker of more advanced disease.

FAI is a common cause of OA of the hip. It can be caused by decreased offset of the femoral head and neck, resulting in abutment of the femoral neck against the acetabular rim (cam impingement) and abutment of this area into the well-constrained socket (pincer impingement)within normal range of motion [15]. This repetitive mechanical trauma to the hip joint causes mechanical wear of the labrum and articular cartilage; left untreated, it causes pain, labral tears, and chondral injuries leading to progressive OA of the hip. The identification of FAI as a cause of OA allows appropriate therapy early and thus delays or prevents end-stage arthritis.MR imaging and MR arthrography are accurate noninvasive imaging modalities able to demonstrate acetabular labral disease and adjacent cartilage damage as well as the subchondral cysts and synovial herniation pits associated with impingement. In addition, MR imaging is able to detect underlying subtle anatomic variations of the femoral head-neck junction and acetabulum associated with FAI.

OBJECTIVE:Our objective was to evaluate if whole-body PET with FDG is able to detect bone marrow involvement in patients with multiple myeloma and to assess its appearance and distribution pattern. MATERIALS AND METHODS/METHODS:Seventeen whole-body FDG PET scans were performed in 13 patients with multiple myeloma. Four patients were referred for evaluation of extent of disease pretherapy and nine patients were referred for assessment of therapy response (chemotherapy, radiation therapy, bone marrow transplant). FDG PET images were evaluated for distribution and uptake pattern. Standardized uptake values were obtained to quantify FDG uptake. Results of other imaging examinations (MRI, CT, radiography), laboratory data, biopsies, and the clinical course were used for verification of detected lesions. RESULTS:FDG PET was able to detect medullary involvement of multiple myeloma. There were two false-negative results. In one patient, the radiographic skeletal survey showed subcentimeter lytic lesions within the ribs that were not detected on FDG PET and in the other patient, a lytic lesion detected on radiographs showed only mildly increased FDG uptake that was not identified prospectively. There was one false-positive FDG PET result in a patient who had undergone radiation therapy 3 weeks before PET. FDG PET was helpful in differentiating between posttherapeutic changes and residual/recurrent tumor and in assessing response to therapy. FDG PET resulted in upstaging of disease in four patients, which influenced subsequent management and prognosis. Sensitivity of FDG PET in detecting myelomatous involvement was 85% and specificity was 92%. CONCLUSION/CONCLUSIONS:FDG PET is able to detect bone marrow involvement in patients with multiple myeloma. FDG PET is useful in assessing extent of disease at time of initial diagnosis, contributing to staging that is more accurate. FDG PET is also useful for evaluating therapy response.

OBJECTIVE:To assess and describe post-traumatic articular cartilage injuries isolated to the trochlear groove and provide insight into potential mechanism of injury. MATERIALS AND METHODS/METHODS:We retrospectively evaluated MR imaging findings of all knee MRIs performed at our institution over the last 2 years (2450). Thirty patients met the criteria of a cartilage injury confined to the trochlear groove. In 15 cases, which were included in our study, arthroscopic correlation was available. Each plane was evaluated and graded for the presence and appearance of articular cartilage defects using a standard arthroscopic grading scheme adapted to MR imaging. Any additional pathological derangement was documented and information about the mechanism of injury was retrieved by chart review. RESULTS:In all cases the cartilaginous injury was well demonstrated on MRI. In 13 patients additional pathological findings could be observed. The most frequently associated injury was a meniscal tear in nine patients. In eight cases, the arthroscopic grading of the trochlear injury matched exactly with the MRI findings. In the remaining seven cases, the discrepancy between MRI and arthroscopy was never higher than one grade. In 13 out of 15 of patients trauma mechanism could be evaluated. Twelve patients suffered an indirect twisting injury and one suffered a direct trauma to their knee. CONCLUSION/CONCLUSIONS:The findings of this study demonstrate that MR imaging allows reliable grading of isolated injury to the trochlear groove cartilage and assists in directing surgical diagnosis and treatment. These injuries may be the only hyaline cartilage injury in the knee and meniscal tears are a frequently associated finding. Therefore, it is important to search specifically for cartilage injuries of the trochlear groove in patients with anterior knee pain, even if other coexistent pathology could potentially explain the patient's symptoms.

OBJECTIVE:The purpose of our study was to investigate the potential of FDG positron emission tomography (PET) to distinguish viable tumor from changes caused by therapy in areas with equivocal MR imaging findings in patients with musculoskeletal sarcomas. MATERIALS AND METHODS/METHODS:We evaluated 12 patients (nine males, three females; age range, 9-56 years; mean age, 25 years) with a history of bone or soft-tissue sarcoma who had undergone various treatments (surgery, chemotherapy, radiation therapy, or a combination of treatments) and who presented with clinically suspected recurrent or residual tumor. All patients underwent gadopentetate dimeglumine-enhanced MR imaging and whole-body FDG PET. Imaging results were correlated with histologic findings or with clinical findings from long-term follow-up. RESULTS:In nine patients, MR imaging findings were equivocal in differentiating between posttherapeutic changes and tumor recurrence. FDG PET images showed increased uptake, suggestive of recurrent tumor, in five patients. These findings were confirmed by biopsy. Four patients showed no increased uptake on FDG PET and were closely monitored clinically. No tumor recurrence was found in these patients. One patient showed MR imaging findings suggestive of recurrent tumor that was confirmed on FDG PET and at histology. Two patients underwent a limb salvage procedure before MR imaging, but MR images were deemed inadequate for interpretation because of extensive metallic artifacts. FDG PET was helpful in evaluating these patients for tumor recurrence. CONCLUSION/CONCLUSIONS:FDG PET is a useful adjunct to MR imaging in distinguishing viable tumor from posttherapeutic changes in patients with bone and soft-tissue sarcomas.

OBJECTIVE:The aim of this study was to evaluate the use of MR imaging in the characterization of the Perthes lesion by correlating MR findings with findings at arthroscopy. CONCLUSION/CONCLUSIONS:The use of a combination of axial and abduction-external rotation position sequences on MR images can be helpful in the diagnosis of a Perthes lesion. A fluid-filled joint with capsular distension, caused by either a large amount of effusion or MR arthrography, was found to be helpful in outlining Perthes lesions. Adding the abduction-external rotation position to the protocol in patients in whom Perthes lesion is suspected will increase diagnostic accuracy and may reveal a Perthes lesion not visible on axial images, as was the case in 50% of the patients in our series.

OBJECTIVE:The purpose of our study was to assess the value of a modified three-point Dixon MR technique for evaluating articular cartilage defects in the knee joint on a low-field-strength open magnet, correlated with arthroscopy. SUBJECTS AND METHODS/METHODS:Twenty consecutive patients who underwent both MR imaging and arthroscopy of the knee joint for suspected internal derangement were examined. A modified three-point Dixon MR sequence with a single radiofrequency echo single-scan method for water and fat separation with correction of the static field inhomogeneities was performed on a 0.35-T open magnet to obtain fat suppression. The MR images were prospectively evaluated for the presence and grade of articular cartilage defects. RESULTS:Uniform fat suppression was obtained in all patients using the modified three-point Dixon technique. Fifty-nine cartilage abnormalities were identified in 19 patients on the basis of arthroscopy. Forty-seven of 59 arthroscopically proven abnormalities were prospectively detected on MR imaging. Compared with arthroscopy, the overall sensitivity of the modified three-point Dixon technique in detecting cartilage lesions was 80% and the specificity was 73%. Sixty-five percent of the cartilage abnormalities were graded identically on MR imaging and arthroscopy. CONCLUSION/CONCLUSIONS:The modified three-point Dixon sequence is a useful technique for achieving fat suppression in the knee joint on a 0.35-T open magnet. It is a sensitive and specific technique for the assessment of cartilage abnormalities in the knee.