Yusuhn Kang

Gliomas: Histogram Analysis of Apparent Diffusion Coefficient Maps with Standard- or High-b-Value Diffusion-weighted MR Imaging—Correlation with Tumor Grade

PURPOSE To explore the role of histogram analysis of apparent diffusion coefficient (ADC) maps based on entire tumor volume data in determining glioma grade and to evaluate the diagnostic performance of ADC maps at standard (1000 sec/mm(2)) and high (3000 sec/mm(2)) b values. MATERIALS AND METHODS This retrospective study was approved by the institutional review board, and informed consent was waived. Twenty-seven patients with astrocytic tumors underwent diffusion-weighted magnetic resonance imaging with b values of 1000 and 3000 sec/mm(2), and the corresponding ADC maps were calculated (ADC(1000) and ADC(3000), respectively). Regions of interest containing the lesion were drawn on every section of the ADC map containing the tumor and were summated to derive volume-based data of the entire tumor. Histogram parameters were correlated with tumor grade by using repeated measurements analysis of variance, the Tukey-Kramer test for post hoc comparisons, and an unpaired Student t test. Receiver operating characteristic (ROC) curves were constructed to determine the optimum threshold for each histogram parameter, and sensitivity and specificity were assessed. RESULTS Minimum ADC(1000) and ADC(3000) both decreased with increasing tumor grade. The 50th and 75th percentiles of cumulative ADC(1000) histograms showed significant differences between grades (P = .015 and .001, respectively), while the fifth and 75th percentiles of cumulative ADC(3000) histograms showed such differences (P = .015 and .014, respectively). Minimum ADC and the fifth percentile for both ADC(1000) (P < .001 and P = .024, respectively) and ADC(3000) (P < .001 and P = .001, respectively) proved to be significant histogram parameters for differentiating high- from low-grade gliomas. The diagnostic value of the parameters derived from ADC(1000) and ADC(3000) were compared, and a significant difference (0.202, P = .014) was found between the areas under the ROC curve of the fifth percentiles for ADC(1000) and ADC(3000). CONCLUSION Histogram analysis of ADC maps based on entire tumor volume can be a useful tool for grading gliomas. The fifth percentile of the cumulative ADC histogram obtained at a high b value was the most promising parameter for differentiating high- from low-grade gliomas.

Intrahepatic Mass-forming Cholangiocarcinoma: Enhancement Patterns on Gadoxetic Acid–enhanced MR Images

PURPOSE To evaluate the enhancement patterns of intrahepatic mass-forming cholangiocarcinomas (IMCCs) with emphasis on the hepatobiliary phase (HBP) of gadoxetic acid-enhanced magnetic resonance (MR) imaging. MATERIALS AND METHODS This retrospective study was institutional review board approved, and the requirement for informed consent was waived. Fifty patients (41 men, nine women; mean age, 62.3 years; range, 44-76 years) with IMCC underwent unenhanced and gadoxetic acid-enhanced T1- and T2-weighted MR imaging including dynamic phase and hepatobiliary phase imaging between May 2008 and December 2010. Signal intensity and enhancement patterns of lesions were compared with those of the liver parenchyma in each phase. Conspicuity and margin sharpness of lesions on dynamic phase and HBP images were rated on a 4- or 5-point scale and compared by using the Wilcoxon signed-rank test. Percentage of relative enhancement was compared among pathologic subgroups by using the unpaired Student t test. RESULTS On dynamic phase images, 29 of 48 (60%) lesions showed a thin peripheral rim with centripetal or gradual progression. On HBP images, 48 of 50 (96%) IMCCs were hypointense, and two of 50 (4%) were hyperintense. Subjective ratings of conspicuity and margin sharpness were significantly higher on HBP (median scores, 5 and 4, respectively) (P < .001) than on the dynamic phase (median scores, 4 and 3, respectively) images (P < .001). Additional daughter nodules were found in five patients and intrahepatic metastasis was found in one. Percentage of relative enhancement on HBP images was significantly higher in moderately differentiated (66.4% ± 42.1) than in poorly differentiated (36.84% ± 21.5) tumors (P = .039) and in patients without (59.7% ± 28.8) than in those with (24.9% ± 14.7) (P = .036) lymph node metastasis. CONCLUSION The most prevalent enhancement pattern on gadoxetic acid-enhanced MR images of IMCCs was a thin peripheral rim with internal heterogeneous enhancement during the dynamic phase. HBP images showed increased lesion conspicuity and better delineation of daughter nodules and intrahepatic metastasis, which may aid in the diagnosis of IMCC.

New MRI Grading System for the Cervical Canal Stenosis

OBJECTIVE The purpose of this study was to propose a new MRI grading system for cervical canal stenosis and to evaluate the reproducibility of the system. MATERIALS AND METHODS Cervical canal stenosis was classified according to the T2-weighted sagittal images into the following grades: grade 0, absence of canal stenosis; grade 1, subarachnoid space obliteration exceeding 50%; grade 2, spinal cord deformity; and grade 3, spinal cord signal change. The MRI scans of 82 patients (37 men and 45 women; mean age, 65.2 years; range, 60-86 years) were independently analyzed by six radiologists. Interobserver and intraobserver agreements were analyzed using intraclass correlation coefficient (ICC), along with the percentage agreement and kappa statistics. RESULTS The ICC for interobserver agreement was 0.716-0.802, indicating good-to-excellent agreement. For the distinction among the four grades, the percentage of agreement was 63-64% (κ = 0.60-0.62). The percentage of agreement for the presence of cervical canal stenosis (grade 0 vs grades 1, 2, and 3) was 79-85% (κ = 0.51-0.59). The percentage of agreement for insignificant (grade 0-1) or significant (grade 2-3) stenosis was 81-85% (κ = 0.57-0.66). The percentage of agreement for the presence of spinal cord signal change (grade 0-2 vs grade 3) was 92-95% (κ = 0.70-0.73). The overall intraobserver agreement was excellent, as determined by an ICC of 0.768. CONCLUSION The new grading system provides a reliable assessment of cervical canal stenosis.

MR imaging of myxofibrosarcoma and undifferentiated sarcoma with emphasis on tail sign; diagnostic and prognostic value.

AbstractObjectivesTo assess the prevalence of the tail sign in soft tissue sarcomas and determine whether the local recurrence rate differed based on the presence of the tail sign.MethodsIn our retrospective study, myxofibrosarcoma (MFS, n = 25) and undifferentiated sarcoma (US, n = 38) comprised group 1, and the remaining tumours (n = 115) were assigned to group 2. Location, size, and imaging features of the tumours were assessed on MRI. The radiological-pathological correlation of the tail sign was analysed.ResultsThe tail sign, thick fascial enhancement extending from the tumour margin, was more common and significantly thicker in group 1. In the subgroup analysis between MFS and US, there was no significant difference in the presence of a tail sign. Histological examination revealed extensive tumour cell infiltrations along the deep fascia from the main mass. Patients with a tail sign had a worse local recurrence-free survival than patients without it, not only in all tumours (p < 0.01), but also in group 1 (p = 0.019)ConclusionsThe tail sign was a common MRI feature of both MFS and US, and was also associated with worse local recurrence-free survival. Radiologists should be aware of these MRI findings and inform the surgeon preoperatively in order to obtain a sufficient surgical margin to minimise the risk of local tumour recurrence.Key Points• The tail sign was a common MRI feature of myxofibrosarcoma and undifferentiated sarcoma. • The tail sign may be associated with worse local recurrence-free survival • Radiologists should be aware of this MRI finding and inform the surgeon

A New MRI Grading System for Cervical Foraminal Stenosis Based on Axial T2-Weighted Images.

Objective The purpose of this study was to evaluate the reliability of a new magnetic resonance imaging (MRI) grading system for cervical neural foraminal stenosis (NFS). Materials and Methods Cervical NFS at bilateral C4/5, C5/6, and C6/7 was classified into the following three grades based on the T2-weighted axial images: Grade 0 = absence of NFS, with the narrowest width of the neural foramen greater than the width of the extraforaminal nerve root (EFNR); Grade 1 = the narrowest width of the neural foramen the same or less than (but more than 50% of) the width of the EFNR; Grade 2 = the width of the neural foramen the same or less than 50% of the width of the EFNR. The MRIs of 96 patients who were over 60 years old (M:F = 50:46; mean age 68.4 years; range 61-86 years) were independently analyzed by seven radiologists. Interobserver and intraobserver agreements were analyzed using the percentage agreement, kappa statistics, and intraclass correlation coefficient (ICC). Results For the distinction among the three individual grades at all six neural foramina, the ICC ranged from 0.68 to 0.73, indicating fair to good reproducibility. The percentage agreement ranged from 60.2% to 70.6%, and the kappa values (κ = 0.50-0.58) indicated fair to moderate agreement. The percentages of intraobserver agreement ranged from 85.4% to 93.8% (κ = 0.80-0.92), indicating near perfect agreement. Conclusion The new MRI grading system shows sufficient interobserver and intraobserver agreement to reliably assess cervical NFS.

Maximum standardised uptake value of quantitative bone SPECT/CT in patients with medial compartment osteoarthritis of the knee

AIM To evaluate the correlation between the maximum standardised uptake value (SUVmax) from bone single-photon-emission computed tomography/computed tomography (SPECT/CT) and other imaging parameters for medial compartment osteoarthritis (OA) of the knee. MATERIALS AND METHODS Patients (n=26; male:female=2:24; age, 55.3±5.8 years) underwent quantitative knee SPECT/CT using technetium-99m (Tc-99m) hydroxymethylene diphosphonate (HDP) before surgical operation for medial OA of the knee. SUVmax was calculated using dedicated quantitative software. Visual grades of tracer uptake on bone SPECT/CT and Kellgren-Lawrence (KL) OA scores on plain radiographs were assessed using a five-point scale. Magnetic resonance imaging (MRI) scores (n=22) and patient symptom scores were also assessed. RESULTS The operated knees (n=34) had a greater SUVmax than the non-operated knees (n=18) in the medial compartment (14.1±6.1 versus 5.3±4.4, p<0.0001). In the medial compartment, the SUVmax was significantly correlated with SPECT/CT visual grades (rho=0.794, p<0.0001), KL scores (rho=0.703, p<0.0001), and MRI scores (rho=0.714-0.808, p≤0.0002); however, SUVmax and other imaging parameters were not correlated with patient symptom scores (p>0.05). CONCLUSIONS The SUVmax of quantitative bone SPECT/CT was highly correlated with traditional imaging parameters for medial compartment OA severity of the knee. Quantitative bone SPECT/CT is a promising imaging technique for the objective assessment of knee OA.

Metal Artifact Reduction for Orthopedic Implants (O-MAR): Usefulness in CT Evaluation of Reverse Total Shoulder Arthroplasty

OBJECTIVE The objective of this study is to evaluate the effect of the metal artifact reduction algorithm for orthopedic implants (O-MAR) on CT image quality for patients with reverse total shoulder arthroplasty (RTSA), with emphasis placed on the evaluation of bone in the vicinity of prostheses. MATERIALS AND METHODS Sixty-five patients who underwent CT scanning after RTSA were enrolled in the study. Two radiologists analyzed the images reconstructed with filtered back projection (FBP) with or without O-MAR processing. Images were evaluated to determine the degree of streaking artifacts, the confidence in depicting various structures around the prosthesis, and the presence of pseudolesions. The mean CT number and SD of the selected ROIs placed in the greater tuberosity, glenoid bone, and deltoid muscle were recorded. For measurements from the greater tuberosity and glenoid bone, the frequency with which the measurement met the typical CT number of bone was calculated. RESULTS O-MAR images showed less metal streak artifact and noise and provided better visualization of the axillary neurovascular bundle compared with FBP images, with a statistically significant difference (p < 0.001 for all). FBP images were found to be statistically significantly better than O-MAR images, offering better visualization of bone cortex, bone trabeculae, and the bone-prosthesis interface (p < 0.001 for all). Scapular pseudonotching was observed on 4.6% of FBP images and 36.9% of O-MAR images. The pseudocemented appearance was noted on 47.7% of O-MAR images but was not seen on FBP images. CONCLUSION The use of O-MAR improved CT image quality for patients with RTSA in the aspect of metal artifact reduction and soft-tissue profile. However, O-MAR tends to degrade depiction of the bone trabeculae and bone cortex and generate new artifacts, including a pseudocemented appearance and scapular pseudonotching.

Delayed Gadolinium-enhanced MR Imaging of Cartilage: A Comparative Analysis of Different Gadolinium-based Contrast Agents in an ex Vivo Porcine Model

Purpose To compare the delayed gadolinium-enhanced magnetic resonance (MR) imaging of cartilage (dGEMRIC) indexes acquired with different gadolinium-based contrast agents (GBCAs), with emphasis on the difference in electrical charge, and to evaluate the feasibility of the use of GBCAs other than gadopentetate dimeglumine with a double negative charge (Gd-DTPA2-) as alternatives at dGEMRIC. Materials and Methods Intact porcine patellae (n = 44) were divided into four groups according to GBCA used: Gd-DTPA2-, double negative gadobenate dimeglumine (Gd-BOPTA2-), single negative gadoterate meglumine (Gd-DOTA-), and nonionic gadobutrol (Gd-DT-DO3A). Patellae in each group were further assigned to control (n = 3) or trypsin-treated (n = 8) groups and were immersed in GBCA solutions prepared at a concentration of 2.5 mmol/L. T1 maps were acquired at 10-minute intervals at 0-120 minutes. The difference between postcontrast R1 and precontrast R1 (ΔR) and the time ΔR curves were plotted. Patellae were stained with safranin-O to evaluate the proteoglycan content of the cartilage. A linear mixed-effects model was used to analyze the time ΔR curves, and Student t tests and Mann-Whitney U tests were used to compare dGEMRIC indexes between groups. Results The difference in the estimated slopes of the time ΔR curves between control and trypsin-treated groups were greatest with Gd-BOPTA2-, followed by Gd-DTPA2-, Gd-DOTA-, and Gd-DT-DO3A, with differences in the estimated slopes of 0.037, 0.022, 0.018, and 0.011, respectively. The slope difference between control and trypsin-treated groups was significantly greater with Gd-BOPTA2- (P < .001) and significantly smaller with Gd-DT-DO3A (P = .004) in comparison with that with Gd-DTPA2-. Only the GBCAs with double negative charges showed significant differences in both the T1 measured after equilibration of cartilage with GBCA solution and the ΔR at 90 and 120 minutes between the control and trypsin-treated groups. Conclusion Double negative GBCAs produced better contrast between normal and degenerated cartilage than did those with a single negative charge and nonionic GBCAs at the same concentration for dGEMRIC. Because Gd-BOPTA2-, a high-relaxivity GBCA, showed higher contrast than did Gd-DTPA2-, Gd-BOPTA2-may be useful as an alternative GBCA for dGEMRIC.

Assessment of the Postoperative Appearance of the Rotator Cuff Tendon Using Serial Sonography After Arthroscopic Repair of a Rotator Cuff Tear

The purpose of this study was to evaluate serial changes in sonographic findings of a rotator cuff tendon after rotator cuff repair.

MRI Findings of New Uptake in the Femoral Head Detected on Follow-Up Bone Scans

OBJECTIVE. The purpose of this article is to suggest clinical indications for MRI in patients with breast cancer who have new uptake lesions in the femoral head on follow-up bone scans, by evaluating the incidence and causes of new uptake lesions. MATERIALS AND METHODS. Between January 2002 and July 2013, a total of 145 patients with breast cancer who showed new uptake in the femoral head on follow-up bone scans were included in our study. They were classified into two groups: group 1 consisted of 125 patients without known bone metastases, and group 2 consisted of 20 patients who already had bone metastases other than that in the femoral head. The Fisher exact test was performed for the statistical analysis. Thereafter, we reviewed MR images for characterization of the new abnormal uptake in the femoral head. RESULTS. New uptake lesions in the femoral head were metastatic in only 4.8% (6/125) of group 1 patients but in 75% (15/20) of group 2 patients (p < 0.0001). In both groups, no patient with a single uptake lesion in the femoral head had bone metastasis, whereas all patients with more than five new uptake lesions, including those of the femoral head, showed bone metastasis. Most MRI diagnoses for new uptake in the femoral head were fibrocystic change (15/30, 50%) and subchondral fracture (11/30, 36.7%). CONCLUSION. Most of the new uptake lesions in the femoral head detected on the follow-up bone scans in patients with breast cancer were benign. However, MRI could be considered in patients with known bone metastasis or with multiple new uptake lesions on bone scans.