Deep Learning Algorithm for Simultaneous Noise Reduction and Edge Sharpening in Low-Dose CT Images:A Pilot Study Using Lumbar Spine CT

Objective@#The purpose of this study was to assess whether a deep learning (DL) algorithm could enable simultaneous noise reduction and edge sharpening in low-dose lumbar spine CT. @*Materials and Methods@#This retrospective study included 52 patients (26 male and 26 female; median age, 60.5 years) who had undergone CT-guided lumbar bone biopsy between October 2015 and April 2020. Initial 100-mAs survey images and 50-mAs intraprocedural images were reconstructed by filtered back projection. Denoising was performed using a vendor-agnostic DL model (ClariCT.AI TM , ClariPI) for the 50-mAS images, and the 50-mAs, denoised 50-mAs, and 100-mAs CT images were compared. Noise, signal-to-noise ratio (SNR), and edge rise distance (ERD) for image sharpness were measured. The data were summarized as the mean ± standard deviation for these parameters. Two musculoskeletal radiologists assessed the visibility of the normal anatomical structures. @*Results@#Noise was lower in the denoised 50-mAs images (36.38 ± 7.03 Hounsfield unit [HU]) than the 50-mAs (93.33 ± 25.36 HU) and 100-mAs (63.33 ± 16.09 HU) images (p < 0.001). The SNRs for the images in descending order were as follows: denoised 50-mAs (1.46 ± 0.54), 100-mAs (0.99 ± 0.34), and 50-mAs (0.58 ± 0.18) images (p < 0.001). The denoised 50-mAs images had better edge sharpness than the 100-mAs images at the vertebral body (ERD; 0.94 ± 0.2 mm vs. 1.05 ± 0.24 mm, p = 0.036) and the psoas (ERD; 0.42 ± 0.09 mm vs. 0.50 ± 0.12 mm, p = 0.002). The denoised 50-mAs images significantly improved the visualization of the normal anatomical structures (p < 0.001). @*Conclusion@#DL-based reconstruction may enable simultaneous noise reduction and improvement in image quality with the preservation of edge sharpness on low-dose lumbar spine CT. Investigations on further radiation dose reduction and the clinical applicability of this technique are warranted.

Fat Quantification in the Vertebral Body: Comparison of Modified Dixon Technique with Single-Voxel Magnetic Resonance Spectroscopy

OBJECTIVE: To compare the lumbar vertebral bone marrow fat-signal fractions obtained from six-echo modified Dixon sequence (6-echo m-Dixon) with those from single-voxel magnetic resonance spectroscopy (MRS) in patients with low back pain. MATERIALS AND METHODS: Vertebral bone marrow fat-signal fractions were quantified by 6-echo m-Dixon (repetition time [TR] = 7.2 ms, echo time (TE) = 1.21 ms, echo spacing = 1.1 ms, total imaging time = 50 seconds) and single-voxel MRS measurements in 25 targets (23 normal bone marrows, two focal lesions) from 24 patients. The point-resolved spectroscopy sequence was used for localized single-voxel MRS (TR = 3000 ms, TE = 35 ms, total scan time = 1 minute 42 seconds). A 2 × 2 × 1.5 cm³ voxel was placed within the normal L2 or L3 vertebral body, or other lesions including a compression fracture or metastasis. The bone marrow fat spectrum was characterized on the basis of the magnitude of measurable fat peaks and a priori knowledge of the chemical structure of triglycerides. The imaging-based fat-signal fraction results were then compared to the MRS-based results. RESULTS: There was a strong correlation between m-Dixon and MRS-based fat-signal fractions (slope = 0.86, R² = 0.88, p 20%). CONCLUSION: Given its excellent agreement with single-voxel-MRS, 6-echo m-Dixon can be used for visual and quantitative evaluation of vertebral bone marrow fat in daily practice.

Dual-Layer Spectral Detector CT Discography of the Lumbar Spine: A Preliminary Study

PURPOSE@#To assess the feasibility of spectral detector CT (SDCT) with axial maximum-intensity projection (MIP) reconstruction for the evaluation of lumbar CT discography.@*MATERIALS AND METHODS@#We retrospectively evaluated 44 disc levels from 18 patients who underwent CT discography on a dual-layer SDCT between May 2016 and July 2017. We compared the distribution of contrast material between conventional CT and SDCT-based iodine maps using the Jaccard index (JI) and Dice similarity coefficient (DSC). Qualitative analysis of the post-discogram features was done according to the Dallas discogram description, and changes in reading time and diagnostic confidence were analyzed.@*RESULTS@#The intermethod variability between conventional CT and SDCT was good, with a mean DSC of 0.93 and a mean JI of 0.87. The mean sensitivity and positive predictive value of the SDCT-based method were 90% and 96%, respectively. The addition of SDCT-based axial MIP iodine maps increased the diagnostic confidence (p = 0.025) and reduced the reading time in both reviewers (p < 0.001).@*CONCLUSION@#SDCT discography demonstrates the distribution of contrast medium within the disc similarly to conventional CT. Additionally, axial MIP iodine maps using SDCT allow for the fast evaluation of disc pathology with reduced reading time and can increase diagnostic confidence.

Quantitative Analysis of Disc Degeneration Using Axial T2 Mapping in a Percutaneous Annular Puncture Model in Rabbits

OBJECTIVE: To evaluate T2 relaxation time change using axial T2 mapping in a rabbit degenerated disc model and determine the most correlated variable with histologic score among T2 relaxation time, disc height index, and Pfirrmann grade. MATERIALS AND METHODS: Degenerated disc model was made in 4 lumbar discs of 11 rabbits (n = 44) by percutaneous annular puncture with various severities of an injury. Lumbar spine lateral radiograph, MR T2 sagittal scan and MR axial T2 mapping were obtained at baseline and 2 weeks and 4 weeks after the injury in 7 rabbits and at baseline and 2 weeks, 4 weeks, and 6 weeks after the injury in 4 rabbits. Generalized estimating equations were used for a longitudinal analysis of changes in T2 relaxation time in degenerated disc model. T2 relaxation time, disc height index and Pfirrmann grade were correlated with the histologic scoring of disc degeneration using Spearman's rho test. RESULTS: There was a significant difference in T2 relaxation time between uninjured and injured discs after annular puncture. Progressive decrease in T2 relaxation time was observed in injured discs throughout the study period. Lower T2 relaxation time was observed in the more severely injured discs. T2 relaxation time showed the strongest inverse correlation with the histologic score among the variables investigated (r = -0.811, p < 0.001). CONCLUSION: T2 relaxation time measured with axial T2 mapping in degenerated discs is a potential method to assess disc degeneration.

MR Findings of the Osteofibrous Dysplasia

OBJECTIVE: The aim of this study was to describe MR findings of osteofibrous dysplasia. MATERIALS AND METHODS: MR images of 24 pathologically proven osteofibrous dysplasia cases were retrospectively analyzed for a signal intensity of the lesion, presence of intralesional fat signal, internal hypointense band, multilocular appearance, cortical expansion, intramedullary extension, cystic area, cortical breakage and extraosseous extension, abnormal signal from the adjacent bone marrow and soft tissue and patterns of contrast enhancement. RESULTS: All cases of osteofibrous dysplasia exhibited intermediate signal intensity on T1-weighted images. On T2-weighted images, 20 and 4 cases exhibited heterogeneously intermediate and high signal intensity, respectively. Intralesional fat was identified in 12% of the cases. Internal low-signal bands and multilocular appearance were observed in 91%. Cortical expansion was present in 58%. Intramedullary extension was present in all cases, and an entire intramedullary replacement was observed in 33%. Cortical breakage (n = 3) and extraosseous mass formation (n = 1) were observed in cases with pathologic fractures only. A cystic area was observed in one case. Among 21 cases without a pathologic fracture, abnormal signal intensity in the surrounding bone marrow and adjacent soft tissue was observed in 43% and 48%, respectively. All cases exhibited diffuse contrast enhancement. CONCLUSION: Osteofibrous dysplasia exhibited diverse imaging features ranging from lesions confined to the cortex to more aggressive lesions with complete intramedullary involvement or perilesional marrow edema.

Comparison of Image Quality of Shoulder CT Arthrography Conducted Using 120 kVp and 140 kVp Protocols

OBJECTIVE: To compare the image quality of shoulder CT arthrography performed using 120 kVp and 140 kVp protocols. MATERIALS AND METHODS: Fifty-four CT examinations were prospectively included. CT scans were performed on each patient at 120 kVp and 140 kVp; other scanning parameters were kept constant. Image qualities were qualitatively and quantitatively compared with respect to noise, contrast, and diagnostic acceptability. Diagnostic acceptabilities were graded using a one to five scale as follows: 1, suboptimal; 2, below average; 3, acceptable; 4, above average; and 5, superior. Radiation doses were also compared. RESULTS: Contrast was better at 120 kVp, but noise was greater. No significant differences were observed between the 120 kVp and 140 kVp protocols in terms of diagnostic acceptability, signal-to-noise ratio, or contrast-to-noise ratio. Lowering tube voltage from 140 kVp to 120 kVp reduced the radiation dose by 33%. CONCLUSION: The use of 120 kVp during shoulder CT arthrography reduces radiation dose versus 140 kVp without significant loss of image quality.

Visual MRI Grading System to Evaluate Atrophy of the Supraspinatus Muscle

OBJECTIVE: To investigate the interobserver reproducibility and diagnostic feasibility of a visual grading system for assessing atrophy of the supraspinatus muscle on magnetic resonance imaging (MRI). MATERIALS AND METHODS: Three independent radiologists retrospectively evaluated the occupying ratio of the supraspinatus muscle in the supraspinatus fossa on 192 shoulder MRI examinations in 188 patients using a 3-point visual grading system (1, > or = 60%; 2, 30-59%; 3, < 30%) on oblique sagittal T1-weighted images. The inter-reader agreement and the agreement with the reference standard (3-point grades according to absolute occupying ratio values quantitatively measured by directly contouring the muscles on MRI) were analyzed using weighted kappa. The visual grading was applied by a single reader to a group of 100 consecutive patients who had undergone rotator cuff repair to retrospectively determine the association between the visual grades at preoperative state and postsurgical occurrences of retear. RESULTS: The inter-reader weighted kappa value for the visual grading was 0.74 when averaged across three reader pairs (0.70-0.77 for individual reader pairs). The weighted kappa value between the visual grading and the reference standard ranged from 0.75 to 0.83. There was a significant difference in retear rates of the rotator cuff between the 3 visual grades of supraspinatus muscle atrophy on MRI in univariable analysis (p < 0.001), but not in multivariable analysis (p = 0.026). CONCLUSION: The 3-point visual grading system may be a feasible method to assess the severity of supraspinatus muscle atrophy on MRI and assist in the clinical management of patients with rotator cuff tear.

Accuracy of Preoperative MRI with Microscopy Coil in Evaluation of Primary Tumor Thickness of Malignant Melanoma of the Skin with Histopathologic Correlation

OBJECTIVE: The purpose of this study was to evaluate the accuracy of a preoperative MRI with microscopy coils in determining the primary tumor thickness of malignant melanoma with histopathologic correlation. MATERIALS AND METHODS: Eleven patients with histopathologically confirmed malignant melanoma were included in this study. MR images of the tumors were obtained with a 47-mm microscopy coil on 1.5T MR scanners and were evaluated by two radiologists, who assessed the thickness of the primary tumor on T2-weighted images (T2WI) and gadolinium-enhanced T1-weighted images with fat suppression (Gd-T1WI) and compared the results with the histopathologic findings as the reference standard. Correlations between tumor thickness on MRI and histopathologic examination were assessed using concordance correlation coefficients (CCCs). Inter- and intraobserver variabilities of tumor measurements were also assessed by intraclass correlation coefficient (ICC). RESULTS: Among the 11 cases included in the study, 10 cases from the same number of patients were managed with surgical excision and one case was confirmed with punch biopsy. The primary tumor thickness measured on T2WI showed better correlation with histopathologic results, as compared with measurements taken on Gd-T1WI: the CCC of measurements on T2WI ranged from 0.64 to 0.78, indicating a substantial agreement, whereas the CCC of measurements on Gd-T1WI ranged from 0.50 to 0.61, indicating a moderate to substantial agreement. Inter- and intraobserver agreements of readers 1 and 2 were excellent for both T2WI and Gd-T1WI, with ICC ranging from 0.86 to 0.99. CONCLUSION: MR imaging with microscopy coils may be an accurate technique in the preoperative assessment of tumor thickness in malignant melanoma, especially on T2-weighted images.

Musculoskeletal Application of Ultrasound Elastography: Soft Tissue Lipoma

PURPOSE: To investigate the tissue elastic properties of soft tissue lipomas using real-time freehand elastography. MATERIALS AND METHODS: Conventional ultrasonography (US) and real-time freehand US elastography were performed in nine patients (M:F = 4:5; mean age, 53 years; 29-64 years) with soft-tissue lipoma confirmed by surgical resection. The elastogram was color-coded by 256 scales according to the degree of strain induced by light compression. The relative strains for lipoma and surrounding soft tissue were measured and mean strains were examined by using a Wilcoxon signed rank test. RESULTS: The elastograms showed red to sky-blue color in all lipomas and predominantly black in surrounding soft tissue. The mean relative strain (+/-standard deviation) was 67.9+/-28.5, 77.1+/-25.3, 63.3+/-31.2, and 15.7+/-18.3 for total, intramuscular, and subcutaneous lipoma, and surrounding soft tissue, respectively. The mean strain of the lipoma was significantly higher than one of surrounding soft tissue (p = .008, Wilcoxon signed rank test). CONCLUSION: Real-time elastography yields characteristic elastographic features of soft tissue lipoma distinguishing from those of adjacent soft tissues.

CT Evidence for Subchondral Trabecular Injury of the Femoral Head in Transient Osteoporosis of the Hip: A Case Report

A 28-yr-old woman presented with both hip pain that started sequentially during the peripartum period. Diagnosis of transient osteoporosis of the hip (TOH) was made based on typical findings of plain radiographs and magnetic resonance images. The subchondral trabeculae of the femoral head were evaluated on serially taken coronal multiplanar reformation computerized tomogram images. At 4 weeks after pain onset, marked decrease in the sclerotic density with irregular discontinuation was observed in the primary compression trabeculae. At 12 weeks, a focal area of irregular thickening of trabeculae was observed. At 20 weeks, sclerotic density of trabeculae recovered markedly and the focal area of irregular trabecular thickening disappeared. At 1 yr, subchondral trabeculae recovered almost completely. The evidence of subchondral trabecular injury was observed in the femoral heads of TOH.

Fibroblastic Type Osteosarcoma of the Ulna: a Case Report of a Tumor in a Rare Location with Atypical Imaging Findings

The ulna is a rare site of origin for osteosarcoma, and purely osteolytic osteosarcomas are uncommonly noted on conventional radiographs. We present a patient with a lytic lesion of the distal ulna for which imaging findings suggested an aneurysmal bone cyst. The lesion was histologically confirmed to be a fibroblastic osteosarcoma.

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.

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.

MR Imaging Findings of Mercury Deposits in the Upper Arm: A Case Report

The incidental injection of metallic mercury into soft tissue is a rare event in the general population. Mercury can produce local inflammation, abscesses, granuloma, and membranous fat necrosis. Herein, we report a rare case of soft tissue mercury deposits with imaging findings, including magnetic resonance (MR) imaging findings, located at the mercury droplet deposits which appear as signal voids on all sequences, with surrounding intermediate to high signal intensity on the T2- weighted image.

Therapeutic Effect of Epidural Steroid Injection in Patients Suspected of having an Internal Disc Disruption: A Prospective Case Study

PURPOSE: To assess the effect of the epidural steroid injection for patients suspected of having an internal disc disruption. MATERIALS AND METHODS: Thirteen patients at the pain intervention clinic that received a lumbar interlaminar epidural steroid injection and were suspected of having an internal disc disruption were prospectively enrolled in this study. The treatment outcome was assessed using a 5-point patient satisfaction scale (no pain, much improved, slightly improved, no effect, aggravated) two weeks after injection. A successful outcome required a patient satisfaction scale of "much improved" or "no pain". All patients received follow-up for two months. Two radiologists evaluated the presence of HIZ (high intensity zone), a dark disc by MR (n = 10) and a diffuse bulging disc by CT (n = 3). RESULTS: Nine (69%) of the 13 patients achieved a successful outcome two weeks after injection. These nine patients showed no recurrence during the two months months follow-up. Of the 22 abnormal discs demonstrated by MRI and CT, MRI showed a dark disc in six patients and HIZ in 13 patients. CT showed diffuse bulging in three discs. Nine of 10 patients showed at least one HIZ. CONCLUSION: An lumbar interlaminar epidural steroid injection might be an effective tool for managing patients suspected of having an internal disc disruption.

A Chondroblastoma Versus a Giant Cell Tumor: Emphasis on the MR Imaging Features

PURPOSE: To assess the MR imaging features in differentiating a chondroblastoma (CB) from a giant cell tumor (GCT), with an emphasis on the accompanying peritumoral bone marrow edema. MATERIALS AND METHODS: MR imaging findings in 20 patients with CB were compared with the imaging features of 22 patients with GCT. The location of the lesion, signal intensity, adjacent cortical change, degree of accompanying bone marrow edema, synovitis in the adjacent joint and cystic change were analyzed. The findings of CB and GCT were examined statistically with use of Fisher's exact test. RESULTS: The incidence ratios of MR imaging findings were as follows (CB:GCT). Metaphyseal dominant involvement (2:21), partial cortical disruption (2:14), extensive bone marrow edema surrounding the tumor (14:0) and synovitis in the adjacent joint (11:2) were statistically different in incidence between CB and GCT (p < 0.01). The inhomogeneous signal intensity (17:17) and cystic change (10:15) were not different in incidence between a CB and a GCT. CONCLUSION: The presence of metaphyseal dominant involvement and cortical disruption favors a diagnosis of a GCT rather than a CB. In contrast, extensive bone marrow edema surrounding the tumor and synovitis in the adjacent joint are highly indicative of a CB.

Usefulness of Fluoroscopy-Guided Intra-articular Injection of the Knee

PURPOSE: To determine the accuracy of the intra-articular location of hyaluroinc acid injection using a blind approach and to establish the usefulness of fluoroscopy-guided intra-articular injection. MATERIALS AND METHODS: A fluoroscopy unit was used for 368 intra-articular injections of hyaluronic acid to 93 knees in 65 patients. Initially, blind needle positioning was conducted on the fluoroscopy table. The failure rate of the blind approach among the 368 injections was evaluated, and a relationship between the Kellgren-Lawrence grade (K-L grade) and the incidence of repeated failures using the blind approach was determined for injections to 52 knees in 37 patients who received a complete cycle of injections (five consecutive injections with a one-week interval between injections). RESULTS: Using a blind approach, 298 of 368 trials (81.2%) resulted in a needle tip being placed in an intra-articular location, while 70 of 368 trials resulted in an extra-articular placement of the needle tip. Among 52 knees to which a complete cycle of injections (five consecutive injections with a one-week interval between injections) was administered, repeated failure of intra-articular placement using the blind approach was seen for 18 knees (34.6%); a more severe K-L grade assigned was associated with a higher rate of repeated failure. However, the trend was not statistically significant based on the Chi-squared test (p value = 0.14). CONCLUSION: Fluoroscopy-guided needle placement may be helpful to ensure therapeutic intra-articular injection of the knee.

Percutaneous Spine Injection: Considerations for Improving Treatment

PURPOSE: To discuss the causes of treatment failure in percutaneous spine injections for low back pain or radiculopathy by analyzing patients who have experienced negative treatment effect on their first visit and a positive treatment effect on their second visit. MATERIALS AND METHODS: The authors reviewed the cases of 24 patients who visited the pain intervention outpatient department in our hospital due to back pain or radiculopathy. All patients reviewed experienced a negative treatment effect following their first spine injection, but a positive treatment effect following the second injection. The dates of the cases range from June 2003 to May 2004. Two radiologists analyzed the possible causes of the negative treatment effect following the first injection therapies by considering clinical aspects as well as reviewing radiological images. RESULTS: The most common condition was the presence of the change in the level of the second selective nerve root block (n=13). In seven cases, the methods for administering the injections were changed to facet block (n=2), midline epidural block (n=1), selective nerve root block (n=3) and caudal epidural block (n=1). In four cases, there were no changes in the methods for administering the injections nor were there any changes in the level of the selective nerve root block between first and second visit. In those cases, after reviewing spot radiographs performed during injection, we attributed the causes of failure of injection therapy to an inappropriate distribution of drugs. CONCLUSION: We can improve the effect of percutaneous spine injections for low back pain or radioculopathy by determining the exact level of perineural root block, trying alternative methods, and insuring a good distribution of the injected drugs.

Internal Disc Derangement in Patients with Low Back Pain: Correlation of MR Imaging and Provocative Discography and CT Discography

PURPOSE: The aim of this study was to correlate the MR imaging abnormalities of the lumbar intervertebral discs, with emphasis being placed on the high intensity zone (HIZ) with the use of discography for pain provocation and disc morphologic evaluation of the disc. MATERIALS AND METHODS: Consecutive patients with low back pain unresponsive to conservative treatment, and who were being considered for spinal fusion had MRI performed, and this was followed by lumbar discography. The MR imaging, discography and CT discography (CTD) were evaluated for all of the 19 patients. Forty-three lumbar discs in 19 patients were included in this study. The findings of MR and CTD images were evaluated retrospectively with the professional opinion and agreement of two radiologists. MR images were assessed for the presence or absence of decreased T2-wighted signal intensity, decreased disc height, annular bulging, HIZ on T2-weighted images and disc herniation. The results of pain provocation were graded as 0, nonconcordant pain; 1, definite pain, but only as part of the symptom complex; 2, concordant pain. The morphology of CTD was analyzed for presence or absence of disc degeneration, radial tearing and extravasation of the contrast agent. The presence of radial tearing was defined as contrast extension to the outer third of the annulus. The prevalence of all MR abnormalities was calculated, and the data were compared with disc morphologic characteristics and the pain response on provocative discography. We used the chi-square test to analyze the results. RESULTS:Grade 1 and 2 discogenic pain was observed in 8 (19%) and 12 disc levels (28%), respectively. All of the seven non-degenerated discs on MR had no pain response. The decreased SI on T2-weighted image, annular bulging and HIZ were significantly correlated with discogenic pain. Extravasation of contrast media had good correlation with annular bulging and disc herniation on MRI. Radial tearing on CT discography correlated significantly with HIZ. The HIZ was detected in 14 levels (32.6%). The HIZ on MRI correlated significantly with the pain provocation and radial tearing noted on the discograms. CONCLUSION: Several MR imaging findings correlated significantly with the severity of pain provocation to discography. For patients with symptomatic low back pain, the HIZ observed on MR may represent a painful outer annular disruption.

Posterior Epidural Fat on Sagittal MR Images: Can it Help in Distinguishing Between Isthmic and Degenerative Lumbar Spondylolisthesis?

PURPOSE: We tried to assess the value of posterior epidural fat for distinguishing isthmic spondylolisthesis from degenerative lumbar spondylolisthesis on midline sagittal MR images. MATERIALS AND METHODS: The midline sagittal MR images of the lumbar spines were retrospectively studied for 50 patients without spondylolisthesis, for 78 patients with isthmic spondylolisthesis and for 43 patients with degenerative spondylolisthesis. The anteroposterior diameter of the posterior epidural fat (ADEF) was measured at each intervertebral disc level by two radiologists and these values were then compared between each group. To normalize for difference of body size, the posterior epidural fat ratio (PEFR) at each level of spondylolisthesis and at L1-2 were also determined for each level of spondylolisthesis, and the PERF was compared between each group. Statistical analysis was performed by the chi-square method. RESULTS:For the patients with isthmic spondylolisthesis, the ADEFs at the spinal levels with spondylolisthesis were significantly greater than those ADEFs in the control group that were measured at the corresponding disc levels (p<0.05). For the patients with degenerative spondylolisthesis, the ADEFs at the spinal level with spondylolisthesis were significantly less than the ADEFs in the control group that were measured at the corresponding disc levels (p<0.05). The PEFRs obtained at L4-5 were 1.37+/-0.12 for the control group, 2.61+/-1.31 for the patients with isthmic spondylolisthesis, and 0.60+/-0.05 for the patients with degenerative spondylolisthesis. The PEFRs obtained at L5-S1 were 2.25+/-1.32 for the control group, 3.47+/-1.69 for the patients with isthmic spondylolisthesis and 1.65+/-0.18 for the patients with degenerative spondylolisthesis. At both levels, the PEFRs were greatest for the isthmic spondylolisthesis group and smallest for the degenerative spondylolisthesis group, and all the differences were statistically significant. CONCLUSION: The posterior epidural fat, which is easily seen structure on the midline sagittal MR image, is significantly increased in isthmic spondylolisthesis, but it is decreased in degenerative spondylolisthesis, and this could be useful in distinguishing isthmic spondylolisthesis from degenerative spondylolisthesis.