Biomedical subjects
W G Totty
Publications and source records attributed to W G Totty.
Pictorial review: magnetic resonance imaging of benign soft tissue masses of the hand and wrist.
Magnetic resonance imaging (MRI) is the imaging method of choice for evaluating the presence and extent of soft tissue masses. It is particularly useful for assessing masses in the wrist and hand, where benign lesions predominate. A specific diagnosis may be made, or strongly suspected, from the characteristic MRI features found in certain conditions like ganglion, haemangioma, arteriovenous malformation, giant cell tumour of the tendon sheath and lipoma.
Acromial arch shape: assessment with MR imaging.
PURPOSE: To test the hypothesis that acromial shape is comparable on supraspinatus outlet view radiographs and parasagittal magnetic resonance (MR) images. MATERIALS AND METHODS: Supraspinatus outlet view radiographs of a dried scapula were obtained in the neutral position and with various degrees of caudal, cranial, anterior, and posterior angulation. Sagittal MR images of 41 asymptomatic and 39 symptomatic shoulders were reviewed and compared with outlet view radiographs from the 39 symptomatic cases. Acromial shape was assessed with published classification schemes. RESULTS: Minor variations in angulation produced changes in apparent acromial shape and thickness on the radiographs. MR imaging from a lateral to a more medial section changed the shape or thickness grade in 39 of 41 asymptomatic shoulders. There was poor correlation between findings at radiographic and MR assessment of acromial shape in the symptomatic group. CONCLUSION: Apparent acromial shape is sensitive to minor changes in radiographic technique and MR section viewed.
MR diagnosis of rotator cuff tears of the shoulder: value of using T2-weighted fat-saturated images.
OBJECTIVE: The purpose of this study was to compare the use of fat-saturated T2-weighted spin-echo MR imaging with that of conventional T2-weighted spin-echo MR imaging to detect full- and partial-thickness tears of the rotator cuff of the shoulder, using arthroscopy as the standard for the diagnosis. SUBJECTS AND METHODS: Forty-nine consecutive patients with shoulder pain who had both MR imaging and arthroscopy of their affected shoulders were studied. The study group consisted of 10 patients with full-thickness tears of the rotator cuff, 20 with partial-thickness tears of the rotator cuff, and 19 with intact rotator cuff tendons proved arthroscopically. All patients had T1-weighted, conventional T2-weighted, and fat-saturated T2-weighted MR images obtained in a plane slightly oblique to the coronal plane along the long axis of the supraspinous tendon. The images were divided into two sets, one including both T1-weighted and conventional T2-weighted images, the other including T1-weighted and fat-saturated T2-weighted images. Two musculoskeletal radiologists reviewed each set of MR images in a blinded fashion. The reviewers were asked to decide whether the rotator cuff showed a full-thickness tear, a partial-thickness tear, or no tear on each set of images. In the case of partial-thickness tears, the reviewers were asked to indicate which surface (bursal or joint) of the rotator cuff was affected. These data were correlated with the arthroscopic findings and with each other using McNemar and kappa analysis. RESULTS: Detection of full-thickness tears was excellent for both reviewers using either imaging technique. However, when the fat-saturated technique was used, the sensitivity increased significantly, from 80% to 100%. Detection of partial-thickness tears was poor with conventional spin-echo MR imaging (15%). Although significantly improved when fat saturation was used (35%), detection rates were still lower than rates reported in the literature. Identification of the torn surface of the rotator cuff was correct in 50% of cases in which partial-thickness tears were successfully identified. Fat saturation decreased the specificity of identification of both partial and full-thickness tears of the rotator cuff but significantly increased the specificity with which intact rotator cuffs were identified. CONCLUSION: Use of the fat-saturation technique improved detection of both full-thickness and partial-thickness tears of the rotator cuff on MR images compared with standard spin-echo imaging techniques. Despite this improvement, detection of partial-thickness tears was poor with both techniques. Furthermore, correct identification of which surface of the rotator cuff was torn in patients with partial tears was nearly random.
The normal shoulder: common variations that simulate pathologic conditions at MR imaging.
The appearance of the supraspinatus tendon and anterior capsular mechanism was analyzed in 60 asymptomatic shoulders with magnetic resonance (MR) imaging. The images were reviewed with special attention to findings that simulate pathologic conditions, as defined by means of currently accepted criteria. On T1-weighted and proton-density (PD) spin-echo (SE) images, intermediate signal intensity was present within the supraspinatus tendon in most shoulders. Focal signal intensity within the distal tendon was particularly common finding, being present in 95% (57 of 60) of shoulders on PD images. Focal obliteration of the subacromial-subdeltoid fat stripe and acromioclavicular joint arthrosis were seen in 95% (57 of 60) and 48% (29 of 60) of the subjects, respectively. There was considerable variation in the shape of the anterior glenoid labrum-glenohumeral ligament (GHL) complex. The labrum may appear triangular, round, crescentic, or absent. The middle and inferior GHLs lie in proximity to the upper half of the anterior labrum; the cleavage plane between the ligaments and the labrum can mimic a tear at MR imaging.
Calcaneal and pelvic fractures: diagnostic evaluation by three-dimensional computed tomography scans.
A major application of three-dimensional (3D) computed tomography (CT) is in the imaging of the skeleton. 3D CT has a potentially important role in determining the presence, type, and extent of fractures, especially of the calcaneus and pelvis. The objective of this study was to compare the diagnostic sensitivity and specificity of 3D CT, CT slices, and plain radiography in the detection and characterization of calcaneal and pelvic fractures. 3D CT reconstructions were obtained by two methods, surface reconstruction and volumetric techniques. Twenty-eight patients were imaged with CT, 3D CT, and plain radiography. The opinion of a musculoskeletal radiologist with access to all images plus clinical history, surgical findings, and follow-up findings was taken as truth. Four additional musculoskeletal radiologists read these cases in a blinded fashion and ranked the modalities with regard to perceived utility. Receiver operating characteristic analysis was used to determine the relative value of each modality in terms of diagnostic quality. All imaging modalities performed comparably in the diagnosis of fractures. CT slices and plain-films were the most useful for more difficult diagnostic tasks such as fracture stability, and the presence of comminution and estimation of the number of fragments. The results suggest that for skeletal areas with complicated anatomy (such as the pelvis and calcaneus), the diagnostic value of 3D CT is often equivalent to that of conventional methods.
Cross-sectional imaging of the patellofemoral joint and surrounding structures.
Computed tomography (CT) and magnetic resonance (MR) imaging are extremely useful in the accurate diagnosis of anterior knee pain, a common complaint arising from numerous causes (including fracture, chondromalacia patellae, and alignment and tracking abnormalities). Plain CT is effective for evaluating intraosseous lesions of the knee. Although CT arthrography provides excellent visualization of the patellar articular cartilage, the technique is expensive and invasive. Cine CT is an excellent method for assessing patellofemoral tracking and alignment. Kinematic MR imaging can also perform this function. In addition, MR imaging can provide valuable information concerning the status of patellar cartilage. Although MR imaging can accurately show high-grade chondromalacia patellae, it is less accurate in the detection of low-grade disease. The authors believe that MR imaging and plain radiography offer radiologists the greatest latitude in making a specific diagnosis of the cause of anterior knee pain; however, CT is a useful alternative.
Renal transplants: can acute rejection and acute tubular necrosis be differentiated with MR imaging?
Magnetic resonance (MR) imaging was used in 40 renal transplant recipients to determine whether this modality can enable distinction of acute tubular necrosis (ATN) and acute rejection by means of corticomedullary differentiation (CMD). Each patient underwent initial MR imaging after allograft renal transplantation. Twenty-nine of these 40 patients (72%) also underwent subsequent follow-up MR imaging. Seventeen studies were obtained during episodes of ATN; 12 of these studies (71%) showed poor CMD. Eleven studies were obtained during episodes of acute rejection; eight of these studies (73%) showed poor CMD. In addition, six of seven studies (86%) showing various combinations of renal disease (ATN, acute rejection, chronic rejection, and cyclosporine toxicity) also showed poor CMD. Loss of CMD is reversible after improvement of ATN and acute rejection. Because loss of CMD is a nonspecific though sensitive sign reflecting renal transplant dysfunction, MR imaging is of limited value in the differentiation of ATN from acute rejection.
MR examination of the knee: interpretation with multiscreen digital workstation vs hardcopy format.
A multiscreen imaging workstation was compared with conventional hardcopy format for diagnostic interpretation of MR images of the knee. MR examinations from 30 patients were interpreted by two observers using film displayed both on a standard film panel alternator and an eight-screen digital workstation. Arthroscopic examination of these patients disclosed 30 meniscal tears and five anterior cruciate ligament tears in 28 patients. Two patients had normal arthroscopic examinations. The MR examinations were evaluated with a five-point confidence rating scale. Results were correlated with arthroscopic findings, and receiver-operating-characteristic curves were generated from these data. No significant difference was found between the areas under the receiver-operating-characteristic curves for film and digital display. The time required for image interpretation was greater when using the digital workstation than when using the film by a factor of approximately 2.7. Our data indicate that a multiscreen digital workstation can be used for interpreting MR examinations of the knee without impairment of diagnostic performance, but with increased time required for image interpretation when compared with radiographic film and a film panel alternator.
Magnetic resonance imaging of ankle injuries.
Stress placed on the ankle from sport activity predisposes it to a variety of injuries. MRI, with its multiplanar capability and excellent soft tissue contrast, is uniquely suited for examining the complex anatomy of the ankle. It is the procedure of choice for imaging suspected tendon and cartilage damage. It is also highly sensitive in detecting radiographically occult bone injuries. This review first addresses technical factors important in generating high-resolution images that are crucial for accurate diagnosis in this area. Pathogenesis and MRI appearance of commonly encountered sport-related soft tissue and bone injuries around the ankle are presented and discussed.
Magnetic resonance imaging of peripheral nerve sheath tumors. Assessment by numerical visual fuzzy cluster analysis.
A retrospective, nonblinded review of ten nerve sheath tumors (four malignant) selected for pathologic proof and complete magnetic resonance (MR) evaluation was performed to assess the primary tumor location, signal pattern, and extent of reactive zone. A modification of visual fuzzy cluster analysis (VFCA) that emphasized the number of visual fuzzy clusters in each mass was developed to assess the neural tumors. The MR findings were correlated with the findings at surgery and histopathology. There were six men and four women, aged 19 to 62 years (mean, 43). Nine tumors involved the lower extremity. In all tumors, MRI correctly identified the nerve trunk of origin. Tumor dimensions were generally overestimated by MRI. Three internal signal patterns were observed: homogeneous (1/1 benign), finitely inhomogeneous (5/5 benign), and hectically inhomogeneous (4/4 malignant). The number of visual fuzzy clusters (VFCRs) for each sequence did not allow reliable separation of benign and malignant entities, but when considered in aggregate, benign and malignant lesions segregated in different clusters. This implies that the likelihood of malignancy increases as the number of MR-identifiable tissue types per lesion increase. Three types of reaction (edema) were observed best on long repetition time/echo time (TR/TE) sequences, confined to immediate peritumoral region, intracompartmental, and extracompartmental. The first two patterns correlated well with clinicopathologic findings; however, the third pattern did not. Separation of indolent (benign) cellular masses from aggressive (malignant) ones by MR characteristics is difficult but VFCA shows promise for aiding this differentiation and deserves further investigation in larger study populations.
The knee after partial meniscectomy: MR imaging features.
The magnetic resonance (MR) examinations of 51 menisci treated by means of partial meniscectomy were reviewed. Menisci were divided into three groups: group 1, near normal length without osteoarthritis; 2, substantially shortened without osteoarthritis; and 3, any length with osteoarthritis. Group 1 menisci resembled normal menisci except for mild shortening and frequent signal inhomogeneity (56%). Group 2 menisci varied in appearance, with marked contour irregularity simulating fragmentation in 40% of segments despite a normal postoperative appearance at follow-up arthroscopy. Group 3 menisci appeared similar to menisci of the same length without osteoarthritis. Arthroscopic correlation, available for 23 menisci (45%), confirmed the MR diagnosis of a tear in 11 and no tear in 49 and revealed an unsuspected tear in three meniscal segments. There is a spectrum of normal MR appearances after partial meniscectomy. Standard MR criteria can be used to diagnose tears in the absence of marked contour irregularity; however, the diagnosis of tears of segments with marked contour irregularity must be made cautiously, since this irregularity can mimic a tear and was not predictive of an arthroscopically visible tear.
Subtalar arthrosis: evaluation with CT.
The surgical implantation of a Silastic wedge into the lateral subtalar joint (subtalar arthrosis) is designed to restrict the osseous malalignment associated with a flexible or neurogenic flatfoot deformity. We used CT to examine patients who had persistent pain after a subtalar arthrosis and retrospectively reviewed our experience with CT scans of 13 subtalar implants (seven patients) during a 3.5-year period. The CT scans of four asymptomatic subtalar implants showed each implant in the expected position and orientation, and the findings were considered normal. Conversely, the findings on CT scans of all nine painful implants (seven patients) were interpreted as abnormal. The scans showed oblique orientation of four implants (44%), loosening of three implants (33%), extruded methyl methacrylate in the subtalar joint in two implants (22%), and abnormal calcaneal recession in two implants (22%). Five of the nine painful implants were revised with improvement or resolution of symptoms. Our experience suggests that CT scanning of the subtalar joint can show the position and orientation of a subtalar implant and identify causes of persistent pain after a subtalar arthrosis.
Measurement of fat distribution by magnetic resonance imaging.
Because of the important role of intra-abdominal fat in predicting increased risk for diabetes, hypertension, and heart disease, methods to quantify intra-abdominal fat are needed. Computed tomography defines quantity of intra-abdominal fat but is associated with significant radiation risk. We explored using magnetic resonance imaging (MRI) to measure amount and distribution of intra-abdominal fat. Because MRI has no known risk, the same subject can be studied repeatedly. Six subjects with percent body fat ranging from 14% to 44% had MRI scans of the chest, abdomen, and thigh on two separate occasions. Total abdominal fat and subcutaneous abdominal fat correlated with percent total body fat as determined from hydrostatic weighing (r = .99, P less than .001). Intra-abdominal fat correlated with the ratio of widest abdominal to widest hip circumference (r = .85, P less than .05). Reproducibility of the MRI measurements of fat was less than 3% for total body areas, less than 5% for subcutaneous fat areas, and less than 10% for internal fat areas. Reproducibility was better in individuals with higher percent total body fat. We conclude that MRI can reliably measure fat areas with no radiation risk to the patient.
Proton spectroscopic imaging (Dixon method) of the liver: clinical utility.
The contribution of proton spectroscopic (PS) imaging to magnetic resonance (MR) imaging of the liver was assessed at 0.5 T in 55 patients with known or suspected hepatic malignancy. PS images were compared subjectively with T1- and T2-weighted spin-echo (SE) images for hepatic lesion detection and conspicuity. For hepatic metastases (n = 27), PS images were equal to T1-weighted images in lesion detection in 17 patients but showed fewer lesions in five patients and false-negative results in two. When compared with T2-weighted images, PS images depicted more lesions in six patients, an equal number of lesions in 18, and fewer lesions in two. Hepatomas (n = 8) were detected with each sequence in all patients. Hepatomas were often more conspicuous on PS images than on T2-weighted images; they were of equal conspicuity on PS and T1-weighted images in most cases. Whereas fatty infiltration (n = 16) appeared on PS images as areas of low signal intensity similar to that of paraspinal muscle, it produced no detectable abnormality on either T1- or T2-weighted images. PS imaging is inferior to T1-weighted SE imaging in the detection of hepatic metastases. The major role of PS imaging at intermediate field strength is to differentiate focal fatty infiltration from hepatic metastases.
Shoulder joint: arthrographic CT and long-term follow-up, with surgical correlation.
One hundred two computed tomographic (CT) arthrograms of the shoulder were retrospectively reviewed and compared with conventional double-contrast arthrograms from 101 patients (24 females and 77 males aged 9-70 years). One- to 4-year follow-up was obtained in 84 patients, 40 of whom underwent open-shoulder surgery or arthroscopy. Morphology of the normal portions of each labrum was categorized according to length, width, and tip shape. Correlation between morphology and age was weak, but abnormal labra were more common in younger patients. Conventional radiography was more accurate for detecting bony glenoid margin fractures, but CT was more accurate for detecting Hill-Sach fractures. CT was also more reliable than conventional arthrography in the detection of rotator cuff tears. Hence, few if any conventional radiographs are necessary between contrast material injection and CT imaging. A reduction in the number of images obtained will result in decreased radiation dose, less cost, and shorter examination time without loss of diagnostic accuracy.
MR imaging of the knee: comparison of three-dimensional FISP and two-dimensional spin-echo pulse sequences.
Two-dimensional (2D) spin-echo (SE) sequences and three-dimensional (3D) FISP (fast imaging with steady precession) sequences of the knee with the same section thickness and field of view were directly compared in 54 patients, 17 of whom underwent subsequent follow-up (15 arthroscopic and two arthrographic examinations). In those patients with follow-up, each sequence demonstrated 100% sensitivity, 80% specificity, and 94% accuracy for evaluation of the medial meniscus and 100% sensitivity, 100% specificity, and 100% accuracy for evaluation of the lateral meniscus. SE imaging demonstrated 100% sensitivity, 100% specificity, and 100% accuracy for evaluation of the anterior cruciate ligament, while 100% sensitivity, 82% specificity, and 88% accuracy were achieved with FISP imaging. In the 37 patients without follow-up, only two discrepancies were found between the 2D SE and the 3D FISP images for meniscal evaluation. Three discrepancies were found in the evaluation of the anterior cruciate ligament, two of which were likely false-positive 3D FISP results. We conclude that 2D SE and 3D FISP imaging provide comparable data for meniscal evaluation. FISP images are slightly less accurate than SE images of comparable resolution for the evaluation of the anterior cruciate ligament.
Ascending lower limb phlebography: comparison of ioversol and iothalamate meglumine.
Fifty patients undergoing ascending phlebography of a lower limb were evaluated, in a randomized double-blind fashion, to compare the efficacy, patient tolerance, and safety of two different contrast agents. Ioversol-240 (MP-238), a new nonionic agent, and iothalamate-202 (Conray 43), an established ionic agent, were the contrast agents used. Twenty-five patients were injected with iothalamate and 25 with ioversol. The phlebograms were evaluated for diagnostic quality and the patients for symptoms, with special reference to complaints of heat and pain. No significant difference was demonstrated between the two agents in either examination quality or patient tolerance. No major contrast-related reactions were recorded. We conclude that ioversol-240 appears to be a safe and acceptable alternative to iothalamate-202.