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J S Swan

Publications and source records attributed to J S Swan.

At least 19 recordsLinked to original sources
PubMed2000

3D MR DSA: effects of injection protocol and image masking.

The purpose of this study was to investigate the effect on three-dimensional (3D) magnetic resonance digital subtraction angiography (MR DSA) images of various injection protocol parameters (ie, injection order, volume, and rate), as well as image masking. The pelves of 10 normal volunteers were scanned using seven different contrast agent volume/injection rate combinations. Subtraction of a precontrast mask image resulted in vascular image contrast improvements of between 4.0 and 7.7 times. Image quality and smaller vessel image contrast in the masked data decreased with increasing injection number. Data acquired with a high (0.150 mmol kg(-1)) volume yielded the highest quality images, although only small nonsignificant differences in image quality and large vessel conspicuity were found between images obtained using the high and medium (0.075 mmol kg(-1)) volumes. Images acquired with a low (0. 038 mmol kg(-1)) volume, while of lower image contrast, were judged to be of reasonable quality, especially when acquired as the first or second injection. Injection rate (1 ml s(-1), 2 ml s(-1), and 4 ml s(-1)) was not found to affect the images significantly, although selection of an injection rate that gave an injection duration of approximately 10 seconds tended to give better vascular image contrast. Based on these data, a series of escalating volumes for multi-injection examination is proposed. J. Magn. Reson. Imaging 2000;12:476-487.

Adult↗
PubMed2000

Method for rapidly determining and reconstructing the peak arterial frame from a time-resolved CE-MRA exam.

A method that determines the information necessary to reconstruct a single vascular image from a time-resolved CE-MRA exam is presented. Raw k-space data are used to approximate the time course of the contrast passage prior to image reconstruction. The resulting k-space contrast curve is used to select the data corresponding to peak arterial enhancement. These data are reconstructed and immediately presented for physician review, with the entire time-series of images available at a later time for more detailed diagnosis. This approach dramatically reduces the latency between acquisition of large 4D (3D plus time) data sets and presentation of a diagnostic quality time frame. This algorithm has proven successful in the imaging of several anatomical regions and-in exams that do not require a breath hold-permits the use of an acquisition method that produces a contrast-enhanced angiogram without a timing scan.

Arteries↗
PubMed2000

Magnetic resonance angiography of aorto-iliac disease.

BACKGROUND: Four different techniques for aorto-iliac magnetic resonance angiography (MRA) were assessed for accuracy using a digital subtraction angiography (DSA) gold standard. Surgeons' confidence in their ability to generate treatment plans with MRA and DSA was assessed, in consultation with a radiologist. METHODS: Two different two-dimensional (2D) time-of-flight (TOF) sequences, a phase-contrast sequence, and a contrast-enhanced (CE) MRA sequence were used. Receiver operating characteristic (ROC) curves were plotted and areas (A(z)) calculated from radiologists' readings. Surgeons' confidence in their ability to utilize the images for treatment planning was assessed with a 5-point Likert scale. Thirty-six patients were evaluated. RESULTS: CE MRA had a sensitivity, specificity, and A(z) of.92,.93, and.96, respectively, for stenoses 50% or greater. CE MRA performed better than other sequences, but the improvement compared with gated 2D TOF was not statistically significant. Interobserver agreement for CE MRA and DSA yielded identical Kappa values. Surgeons were most confident in DSA, followed by CE MRA, which was significantly preferred to other techniques. CONCLUSIONS: CE MRA closely approximates DSA in terms of diagnostic accuracy. Surgeons considering treatment plans are confident in the CE MRA technique, relative to other MRA methods.

Adult↗
PubMed1999

Comparison of treatment plans for lower extremity arterial occlusive disease made with electrocardiography-triggered two-dimensional time-of-flight magnetic resonance angiography and digital subtraction angiography.

BACKGROUND: The purpose of the study was to determine whether preoperative treatment plans for patients with lower extremity ischemia can be made with electrocardiography (EKG)-triggered two-dimensional (2D) time-of-flight (TOF) magnetic resonance angiography (MRA) as accurately as digital subtraction angiography (DSA). METHODS: Forty patients were prospectively evaluated with the combination of EKG-triggered 2D TOF MRA, DSA, and pulse volume recordings. Blinded reviewers graded arterial segments for disease severity. Accuracy of separate MRA- and DSA-based treatment plans was compared with the procedures performed based on all available information. RESULTS: There was an 86% exact match between MRA- and DSA-based plans (92% MRA and 94% DSA accuracy). The MRA-based plan accurately predicted 90% of suprainguinal and 95% of infrainguinal procedures, whereas the DSA-based plan accurately predicted 100% of suprainguinal and 85% of infrainguinal procedures. Two-year primary patency was 83% for all procedures. Radiologists' review of disease severity resulted in a mean exact correlation between studies of 81% (kappa = 0.64). The agreement between radiologists interpreting the MRA was 84% (kappa = 0.7) compared with 82% (kappa = 0.66) for the DSA. CONCLUSIONS: MRA- and DSA-based preoperative management plans were of comparable efficacy. Significant interobserver variability was seen with the interpretations of both preoperative studies. EKG-triggered 2D TOF MRA can be used to plan arterial reconstructions; however, all patients require arterial pressure measurements prior to suprainguinal repair and confirmatory intraoperative angiography during infrainguinal revascularization.

Aged↗
PubMed1998

Contrast-enhanced 3D MR DSA of the carotid artery bifurcation: preliminary study of comparison with unenhanced 2D and 3D time-of-flight MR angiography.

PURPOSE: To compare the delineation of stenosis at the carotid artery bifurcation on three-dimensional (3D) magnetic resonance (MR) digital subtraction angiographic (DSA) images with that on two-dimensional (2D) and 3D time-of-flight (TOF) MR angiographic images. MATERIALS AND METHODS: Twenty-six patients with 29 carotid artery bifurcations and symptoms of cerebral ischemia underwent 3D MR DSA. A time-resolved series was generated with 3D MR DSA after the bolus injection of gadodiamide. The resolution for a carotid artery examination was 0.4 x 0.4 x 1.0 mm, with volumes reconstructed at 4.5-second intervals. The 3D MR DSA images were compared with contemporaneously acquired unenhanced 2D and 3D TOF images. Two observers ranked the 2D and 3D TOF MR angiographic and 3D MR DSA images according to the following: (a) stenosis delineation, (b) internal carotid artery delineation, (c) intravascular signal intensity, and (d) diagnostic confidence. RESULTS: The mean ranking for diagnostic confidence was 1.10 (1 = best technique, 3 = worst technique) for 3D MR DSA. Compared with the pooled 2D TOF and 3D TOF ranks, the 3D MR DSA rank was significantly better (P < .01). Similar levels of statistical significance were found for the other criteria. CONCLUSION: Three-dimensional MR DSA improves the delineation of carotid arterial stenosis by virtually eliminating saturation effects and reducing intravoxel dephasing. Surface morphology and nearly occluded vessels ("string sign") were easily identified. Confidence in identifying carotid arterial occlusions was also very high with this technique.

Angiography, Digital Subtraction↗
PubMed1998

Hashimoto's thyroiditis and insulin-dependent diabetes mellitus: differences among individuals with and without abnormal thyroid function.

Insulin-dependent diabetes mellitus probands from the Familial Autoimmune and Diabetes Study were evaluated for autoimmune thyroid disease (n = 265). The prevalence of Hashimoto's thyroiditis was 26.6%; 42.0% of these individuals were euthyroid, and 58.0% were hypothyroid. There was a female predominance among hypothyroid and euthyroid Hashimoto's cases compared to those with no thyroid disease (75% vs. 72.4% vs. 41.6%; P < 0.001). Insulin-dependent diabetes mellitus patients with hypothyroid Hashimoto's thyroiditis were more likely to report another autoimmune disease compared to euthyroid Hashimoto's patients or individuals with no thyroid disease (30.8% vs. 17.2% vs. 13.9%; P < 0.01). Sex-specific analysis revealed that this difference was significant for men but not for women. Both euthyroid and hypothyroid Hashimoto's cases were more likely to have a family history of the disease (66.7% vs. 69.2% vs. 47.7%; P < 0.05). No differences were observed in the prevalence of DQA1*0501-DQB1*0201 or DQA1*0301-DQB1*0302 across the three groups. Body mass index, lipid levels, glycemic control, and diabetes complications were also similar. However, euthyroid Hashimoto's women were more likely to report spontaneous abortions than those with hypothyroid Hashimoto's thyroiditis or no thyroid disease (23.8% vs. 61.5% vs. 29.1%; P < 0.05). These data suggest that gender-specific risk factors may be primary determinants of Hashimoto's thyroiditis and other autoimmune diseases among women. However, disease-specific determinants may also increase susceptibility to other autoimmune diseases.

Abortion, Spontaneous↗
PubMed1997

MR and conventional angiography: work in progress toward assessing utility in radiology.

RATIONALE AND OBJECTIVES: The authors assessed health-related quality of life changes associated with peripheral x-ray angiography and magnetic resonance (MR) angiography. MATERIALS AND METHODS: Utility (the desirability or preference that individuals exhibit for a particular health state) was assessed in 30 patients with peripheral vascular disease referred for angiography by using a rating scale, additional categoric scaling questions to separate preference from experience, a willingness-to-pay technique, functional and cognitive status questions, and a time trade-off technique. All patients underwent both MR angiography and x-ray angiography. RESULTS: Patients reported significantly (P < .05) less anxiety after the test, less pain after the test, fewer new physical limitations, and less effect on performance of daily activities with MR angiography. Findings from the overall rating scale and categoric scaling questions also significantly (P < .05) favored MR angiography. Patients were willing to pay a mean of 2.12% of annual income to avoid MR angiography and a mean of 7.41% to avoid x-ray angiography. The median quality-adjusted life gain required by patients to undergo the procedures was 52.5-60 days for x-ray angiography and 10.5 days for MR angiography, without discounting. CONCLUSION: X-ray angiography has more profound short-term adverse effects on life than does MR angiography. Preference-based measures can be adapted to elicit patient values for short-term health states as seen in radiology.

Angiography↗
PubMed1997

Molecular epidemiology of autoimmune thyroid disease.

This paper presents preliminary data regarding the prevalence and risk factors for autoimmune thyroid disease in IDDM probands ascertained from the Children's Hospital of Pittsburgh IDDM Registry for 1950-1965 (n = 669). Living IDDM probands who participated in the 1990 follow-up survey (n = 380) were recruited for the Familial Autoimmune and Diabetes Study. Siblings and parents were also invited to participate. To date, 255 IDDM probands and 597 parents and siblings have been evaluated. The diagnosis of autoimmune thyroid disease was based on a clinical evaluation, medical history, and laboratory determinations. Graves disease was rare in this cohort (n = 5). However, Hashimoto's thyroiditis was common among women. Prevalence rates ranged from 54% for IDDM women age < 40 years to 75% for those > 50 years. Corresponding age-specific estimates for female relatives were 22% and 44%, respectively. Approximately one-half of the Hashimoto's individuals were euthyroid; they were more likely to have other autoantibodies and a positive family history than those who were hypothyroid or had no thyroid disease. Genetic analyses revealed a 2-fold increase in DQA1*0501-DQB1*0201 among the Hashimoto's compared to the non-Hashimoto's haplotypes. These findings suggested that Hashimoto's thyroiditis was common in IDDM families, which may be due, in part, to common disease susceptibility genes.

Adolescent↗
PubMed1996

MR angiography with three-dimensional MR digital subtraction angiography.

We have developed a time-resolved, contrast-enhanced, volume-imaging technique for magnetic resonance (MR) angiography, known as three-dimensional (3D) MR digital subtraction angiography (DSA). This technique greatly improves MR angiogram quality because it combines the injection of a contrast agent with the ability to image the temporal passage of this agent and, thereby, obviates the need for timing scans or other complicated synchronization schemes. Three-dimensional MR DSA also represents a potential improvement in the sense that, relative to DSA and computed tomography (CT) angiography, the contrast agent is less toxic. Additionally, unlike CT angiography, images may be acquired during the passage of the contrast agent. Therefore, 3D MR DSA shows the sequential passage of contrast through the arterial and venous system, followed by uptake in various organs. Unlike conventional DSA, 3D MR DSA imaging acquires full volume datasets, which allows subsequent reprojection and reformatting. Because images are obtained at approximately 2-6 s time intervals using a temporal aperture on the order of several seconds, motion (such as respiration) causes only a temporary disruption of image quality, similar to that observed in MR fluoroscopy. These temporal characteristics also make the proposed sequence insensitive to variations in the shape and timing of the contrast-pass curve. Although the individual time-resolved images will have somewhat decreased signal-to-noise ratio (SNR) relative to nontime-resolved scans collected in the same acquisition time, the SNR improvement due to the gadolinium appears to accommodate this trade-off. Additionally, if motion between successive images is small, then the full suite of temporal processing schemes, previously investigated in connection with DSA and time-resolved two-dimensional (2D) MR, such as mask mode subtraction, simple matched filtering and Eigen filtering, can be used to obtain composite images. These derived images generally have an increased SNR or negligible venous signal if an arterial-phase image is not obtained in the early time-resolved images. In summary, 3D MR DSA will significantly advance MR angiography because of the following intrinsic advantages: (1) improved signal-to-noise, (2) scan orientation may be chosen independently of the direction of blood flow, (3) uniform vascular signal, even from regions of complex flow, (4) minimization of motion artifacts, (5) greatly reduced sensitivity to variation in the shape and timing of the contrast bolus, (6) ability to be reformatted or reprojected, and (7) ability to apply a variety of temporal postprocessing techniques.

Angiography, Digital Subtraction↗
PubMed1995

Development of a phased-array coil for the lower extremities.

A phased-array coil was developed to facilitate imaging the vasculature of the lower extremities. The array consists of four surface coils placed in a Plexiglas "I-beam" frame that are configured to allow bilateral studies with up to a 40-cm field of view (FOV). Data from phantoms indicate an increase in signal-to-noise ratio (SNR) in the regions of interest by an average factor of 2.8 +/- 0.9 over that of the body coil. Preliminary in vivo data have also been obtained from n = 8 subjects and demonstrate significant improvements in image quality. The coil design described here should lead to reduced scan times through the ability to image both legs simultaneously with less need for patient repositioning.

Angiography, Digital Subtraction↗
PubMed1995

MR imaging of a meniscal ossicle.

We report the MR appearance of a meniscal ossicle, which is an unusual etiology for knee pain. The role of MR in differentiating a meniscal ossicle from a loose body is presented. The MR images also demonstrated associated tibial cartilage thinning and a possible meniscal tear. These MR findings led to arthroscopic treatment rather than conservative management. A review of the literature on meniscal ossicles is also presented.

Adult↗
PubMed1995

Musculoskeletal neoplasms: preoperative evaluation with MR angiography.

PURPOSE: To assess the ability of magnetic resonance (MR) angiography to depict vascularity of musculoskeletal neoplasms. MATERIALS AND METHODS: Two-dimensional (2D) time-of-flight (TOF) MR angiography was compared with conventional arteriography during staging of musculoskeletal tumors in 23 prospective examinations. Phase-contrast (PC) MR angiography was also performed in 19 cases and evaluated as a possible supplement to 2D TOF imaging. RESULTS: Of named vessels, 92% in proximity to tumor were noted by blinded readers. The PC technique provided supplemental data in 47% of cases, usually related to better delineation of in-plane feeder vessels and areas with pulsatile blood flow. Of the 28 branch feeder vessels, 23 were noted on both conventional arteriograms and MR angiograms in a nonblinded review, but 16 were difficult to distinguish as feeders because of lack of associated tumor blush. CONCLUSION: MR angiography has promise to replace conventional arteriography for orthopedic preoperative planning.

Adolescent↗
PubMed1994

MR angiography of the pelvis with variable velocity encoding and a phased-array coil.

PURPOSE: To evaluate the feasibility of an automated variable velocity-encoding sequence and improve the signal-to-noise ratio (S/N) on magnetic resonance angiograms with use of phase contrast and a pelvic phased-array coil. MATERIALS AND METHODS: Three cardiac-gated, two-dimensional (2D), phase-contrast (PC) sequences were evaluated in 10 healthy subjects. A 2D gated PC sequence with variable velocity encoding (velocity-optimized phase contrast [VOPC]) was compared with gated 2D PC sequences performed with high or low constant velocity encoding. S/Ns in VOPC images obtained with a pelvic phased-array coil were compared with those in VOPC images obtained with a body coil. RESULTS: Two blinded readers preferred VOPC for simultaneous display of large and small blood vessels in one acquisition compared with constant low (P = .0105) and high (P = .0067) velocity encoding and for overall image interpretation. VOPC images obtained with the pelvic coil had a 68%-100% better S/N compared with those obtained with the body coil. CONCLUSION: Use of a phased-array coil and variable velocity encoding improves depiction of segmental vascular anatomic structures of the pelvis.

Blood Flow Velocity↗
PubMed1994

MR diagnosis of meniscal tears: analysis of causes of errors.

OBJECTIVE: MR imaging of the knee is an accurate method for diagnosing meniscal tears. However, MR findings do not always agree with surgical findings. In a retrospective study, we analyzed the various causes of incorrect MR diagnoses. MATERIALS AND METHODS: We reviewed a series of 400 MR examinations for suspected meniscal tears in which the diagnostic accuracy was 90%. In this group, we found 70 patients in whom the original MR diagnosis did not agree with the surgical findings. Three musculoskeletal radiologists independently reviewed each of the 70 MR examinations without knowledge of the original interpretation or the surgical findings. Their interpretations and the MR images then were correlated with the surgical findings. The original incorrect diagnoses were categorized as being due to unavoidable errors, errors in interpretation, or errors made because of equivocal MR findings of a tear. Unavoidable errors were defined as false-positive and false-negative diagnoses that could not be avoided, even in retrospect. RESULTS: Of the 83 original diagnostic errors made in the MR evaluation of 800 menisci, 33 (40%) were unavoidable errors, 32 (39%) were due to equivocal MR findings, and 18 (21%) were due to interpretation errors. The unavoidable errors consisted of 21 missed meniscal tears and 12 false-positive MR diagnoses. In the false-positive cases, the menisci were interpreted as torn on MR images by all three observers, but no tear was found at arthroscopy. Subtle MR findings that were equivocal for a tear caused both false-positive and false-negative diagnoses. Seven of the 18 interpretation errors occurred when normal variants were mistaken for a tear. CONCLUSION: Using conventional coronal and sagittal spin-echo MR imaging, we could not identify 21 (6%) of the 333 meniscal tears, even in retrospect. In addition, subtle findings that are equivocal for a tear may still make MR diagnosis of every torn meniscus difficult even for experienced radiologists. Unavoidable false-positive diagnoses due to healed tears or tears missed at arthroscopy are an infrequent problem occurring in only 1.5% of the original 800 menisci evaluated with MR imaging.

Diagnostic Errors↗
PubMed1993

Generalized matched filtering for time-resolved MR angiography of pulsatile flow.

Generating flow-specific images (arteriograms, venograms) with optimal signal-to-noise ratios for time-resolved MR angiography is a conditional maximum problem, and its solutions are generalized matched filters. We have investigated six matched filters, corresponding to all possible combinations of three flow suppression conditions and two signal-to-noise ratio maximization procedures. Four of these matched filters correspond to previously described methods: the subtractive matched filter, the standard deviation, the global venous eigenimage and the global arterial eigenimage. The two others are referred to here as the local venous eigenimage and the local arterial eigenimage. These six matched filters have been applied to 2D time-resolved phase contrast angiographic data. The local arterial eigenimage is found to be the most effective in suppressing undesired venous flow and preserving desired arterial flow.

Blood Flow Velocity↗