Expect the unexpected: thoughts, insights and musing about research in radiology.
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Biomedical Research↗
Biomedical subjects
J Shannon Swan
Publications and source records attributed to J Shannon Swan.
A software application for multiattribute utility models.
RATIONALE AND OBJECTIVES: A software application for the building of preference-weighted quality of life instruments was constructed. The purpose of this application is to make the process of building such instruments with multiattribute utility (MAU) methods more accessible to physician investigators. Our application, "multiattribute outcomes evaluator" or "MOE," could facilitate the use of such methods for constructing disease-specific instruments for assessing the cost-effectiveness of new treatments. MOE could also be useful for building outcomes measures that are intended to aid individual decision making, assessment of patient satisfaction with care, or measuring of multiattribute outcomes that do not need to be scaled for cost-effectiveness analysis. MATERIALS AND METHODS: MOE was programmed in Visual Basic and runs atop a Microsoft Access data base. Data from groups or individuals can be stored, and valuations of health states can be performed using standard gambles and rating scale methods. Solutions to MAU models with multiplicative or additive utility independence are possible with this application. RESULTS: Initial tests of the program algorithms have been successful. CONCLUSION: We anticipate The MOE approach to MAU modeling will be a useful tool for health services researchers.
Humans↗
Process utility for imaging in cerebrovascular disease.
RATIONALE AND OBJECTIVES: The morbidity associated with a diagnostic test can influence its cost-effectiveness, but the quantification of that morbidity is controversial. Accounting for pain and invasiveness requires the measurement of "process utility" in addition to the expected value of testing. An original time trade-off variant was applied to the imaging evaluation of cerebrovascular disease, for which differences in morbidity are important to patients. MATERIALS AND METHODS: A "waiting trade-off" (WTO) was used to evaluate the preferences of 89 patients for magnetic resonance (MR) angiography and conventional x-ray angiography. Patients were experienced with both tests. A weighted difference was calculated between the period a patient was willing to wait for a test result and treatment after a hypothetical "ideal" test and the choice to undergo conventional angiography or MR angiography with immediate treatment. A rating scale was used to check the convergent validity of the WTO. RESULTS: Paired data showed a highly significant difference (P = .0001) between the mean preference for conventional and MR angiography, favoring the latter and translating into a difference of 5 quality-adjusted life days. The more negatively patients judged their conventional angiographic experience, the longer they were willing to wait for the ideal test result. CONCLUSION: The WTO provides a reasonable estimate of the relative morbidity of more invasive conventional angiographic procedures and provides a quality-adjustment term for economic analysis. Such an approach may enable more complete evaluation of the effects of other processes on medical care.
Adolescent↗
Rapid generation of preview images for real-time 3D MR angiography.
In 3D real-time MR angiography the reconstruction of images from large raw datasets via Fourier transforms with minimal delays is problematic. In this study strategies for reconstructing time-resolved three-dimensional (3D) datasets at a rate substantially faster than conventional 3D MR image reconstruction were investigated on general-purpose computer hardware. Moderate quality 'preview images' were generated from k-space subsets to reduce image reconstruction times from more than 50 s to 0.3 s per image volume. A blinded review of 3D TRICKS patient examinations showed that these moderate-quality images were sufficient for providing immediate feedback and guiding the subsequent reconstruction of selected time frames (p < 0.05). Fourier projection (reconstruction from a central k-space slice) was the most efficient reconstruction technique. However, the reduction of the reconstructed volume in all three dimensions resulted in higher contrast and better image quality while allowing reconstruction in near-to-real-time (less than 1 s per image volume). The use of such preview images in a real-time system allows for fast feedback from dynamic 3D datasets, enables scanner interaction with minimal latencies and can substantially reduce the postprocessing times.
Angiography↗
Time-resolved three-dimensional contrast-enhanced MR angiography of the peripheral vessels.
PURPOSE: To compare the diagnostic accuracy of time-resolved three-dimensional contrast material-enhanced magnetic resonance (MR) angiography with that of conventional angiography for imaging the lower extremity vasculature. MATERIALS AND METHODS: Sixty-nine patients who were evaluated for possible surgical intervention underwent conventional angiography (ie, digital subtraction angiography [DSA]) and contrast-enhanced MR angiography (ie, time-resolved imaging of contrast kinetics [TRICKS]). Two independent, blinded readers evaluated vessel stenosis and occlusion at DSA and MR angiographic image readings. Sensitivity, specificity, positive and negative predictive values, and area under the receiver operating characteristic curve were analyzed with repeated-measures analysis of variance. The Cohen kappa test was performed to examine interreader variability. RESULTS: At pooled readings, contrast-enhanced MR angiography had a sensitivity of 78% and a specificity of 98% for detection of occlusion. For detection of significant stenosis (at least one > or = 50% stenosis), sensitivity and specificity were 77% and 91%, respectively. Interreader agreement was high for detection of both occlusion (kappa = 0.76) and significant stenosis (kappa = 0.68). Sensitivity increased as MR angiographic technical parameters were optimized. When improvements resulting from coil type and injection protocol were considered, the sensitivity and specificity of TRICKS MR angiography were 89% and 97%, respectively, for occlusion detection and 87% and 90%, respectively, for significant stenosis detection. CONCLUSION: Contrast-enhanced TRICKS MR angiography is a feasible and minimally invasive means of acquiring angiograms of the peripheral vasculature with high sensitivity and specificity.
Adult↗