bluuebunny/crossref_metadata_2025_split huggingface dataset:
MRI efficacy and effectiveness research: Who needs it and who pays for it?
Authors: Harms Steven E. , Radensky Paul , Sunshine Jonathan , Davis David O. , Okunieff Paul , Farr Christopher , Spettell Claire 
Published: March 2007

AbstractThis article is a summary of the workgroup on Audience/Funding at the recent Society of Magnetic Resonance Workshop on Efficacy and Effectiveness of Imaging: An Evaluation of Methodologies.
Economics of MRI technology
Authors: Bell Robert A. 
Published: March 2007

AbstractMRI development in the United States is reviewed from 1983 to the present with the intent of projecting future utilization and reimbursement. Since 1992, a decreasing rate of new installations and an aging installed base have markedly lowered the ratio between fixed and variable costs, thereby improving the ability to project cost per study. Variable costs are now estimated to average $175 to $200 per examination, up sharply from earlier reports. Actual costs per study usually exceed $400, even for high volume sites. Major cost contributors are reviewed and methods for identifying impediments to efficient operation are suggested.
Health economics in diagnostic imaging
Authors: Högström B , Sverre J‐M 
Published: March 2007

AbstractNew technologies, such as magnetic resonance imaging, are frequently cited as major contributors to the growth of national health care expenditure. The cost‐effectiveness of this modality is commonly challenged, and the lack of health economic documentation increases the level of criticism. Some common methods for evaluating imaging methods with regard to efficacy, cost, and benefits are, therefore, reviewed. Limitations in the assessment of diagnostic imaging are discussed, together with some suggestions as to which methodological approaches may be useful in this field of research.
Evaluation of the quality of clinical research studies of magnetic resonance angiography: 1991‐1994
Authors: Sostman H. Dirk , Beam Craig A. 
Published: March 2007

AbstractTo evaluate the quality of clinical research studies of magnetic resonance angiography (MRA), the authors reviewed studies of carotid, renal, and lower extremity MRA published in English during 1991‐1994. The purpose, design, and implementation of the study, and the type of statistical information presented, were evaluated. The results were compared with those of previous studies that assessed the quality of MRI research. Fifty‐nine studies of renal (n=10), carotid (n=29), and lower extremity (n=20) MRA were identified; 30 met the inclusion criteria for the analysis. In these papers, presentation of a reference standard was routine, observer blinding was usual, information often was given about patient selection and exclusion, sample sizes were always given, and parameter estimates and statistical analyses were common. However, evidence of research planning was not routine, measurement of interobserver variability was occasional, variability of parameter estimates was usually not estimated, and validation of statistical assumptions was uncommon. On balance the authors conclude that the scientific quality of recent investigations of MRA is better than that of older studies of MRI.
Malignant liver lesions: Comparison of spiral CT arterial portography and MR imaging for diagnostic accuracy, cost, and effect on patient management
Authors: Semelka Richard C. , Schlund James F. , Molina Paul L. , Willms Ann Bagley , Kahlenberg Morton , Mauro Matthew A. , Weeks Susan M. , Cance William G. 
Published: March 2007

AbstractWe compared two imaging techniques, spiral CT arterial portography (CTAP) and MR imaging, for diagnostic accuracy, procedural cost, and effect on management of 26 patients referred for hepatic surgery for suspected limited malignant liver disease. CTAP and MR imaging were done within a 1‐week period (19 within 24 hours); the results of the studies were interpreted prospectively by separate reviewers. Surgical data were evaluated in conjunction with imaging data in 10 patients. Lesion detection and segmental involvement were determined and sensitivity and specificity were calculated. Procedural cost was determined from hospital billing codes. Effect on patient management was determined by the referring oncologic surgeon. CTAP and MR imaging showed 185 and 176 true‐positive malignant lesions, 15 and zero false‐positive malignant lesions, zero and 18 true‐negative malignant lesions, and 13 and 22 falsenegative malignant lesions, respectively. CTAP and MR imaging showed 107 and 105 true‐positive segments, 11 and zero false‐positive segments, 80 and 91 true‐negative segments, and four and six false‐negative segments, respectively. There was a significant difference in specificity of segmental involvement between MR imaging (1.0 ± 0) compared with CTAP (0.88 ± 0.05), P=.03. Total procedural cost was $3,499 for CTAP and $1,224 for MR imaging. CTAP findings did not change patient management over MR imaging findings in any patient, whereas MR imaging findings resulted in a change in patient management over CTAP findings in seven patients (P=.015). The results of our study suggest that MR imaging has higher diagnostic accuracy and greater effect on patient management than CTAP does and is 64% less expensive.
Detection of deep venous thrombosis: Prospective comparison of MR imaging and sonography
Authors: Evans Avery J. , Sostman H. Dirk , Witty Lynn A. , Paulson Erik K. , Spritzer Charles E. , Hertzberg Barbara S. , Carroll Barbara A. , Tapson Victor F. , Saltzman Herbert A. , Delong David M. 
Published: March 2007

AbstractSeventy‐five patients (41 women and 34 men, 20‐85 years old) with clinically suspected deep venous thrombosis (DVT) were examined with MR imaging and sonography. In 26 patients, the final diagnosis was acute femoropopliteal DVT. The sensitivity of MR imaging for detecting this disease was 100% with a 95% confidence interval (CI) of 87‐100%; the specificity was 100% with a CI of 92‐100%; and the accuracy was 96% with a CI of 89‐99%. The correspond‐ ing sensitivity of sonography was 77% with a CI of 53‐92%; the specificity was 98% with a CI of 89‐100%; and the accuracy was 83% with a CI of 72‐90%. In four of the 75 patients, MR images revealed thrombus of the pelvis (n=1) or calf (n=3) without femoropopliteal involvement. The estimated prevalence of isolated calf and/or pelvic DVT was 5% with a CI of 1‐13%. MR imaging is significantly more sensitive (P=.02) and accurate (P < .01) than sonography in the detection of lower extremity DVT, but there was no difference in the specificity of MR imaging and that of sonography (P=.31).
The impact of field strength on image quality in MRI
Authors: Rutt Brian K. , Lee Donald H. 
Published: March 2007

AbstractAs clinical MRI has evolved, there have been numerous arguments for the use of different field strengths. Those favoring high magnetic field (1.5 T and above) include higher signal‐to‐noise ratio, capability for MR spectroscopy, and other forms of functional MRI, high speed imaging, and high resolution imaging. However, cost remains a significant limitation to the wider dissemination of high field MRI. There are definite cost advantages (capital, operating, siting) to the use of lower field MRI. Much debate has occurred over the past decade regarding the relative diagnostic benefits of high field MRI versus lower field MRI, but few randomized, controlled clinical trials have compared diagnostic accuracy of MRI at various field strengths. In this article, we review the physical principles of the field strength dependence of MRI in relation to image quality. The assessment of the importance of field strength in MR is incomplete without some analysis of diagnostic accuracy versus field strength. Such analysis is difficult to accomplish in an unbiased manner. The use of receiver‐operator‐characteristic (ROC) analysis is probably the best available method to measure diagnostic accuracy of various imaging methods without bias. An ROC study of diagnostic accuracy of 0.5 T versus 1.5 T MRI, examining several common clinical categories, has recently been conducted at our institution. Results from this study demonstrate diagnostic equivalence between these two field strengths in at least two common clinical disease categories (MS and internal derangement of the knee). These results are discussed and related to results from previous field strength studies.
Future cost‐effective MRI will be at high field
Authors: Bradley William G. 
Published: March 2007

AbstractThe most cost effective MR imaging system is the one that provides the highest quality images (allowing the earliest possible diagnosis), the largest number of applications (allowing bundling of services and one‐stop shopping for consumers), and the highest throughput (should it become necessary to scan a large number of patients in a capitated world). When all other parameters are normalized (eg, the skill and training of the radiologist and technologist as well as the RF, computer, and gradient subsystems), high field provides faster, higher resolution, thinner slice, and higher contrast MR images than low field. For these reasons, high field MRI will remain more cost effective than its lower field counterparts in the future.
Cardiovascular applications of magnetic resonance flow and velocity measurements
Authors: Szolar Dieter H. , Sakuma Hajime , Higgins Charles B. 
Published: March 2007

AbstractWith recent developments of MR techniques for blood flow measurements, qualitative and quantitative information on both flow volume and flow velocity in the major vessels can be obtained. MR flow quantitation uses the phase, rather than the amplitude of the MR signal, to reconstruct the images. Previous validation studies have demonstrated the accuracy of the phase shift techniques for measuring flow velocities. This technique is now being applied successfully in the cardiovascular system to quantify global and regional ventricular function, valvular heart disease, pulmonary artery disease, thoracic aortic disease, congenital heart disease, and ischemic heart disease.
Experimental and theoretical studies of vessel contrast‐to‐noise ratio in intracranial time‐of‐flight MR angiography
Authors: Du Yiping P. , Parker Dennis L. , Davis Wayne L. , Cao Guang , Buswell Henry R. , Goodrich K. Craig 
Published: March 2007

AbstractCNR studies were performed for human intracranial vessels in 3D MRA data sets. The CNR dependency of different imaging parameters, such as flip angle, field of view, echo time, repetition time, and echo readout symmetry, was studied for vessels in the region of the circle of Willis. A theoretical model was developed for MR vascular imaging based on the Bloch equations and Fourier imaging theory. This model predicts the MR image intensity of vessels from basic subject parameters, such as the relaxation times of blood and stationary tissue, vessel dimension, and flow velocity, and the parameters of the imaging technique, such as flip angle, voxel volume, repetition time, and echo time. For most experiments, the model was found to fit the experimental results well. The validity of this model allows the optimization of imaging parameters to maximize vessel CNR in MR angiography.
Surface coil phased arrays for high‐resolution imaging of the carotid arteries
Authors: Hayes Cecil E. , Mathis C. Mark , Yuan Chun 
Published: March 2007

AbstractAn MR phased‐array coil assembly was developed to obtain high‐resolution images of atherosclerotic plaques in the carotid artery. Images of volunteers and patients obtained by using alternative coil designs provided a subjective assessment of the coils' performance, field of view, ease of use, and susceptibility to motion artifacts. A quantitative measurement performed on a phantom indicated that a two‐coil phased‐array design should produce a 37% better signal‐to‐noise ratio at the carotids than would a conventional single 3‐inch surface coil.
Improved reproducibility in measuring LV volumes and mass using multicoil breath‐hold cine MR imaging
Authors: Sakuma Hajime , Globits Sebastian , Bourne Michael W. , Shimakawa Ann , Foo Thomas K. , Higgins Charles B. 
Published: March 2007

AbstractThere is a generally recognized need for improvement in quality of fast cardiac MR images. Consequently, breath‐hold cine MR images were obtained with multiple surface coils connected to phased array receivers, and C/N, intra‐observer and inter‐observer variabilities for LV volumes and mass were evaluated. Two sets of short‐axis images of the LV, one with multiple surface coils and another with a body coil, were acquired in eight subjects with a fast cine MR sequence using k‐space segmentation (TR/TE=7/2.2 msec, temporal resolution=56 msec). C/N with multicoil imaging was 32.2 ± 7.6 (mean ± SD), significantly higher than that with a body coil (11.0 ± 3.3, P < .01). The mean percentage differences in intra‐observer and inter‐observer measurements with multicoil imaging were significantly better than those with a body coil. In conclusion, multicoil imaging provides significant gain in C/N on breath‐hold cine MRI of the heart. In addition, intra‐observer and inter‐observer reproducibilities are improved with multicoil imaging.
Optimizing fast spin echo acquisitions for hepatic imaging in normal subjects
Authors: Spritzer Charles E. , Keogan Mary T. , DeLong David M. , Dahlke Jerry , MacFall James R. 
Published: March 2007

AbstractThe purpose of this study was to determine which implementations of a T2‐weighted fast spin‐echo sequence of the liver resulted in observer preference in normal subjects. Five volunteers were scanned with a series of fast spin‐echo sequences modified to allow for flow compensation, respiratory triggering (RT), ECG triggering, randomized phase encoding (RPE), breathholding, and echo train length (ETL). Images were compared with conventional 2500/40/80 msec spin‐echo images using flow compensation and spatial presaturation by two observers blinded to the specific sequence parameters. All FSE sequences were completed in less than the 12 minutes necessary to perform a conventional spin‐echo sequence. The most preferred fast spin‐echo sequence employed flow compensation, RT, and used an 8 ETL. Analysis of image preference, signal to noise, and contrast to noise showed that RT was the single most important variable in determining each image response (P < .01, P < .02, P < .01, respectively). There was some evidence that images obtained with an 8 ETL were preferred over those using a 16 ETL (P=.07). No other variables approached statistical significance although one reader preferred images with flow compensation in the frequency direction to those either not flow compensated or flow compensated in the slice direction. Respiratory triggered fast spin‐echo images combined with flow compensation in the frequency direction and using ETL=8 can provide image quality equal to conventional spin‐echo sequences with significant time savings.
Metastatic melanoma: Correlation of MRI characteristics and histopathology
Authors: Premkumar Ahalya , Marincola Francesco , Taubenberger Jeffery , Chow Catherine , Venzon David , Schwartzentruber Douglas 
Published: March 2007

AbstractTo correlate the findings on MRI with histopathology of metastatic melanoma, MRI was performed on 29 patients with 36 lesions, using spin‐echo and inversion recovery sequences. Histopathologic examination of lesions was performed within 4 weeks of imaging. Lesions were categorized according to cell type and were also evaluated for the presence and extent of melanin, iron, and necrosis. These data were then correlated with the signal intensities of the lesions. Enhancement of lesions after injection of intravenous gadolinium was calculated and correlated to vascularity of the tumor. Melanin was present more frequently in lesions appearing hyperintense or with mixed signal intensity (12/15) than in those appearing hypo‐ or isointense (6/21) on the T1‐weighted sequence. This trend was significant (P=.013). Also, more lesions appearing mixed, ie, having both hypo‐ and hyperintense components, contained melanin (15/23), as opposed to lesions that appeared to be only hyperintense (3/13) on the STIR sequence. There was no clear association between signal intensity and melanin content on the T2‐weighted sequence. There was no significant association between the signal intensities on the MR images and the iron content, tumor size, or tumor cell type of these lesions. There was no clear association between enhancement after gadolinium injection and vascularity, as assessed by histology. The authors concluded in this study that T1 shortening and hypointensity on the STIR sequence seen in patients with metastatic melanoma are most closely related to the melanin content of the tumor.
Pulsed magnetization transfer contrast for MR imaging with application to breast
Authors: Santyr Giles E. , Kelcz Frederick , Schneider Erika 
Published: March 2007

AbstractThe relative populations and transverse relaxation times of the solid‐like hydrogen pool (PB and T2B) and the magnetization transfer (MT) rates between the solid‐like and liquid‐like hydrogen pools (K) have been determined for three different agar gel concentrations (2%, 4%, and 8% by weight) as well as excised fibroglandular breast tissue specimens. PB was determined to be .003(.001), .01(.002), .02(.01), and .06(.01); T2B was determined to be 13.0(.2), 14.0(.1), 14.5(.1) and 15.2(1.3) μs; and K was determined to be 0.78(.01), 1.15(.02), 2.00(.02), and 3.55(1.5) sec−1 for the 2%, 4%, and 8% agar gels and the fibroglandular tissue, respectively. The image signal intensities of a pulsed MTC‐prepared gradient‐echo imaging technique are predicted using these MT parameters and are shown to agree well with experimental data obtained from a clinical MR imaging system. This technique is shown to suppress signal intensity of fibroglandular breast tissue by 40%–50% without exceeding SAR limits (≤ 8W/kg) and is helpful for visualizing lesions and silicone implants.
Breath‐hold MR measurements of blood flow velocity in internal mammary arteries and coronary artery bypass grafts
Authors: Sakuma Hajime , Globits Sebastian , O'sullivan Margaret , Shimakawa Ann , Bernstein Matt A. , Foo Thomas K. F. , Amidon Thomas M. , Takeda Kan , Nakagawa Tsuyoshi , Higgins Charles B. 
Published: March 2007

AbstractBreath‐hold velocity‐encoded cine MR (VENC‐MR) imaging is a feasible method for measuring phasic blood flow velocity in small vessels that move during respiration. The purposes of the current study are to compare breathhold VENC‐MR measurements of flow velocities in the internal mammary arteries (IMA) with nonbreath‐hold measurements and to characterize the systolic and diastolic flow velocity curves in a cardiac cycle in native IMA and IMA grafts. Flow velocity in 30 native IMA and 8 IMA grafts were evaluated with a breath‐hold VENC‐MR sequence with K‐space segmentation and view‐sharing reconstruction(TR/TE=16/9 msec, VENC=100 cm/s). In 10 native IMA, nonbreathhold VENC‐MR images were acquired as well for comparison. Breath‐hold VENC‐MR imaging showed significantly higher systolic and diastolic peak velocities in native IMA (43.1 cm/second ± 15.0 and 10.0 cm/second ± 4.8), in comparison to those of nonbreath‐hold VENC‐MR imaging (27.6 cm/second ± 10.2 and 7.3 cm/second ± 3.9, P<.05). The diastolic/systolic peak velocity ratio in the IMA grafts (.88 ± .41) was significantly higher than that in native IMA (.24 ± .08, P<.01). Interobserver variability in the flow velocity measurement was less than 4%. Breath‐hold VENC‐MR imaging demonstrated higher peak flow velocity in the IMA than nonbreath‐hold VENC‐MR imaging. This technique is a rapid and effective method for the noninvasive assessment of blood flow velocity in IMA grafts.
Tissue characterization of intracranial tumors by magnetization transfer and spin‐lattice relaxation parameters in vivo
Authors: Kurki Timo , Lundbom Nina , Komu Markku , Kormano Martti 
Published: March 2007

AbstractT1s and magnetization transfer (MT) parameters of 36 intracranial tumors were determined in vivo at 0.1 T to assess their use in tissue characterization. The mobile water relaxation times (T1w) did not differ between tumor groups, whereas the T1s, the apparent MT relaxation times (T1a), and the parameters MT contrast (MTC) differed significantly between several tumor types. The MT rates (Rwm) demonstrated the most significant differences; Rwm values could reliably separate high grade and low grade gliomas. T1ws of the tumors were commonly in the same range as that of normal gray matter, whereas other parameters differed from those of normal brain. The results indicate that MT rates are superior to other parameters in the characterization of intracranial tumors and may be also useful clinically in the grading of gliomas.
Macroscopic and microscopic assessments of disease burden by MRI in multiple sclerosis: Relationship to clinical parameters
Authors: Gasperini Claudio , Horsfield Mark A. , Thorpe John W. , Kidd Desmond , Barker Gareth J. , Tofts Paul S. , Macmanus David G. , Thompson Alan J. , Miller David H. , McDonald W. Ian 
Published: March 2007

AbstractWe have evaluated macroscopic white matter abnormalities (visible lesions) together with microscopic abnormalities in the normal appearing white matter (NAWM) of patients with multiple sclerosis (MS) to determine their relative contributions to the development of disability. The total visible lesion volume (TLV) was computed as a measure macroscopic changes, whereas both texture analysis and T2 were used as possible indicators of diffuse disease in the NAWM. Dual echo T2‐weighted SE images were obtained from 41 patients with definite MS: 10 primary progressive (PP), 11 secondary progressive (SP), 10 benign (BE), 10 early relapsing remitting (ERR), as well as from 10 healthy controls. Calculation of T2 and texture parameters were performed in a region of frontal NAWM of patients and controls. The TLV of each patient was measured using a semiautomated lesion detection program.No significant differences were found between the controls and the patients for all texture parameters examined. However, NAWM T2 was longer in the patients than in the controls (P = .02). Mean TLV was highest for SP and lowest for BE and ERR patients. A significant correlation was found between TLV and EDSS (P < .01) but not between NAWM T2 or texture and expanded disability status score (EDSS).Our study suggest that: (a ) diffuse changes are present in NAWM, (b) texture analysis is unable to detect any subtle structure in the NAWM abnormalities, possibly because of the limited image resolution; (c) in the development of disability in MS, macroscopic lesions are more important than microscopic abnormalities in the NAWM.