Functional MR imaging versus Wada test for evaluation of language lateralization: cost analysis

PURPOSE: To compare the total direct costs (fixed and variable costs) of functional magnetic resonance (MR) imaging and of the Wada test for evaluation of language lateralization. MATERIALS AND METHODS: The direct fixed and variable costs of functional MR imaging (performed in 21 patients with mean age +/- SD of 15.5 years +/- 8.9) and of the Wada test (performed in 18 patients aged 19.2 years +/- 5.4) were determined prospectively with time and motion analyses. The labor of all personnel involved in evaluations of language lateralization was tracked, and involvement times were recorded to the nearest minute. All material items used in the studies were recorded. Costs of labor and of materials were determined from personnel reimbursement data and from vendor pricing, respectively. Direct fixed costs were determined from hospital accounting department records. Means (+/- SDs) were calculated for all direct fixed and variable costs. Total direct costs were determined for each procedure and compared by using the Student t test. RESULTS: The total direct costs of the Wada test (US dollars 1130.01 +/- US dollars 138.40) and of functional MR imaging (US dollars 301.82 +/- US dollars 10.65) were significantly different (P <.001). The cost of the Wada test was 3.7 times higher than that of functional MR imaging. CONCLUSION: Substantial savings are achievable with the use of functional MR imaging instead of the Wada test to evaluate language lateralization.     

MR imaging of the temporomandibular joint: comparison of images of autopsy specimens made at 0.3 T and 1.5 T with anatomic cryosections

We made MR images of 39 autopsy specimens of the temporomandibular joint at 0.3 and 1.5 T and compared the images with anatomic cryosections. Imaging time and slice thickness were the same on scans made at each field strength. The purpose was to determine which field strength provides the best scans for imaging of the joint. Additionally, we used imaging times two and four times longer on the 0.3-T scanner to assess to what extent image quality and diagnostic accuracy could be improved. The cryosections showed that 27 of the joints were normal. Twelve had disk displacements. Ten of the joints with disk displacement also had disk deformities, and seven had bony abnormalities. Investigators who analyzed the MR images had no knowledge of the findings on the cryosections. The disk position, disk configuration, and bony abnormalities were correctly diagnosed in 85%, 77%, and 100%, respectively, on 1.5-T MR images compared with 46%, 41%, and 85%, respectively, on the 0.3-T images. When the imaging time was increased by a factor of four, the accuracy rate on the 0.3-T system became comparable to that of the 1.5-T MR scanner: 73% for disk position, 67% for disk configuration. The results suggest that the diagnostic quality of MR images of the temporomandibular joint is better on scans made at 1.5 T than on those done at 0.3 T when comparable imaging times are used.     

Colorectal liver metastases: CT, MR imaging, and PET for diagnosis--meta-analysis

PURPOSE: To perform a meta-analysis to obtain sensitivity estimates of computed tomography (CT), magnetic resonance (MR) imaging, and fluorine 18 fluorodeoxyglucose (FDG) positron emission tomography (PET) for detection of colorectal liver metastases on per-patient and per-lesion bases. MATERIALS AND METHODS: MEDLINE, EMBASE, Web of Science, and CANCERLIT databases and Cochrane Database of Systematic Reviews were searched for relevant original articles published from January 1990 to December 2003. Criteria for inclusion of articles were as follows: Articles were reported in the English, German, or French language; CT, MR imaging, or FDG PET was performed to identify and characterize colorectal liver metastases; histopathologic analysis (surgery, biopsy, or autopsy), intraoperative observation (manual palpatation, intraoperative ultrasonography [US]), and/or follow-up US was the reference standard; and data were sufficient for calculation of true-positive or false-negative values. A random-effects linear regression model was used to obtain sensitivity estimates in assessment of liver metastases. RESULTS: Of 165 identified relevant articles, 61 fulfilled all inclusion criteria. Sensitivity estimates on a per-patient basis for nonhelical CT, helical CT, 1.5-T MR imaging, and FDG PET were 60.2%, 64.7%, 75.8%, and 94.6%, respectively; FDG PET was the most accurate modality. On a per-lesion basis, sensitivity estimates for nonhelical CT, helical CT, 1.0-T MR imaging, 1.5-T MR imaging, and FDG PET were 52.3%, 63.8%, 66.1%, 64.4%, and 75.9%, respectively; nonhelical CT had lowest sensitivity. Estimates of gadolinium-enhanced MR imaging and superparamagnetic iron oxide (SPIO)-enhanced MR imaging were significantly better, compared with nonenhanced MR imaging (P = .019 and P < .001, respectively) and with helical CT with 45 g of iodine or less (P = .02 and P < .001, respectively). For lesions of 1 cm or larger, SPIO-enhanced MR imaging was the most accurate modality (P < .001). CONCLUSION: FDG PET had significantly higher sensitivity on a per-patient basis, compared with that of the other modalities, but not on a per-lesion basis. Sensitivity estimates for MR imaging with contrast agent were significantly superior to those for helical CT with 45 g of iodine or less.     

High-resolution MR cisternography of the cerebellopontine angle, obtained with a three-dimensional fast asymmetric spin-echo sequence in a 0.35-T open MR imaging unit.

High-resolution MR cisternography performed with 3D fast asymmetric spin-echo imaging (3D fast spin-echo with an ultra-long echo train length and asymmetric Fourier imaging) was optimized in a 0.35-T open MR imaging unit. The 0.35- and 1.5-T images of the two volunteers and three patients with acoustic schwannomas were then compared. The optimal parameters for images obtained by 3D fast asymmetric spin-echo imaging at 0.35 T were as follows: field of view, 15 cm; matrix, 256 x 256 x 40; section thickness, 1 mm; echo train length, 76; and imaging time, 10 minutes 44 seconds. Scans obtained from both normal volunteers showed the facial, cochlear, and superior and inferior vestibular nerves separately in the internal auditory canal on both 0.35- and 1.5-T images. All three acoustic schwannomas were depicted on both 0.35- and 1.5-T images. Screening for disease at the cerebellopontine angle and in the internal auditory canal, without the administration of contrast material on a low-field open MR imaging unit and within a clinically acceptable imaging time, may be possible. Further controlled prospective studies are required, however, before implementation on a wide basis. If proved effective, this may be of particular value for reducing healthcare costs and for imaging claustrophobic and pediatric patients in an open system.     

Trends in Diagnostic Imaging Medicare Reimbursements: 2007 to 2019

PurposeThe aim of this study was to evaluate recent trends in Medicare reimbursement rates for various imaging studies.MethodsCommon diagnostic radiologic studies were selected across multiple imaging modalities: bone densitometry, CT, CT angiography, mammography, MR angiography, MRI, nuclear medicine, radiography, and ultrasound. The Physician Fee Schedule Look-Up Tool from CMS was queried for Current Procedural Terminology codes to extract reimbursement data. All monetary data were adjusted for inflation to 2019 US dollars. The compound annual growth rate, average annual change, and total percentage change in reimbursement were calculated on the basis of these adjusted trends.ResultsInflation-adjusted Medicare reimbursement for all imaging modalities decreased between 2007 and 2019. The greatest mean decrease in reimbursement rates was observed for MRI (−$52.08), and the largest decrease in total percentage change was seen for bone densitometry (−70.5%). Nuclear medicine demonstrated the smallest mean decreases in both annual change (−$0.32) and total percentage change (−4.28%).ConclusionsThis study examined Medicare reimbursements for radiologic studies from 2007 to 2019. After accounting for inflation, reimbursement rates were shown to decline for all studies across all imaging modalities except for individual studies in nuclear medicine, radiography, and ultrasound. Further investigation is encouraged to properly model future trends in reimbursement rates.     

Rotator cuff: evaluation with US and MR imaging.

Magnetic resonance (MR) and ultrasound (US) imaging are currently touted for assessment of rotator cuff disease. Optimum clinical imaging techniques include use of (a) a 1.5-T MR imaging unit with small planar coils, proton-density-weighted and T2-weighted fast spin-echo sequences, and 10-12-cm fields of view (yielding 400-470 x 500-625-microm in-plane spatial resolution) and (b) a state-of-the-art commercial US unit with insonation frequencies of 9-13 MHz (yielding 200-400-microm axial and lateral resolution). Proper diagnosis requires familiarity with normal anatomic characteristics and imaging pitfalls. Care must be taken to avoid sonographic tendon anisotropy and MR imaging magic angle effects, which can be misinterpreted as rotator cuff tear. At MR imaging, a complete cuff tear typically appears as either a hyperintense defect or a tendinous avulsion that extends from the bursal to the articular side of the cuff; a partial cuff tear typically appears as a focal hyperintense region that contacts only one surface of the cuff. Complete and partial tears manifest with a wide spectrum of findings at US. MR imaging and US are effective for evaluating rotator cuff injuries, with high reported accuracies for detection of complete tears but more disparate results for detection of partial tears.     

Comparison of CT, low-field-strength MR imaging, and high-field-strength MR imaging. Work in progress

To assess objectively the sensitivity and specificity of low-field-strength (0.064 T) magnetic resonance (MR) imaging, a prospective blind study of 280 examinations was performed to compare low-field-strength MR imaging with computed tomography (CT) and with high-field-strength (1.5-T) MR imaging of the cranium. The sensitivity (defined as the true-positive rate) with high-field MR imaging was superior to that with low-field MR imaging and CT in helping detect overall abnormalities. Sensitivities were generally similar over a broad range of specific cranial central nervous system diseases. Low-field and high-field MR imaging were equivalent in the blind diagnoses of neoplasms and white matter disease, whereas low-field MR and CT were equivalent in the blind diagnoses of contusion, subdural and epidural hematoma, sinus disease, normality, and abnormality. The specificities with low-field MR imaging and CT were substantially better than those with high-field MR imaging.     

MR imaging of the wrist: comparison between 1.5- and 3-T MR imaging--preliminary experience

Institutional review board approval and informed consent were obtained from 25 healthy volunteers and 15 consecutive patients with chronic wrist pain or suspected carpal mass, and 1.5- and 3-T magnetic resonance (MR) imaging of the wrist was prospectively performed with comparable sequence parameters and surface coils of the same geometric design. Imaging protocols at both field strengths included a T1-weighted spin-echo sequence, two intermediate-weighted fast SE sequences with different echo times and with and without fat saturation, and a three-dimensional fast field-echo sequence. The contrast-to-noise ratio (CNR) between muscle and bone and between bone and cartilage was calculated for both field strengths. The visibility of various anatomic structures, including the triangular fibrocartilage complex, carpal ligaments, nerves, and cartilage, was analyzed with a four-point grading scale. CNRs were significantly higher on 3-T MR images than on 1.5-T MR images (P < .001; analysis of variance) for all sequences. Visibility of the triangular fibrocartilage complex and intercarpal ligaments and cartilage was significantly better on 3-T MR images than on 1.5-T MR images (paired sign test).     

Adnexal masses: MR imaging observations at 1.5 T, with US and CT correlation

To assess the role of 1.5-T magnetic resonance (MR) imaging in evaluation of the adnexa, 43 consecutive examinations that revealed 61 adnexal masses were retrospectively reviewed. T1- and T2-weighted images in coronal, axial, and/or sagittal planes were included. Available ultrasound (US) (n = 30) and/or computed tomographic (CT) (n = 9) scans were then correlated with the MR images. On T2-weighted images at least part of all adnexal masses was of higher signal intensity than surrounding muscle and adipose tissue, and therefore the adnexal masses were best seen with these sequences. T1-weighted imaging improved tissue characterization by revealing signal characteristics of fat in teratomas and characteristics of blood in endometriomas or hemorrhagic cysts, pelvic inflammatory disease, ovarian carcinomas, serous cystadenomas, and teratomas. MR imaging provided additional information or increased diagnostic confidence in 25 of 30 patients who underwent US or CT. MR imaging is a promising problem-solving modality after US in the study of adnexal abnormalities.     

Dedicated extremity MR imaging of the foot and ankle

The purpose of this review is to provide illustrative examples of diseases of the foot and ankle when imaged with a low-field MR imaging system. A retrospective review of 268 foot and ankle examinations, performed in our institution within the past 3 years with a 0.2-T (Artoscan Esaote, Genoa, Italy) dedicated extremity MR system was done. Additionally, illustrative comparison with conventional radiography and high-field MR imaging is presented in patients in whom these examinations were also performed. Although motion artifact limited the value of a few studies, in the majority of examinations low-field MR imaging provided diagnostic image quality for the full spectrum of disorders affecting the foot and ankle and seemed to be a feasible alternative to high-field MR imaging in establishing an accurate diagnosis. Received: 23 November 1998; Revision received: 8 February 1999; Accepted: 4 June 1999     

Direct FLASH MR imaging of magnetic field inhomogeneities by gradient compensation

MR images based on gradient echoes are sensitive to artifacts caused by inhomogeneities of the static magnetic field. This paper describes the effects of local gradients in rapid FLASH MR images and presents a way of directly imaging affected areas. The idea is to compensate for signal losses due to mutual cancellation of dephased magnetizations by deliberate "misadjustments" of the refocusing part of the slice selection gradient. In contrast to conventional field imaging techniques no three-dimensional data acquisition or subsequent Fourier analysis is required to obtain images at a particular gradient strength. Conventional as well as inhomogeneity compensated FLASH images have been obtained on phantoms and human heads using a 2.35-T 40-cm magnet and a 1.5-T whole-body system, respectively.     

Wrist and finger joint MR imaging in rheumatoid arthritis.

PURPOSE: To elaborate the best MR imaging protocol for studies in rheumatoid arthritis (RA) and to evaluate the sensitivity and interobserver agreement with respect to detection of bone erosions (MR and radiography) and grading of synovial membrane hypertrophy (MR imaging only). MATERIAL AND METHODS: MR imaging and conventional radiography of wrist and metacarpophalangeal (MCP) joints were performed in 41 RA patients and 3 healthy controls. The following pulse sequences were applied: T1-weighted spin-echo (T1-SE) with and without contrast enhancement, T2-SE, T2-turbo-SE, T1-2D-FLASH, T1-3D-FLASH, fat-saturated-T1-SE, STIR and 3D-DESS. RESULTS: Bone erosions were found by MR compared to radiography in 261 versus 85 bones of the wrist (ratio 3.1) and 59 versus 21 MCP joint quadrants (ratio 2.81). MR and radiography interobserver agreements were both approximately 90%. Likewise, MR scored synovial membrane hypertrophy in wrist and MCP joints with a high interobserver agreement. The most informative MR sequence appeared to be contrast-enhanced T1-SE MR, preferably with fat saturation. A STIR sequence or T2-weighted fat saturation sequence was useful in screening for joint disease. CONCLUSION: The sensitivity of MR is superior to conventional radiography with respect to detection of bone erosions in wrist and MCP joints. The interobserver agreement for MR and radiography was similar. Thus, MR of wrist and finger joints may become a useful supplement to conventional radiography in the evaluation of RA patients in clinical trials and clinical practice.     

Clinically relevant rat model for testing BOLD functional MR imaging techniques by using single-shot echo-planar imaging at 1.5 T

By using a 1.5-T whole-body magnetic resonance (MR) imager, a high-spatial-resolution single-shot echo-planar technique was developed to perform blood oxygen level dependent functional MR imaging of rat sensory cortex during forepaw stimulation. This technique produced cubic 1-mm(3) voxels. Signal-to-noise ratio was 140-160 (43-44 dB). Optimal effective echo time was 50 msec. This system should prove useful for developing new functional MR imaging techniques with rapid adaptation to human use.     

Trabecular bone structure of the calcaneus: comparison of MR imaging at 3.0 and 1.5 T with micro-CT as the standard of reference

PURPOSE: To investigate in vitro the calcaneal trabecular bone structure in elderly human donors with high spatial resolution magnetic resonance (MR) imaging at 3.0 T and 1.5 T, to quantitatively compare MR measures of bone microarchitecture with those from micro-computed tomography (CT), and to compare the performance of 3.0-T MR imaging with that of 1.5-T MR imaging in differentiating donors with spinal fractures from those without spinal fractures. MATERIALS AND METHODS: The study was performed in line with institutional and legislative requirements; all donors had dedicated their body for educational and research purposes prior to death. Sagittal MR images of 49 human calcaneus cadaveric specimens were obtained (mean age of donors, 79.5 years +/- 11 [standard deviation]; 26 male donors, 23 female donors). After the spatial coregistering of images acquired at 3.0-T and 1.5-T MR imaging, the signal-to-noise-ratios and structural parameters obtained at each magnetic field strength were compared in corresponding sections. Micro-CT was performed on calcaneus cores obtained from corresponding regions in 40 cadaveric specimens. Vertebral deformities of the thoracic and lumbar spine were radiographically classified by using the spinal fracture index. Diagnostic performance of the structural parameters in differentiating donors with vertebral fractures from those without was assessed by using receiver operator characteristic (ROC) analysis, including area under the ROC curve (A(z)). RESULTS: Correlations between structural parameters at 3.0-T MR imaging and those at micro-CT were significantly higher (P < .05) than correlations between structural parameters at 1.5-T MR imaging and those at micro-CT (trabecular thickness, r = 0.76 at 3.0 T vs r = 0.57 at 1.5 T). Trabecular dimensions were amplified at 3.0 T because of increasing susceptibility artifacts. Also, higher ROC values were found for structural parameters at 3.0 T than at 1.5 T, but differences were not significant (trabecular thickness, A(z) = 0.75 at 3.0 T vs A(z) = 0.66 at 1.5 T, P > .05). CONCLUSION: MR imaging at 3.0 T provided a better measure of the trabecular bone structure than did MR imaging at 1.5 T. There was a trend for better differentiation of donors with from those without osteoporotic vertebral fractures at 3.0 T than at 1.5 T.     

MR imaging of nitrosyl-iron complexes: experimental study in rats

PURPOSE: To assess the influence of several nitrosyl-iron complexes on proton nuclear spin relaxation rates to establish a magnetic resonance (MR) imaging technique for nitric oxide. MATERIALS AND METHODS: The influence of aqueous phantom solutions of nitrosyl-iron complexes on proton relaxation rates was analyzed for signal enhancement at conventional 1.5-T MR imaging. To induce formation of nitrosyl-iron complexes in a biologic tissue, isolated rat liver was perfused with a saline solution of the NO donor sodium nitroprusside (SNP), and the MR signal intensity was examined thereafter. RESULTS: All investigated nitrosyl-iron complexes shortened the longitudinal, or T1, and transverse, or T2, relaxation times in a concentration-dependent fashion. Relaxivities were highest with a dinitrosyl-iron complex bound to albumin and with a water-soluble mononitrosyl-iron dithiocarbamate complex. The contrast properties of 240 micromol/L of a paramagnetic nitrosyl-iron complex were sufficient to substantially enhance the signal intensity of SNP-perfused rat livers at hydrogen 1 MR imaging. CONCLUSION: Nitrosyl-iron complexes exhibit a contrast effect at MR imaging that can be exploited for NO imaging in living animals and patients with conventional (1)H MR imaging techniques.     

Quantitative MR imaging assessment of prostate gland deformation before and during MR imaging-guided brachytherapy

RATIONALE AND OBJECTIVES: The authors performed this study to document the deformations that occur between pretreatment magnetic resonance (MR) imaging and intraoperative MR imaging during brachytherapy. MATERIALS AND METHODS: MR images obtained at 1.5 and 0.5 T in 10 patients with prostate cancer were analyzed for changes in the shape and substructure of the prostate. Three-dimensional models of the prostate were obtained. The authors measured anteroposterior dimension; total gland, peripheral zone, and central gland volumes; transverse dimension; and superoinferior height. RESULTS: Gland deformations were seen at visual inspection of the three-dimensional models. The anteroposterior dimension of the total gland, central gland, and peripheral zone increased from 1.5- to 0.5-T imaging (median dimension, 4.9, 1.5, and 1.8 mm, respectively), and the increase was greatest in the peripheral zone (P < .05, all comparisons). There was a decrease in the transverse dimension from 1.5- to 0.5-T imaging (median, 4.5 mm; P < .005). The total gland volume and the superoinferior height did not show a statistically significant change. CONCLUSION: There were significant deformations in the shape of the prostate, especially in the peripheral zone, between the two imaging studies. The likely causes of the shape change are differences in rectal filling (endorectal coil used in 1.5-T studies vs obturator in 0.5-T studies) and/or changes in patient position (supine vs lithotomy). These findings suggest that pretreatment images alone may not be reliable for accurate therapy planning. It may be useful to integrate pre-and intraoperative data.     

Larynx: MR imaging at 2.35 T

To study the consequences of an improvement in spatial resolution, the authors compared magnetic resonance (MR) images of nine laryngeal specimens with whole-organ histologic slides of the same specimens. Five of the specimens were obtained during laryngectomies performed on patients with high-stage tumors of the larynx. Four specimens were from patients with no known disease. The MR images were obtained on a 2.35-T system with a closely fitting probe head. A conventional spin-echo sequence was used, with T1- and T2-weighted settings. The in-plane resolution obtained was about 0.3 mm. The T2-weighted images generally showed better contrast and allowed identification of the perichondrium. The resolutions used were not much greater than those clinically available. The findings suggest that there will be important advances in clinical MR imaging of the larynx in the near future.     

Spiral K-space MR imaging of cortical activation

Brain function can be mapped with magnetic resonance (MR) imaging sensitized to regional changes in blood oxygenation due to cortical activation. Several MR imaging methods, including conventional imaging and echo-planar imaging, have been successfully used for this purpose. The authors investigated spiral k-space MR imaging, implemented with an unmodified 1.5-T clinical imager, for imaging of cortical activation. A gradient-echo, spiral k-space imaging method was used to measure activation in the primary visual cortex (number sequence task), primary motor cortex (fist-clenching task), and prefrontal cortex (verbal fluency task). Comparison of conventional and spiral k-space imaging in the visual and motor cortex, in which signal-to-noise ratio, voxel size, and imaging time were matched, showed that artifacts were reduced with the spiral k-space method, while the area and degree of activation were similar. The number of sections that could be imaged in a fixed time interval was increased by a factor of four with this implementation of spiral k-space imaging compared with conventional imaging.     

Evaluation of the acetabular labrum at 3.0-T MR imaging compared with 1.5-T MR arthrography: preliminary experience

Institutional review board approval and informed consent were obtained for this HIPAA-compliant study. The purpose of this study was to prospectively compare imaging of the acetabular labrum with 3.0-T magnetic resonance (MR) imaging and 1.5-T MR arthrography. Eight patients (four male, four female; mean age, 38 years) with hip pain suspicious for labral disease were examined at both MR arthrography and MR imaging. Presence of labral lesions, paralabral cysts, articular cartilage lesions, subchondral cysts, osteophytes, and synovial herniation pits was recorded. There was arthroscopic correlation of findings in five patients. MR imaging depicted four surgically confirmed labral tears that were identified at MR arthrography, as well as one that was not visualized at MR arthrography. MR imaging helped identify all other pathologic conditions that were diagnosed at MR arthrography and helped identify one additional surgically confirmed focal articular cartilage lesion. These results provide encouraging support for evaluation with 3.0-T MR imaging over 1.5-T MR arthrography.     

Multidetector CT of the spine in multiple myeloma: comparison with MR imaging and radiography

OBJECTIVE: The purpose of this study was to compare multidetector CT (MDCT) of the thoracic and lumbar segments of the spine with MR imaging and conventional radiography for bone lesion detection and for evaluating the risk of vertebral fracture in multiple myeloma. SUBJECTS AND METHODS: Eighteen patients with multiple myeloma stage III (according to the criteria of Durie and Salmon) underwent MDCT, conventional radiography, and MR imaging of the lumbar and thoracic spine. MDCT was performed using a standard protocol with no contrast material. Source images were reconstructed using an effective slice thickness of 3 mm with an overlapping reconstruction increment (0.8 mm). Secondary coronal and sagittal multiplanar reformations were exclusively used for establishing the diagnosis. Findings were compared with those of MR imaging and conventional radiography. RESULTS: In all patients, coronal and sagittal multiplanar reformations depicted the extent of osseous destruction and provided detailed information about osseous infiltration and potential bone instability. Compared with conventional radiography, an additional 24 affected vertebrae, 15 additional vertebral fractures, and six vertebrae at further risk of fracture were detected on MDCT. Compared with MR imaging, three additional endangered vertebrae were detected on MDCT. MR imaging alone would have lead to an understaging of five (27.8%) of 18 patients. Using combined radiography and MR imaging, disease in three (16.7%) of 18 patients would have been understaged. CONCLUSION: MDCT seems to be preferable to conventional radiography in evaluating bone destruction in multiple myeloma. In combination with MR imaging, detailed information for staging these tumors is obtained. For the initial staging in patients with multiple myeloma, MDCT in combination with MR imaging seems to be the method of choice.