Fast breath-hold T2-weighted MR imaging reduces interobserver variability in the diagnosis of adenomyosis

OBJECTIVE: We compared two rapid MR imaging T2-weighted pulse sequences with high-resolution turbo spin-echo for the diagnosis of adenomyosis, and we evaluated interobserver variability. SUBJECTS AND METHODS: Fifty-six consecutive patients referred for hysterectomy prospectively underwent MR imaging. Two fast pulse sequences using a breath-hold technique-true fast imaging with steady-state free precession (FISP) and turbo inversion recovery-and turbo spin-echo T2-weighted images of the pelvis were obtained in each patient. The images were analyzed in a blinded manner and independently by three reviewers with different levels of experience for the accuracy of adenomyosis diagnosis, image quality, anatomic visualization, and image artifacts. The accuracy for the diagnosis of adenomyosis on turbo spin-echo T2-weighted imaging combined with one or two fast pulse sequences was evaluated for each reviewer. RESULTS: Twenty-four patients (42.9%) had a histologic diagnosis of adenomyosis. The accuracy for the diagnosis of adenomyosis for reviewers 1, 2, and 3 using turbo spin-echo T2-weighted, true FISP, and turbo inversion recovery sequences was 83.9%, 67.8%, 75%; 83.9%, 67.8, 78.5%; and 87.5%, 73.2%, and 75%, respectively. A difference in the accuracy rate was found among the observers for the three sequences (p < 0.001). Whatever the pulse sequence, the accuracy rate was higher for the reviewer with more experience in gynecologic imaging. The combination of turbo spin-echo T2-weighted imaging with at least one rapid sequence increased the accuracy of observers with little experience in gynecology. With turbo inversion recovery sequences, the image quality score was low for the three reviewers compared with turbo spin-echo T2-weighted and true FISP sequences. The combination of turbo spin-echo T2-weighted and true FISP sequences gave the highest image quality scores. CONCLUSION: Breath-hold T2-weighted sequences optimize the accuracy of MR imaging for the diagnosis of adenomyosis and reduce interobserver variability.     

真实稳态进动快速成像T2^＊加权序列在胎儿MRI中的应用

目的:探讨真实稳态进动快速成像T2*加权序列在胎儿MRI中的临床应用价值.材料和方法:6例中、晚期孕程的孕妇行真实稳态进动快速成像(true FISP)T2*加权序列扫描,评价图像质量、模糊程度、正常胎儿器官显示、胎儿和母体异常的显示以及胎儿信噪比(SNR)及胎儿-孕妇腰椎椎体对比噪声比(F-L CNR)等,并与TSE序列T2WI进行比较.结果:与TSE序列T2WI相比,true FISP序列T2*WI可清楚显示胎头、胎儿肢体、胎儿脊柱、胎儿的脏器解剖结构以及母体子宫、胎盘、脐带等附属结构,胎儿和母体异常显示也较清晰,并能清晰显示灰、白质分界、脑回、脑髓鞘等结构.true FISP序列获得的图像其SNR以及F-L CNR均优于TSE序列.结论:真实稳态进动快速成像T2*加权序列能够清晰显示胎儿及母体的解剖结构,获得的图像具有较高的T2对比,可作为胎儿MR成像的常用序列.     

Cine MR angiography of the heart with segmented true fast imaging with steady-state precession

In five healthy subjects and 18 patients, cine magnetic resonance (MR) imaging of the heart was performed with a true fast imaging with steady-state precession (FISP) sequence. Results were compared both quantitatively and qualitatively with those at cine fast low-angle shot (FLASH) MR imaging. The blood-myocardial contrast-to-noise ratio (CNR) was 2.0 times higher and the normalized (for measurement time and pixel size) blood-myocardial CNR was 4.0 times higher for true FISP compared with FLASH MR imaging. Qualitative scores for image quality were significantly higher with true FISP MR imaging. Segmented cine true FISP MR imaging generated high-contrast MR images of the heart in healthy subjects and in patients with heart disease and produced image quality superior to that with cine FLASH MR imaging.     

Magnetic resonance portal venography: use of fast-acquisition true FISP imaging in the detection of portal vein thrombosis

AIM: To determine the accuracy of true fast imaging with steady-state precession (true FISP) in the diagnosis of portal vein thrombosis in patients with cirrhosis and compare it to contrast-enhanced three-dimensional (3D) magnetic resonance (MR) angiography, the reference standard. MATERIALS AND METHODS: Twenty-four consecutive patients with suspected portal venous thrombosis underwent contrast-enhanced 3D MR angiography and true FISP imaging of the portal vein. All patients had undergone at least one other imaging study, either computed tomography, (CT) or ultrasound. Both sets of MR images were evaluated for patency of the portal venous system and for image quality. RESULTS: Portal vein thrombosis was diagnosed in six of the 24 patients. Four patients with portal vein thrombosis were accurately diagnosed on the true FISP sequence. This sequence also accurately diagnosed the patency of the portal vein in 17 patients. However, the results were inconclusive in three patients. The image quality of the true FISP sequence of the three inconclusive patients was graded as either poor or fair. Of these three patients, contrast-enhanced 3D MR angiography confirmed portal vein thrombosis in two patients and portal vein stenosis in one patient. True FISP imaging had a sensitivity of 67% and a specificity of 100% for the diagnosis of portal vein thrombosis. CONCLUSION: The results of the present study show that the true FISP sequence is useful in diagnosing portal vein thrombosis. It could be employed as an adjunct to contrast-enhanced MR angiography in the severely debilitated patient where respiratory motion may degrade the images or in patients where the use of intravenous contrast medium is not possible due to poor venous access.     

Cardiac function: MR evaluation in one breath hold with real-time true fast imaging with steady-state precession

In 12 healthy volunteers and eight patients with cardiac disease, cine magnetic resonance (MR) imaging in the heart was performed with real-time true fast imaging with steady-state precession (FISP), which permitted evaluation of the entire left ventricle in one breath hold (91 msec per frame, 13 frames per section position, nine short-axis section positions per breath hold). Contrast-to-noise ratios (CNRs) and left ventricular mass and function measurements with this technique were compared in all subjects with single-section true FISP imaging and, in the volunteers only, with segmented fast low-angle shot (FLASH) MR imaging. Myocardium-to-blood CNR was significantly higher for both true FISP sequences compared with the FLASH sequence. Measurements of resting left ventricular function with real-time true FISP imaging were comparable with those derived from a series of separate breath-hold single-section true FISP acquisitions.     

Uterine peristalsis: comparison of transvaginal ultrasound and two different sequences of cine MR imaging

PURPOSE: To compare uterine peristalsis as seen on two different magnetic resonance (MR) imaging sequences and transvaginal ultrasound (TVUS), so as to better determine the best method for evaluating uterine peristalsis. MATERIALS AND METHODS: Eleven women in the periovulatory phase of the menstrual cycle underwent TVUS and cine MR imaging within a time period of three hours. Findings on cine MR images obtained with a serial 60 half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence and a 300 true fast imaging with steady-state precession (FISP) sequence were compared with TVUS. RESULTS: The image quality of the HASTE technique was the best among the three methods, followed by TVUS, and then true FISP technique (P < 0.001). Uterine peristalsis was detected in 100% of subjects using HASTE, 82% with True FISP, and 100% with TVUS. With HASTE technique, true FISP, and TVUS, respectively, endometrial stripping movement was identified in 100%, 82%, and 100%; direction was identified in 100%, 45% (P = 0.014), and 73%; and wave conduction toward the outer myometrium was identified in 55%, 9% (P = 0.025), and 0% (P = 0.014). CONCLUSION: Cine MR imaging by HASTE technique with a time resolution of two seconds best delineated uterine peristalsis compared to that by true FISP technique or with TVUS.     

Left ventricular mass: manual and automatic segmentation of true FISP and FLASH cine MR images in dogs and pigs

PURPOSE: To evaluate the accuracy of manually and automatically segmented true fast imaging with steady-state precession (FISP) and fast low-angle shot (FLASH) cine magnetic resonance (MR) imaging in the determination of left ventricular (LV) mass. MATERIALS AND METHODS: Nine dogs and five pigs underwent cine MR imaging of the entire LV from base to apex. Manual and automatic segmentation times were recorded, and LV masses determined with each were compared with each other and with the true LV mass at autopsy. Estimated mass and true mass at autopsy were compared by calculating the correlation coefficient and the mean difference between the two for each MR sequence and segmentation method. RESULTS: True LV mass at autopsy correlated well with masses determined with manual and automatic contours on true FISP MR images. Mean differences between true LV mass and masses determined from manual contours on true FISP and FLASH images were -0.8 g +/- 2.6 and 3.7 g +/- 6.8, respectively. When manually drawn end-diastolic contours were automatically propagated to end systole, mean differences were 2.0 g +/- 3.6 (P =.05) and 9.1 g +/- 6.5 (P <.05) for true FISP and FLASH images, respectively. For automatic contours, mean differences were 10.6 g +/- 8.5 (P <.05) and 27.7 g +/- 13.4 (P <.05) for true FISP and FLASH images, respectively. Mean automatic segmentation time was six times less than mean manual segmentation time. CONCLUSION: LV mass was determined most accurately by using manual contours on true FISP images. In these animal models, fully automatic segmentation of true FISP images was performed in one-sixth of the time of manual segmentation and yielded LV masses with a mean error of approximately 5% of true LV mass.     

Comparison of MR imaging sequences for liver and head and neck interventions: is there a single optimal sequence for all purposes?

RATIONALE AND OBJECTIVES: To compare the appropriate pulse sequences for interventional device guidance during magnetic resonance (MR) imaging at 0.2 T and to evaluate the dependence of sequence selection on the anatomic region of the procedure. MATERIALS AND METHODS: Using a C-arm 0.2 T system, four interventional MR sequences were applied in 23 liver cases and during MR-guided neck interventions in 13 patients. The imaging protocol consisted of: multislice turbo spin echo (TSE) T2w, sequential-slice fast imaging with steady precession (FISP), a time-reversed version of FISP (PSIF), and FISP with balanced gradients in all spatial directions (True-FISP) sequences. Vessel conspicuity was rated and contrast-to-noise ratio (CNR) was calculated for each sequence and a differential receiver operating characteristic was performed. RESULTS: Liver findings were detected in 96% using the TSE sequence. PSIF, FISP, and True-FISP imaging showed lesions in 91%, 61%, and 65%, respectively. The TSE sequence offered the best CNR, followed by PSIF imaging. Differential receiver operating characteristic analysis also rated TSE and PSIF to be the superior sequences. Lesions in the head and neck were detected in all cases by TSE and FISP, in 92% using True-FISP, and in 84% using PSIF. True-FISP offered the best CNR, followed by TSE imaging. Vessels appeared bright on FISP and True-FISP imaging and dark on the other sequences. CONCLUSION: In interventional MR imaging, no single sequence fits all purposes. Image guidance for interventional MR during liver procedures is best achieved by PSIF or TSE, whereas biopsies in the head and neck are best performed using FISP or True-FISP sequences.     

Accurate quantification of right ventricular mass at MR imaging by using cine true fast imaging with steady-state precession: study in dogs

PURPOSE: To assess the accuracy of cine magnetic resonance (MR) imaging with a segmented true fast imaging with steady-state precession (FISP) technique for right ventricular (RV) mass quantification. MATERIALS AND METHODS: Fourteen dogs were imaged with a 1.5-T clinical MR imaging unit by using an electrocardiographically gated true FISP sequence. Contiguous segmented k-space cine images were acquired from the base of the RV to the apex during suspended respiration (repetition time msec/echo time msec, 3.2/1.6; section thickness, 5 mm; in-plane resolution, 1.0 x 1.3 mm2). After imaging, each dog was sacrificed, and the RV free wall was isolated and weighed. Each MR imaging data set was analyzed twice by each of two independent observers who were blinded to the results of RV mass measurement at autopsy, and the mass measurements at MR imaging were compared with the autopsy results by using linear regression and Bland-Altman analysis. RESULTS: RV mass measurements calculated by using the true FISP cine MR images were nearly identical to those at autopsy (R = 0.82, standard error of the estimate = 1.7 g, P >.05), with a mean difference between the autopsy and MR imaging measurements of 0.3 g +/- 1.7 (1.9% +/- 8.2) (P >.05). Inter- and intraobserver variations were small, with a mean interobserver variability of -0.1 g +/- 2.3 and a mean intraobserver variability of 0.2 g +/- 1.6 at every-section analysis. CONCLUSION: In this animal model, true FISP cine MR imaging enabled accurate quantification of RV mass.     

MR enteroclysis protocol optimization: comparison between 3D FLASH with fat saturation after intravenous gadolinium injection and true FISP sequences

The aim of this study was to introduce the true fast imaging with steady-state precession (FISP) sequence for MR enteroclysis and compare it with the already used T1-weighted fast low-angle shot (FLASH) sequence. Twenty-one patients underwent both MR and conventional enteroclysis. The MR enteroclysis examination was performed after administration of an iso-osmotic water solution through a nasojejunal catheter and the following sequences were included: (a) true FISP; and (b) 3D FLASH with fat saturation after intravenous injection of 20 mg Buscopan or 1 mg glucagon and 0.1 mmol/kg gadolinium chelates. The true FISP sequence provided images with significantly fewer motion artifacts, whereas 3D FLASH was less sensitive to susceptibility and chemical shift artifacts. The homogeneity of endoluminal opacification, wall conspicuity, and distention of the small bowel were very good to excellent and the two sequences presented no statistically significant differences here. True FISP provided significantly better overall image quality than did 3D FLASH. The true FISP sequence can provide good anatomic demonstration of the small bowel on T2-like images and could be combined with T1-weighted FLASH images for an integrated protocol of MR enteroclysis.     

Phase-sensitive inversion-recovery MR imaging in the detection of myocardial infarction

PURPOSE: To prospectively determine if phase-sensitive inversion-recovery (IR) magnetic resonance (MR) imaging eliminates the need to find the precise inversion time (TI) to null the signal of normal myocardium to achieve high contrast between infarcted and normal myocardium. MATERIALS AND METHODS: Informed consent was obtained from each patient for this prospective MR imaging research study, which was approved by the institutional review board. Twenty patients (16 men; four women; mean age, 56 years +/- 12.3) who experienced Q-wave myocardial infarction 2 weeks earlier were examined with a 1.5-T MR system 10 minutes after administration of 0.1 mmol per kilogram of body weight gadobenate dimeglumine. To determine the optimal TI, a TI scout sequence was used. A segmented two-dimensional IR turbo fast low-angle shot (FLASH) sequence and a segmented two-dimensional IR true fast imaging with steady-state precession (FISP) sequence that produces both phase-sensitive and magnitude-reconstructed images were used at TI values of 200-600 msec (TI values were varied in 100-msec steps) and at optimal TI (mean value, 330 msec). Contrast-to-noise ratios (CNRs) of normal and infarcted myocardium and the area of infarcted myocardium were determined. Magnitude-reconstructed IR turbo FLASH images were compared with magnitude-reconstructed and phase-sensitive IR true FISP images. Two-tailed unpaired sample Student t test was used to compare CNRs, and two-tailed paired-sample Student t test was used to compare area of infarction. RESULTS: Mean CNR of images acquired with IR turbo FLASH and IR true FISP (phase-sensitive and magnitude-reconstructed images) at optimal TI (mean value, 330 msec) were 6.6, 6.2, and 6.1, respectively. For a TI of 200 msec, CNR values were -4.3, -4.0, and 7.2, respectively; for TI of 600 msec, CNR values were 3.1, 3.3, and 4.3, respectively. Area of infarcted myocardium was underestimated on magnitude-reconstruction images (P = .002-.03) for short TI values (ie, 200 msec) for both sequences and for a TI of 300 msec for IR true FISP but not on phase-sensitive reconstructed IR true FISP images when compared with IR turbo FLASH images obtained at optimal TI. CONCLUSION: Phase-sensitive image reconstruction results in reduced need for precise choice of TI and more consistent image quality.     

MR evaluation of ventricular function: true fast imaging with steady-state precession versus fast low-angle shot cine MR imaging: feasibility study

Short- and long-axis cine magnetic resonance (MR) images were obtained with a standard fast low-angle shot, or FLASH, sequence and a first-generation true fast imaging with steady-state precession (FISP) sequence on a 1.5-T MR imager. Contrast-to-noise ratios and volumetric left ventricular measurements were compared for manual and automatic segmentation. True FISP images were associated with significantly (P<.01) higher contrast-to-noise ratios and allowed better detection of the endocardial border. True FISP images were provided with short acquisition times and excellent contrast between the myocardium and the ventricular lumen.     

Thoracic aortic dissection and aneurysm: evaluation with nonenhanced true FISP MR angiography in less than 4 minutes

Comprehensive aortic magnetic resonance (MR) examinations currently include multiple nonenhanced and contrast material-enhanced sequences. The authors hypothesized that the nonenhanced true fast imaging with steady-state precession (FISP) portion alone of their comprehensive imaging protocol would be adequate to confidently confirm or exclude dissection or aneurysm of the aorta. In a retrospective review of 29 comprehensive thoracic aortic MR examinations, nonenhanced true FISP MR imaging alone was 100% accurate for determining the presence or absence of dissection or aneurysm.     

Preoperative evaluation of the entire hepatic vasculature in living liver donors with use of contrast-enhanced MR angiography and true fast imaging with steady-state precession

PURPOSE: To preoperatively assess the entire hepatic vasculature in living related liver donors with use of a combination of contrast material-enhanced magnetic resonance (MR) angiography and true fast imaging with steady-state precession (FISP). MATERIALS AND METHODS: Twenty-five living potential liver donors were examined preoperatively on a 1.5T Siemens Sonata system. Twenty-four underwent surgery and two had catheter angiography performed to delineate complex anatomy. Contiguous 5-mm-thick, sub-second true FISP images of the liver were initially obtained during breath-holding in axial and coronal planes (repetition time [TR]/echo time [TE], 3.2/1.6; flip angle, 70 degrees ). MR angiography was performed with use of a three-dimensional (3D) gradient-echo fast low-angle shot (FLASH) pulse sequence (TR/TE, 3.0/1.2; flip angle, 25 degrees ), with 40 mL of Gadolinium DTPA injected at a rate of 2 mL/sec. One precontrast and two postcontrast coronal 3D volumes were acquired, each in a 20-second breath-hold, and two subtracted 3D sets were calculated. Arterial anatomy was assessed with use of maximum-intensity projection, volume rendering, and multiplanar reformatting algorithms. Hepatic and portal venous anatomy was evaluated with use of the true FISP images and the venous phase of the MR angiogram. Visualization of hepatic arterial branches was noted. Visualization of portal vein branches was scored on a scale of 0-5. The presence of anatomic variants was noted. Vascular anatomy was confirmed at the time of surgery and at catheter angiography. RESULTS: Segmental branch vessels were visualized on MR angiography in the majority of cases. The segment four branch was identified in 96% patients. Variant arterial anatomy was seen in 50% of patients. MR angiography detected 10 of 11 arterial variants found at surgery and angiography. Visualization of portal vein branches was generally higher with true FISP compared to MR angiography. Twenty-four percent of patients had variant portal venous anatomy. Caudal hepatic veins were identified in 60% of patients, of which eight were significant (>5 mm). Hepatic and portal venous anatomy was accurately predicted by true FISP and MR angiography in all patients who went on to undergo surgery. CONCLUSION: Preoperative imaging with use of a combination of contrast-enhanced MR angiography and true FISP provides a comprehensive assessment of the entire hepatic vasculature in living liver donors.     

T2-Weighted fast MR imaging with true FISP versus HASTE: comparative efficacy in the evaluation of normal fetal brain maturation

OBJECTIVE: This study compares the relative efficacy of two fast T2-weighted MR imaging techniques-fast imaging with steady-state free precession (true FISP) and half-Fourier acquisition single-shot turbo spin-echo (HASTE)-in the evaluation of the normal fetal brain maturation during the second and third trimesters of gestation. SUBJECTS AND METHODS: The brain maturation of 10 normal nonsedated fetuses (5 during the second trimester and 6 during the third trimester of gestation [1 fetus underwent 2 examinations]) was examined by both techniques using a Vision+ 1.5-T MR system. We specifically looked for developing events, including white matter myelination, neuronal migration, and cortical sulcation. Image quality was graded according to the presence or absence of undesirable blurring. RESULTS: The specific absorption rate was lower for true FISP than for HASTE by a factor of 3 at equivalent imaging conditions. HASTE and true FISP provide comparable image quality in the second trimester when myelination of the cerebrum has not begun. Neuronal migration could be recognized as hypodense bands on both sequences during the second trimester. Myelination beginning at the third trimester was better delineated with true FISP than with HASTE because of point spread function-related blurring effects inherent in HASTE that hampered visualization of short-T2 structures. Cortical sulcation was well delineated by both sequences. CONCLUSION: With relatively superior image quality and significantly lower radiofrequency absorption than HASTE, true FISP is a safer and more effective alternative in the prenatal evaluation of normal fetal brain.     

Fast magnetic resonance imaging in steady-state precession (true FISP) in the prenatal diagnosis of a congenital brain teratoma

Teratomas are the most common congenital intracranial tumor. Although fetal magnetic resonance (MR) imaging is becoming more popular for prenatal diagnosis, only 2 cases of congenital intracranial teratoma have been reported, and these cases relied on half-Fourier single-shot turbo spin echo (HASTE) imaging. We report the first known case of congenital intracranial teratoma diagnosed by means of a fast imaging in steady-state precession (true FISP) MR sequence. True FISP can be obtained in almost 20 seconds and provides superior contrast resolution compared with HASTE.     

Invited. Interactive MRI-guided radiofrequency interstitial thermal ablation of abdominal tumors: Clinical trial for evaluation of safety and feasibility

This clinical trial was performed to evaluate the safety and feasibility of interactive MR-guided radiofrequency (RF) interstitial thermal ablation (ITA) performed entirely within the MR imager. RF-ITA was performed on 11 intra-abdominal metastatic tumors during 13 sessions. The RF electrode was placed under MR guidance on a .2-T system using rapid fast imaging with steady state precession (FISP) and true FISP images. A custom 17-gauge electrode was used and was modified in four sessions to allow circulation of iced saline for cooling during ablation. Tissue necrosis monitoring and electrode repositioning were based on rapid T2-weighted and short-inversion-time inversion recovery (STIR) sequences. Morbidity and toxicity were assessed by clinical and imaging criteria. The region of tissue destruction was visible in all 11 tumors treated, as confirmed on subsequent contrast-enhanced images. No significant morbidity was noted, and patient discomfort was minimal. In conclusion, interactive MR-guided RF-ITA is feasible on a clinical .2-T C-arm system with supplemental interventional accessories with only minor patient morbidity. The ability to completely ablate tumors with RF-ITA depends on tumor size and vascularity.     

Is true FISP imaging reliable in the evaluation of venous thrombosis?

OBJECTIVE: The objective of our study was to evaluate the accuracy of true fast imaging with steady-state precession (FISP) in the diagnosis of venous thrombosis using gadolinium-enhanced 3D T1-weighted gradient-echo images and correlative imaging as the gold standard. MATERIALS AND METHODS: Twenty-five MR examinations were retrospectively reviewed independently by two radiologists to rule out thrombosis in the central veins of the body. The presence of venous thrombus was assessed separately in 80 veins using true FISP and gadolinium-enhanced T1-weighted images. Diagnosis was confirmed by another imaging technique (sonography, CT, and/or conventional venography) in all positive cases. Negative examinations were confirmed using imaging, clinical follow-up, or both. RESULTS: Venous thrombosis was present in 25 veins in 18 patients. True FISP images had a lower sensitivity (66%) and specificity (70.9%) for the diagnosis of venous thrombosis than gadolinium-enhanced MR images (p < 0.01). CONCLUSION: True FISP images have lower sensitivity and specificity in the diagnosis of venous thrombosis than gadolinium-enhanced T1-weighted gradient-echo images. True FISP images should not be used exclusively for the diagnosis of venous thrombosis.     

Coronary artery bypass graft patency: assessment with true ast imaging with steady-state precession versus gadolinium-enhanced MR angiography

PURPOSE: To compare the accuracy of multisection true fast imaging with steady-state precession (FISP) with gadolinium-enhanced magnetic resonance (MR) angiography for the detection of coronary artery bypass graft patency. MATERIALS AND METHODS: Twenty-five patients with coronary artery bypass grafts who had recently undergone conventional coronary angiography underwent MR angiography with a 1.5-T system. True FISP angiographic images were acquired in transverse and coronal planes. Coronal cardiac-gated MR angiography was performed with 0.2 mL per kilogram of body weight of gadopentetate dimeglumine injected at a rate of 2 mL/sec. With conventional angiography as the reference standard, the sensitivity, specificity, and accuracy of each technique for the detection of graft patency were determined. Image quality and duration of analysis were determined by two experienced radiologists. RESULTS: In 25 patients, 46 of 56 venous grafts were patent and 22 of 23 arterial grafts were patent. In all grafts at true FISP angiography, sensitivity for patency was 84% (57 of 68 grafts), specificity was 45% (five of 11 grafts), and accuracy was 78% (62 of 79 grafts). At MR angiography, sensitivity was 85% (58 of 68 grafts), specificity was 73% (eight of 11 grafts), and accuracy was 84% (66 of 79 grafts) (difference not significant). Image quality scores were similar with both techniques, but duration of analysis was significantly longer with MR angiography than with true FISP angiography (29 minutes 24 seconds vs 14 minutes 6 seconds, P <.001). CONCLUSION: Accuracy for detection of coronary artery bypass graft patency was similar with gadolinium-enhanced MR angiography and true FISP angiography, with a trend toward more false-positive findings for occlusion and reduced visualization of arterial grafts with true FISP angiography.     

Diagnosis of articular cartilage abnormalities of the knee: prospective clinical evaluation of a 3D water-excitation true FISP sequence

PURPOSE: To prospectively evaluate the accuracy of three-dimensional (3D) water-excitation true fast imaging with steady-state precession (FISP) in the assessment of cartilage abnormalities of the knee, by using surgery as the reference standard. MATERIALS AND METHODS: The study was approved by the hospital institutional review board. Written informed consent was obtained from all patients. Twenty-nine patients (30 knees) with a mean age of 56 years (range, 18-86 years) were prospectively evaluated with a sagittal 3D true FISP magnetic resonance (MR) sequence. The mean interval between MR imaging and surgery was 1 day (range, 0-9 days). During surgery, the articular surfaces of the knee were evaluated by using a modified Noyes score. The MR images were evaluated by two blinded readers on two separate occasions. Diagnostic performance was evaluated by setting the cutoff for abnormality between grade 1 (intact cartilage surface) and grade 2 (cartilage defects). Statistical methods used included calculation of sensitivity, specificity, and accuracy, with 95% confidence intervals (Wilson score method) and calculation of kappa values with standard errors. RESULTS: Overall sensitivity, specificity, and accuracy for the two readers and the two evaluations ranged from 56% to 66%, 78% to 93%, and 71% to 75%, respectively. Interobserver agreement was substantial for both the first (kappa = 0.73) and the second (kappa = 0.65) evaluation. Intraobserver agreement was almost perfect (kappa = 0.84) for reader 1 and moderate (kappa = 0.60) for reader 2. CONCLUSION: The 3D water-excitation true FISP MR sequence allows assessment of the articular cartilage of the knee with moderate-to-high specificity and low-to-moderate sensitivity.