Left ventricular thrombi: evaluation with spin-echo and gradient-echo MR imaging.

Gradient-echo (GRE) and spin-echo (SE) magnetic resonance (MR) imaging was performed in 31 patients with chronic left ventricular (LV) thrombi. Thrombi were confirmed or excluded at surgery or by means of other corroborative diagnostic techniques. MR images were evaluated by three reviewers without knowledge of results of corroborative studies. Diagnoses were graded unequivocal if agreed on by three observers and probable if agreed on by two observers. With SE imaging, 12 of 18 confirmed thrombi were detected unequivocally, five were considered probable, and one was not detected. With GRE imaging, 16 of the 18 thrombi were visualized unequivocally; two were considered probable. With SE technique, thrombus was unequivocally excluded in nine of 13 cases and exclusion was considered probable in four. One finding was false-negative. Exclusion of thrombus with GRE imaging was unequivocal in 10 of 13 cases and probable in two, and one finding of thrombus was false-positive. GRE imaging resulted in improved differentiation of thrombi from the surrounding blood pool and myocardium and thus was diagnostically superior to SE imaging in detection of LV thrombi.     

Experimental hyaline cartilage lesions: two-dimensional spin-echo versus three-dimensional gradient-echo MR imaging.

The value of magnetic resonance (MR) imaging, with two-dimensional (2D) spin-echo and FISP (fast imaging with steady-state precession) and FLASH (fast low-angle shot) three-dimensional (3D) gradient-echo sequences, for the detection of hyaline cartilage defects of the femoral condyle and the tibial plateau, was investigated in an animal model. In eight dogs, the anterior cruciate ligament was transected in one knee joint, resulting in rapid development of osteoarthritis with degeneration of the hyaline cartilage. At autopsy, 24 cartilage lesions were found, which were classified into four grades. The overall detection of cartilage lesions with MR imaging was poor. Only five of the 24 lesions were visible on 2D spin-echo images, while 11 of 24 were visible on 3D FISP images and 15 of 24 were seen on 3D FLASH images. The best results were obtained in advanced stages of cartilage degeneration, involving ulceration and complete abrasion of the cartilage layer. Signal loss or signal intensity increase in the cartilage layer was seen inconsistently in grades 3 and 4 degeneration. In this animal model, 2D spin-echo imaging was inadequate for the diagnosis of hyaline cartilage lesions, while 3D gradient-echo imaging permitted satisfactory diagnosis in only grade 4 cartilage disease.     

MR imaging of Parkinson disease with spin-echo and gradient-echo sequences

High-field MR with both spin-echo and gradient-echo sequences was performed in 21 patients with (idiopathic, drug-responsive) Parkinson disease. The use of gradient echoes allowed more sensitive detection than did spin echoes of susceptibility changes in the putamina and substantia nigra. No statistically significant difference in putaminal hypointensity on long TR/long TE spin-echo sequences or on T2*-weighted images using gradient-echo sequences was observed between Parkinson patients and controls. There was also no statistically significant difference in the frequency of restoration of the signal intensity of the substantia nigra between the two groups of patients. The width of the pars compacta of the substantia nigra in patients with Parkinson disease was 2.12 + 0.82 mm (mean +/- SD). This value in age- and gender-matched controls was 2.67 +/- 0.5. Comparing these two groups with an unpaired t test resulted in a p value less than or equal to .005. Our MR study with spin-echo and gradient-echo images in Parkinson and control patients was able to substantiate and elaborate on previously described MR features of Parkinson disease.     

Perfusion-sensitive MR imaging of gliomas: comparison between gradient-echo and spin-echo echo-planar imaging techniques

BACKGROUND AND PURPOSE: The different sensitivities to vessel size of gradient-echo echo-planar imaging (GE-EPI) and spin-echo EPI (SE-EPI) might indicate the relative cerebral blood volumes (rCBVs) of different tumor sizes. The techniques of GE-EPI and SE-EPI were compared for detecting low- versus high-grade gliomas. METHODS: Six patients with low-grade gliomas and 19 patients with high-grade gliomas underwent two perfusion-sensitive MR procedures, one produced by a GE- and the other by an SE-EPI technique. Maximum rCBV ratios normalized with rCBV of contralateral white matter were calculated for evaluation. P <.05 was considered statistically significant. RESULTS: Maximum rCBV ratios of high-grade gliomas obtained with the GE-EPI technique (mean, 5.0 +/- 2.9) were significantly higher than those obtained with the SE-EPI technique (mean, 2.9 +/- 2.3) (P =.02). Maximum rCBV ratios of low-grade gliomas obtained with the GE-EPI technique (mean, 1.2 +/- 0.7) were almost equal to those obtained with the SE-EPI technique (mean, 1.2 +/- 0.6), and there was no significant difference (P =.66). The difference in the maximum rCBV ratios between the low- and high-grade gliomas reached significance when obtained with the GE-EPI technique (P =.01). CONCLUSION: The GE-EPI technique seems more useful for detecting low- versus high-grade gliomas than the SE-EPI technique.     

Musculoskeletal MR imaging: turbo (fast) spin-echo versus conventional spin-echo and gradient-echo imaging at 0.5 tesla

The value of T2-weighted fast spin-echo imaging of the musculoskeletal system was assessed in 22 patients with various neoplastic, inflammatory, and traumatic disorders. Images were acquired with high echo number (i.e., echo train length) fast spin-echo (FSE; TR 2000 ms, effective TE 100 ms, echo number 13, lineark-space ordering), conventional spin-echo (SE; TR 2000 ms, TE 100 ms) and gradient-echo (GRE) sequences (TR 600 ms, TE 34 ms, flip angle 25°). Signal intensities, signal-to-noise ratios, contrast, contrast-to-noise ratios, lesion conspicuousness, detail perceptibility, and sensitivity towards image artifacts were compared. The high signal intensity of fat on FSE images resulted in a slightly inferior lesion-to-fat contrast on FSE images. However, on the basis of lesion conspicuity, FSE is able to replace time-consuming conventional T2-weighted SE imaging in musculoskeletal MRI. In contrast, GRE images frequently showed superior lesion conspicuity. One minor disadvantage of FSE in our study was the frequent deterioration of image quality by blurring, black band, and rippling artifacts. Some of these artifacts, however, can be prevented using short echo trains and/or short echo spacings.     

Renal carcinoma: detection of venous extension with gradient-echo MR imaging.

Magnetic resonance (MR) imaging has been proposed as a noninvasive alternative to vena cavography and computed tomography for the detection of venous extension of renal adenocarcinoma. However, spin-echo MR images may be compromised by the presence of flow-related artifacts, extrinsic compression, and respiratory or cardiac motion artifacts. Use of gradient-recalled echo (GRE) sequences is advantageous for imaging of vascular structures. To investigate the detection of vascular extension of tumor with the GRE technique, findings in the preoperative GRE MR images of 26 patients with renal adenocarcinoma were compared with findings at surgery and pathologic examination. Vena cava thrombus was correctly identified in 13 of 13 patients (100%). Renal vein thrombus was correctly identified in 23 of 26 patients (88%), and right atrial thrombus was correctly identified in four of five patients (80%). Use of GRE sequences allows accurate assessment of vascular structures that is sufficient for surgical planning.     

Intracranial hemorrhage: gradient-echo MR imaging at 1.5 T. Comparison with spin-echo imaging and clinical applications

Fifty-seven patients with hemorrhagic intracranial lesions were examined with magnetic resonance (MR) imaging at 1.5 T with use of both spin-echo (SE) and gradient-echo-acquisition (GEA) techniques to assess the clinical applications and limitations of GEA in evaluation of intracranial hemorrhage at high field strength. All GEA images were obtained with a long echo time and short flip angle to emphasize T2*-based contrast. In 30 of 61 cases, GEA images demonstrated more hemorrhagic lesions than SE images. In 14 of 61 cases, GEA images failed to depict the lesion or obscured the specific diagnosis (as depicted by SE MR imaging). The authors believe that GEA imaging in its current form has a limited but definite adjunctive role in the evaluation of intracranial hemorrhage at high field strength.     

Hematopoietic bone marrow in the adult knee: spin-echo and opposed-phase gradient-echo MR imaging

Hematopoietic bone marrow in the distal femur of the adult may be mistaken for a pathologic marrow process in magnetic resonance imaging of the knee. We investigated the incidence of hematopoietic marrow in the distal femur in a series of 51 adult patients and compared spin-echo (TR/TE in ms: 500/35, 2000/80) and opposed-phase gradient-echo (0.35 T, TR/TE in ms: 1000/30, = 75°) magnetic resonance images. Zones with intermediate to low signal intensity on T1-weighted spinecho and opposed-phase gradient-echo sequences representing hematopoietic marrow within high signal intensity fatty marrow were observed in 18 of the 51 patients. Five patterns of marrow signal reduction were identified; type 0: uniform high signal, i.e., no signal change; type I, focal signal loss; type II, multifocal signal loss without confluence; type III, confluent signal loss; and type IV, complete homogeneous reduction in marrow signal. Opposed-phase gradient-echo sequences demonstrated markedly greater red-yellow marrow contrast than conventional spin-echo sequences. Follow-up studies in three patients using a gradient-echo sequence with TE varying from 10 to 21 ms at 1-ms increments showed a cyclic increase and decrease in red and yellow marrow signal intensity depending on the TE. The contribution of intravoxel chemical shift effects on red-yellow marrow contrast in opposed-phase gradient-echo images was verified by almost complete cancellation of the TE-dependent marrow signal oscillation with use of a chemically selective pulse presaturating the water protons.Hematopoietic marrow in the adult distal femur in the absence of hematologic abnormalities is found primarily in women of menstruating age. It may be residual and may represent a biologic variation in the normal adult pattern of red-yellow marrow distribution. Reconverted red marrow appears to be related to increased erythrocyte demand. Residual and reconverted red marrow should not be mistaken for bone marrow malignancy. Opposed-phase gradient-echo imaging is easily implemented and appears ideally suited to monitor the distribution of hematopoietic marrow as a function of age and erythrocyte demand in vivo.     

Diagnosis of abdominal venous thrombosis by means of spin-echo and gradient-echo MR imaging: analysis with receiver operating characteristic curves

The authors compared the accuracy of spin-echo (SE) and gradient-echo (GRE) magnetic resonance images in diagnosis of abdominal venous thrombosis. Images of 292 abdominal veins in 72 patients were reviewed in a blinded manner by three radiologists, with seven levels of confidence for diagnosis. Corroborative studies proved thrombosis (n = 95) and vessel patency (n = 197). Receiver operating characteristic (ROC) curves were constructed for SE images alone, GRE images alone, and SE and GRE images combined. At specificities of 90% and 95%, thrombi were identified with sensitivities, respectively, of 76% and 63% with SE images, 74% and 58% with GRE images, and 88% and 82% with combined SE and GRE images. The area under the ROC curve for SE and GRE images combined (0.958 +/- 0.011 [standard deviation]) was significantly larger (P less than .001) than that for SE images alone (0.913 +/- 0.018) and GRE images alone (0.921 +/- 0.016). It is concluded that combination of SE and GRE images significantly increases the accuracy of diagnosis of abdominal venous thrombosis.     

Osteodensitometry of human heel bones by MR spin-echo imaging: comparison with MR gradient-echo imaging and quantitative computed tomography

The aim of the study was to investigate whether quantitative magnetic resonance (MR) fast spin-echo (FSE) imaging with moderate spatial resolution enables osteodensitometry in peripheral yellow bone marrow. Signal intensities in T1-weighted FSE images from yellow bone marrow indicate the amount of adipose tissue per volume. The signal intensity in marrow regions with spongy bone was assessed and compared to signal intensity of pure fatty marrow (100%). Heel bones of 30 patients with suspected osteoporosis were analyzed and the FSE images were compared with results from parallel MR gradient-echo (GE) imaging and quantitative computed tomography (QCT) examinations. High correlation was found between FSE imaging and QCT [r = 0.91 in the dorsal region of interest (ROI); r = 0.86 in ventral ROI]. Linear correlation coefficients between GE imaging and QCT were slightly lower in the dorsal part (r = -0.86) and considerably lower in the ventral part (r = -0.68). Correlation between the two MR techniques amounted to r = -0.72/-0.61 (dorsal/ventral). The high correlation between FSE imaging and bone mineral density (BMD) allows possible clinical applications of FSE imaging for diagnosis of osteoporosis. Further improvements of the accuracy using reference phantoms might be possible.     

MR imaging of the knee in the sagittal projection: comparison of three-dimensional gradient-echo and spin-echo sequences

Fifty patients with suspected internal derangement of the knee had arthroscopic examinations after MR imaging with both a standard T1-weighted spin-echo (SE) sequence and a three-dimensional (3-D) gradient-echo sequence. This series permitted correlative evaluation of 100 menisci and 50 anterior cruciate ligaments. Meniscal tears were diagnosed when intrameniscal signal communicated with the meniscal surface. Criteria for diagnosing anterior cruciate ligament disruption included absence or discontinuity of the ligament, ligamentous laxity, and hyperflexion of the posterior cruciate ligament. Arthroscopic surgery confirmed the presence of 39 meniscal tears and 11 anterior cruciate ligament tears in this population. The sensitivity and specificity of the SE sequence for the diagnosis of meniscal tears were 77% and 98%, respectively. The 3-D gradient-echo sequence had a sensitivity of 87% and a specificity of 88%. For disruption of the ligament, the SE technique had a sensitivity of 82% and a specificity of 95% and the 3-D technique had a sensitivity of 64% and a specificity of 100%. Although these differences in sensitivity and specificity are not statistically significant at the p less than .05 level, probably because of the small sample size, the results show the relative strengths and weaknesses of the two imaging sequences. These data suggest that because of the complementary results of the two MR techniques, both the SE and the 3-D gradient-echo sequences have a role in the diagnosis of knee injuries.     

MR imaging of the lungs: value of short TE spin-echo pulse sequences.

OBJECTIVE. An experimental short echo delay (TE = 7 msec) T1-weighted spin-echo sequence was compared with a conventional (TE = 20 msec) T1-weighted spin-echo sequence in the assessment of normal and abnormal lung parenchyma. Comparison was also made with high-resolution CT of abnormal lung parenchyma. SUBJECTS AND METHOD. At 1.5 T, an experimental short echo delay T1-weighted multislice spin-echo sequence (TR = RR interval, TE = 7 msec) was compared with an optimal conventional T1-weighted spin-echo sequence (TR = RR interval, TE = 20 msec, spatial presaturation). Ten healthy volunteers were examined with both sequences. The mean signal intensity and signal-to-noise ratios were calculated in lung parenchyma for both sequences. Two radiologists compared the visualization of normal lung parenchymal structures with the two techniques. In 24 patients with diffuse lung disease, results with both MR sequences and with high-resolution CT were compared. RESULTS. The signal intensity was significantly greater (p < .001) with the TE of 7 msec than with the TE of 20 msec, resulting in a 3.5-fold improvement in the signal-to-noise ratio. The 7-msec TE improved visualization of lung parenchymal structures, including peripheral vessels, interlobular septa or veins, and centrilobular arteries. In the patients with diffuse lung disease, pulmonary parenchymal abnormalities were better visualized on the images with TEs of 7 msec than on images with TEs of 20 msec. When compared with high-resolution CT, the sequence with a TE of 7 msec provided comparable assessment of air-space opacification and dense consolidation, but it was inferior to high-resolution CT in the anatomic assessment of lung parenchyma. CONCLUSION. This experimental spin-echo sequence with a TE of 7 msec significantly improves the signal-to-noise ratio, allowing improved visualization of normal and abnormal pulmonary parenchyma when compared with conventional spin-echo images with a TE of 20 msec. Although anatomic detail remains inferior to that seen with high-resolution CT, the improved image quality with a TE of 7 msec suggests that assessment and follow-up of parenchymal lung disease might be possible with MR, thereby avoiding ionizing radiation.     

Deep venous thrombosis: experience with gradient-echo MR imaging in 66 patients

The medical records of 66 patients who underwent evaluation for possible deep venous thrombosis (DVT) by means of gradient-echo (GRE) magnetic resonance (MR) imaging were reviewed. Confirmatory venograms were obtained in 26 patients; in the other 40, the accuracy of GRE MR imaging was assessed by means of clinical follow-up, which ranged from 1 to 23 months (mean, 7.7 months). Findings in GRE MR images were negative in 42 patients (64%) and positive in 24 patients (36%). In patients who underwent confirmatory venography, the sensitivity of GRE MR imaging was 100% and the specificity was 92.9%. No patient with a negative GRE MR study developed DVT or pulmonary emboli during the follow-up period. Although seven patients in this group died, the single autopsy showed no evidence of pulmonary embolism, and no clinical evidence existed to suggest that pulmonary embolism was the cause of death in any of the other six patients. It is concluded that GRE MR imaging is an accurate, noninvasive means of detecting DVT.     

Renal cancer staging: Comparison of contrast-enhanced CT and gadolinium-enhanced fat-suppressed spin-echo and gradient-echo MR imaging

Fifty-three consecutive patients with 61 solid or complex non-fat-containing renal masses compatible with renal cancer were examined with contrast-enhanced computed tomography (CT) and magnetic resonance (MR) imaging with pre- and postcontrast FLASH (fast low-angle shot) and fat-suppressed spin-echo sequences. CT and MR imaging were performed within a 1-month interval. CT and MR images were prospectively interpreted. Tumor detection and staging were determined in all patients. CT and MR imaging enabled detection of 54 and 58 of 61 renal tumors, respectively. CT and MR imaging showed 34 and 35 of 38 histologically proved renal tumors, respectively, in 31 patients. Tumor size on CT and MR images demonstrated good correlation and correlated well with the size of pathologic specimens of 34 of 38 resected tumors detected with CT and MR imaging (r =.99). Of the 31 tumors in 31 patients who underwent surgical resection, 24 were correctly staged with CT and 29 with MR imaging. CT and MR imaging both enabled correct staging of four of five additional tumors with biopsy proof of tumor stage. A moderate difference in staging was observed between CT and MR imaging (P =.05). CT showed 13 and MR imaging 15 of 15 tumor thrombi. CT and MR imaging both showed 11 of 11 cases of adenopathy. The results suggest that MR imaging is moderately better than CT for the detection and staging of renal cancer.     

Intracranial lesion enhancement with gadolinium: T1-weighted spin-echo versus three-dimensional Fourier transform gradient-echo MR imaging.

The conspicuity of lesion enhancement with gadopentetate dimeglumine was evaluated subjectively and quantitatively through calculation of contrast-to-noise ratios (C/Ns) on T1-weighted three-dimensional (3D) Fourier transform (FT) gradient-echo (GRE) and two-dimensional (2D) FT spin-echo (SE) images of the brain in 406 consecutive patients. One hundred one enhancing intracranial lesions were present in 61 patients, including intra-(n = 76) and extraaxial (n = 25) processes of neoplastic (n = 68), infectious or inflammatory (n = 13), ischemic (n = 11), or vascular (n = 9) origin. Enhancement was apparent in all lesions on 2DFT SE and 3DFT GRE images, with similar subjective conspicuity in 86.8% (87 of 101) of lesions. Quantitative C/N measurements for 2DFT SE (mean, 17.6) and 3DFT GRE (mean, 17.2) imaging were not significantly different (P = .72). These findings, along with the other advantages of 3DFT GRE imaging, indicate that 3DFT GRE examinations are likely to play a major role in the performance of contrast-enhanced MR imaging of the brain.     

Focal nodular hyperplasia of the liver on ferumoxides-enhanced MR imaging: features on conventional spin-echo, fast spin-echo and gradient-echo pulse sequences

The aim of this study was to assess the efficacy of a superparamagnetic iron oxide, ferumoxides, in the detection and characterization of focal nodular hyperplasia (FNH) on MR conventional spin-echo (SE), fast spin-echo (FSE) and gradient-echo (GRE) images. Fourteen adults with 27 FNHs were evaluated at 1.5 T before and after injection of ferumoxides. T1-weighted and T2-weighted SE, T2-weighted FSE and T2^*-weighted GRE sequences were used and analysed qualitatively and quantitatively. One hundred percent of FNHs showed a significant postcontrast decrease in signal intensity on T2- and T2*-weighted images. Heavily T2-weighted SE images showed the maximum decrease in FNH signal-to-noise ratio (S/N). Postcontrast GRE T2^*-weighted images improved the detection of the central scar and the delineation of FNHs and demonstrated the best lesion-to-liver contrast-to-noise ratio (C/N). Postcontrast T1-weighted SE images showed the least lesion-to-liver C/N. Ferumoxides-enhanced MR imaging can help detect and characterize FNH. Conventional pre- and postcontrast T2-weighted SE images and postcontrast GRE T2*-weighted images should be used preferentially. Received: 30 November 1998; Revised: 5 April 1999; Accepted: 6 April 1999