Staging of spinal metastasis using special techniques of magnetic resonance imaging

The diagnosis of spine metastasis is a problem of great interest which leaves many questions unanswered. In this field MR imaging plays a fundamental role, as the only technique able to directly demonstrate the changes in bone marrow tissue, bound to tumoral activity. The introduction of gradient-echo (GE) sequences has helped reduce examination time. Moreover, with the accurate choice of pulse-sequence parameters (TR, TE, flip angle) additional information is acquired which is not yielded by conventional spin-echo (SE) sequences. Our study was aimed at evaluating MR sensitivity in the different stages of bone metastatic evolution. The comparative adequacy was evaluated of combined bone scintigraphy and conventional radiology versus MR imaging in 62 patients with vertebral metastases. Time interval between bone scan and/or radiological study and MR exam ranged from 10 days to 8 months. SE and GE T1-weighted images, and SE and GE T2-weighted images on the sagittal plane were employed, and axial images; coronal images were rarely acquired. Metastases were demonstrated by MR imaging at 122 vertebral levels, versus 88 true positives of combined scintigraphy and conventional radiology. Scintigraphic false-positives were observed at 15 vertebral levels, versus 9 with radiography. GE sequences were superior to SE ones in detecting vertebral morphologic lesions and bone marrow involvement thanks to their improved resolution and sensitivity. Moreover, GE sequences demonstrated tumoral bone marrow spread and persistent tumoral activity in the follow-up of spine metastases. Our results point to GE sequences as those of choice because of their higher resolution and sensitivity, which also allow response to treatment to be evaluated.     

CT-MR image data fusion for computer assisted navigated neurosurgery of temporal bone tumors

PURPOSE: To demonstrate the value of multi detector computed tomography (MDCT) and magnetic resonance imaging (MRI) in the preoperative work up of temporal bone tumors and to present, especially, CT and MR image fusion for surgical planning and performance in computer assisted navigated neurosurgery of temporal bone tumors. MATERIALS AND METHODS: Fifteen patients with temporal bone tumors underwent MDCT and MRI. MDCT was performed in high-resolution bone window level setting in axial plane. The reconstructed MDCT slice thickness was 0.8 mm. MRI was performed in axial and coronal plane with T2-weighted fast spin-echo (FSE) sequences, un-enhanced and contrast-enhanced T1-weighted spin-echo (SE) sequences, and coronal T1-weighted SE sequences with fat suppression and with 3D T1-weighted gradient-echo (GE) contrast-enhanced sequences in axial plane. The 3D T1-weighted GE sequence had a slice thickness of 1mm. Image data sets of CT and 3D T1-weighted GE sequences were merged utilizing a workstation to create CT-MR fusion images. MDCT and MR images were separately used to depict and characterize lesions. The fusion images were utilized for interventional planning and intraoperative image guidance. The intraoperative accuracy of the navigation unit was measured, defined as the deviation between the same landmark in the navigation image and the patient. RESULTS: Tumorous lesions of bone and soft tissue were well delineated and characterized by CT and MR images. The images played a crucial role in the differentiation of benign and malignant pathologies, which consisted of 13 benign and 2 malignant tumors. The CT-MR fusion images supported the surgeon in preoperative planning and improved surgical performance. The mean intraoperative accuracy of the navigation system was 1.25 mm. CONCLUSION: CT and MRI are essential in the preoperative work up of temporal bone tumors. CT-MR image data fusion presents an accurate tool for planning the correct surgical procedure and is a benefit for the operational results in computer assisted navigated neurosurgery of temporal bone tumors.     

低场磁共振对膝关节骨挫伤的诊断价值

目的:探讨低场磁共振对外伤性膝关节骨挫伤的临床诊断价值。方法:对53例骨挫伤病例作回顾性分析,重点观察其T1WI、T2WI及STIR上信号改变。结果:本组53例当中X线及CT均未见骨折征象。MRI检查发现骨挫伤53例,交叉韧带损伤4例,侧副韧带损伤1例。半月板损伤6例,合并有膝关节积液26例。T1WI检出骨挫伤49例,T2WI检出47例,STIR检出53例,骨挫伤表现为斑片状、地图状、T1WI低信号、T2WI、STIR高信号。结论:磁共振是目前膝关节骨挫伤的最佳有较检查方法,其中STIR序列能准确显示病变的范围与严重程度,是检查的最佳序列。     

MR contrast arthrography (MRA) in osteochondrosis dissecans.

Osteochondrosis dissecans (OCD) is a lesion that characteristically affects the articular cartilage and subchondral bone with the potential of fragmentation and separation. Exact assessment of cartilaginous and subchondral bony changes is mandatory for the planning of adequate treatment. Therefore, we examined 25 knees using spin echo (SE) and gradient echo (GE) sequences on a 1.5 T superconducting unit prior to and following intraarticular administration of 40 ml of a 2 mmol/L Gd-DTPA solution (MR arthrography). For evaluation (staging) a modified Clanton and DeLee scheme was employed. Verification by arthroscopy or arthrotomy was available in 24 cases. A correct diagnosis of OCD with regard to its type prior to intraarticular injection of Gd-DTPA was possible in 39.3% using T1-weighted SE sequences and in 57.4% on GE sequences. After intraarticular administration of Gd-DTPA, the rate of correct diagnoses improved to 92.9% on T1-weighted SE sequences and 100% on GE sequences. Magnetic resonance arthrography appears to be helpful for the exact assessment of the articular cartilage overlying OCD lesions as well as for the differentiation between partial and complete separation of cartilaginous or osteocartilaginous fragmentations.     

Fast MR imaging of liver metastasis using FLASH and FISP--optimal sequences for T1- and T2*-weighted images

This paper deals with a study to obtain the optimal sequence of gradient echo (GE) for T1- and T2*-weighted images similar to T1- and T2-weighted images of spin echo (SE). Two GE sequences, fast low angle shot (FLASH) and fast imaging with steady-state precession (FISP), were performed in 15 cases of liver metastasis in various combination of flip angle (FA), repetition time (TR), and echo time (TE). The optimal combinations were summarized as follows: 1) T1-weighted FLASH image with FA of 40 degrees, TR of 22 msec and TE of 10 msec, 2) T1-weighted FISP image with FA of 70 degrees, TR of 100 msec, TE of 10 msec, 3) both T2*-weighted FLASH and FISP images with FA of 10 degrees, TR of 100 msec and TE of 30 msec. Not only to provide the adequate T1- and T2*-weighted images but also to enable breath-holding MR imaging, GE sequences can optionally take place SE in cases of deteriorated images caused by moving artifacts. Other applications support the re-examination and further detailing when required, conveniently rather in short time.     

MR imaging of the knee in patients with medial unicompartmental arthroplasty: comparison among sequences at 1.5 T

Purpose

This study was done to test a series of magnetic resonance (MR) imaging sequences of the knee after medial unicompartmental arthroplasty.

Materials and methods

Four patients who had undergone Oxford III medial unicompartmental arthroplasty underwent 1.5-T MR imaging of the operated knee using coronal sequences: T1-weighted spin-echo (SE), T1-weighted turbo SE (TSE), proton-density (PD)- and T2-weighted TSE, T1-weighted gradient echo (GE), short-tau inversion recovery (STIR), multi echo data image combination (MEDIC), T2*-weighted GE, volumetric interpolated breath-hold examination (VIBE), and dual-echo steady state (DESS). For each sequence, we evaluated the visibility of the anatomical structures of the central pivot, lateral compartment, and anterior compartment using a semiquantitative score (0=total masking; 1=insufficient visibility; 2=sufficient visibility; 3=optimal visibility). The sum of the scores given to each sequence was divided by the maximal sum, obtaining a percentage visibility index. Friedman and sign tests were used for statistical analysis.

Results

MR examination time was 30–32 min. No patients reported pain, heat or other local discomfort. The visibility index ranged between 83% and 89% for the first four sequences without significant differences among them, 58% for STIR and 11%–36% for the last five sequences. Significant differences were found between each of the four first sequences and the remaining sequences (p<0.004) and between STIR and the last five sequences (p<0.008).

Conclusions

MR imaging of the knee after medial unicompartmental arthroplasty was not associated with adverse events. An imaging protocol including SE, TSE and STIR sequences could be used to study the knee with unicompartmental arthroplasty.     

磁共振各序列在骨挫伤及骨转移诊断中的应用

目的:探讨磁共振各序列在骨挫伤及骨转移诊断中的应用价值。方法:对商丘市第一人民医院的45例骨挫伤及骨转移患者行磁共振检查,磁共振扫描前经CR或CT扫描。使用GESigna Contour 0.5T超导型扫描机,脊柱扫描使用脊柱线圈,膝关节扫描使用膝关节线圈,行矢状位、冠状位及横断扫描。扫描序列包括各序列。结果:所有45例接受磁共振检查的患者中,骨转移并骨损伤10例,膝关节骨挫伤合并半月板、韧带损伤22例,骨转移并伴有相邻椎体脊髓水肿13例。结论:对于骨挫伤及骨转移脂肪抑制序列T2WI检查好于TSET2WI及FL2DT2WI,与SET1WI相结合能够更敏感的发现骨挫伤及骨转移改变。     

Magnetic resonance findings in chronic osteomyelitis fistula

INTRODUCTION: Osteomyelitis is a common inflammatory process caused by an infection which is usually from gram-positive germs. Acute, subacute and chronic forms can be distinguished both clinically and radiographically, each of them presenting different patterns but which are not always easy to recognize. Besides clinical-laboratory data, imaging methods are also useful to make the diagnosis; in chronic forms, MRI has higher sensitivity in recognizing the active foci and the presence of sinus tracts than the other techniques. MATERIAL AND METHODS: We examined nine patients with suspected chronic osteomyelitis with a sinus tract, all of them submitted to radiographic and MR examinations. MRI was performed with a .5 T magnet using a surface coil for joint studies; T1-weighted SE (TR 300-500, TE 20), T2-weighted GE (TR 500-700, TE 20, FA 35 degrees) and FIR sequences with fat suppression (TR 3000, TE 20, TI 100) were performed on the axial, sagittal and coronal planes. Three patients underwent CT too. RESULTS: Radiography showed the osteostructural changes as osteolytic and osteosclerotic areas. CT depicted not only the changes seen radiographically, but also increased bone marrow density. MRI demonstrated active foci of bone marrow appearing as low-intensity areas in T1, with increased intensity in T2 GE and fat-suppressed FIR images; it also depicted the sinus tracts as areas of decreased signal on T1 and of increased signal on FIR images. CONCLUSIONS: Based on our experience and in agreement with the literature data, we believe that MRI is more useful to diagnose the active foci of bone marrow and the sinus tracts in chronic osteomyelitis, especially with T1-weighted SE and fat-suppressed FIR sequences.     

The knee joint in early juvenile idiopathic arthritis. An ROC study for evaluating the diagnostic accuracy of contrast-enhanced MR imaging

Purpose: Diagnosis of juvenile idiopathic arthritis (JIA) remains difficult due to unspecific clinical and laboratory findings, especially in early stages of the disease. The purpose of our study was to determine the sensitivity and specificity of MR imaging in diagnosing JIA of the knee joints.Material and Methods: Forty children (3-17 years old) clinically diagnosed with JIA (follow-up >1 year) of a knee joint and a control group of 40 children with painful knee joints (MR diagnosis: bone bruise of the knee (n=7), normal knee joint (n=12), osteomyelitis (n=6), septic arthritis (n=2), bone tumor (n=7) and miscellaneous bone lesions (n=6)) were examined using a 1.5 T MR unit. T1-weighted spin-echo (SE), T2-weighted fast SE, contrast-enhanced T1-weighted SE and 2D gradient echo sequences were performed. The receiver operating characteristic (ROC) curves evaluation was conducted by 5 independent radiologists.Results: The positive criteria for diagnosing JIA were joint effusions (n=40), contrast-enhancing synovitis (n=39), cartilage lesions (n=15), subchondral erosions and bony destruction (n=1). Sensitivity and specificity were 93.5% and 92.5%, respectively. Both cases of septic arthritis were misdiagnosed as JIA by all radiologists.Conclusion: Contrast-enhanced MR imaging seems to be a highly sensitive tool in establishing the diagnosis of JIA.     

Efficacy of contrast medium use for neuroimaging at 3.0 T: utility of IR-FSE compared to other T1-weighted pulse sequences

As inversion-recovery (IR) technique improves T1 contrast at high field strength, signal enhancement by T1-shortening contrast media may be affected. To clarify the different enhancement properties at 3.0 T, the authors compared T1-weighted sequences. Twelve contrast-enhancing lesions were investigated by spin-echo (SE), inversion recovery fast spin-echo (IR-FSE), two-dimensional gradient-echo (2D GE), and magnetization-prepared three-dimensional gradient-echo (3D GE) sequences and evaluated by comparing signal-intensity enhancements within the lesions. In addition, signal-to-noise-ratios (SNR) and contrast-to-noise-ratios (CNR) were measured. On average, signal enhancement of the lesions amounted to 60% for SE, 57% for IR-FSE, 32% for 2D GE, and 35% for 3D GE images. CNR of gray matter versus white matter was significantly higher for IR SE and GE imaging than for genuine SE and 2D GE acquisitions (Wilcoxon test), while 2D GE imaging alone had an excellent SNR. As IR-FSE images provide an excellent CNR for gray and white matter in the brain and contrast enhancement performs almost similarly well compared with SE imaging, this technique appears to be well suited for T1-weighted neuroimaging without and with contrast enhancement at 3.0 T. However, the inherent blurring of the IR-FSE can lead to poor performance for very small lesions.     

Assessment of hemorrhage in pituitary macroadenoma by T2*-weighted gradient-echo MR imaging

BACKGROUND AND PURPOSE: Intratumoral hemorrhage occurs frequently in pituitary macroadenoma and manifests as pituitary apoplexy and recent or old silent hemorrhage. T2*-weighted gradient-echo (GE) MR imaging is the most sensitive sequence for the detection of acute and old intracranial hemorrhage. T2*-weighted GE MR imaging was used to investigate intratumoral hemorrhage in pituitary macroadenomas. MATERIALS AND METHODS: Twenty-five consecutive patients who underwent total or subtotal resection of pituitary macroadenoma with heights from 17 to 53 mm, including 1 patient with classic pituitary apoplexy, underwent MR imaging before surgery, including T2*-weighted GE MR imaging. For histologic assessment of the hemorrhage in whole surgical specimens, we used hematoxylin-eosin staining. RESULTS: T2*-weighted GE MR imaging detected various types of dark lesions, such as "rim," "mass," "spot," and "diffuse" and combinations, indicating clinical and subclinical intratumoral hemorrhage in 12 of the 25 patients. The presence of intratumoral dark lesions on T2*-weighted GE MR imaging correlated significantly with the hemorrhagic findings on T1- and T2-weighted MR imaging (P < .02 and <.01, respectively), and the surgical and histologic hemorrhagic findings (P < .001 and <.001, respectively). CONCLUSION: T2*-weighted GE MR imaging could detect intratumoral hemorrhage in pituitary adenomas as various dark appearances. Therefore, this technique might be useful for the assessment of recent and old intratumoral hemorrhagic events in patients with pituitary macroadenomas.     

外伤性膝关节前外侧韧带损伤的MR影像特征及相关性分析

目的探讨外伤所致膝关节前外侧韧带损伤病人的MR影像特征,并分析其与前交叉韧带撕裂、外侧半月板撕裂及骨挫伤的相关性,为深入研究前外侧韧带对膝关节稳定性的作用提供可靠依据。方法回顾性分析2016年1月—2017年2月间因外伤进行膝关节MRI检查的320例病人(共321膝)的影像资料。采用美国GE公司生产的Signa HDe 1.5 T MR扫描设备,分别行膝关节斜矢状面T1WI、质子密度加权成像(PDWI)和冠状面、横断面PDWI扫描。根据前外侧韧带的完整性和损伤部位对所有病人进行分类统计。采用独立性卡方检验对前外侧韧带撕裂与前交叉韧带撕裂、外侧半月板撕裂及骨挫伤的相关性进行分析。结果全部病人膝关节MR影像均可显示前外侧韧带,显示率为100%。151/321膝(47.0%;95%CI为41.6%~52.5%)存在前外侧韧带损伤,其中累及胫骨部、股骨部及半月板部的分别为97膝、96膝及65膝。前交叉韧带撕裂158膝,外侧半月板撕裂98膝,股骨外侧髁挫伤58膝,外侧胫骨平台挫伤71膝,分别与前外侧韧带撕裂具有相关性(均P0.001)。结论 MRI检查可以很好地显示前外侧韧带解剖及其损伤情况。膝关节前外侧韧带损伤与前交叉韧带撕裂、外侧半月板撕裂及膝外侧骨挫伤具有相关性。     

Comparison of inversion recovery fast spin-echo (FSE) with T2-weighted fat-saturated FSE and T1-weighted MR imaging in bone marrow lesion detection

 Objective To prospectively compare inversion recovery (IR) fast spin-echo (FSE) with T1-weighted spin-echo (SE) and T2-weighted chemical-shift fat-saturated (FS) FSE magnetic resonance sequences in the detection of bone marrow abnormality. Design. Twenty-nine sets of T1-weighted SE [400–640/10–20 (TR/TE)], T2-weighted FS-FSE [2400–3800/91–112/8 (TR/TE/ETL)], and IR-FSE [3700–6000/12–14/170/8 (TR/TE/T1/ETL)] images were acquired with a 1.5-T magnet in 27 patients with bone marrow lesions. The visibility, margination, and extent of 41 lesions, image quality, contrast, and artifacts were qualitatively and quantitatively compared. Results. The lesions were more conspicuous on the IR-FSE than on the T1-weighted SE and T2-weighed FS-FSE images. The extent of lesions was similar for all three sequences. Image quality was better and there were fewer motion artifacts on the T1-weighted images. The mean lesion contrast-to-noise ratio was significantly higher on the T1-weighted images (p<0.05). Conclusion. The IR-FSE sequence is highly sensitive for detecting bone marrow pathology, with scan time comparable to the T1-weighted SE and T2-weighted FS-FSE sequences.     

Detection of articular cartilage lesions: experimental evaluation of low- and high-field-strength MR imaging at 0.18 and 1.0 T

The objective of this study was to compare the diagnostic performance of a dedicated orthopedic magnetic resonance (MR) imaging system (0.18 T) and a conventional MR imaging system (1.0 T) in the detection of articular cartilage lesions. Fifty knee joint specimens of pigs with artificially created articular cartilage lesions of different diameters, grades (2-3), and localizations, as well as 50 joints with intact articular cartilage, were imaged at 0. 18 and 1.0 T. Diagnostic performance was determined by means of receiver operating characteristics (ROC) analysis with three independent observers. For none of the pulse sequences used at 0.18 T or 1.0 T areas under ROC curves (A(z)) showed significant differences between the three observers. A(z) values from averaged data were as follows: a) 0.18 T: T1-weighted spin echo (SE): 0.70, proton-density-weighted SE: 0.59, T2-weighted SE: 0.61, two-dimensional (2D) gradient-echo (GRE): 0.73, 3D GRE: 0.75; and b) 1.0 T: T1-weighted SE: 0.73, fat-suppressed T2-weighted turbo-SE: 0. 79, 2D fast low-angle shot (FLASH): 0.79, fat-suppressed 3D FLASH: 0. 96, and water-excited 3D double-echo steady state (DESS): 0.96. With the use of 3D pulse sequences, the high-field system demonstrated a significantly better diagnostic performance than the low-field system in the detection of grades 2 and 3 articular cartilage lesions (P < 0.001).     

MR imaging of focal lung lesions: elimination of flow and motion artifact by breath-hold ECG-gated and black-blood techniques on T2-weighted turbo SE and STIR sequences.

Respiratory and cardiac motion correction may result in better turbo spin-echo (SE) imaging of the lung. To compare breath-hold cardiac-gated black-blood T2-weighted turbo SE and turbo short-inversion-time inversion-recovery (STIR) magnetic resonance (MR) imaging pulse sequences with conventional breath-hold turbo SE and half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequences for lesion conspicuity of focal lung lesions, 42 patients with focal lung lesions were prospectively studied with MR imaging at 1.5 T. Helical computed tomography was used as a reference. In comparison with the conventional breath-hold turbo SE sequence, all black-blood sequences had fewer image artifacts arising from the heart and blood flow. The overall image quality for the black-blood turbo SE and turbo STIR sequences was superior to that for the breath-hold turbo SE and HASTE sequence (P < 0.01). Not only focal lung lesions but also surrounding inflammatory changes were clearly visualized with these two sequences. With the HASTE sequence, although several slices could be obtained in one breath-hold, both the tumor and vessels appeared blurred. We conclude that T2-weighted turbo SE and turbo STIR imaging of the lung with effective suppression of flow and motion artifacts provide high-quality images in patients with focal lung lesions.     

Focal hepatic lesions: comparative MR imaging at 0.5 and 1.5 T

Twenty-nine patients with known or suspected malignancy were studied with identical T1-weighted (spin echo [SE] and inversion recovery [IR]) and T2-weighted SE magnetic resonance (MR) imaging at 0.5 and 1.5 T to evaluate the relative sensitivities of these sequences for detecting focal hepatic lesions. At 0.5 T, 98 lesions were detected with the IR sequence, 86 with the T1-weighted SE sequence, and 96 with the T2-weighted sequence. At 1.5 T, 93 lesions were detected with the IR sequence, 70 with the T1-weighted SE sequence, and 99 with the T2-weighted sequence. Although the lack of pathologic correlation precluded establishment of true sensitivity and specificity rates, data showed that magnetic field strength resulted in no significant difference for detecting focal hepatic lesions. No single sequence was shown to be significantly superior, although the T1-weighted SE sequence at 1.5 T was significantly inferior to the other sequences for detecting focal hepatic lesions. T1-weighted SE imaging at 0.5 T was significantly inferior to T1-weighted IR and T2-weighted imaging at both magnetic field strengths for detecting focal lesions in the left lobe of the liver. The authors conclude that T1-weighted IR and T2-weighted sequences alone will result in optimal MR imaging for the detection of focal hepatic lesions at 0.5 and 1.5 T.     

Comparison of MR sequences in early cerebral infarction at 0.5 T

Purpose: To compare the diagnostic values of fluid-attenuated inversion recovery (FLAIR) and gradient spin-echo (GRASE) with those of conventional spin-echo (SE) and fast SE T2-weighted sequences in the evaluation of acute cerebrovascular lesions at 0.5 T.Material and Methods: Twenty-two consecutive patients with the clinical diagnosis of acute cerebrovascular accident were examined by MR imaging within the first 48 h of ictus. MR examination included 5-mm axial conventional SE and turbo SE (TSE) T2-weighted, dual-echo GRASE and FLAIR sequences. The patients also had pre- and postcontrast T1-weighted axial images. Two examiners evaluated the images and scored the conspicuity of the acute lesions.Results: Regardless of location, FLAIR provided the best lesion conspicuity in the detection of acute infarcts, followed by the GRASE sequence. In the posterior fossa, TSE and SE demonstrated the lesions better than GRASE and FLAIR techniques. In the detection of hemorrhagic elements within the ischemic region, TSE demonstrated statistically significant superiority over other sequences.Conclusion: In the detection of acute ischemic lesions in locations other than the posterior fossa, FLAIR provided the best lesion conspicuity among four T2-weighted sequences, including SE, TSE, GRASE and FLAIR. However, for the posterior fossa examination, preference of SE or TSE T2-weighted sequences is suggested.     

The role of T2-weighted fast-spin-echo imaging in the diagnosis of meniscal tears

The objective of this study was to compare the accuracy of T2-weighted fast-spin-echo (FSE) and intermediate-weighted spin-echo (SE) MR imaging in the detection of meniscal tears. Seventy-six patients (152 menisci) who had arthroscopic surgery after MR imaging of the knee were studied. MR imaging included intermediate-weighted SE and T2-weighted FSE sequences. The use of intermediate-weighted conventional SE images, T2-weighted FSE images, and a combination of both sequences were evaluated in the detection of meniscal tears. T2-weighted FSE imaging was slightly less accurate than intermediate-weighted SE imaging in the diagnosis of meniscal tears. Interpretation of the menisci using both intermediate-weighted SE and T2-weighted FSE imaging did not improve the accuracy over intermediate-weighted imaging evaluated in isolation.     

MR imaging in patients with Crohn disease: value of T2- versus T1-weighted gadolinium-enhanced MR sequences with use of an oral superparamagnetic contrast agent

PURPOSE: To prospectively compare oral contrast-enhanced T2-weighted half-Fourier rapid acquisition with relaxation enhancement (RARE) magnetic resonance (MR) imaging with T1-weighted gadolinium-enhanced fast low-angle shot (FLASH) MR and standard examinations in the evaluation of Crohn disease. MATERIALS AND METHODS: Institutional review board approval and informed consent were obtained. Fifty-nine patients with Crohn disease underwent MR imaging after oral administration of a superparamagnetic contrast agent; RARE plain and fat-suppressed sequences and FLASH sequences were performed before and after intravenous injection of gadolinium chelate. References were endoscopic, small-bowel barium, computed tomographic, ultrasonographic, and clinical-biochemical scoring of disease activity. Two radiologists analyzed MR images for presence and extent of Crohn disease lesions, presence of strictures or other complications, and degree of local inflammation. MR findings were correlated with endoscopic, radiologic, and clinical data (kappa statistic and Spearman rank correlation test). RESULTS: T2-weighted MR was 95% accurate, 98% sensitive, and 78% specific for detection of ileal lesions. Agreement between T1- and T2-weighted images ranged from 0.77 for ileal lesions to 1.00 for colic lesions. T2-weighted MR enabled detection of 26 of 29 severe strictures, 17 of 24 enteroenteric fistulas, and all adhesions and abscesses; T1-weighted MR enabled detection of 20 of 29 severe strictures, 16 of 24 enteroenteric fistulas, and all adhesions and abscesses. Complications leading to surgery were found in 12 (20%) patients; these were assessed correctly with either T1- or T2-weighted images. T2-weighted signal intensities of the wall and mesentery correlated with biologic activity (P < .001, r of 0.774 and 0.712, respectively). Interobserver agreement was 0.642-1.00 for T2-weighted and 0.711-1.00 for T1-weighted images. CONCLUSION: T2-weighted MR can depict Crohn disease lesions and help assess mural and transmural inflammation with the same accuracy as gadolinium-enhanced T1-weighted MR. Combination of gadolinium-enhanced T1- and T2-weighted sequences is useful in the assessment of Crohn disease.     

Usefulness of opposed-phase gradient-echo technique in the diagnosis of occult lesions of the knee and comparison with traditional T1-weight sequences (in-phase)

PURPOSE: To investigate the usefulness of opposed-phase gradient-echo (GRE) technique in detecting occult posttraumatic bone injuries in the knee. Occult injuries account for pain and, if not properly treated, may progress to severe chondral and bone damage. An early diagnosis provided by MRI can help avoid interventional procedures. MATERIAL AND METHODS: We submitted to MRI of the knee 51 patients (32 men and 19 women) with negative plain radiographic findings and at least one traumatic bone injury at MRI. MR examinations were performed with a 0.5 T unit and included a conventional SE or GRE T1-weighted sequence and an opposed phase GRE sequence on the coronal or sagittal plane (2-3 minutes acquisition). To assess the lesion number and conspicuity, images were retrospectively reviewed by two readers. Injury conspicuity was graded as: 0 (poorly visible), 1 (visible), and 2 (well visible). Marrow-to-injury signal intensity ratio was calculated in 30 patients: a ROI was positioned in the site of highest signal intensity and adjacent bone marrow and the ratio analyzed with Student's "t"-test. RESULTS: In-phase and out-of-phase images showed 71 injuries in 51 patients. Conventional (in-phase) imaging missed 6/71 lesions. Injury conspicuity on out-of-phase images was of grade 2 in 58 cases (81.6%) and of grade 1 in 13 cases (18.3%), versus 23 (32.3%) and 42 (59.1%), respectively, on conventional images. Injury conspicuity was graded as 0 in 6 cases (8.4%) on conventional images. Quantitative analysis of marrow-to-injury signal intensity ratio showed higher values for out-of-phase GRE than conventional images. CONCLUSION: Opposed-phase GRE are quick sequences available on all MR systems which appear superior to conventional T1-weighted images in detecting occult injuries in the knee. Injuries are more conspicuous because their signal intensity is lower due to the simultaneous presence of fat and water protons, which is typical of bone trauma, GRE sequences make a useful and rapid complement to T1-/T2-weighted fat saturation acquisitions in the study of the post-traumatic knee.