A comparative evaluation of a RARE-based single-shot pulse sequence for diffusion-weighted MRI of musculoskeletal soft-tissue tumors

The purpose of this study was to evaluate the feasibility of a centric-reordered modified rapid acquisition with relaxation enhancement (mRARE) sequence for single-shot diffusion-weighted magnetic resonance imaging (DWI) of soft-tissue tumors in the musculoskeletal system. In the evaluation of this sequence, DWI was performed in a liquid phantom, in excised human tumor samples embedded in bovine muscle, and in nine patients suffering from different types of soft-tissue tumors. The measurements were compared to DWI using a spin-echo sequence and a single-shot echo planar imaging (EPI) sequence. The phantom measurements in water and dimethyl sulfoxide showed a difference of less than 5% when comparing the apparent diffusion coefficients (ADCs) determined by the mRARE sequence and the two other techniques. Comparing mRARE and EPI, the differences in the ADCs were about 10% in the excised tumor tissue and, typically, about 15% in vivo. ADCs between 0.8×10^–3 mm²/s and 1.4×10^–3 mm²/s, depending on the tumor type, were found in solid tumor tissue; in cystic tumor areas, ADCs greater than 2.0×10^–3 mm²/s were determined with the mRARE and the EPI sequences. Diffusion-weighted images of the mRARE sequence were less distorted than those acquired with the single-shot EPI sequence, and provided more anatomic information, since the muscle and fat signals were considerably higher.     

MRI of osteonecrosis

Osteonecrosis is a relatively common condition, which may be idiopathic or secondary to a variety of clinical situations. It may involve the subarticular region of a joint, when it is commonly referred to as ischaemic necrosis, or the metaphyseal regions of long bones, when it is referred to as bone infarction. In both situations, early lesions may be radiographically occult. However, magnetic resonance imaging (MRI) is very sensitive in identifying and characterizing osteonecrosis. This review illustrates the varied MRI features of osteonecrosis that enable a confident diagnosis to be made. Complications and differential diagnosis are also considered.     

Bone marrow characterization in the lumbar spine with inner volume spectroscopic CPMG imaging studies

The authors describe new magnetic resonance (MR) spectroscopic and postprocessing methods for characterizing major proton peaks and their spectral T2 values in many small voxels throughout extensive regions of bone marrow within the adult lumbar spine. The techniques are based on spectroscopic interrogation of 128 voxels along columns oriented through the spine at eight TE values. Mean fat content measurements, based on quantification of the proton peaks of water and saturated fat (-CH₂-)_n, corrected for T2 decay, ranged from 40% to 60%. The mean T2 value of the lipid peak, 113 msec ±21, was significantly longer (P <.001) than that of water (71 msec ± 14). The techniques combine features of MR spectroscopy and imaging most suited for spatially efficient coverage of bone marrow at spectral resolutions sufficient for intravoxel fat or water content measurements. The methods introduced provide a practical, quantitative means for characterizing vertebral marrow in diseases affecting marrow cellularity.     

Magnetic resonance imaging of bone marrow changes in Gaucher disease during enzyme replacement therapy: first German long-term results

Objective: . Since 1991, enzyme replacement therapy (ERT) has been available for patients with Gaucher disease in Germany. The aim of this study was to analyse the MR pattern of bone marrow involvement and response to ERT in Gaucher disease type I. Patients and design: . Thirty patients with Gaucher disease type I had MRI examinations prior to initiation of ERT with alglucerase/imiglucerase and during follow-up. Median MR follow-up and duration of ERT were 36 months. Coronal T1- and T2-weighted spin-echo images of the lower extremities were obtained to evaluate changes in the appearance of yellow marrow. MR images were categorized as having either a homogeneous (type A) or non-homogeneous patchy (type B) appearance of bone involvement and response to ERT was assessed by two radiologists. Results: . Overall, 19 of 30 patients (63%) showed an increased signal intensity on T1- and T2-weighted images after 36 months of ERT, consistent with partial reconversion of fatty marrow during treatment. Focal bone lesions surrounded by a low signal intensity (SI) rim did not respond to ERT, suggesting bone infarcts. Of the 11 patients with bone infarcts (low SI rim lesion), 82% had the non-homogeneous type B pattern (P=0.0021). In 86% of patients with splenectomy, bone infarcts were seen (P<0.05). Conclusions: . MRI using T1- and T2-weighted spin-echo sequences is a valuable, non-invasive method for monitoring bone marrow response in patients receiving ERT. A non- homogeneous patchy signal intensity of bone marrow involvement correlates with the presence of bone infarcts (P=0.0021). Received: 27 July 2000 Revision requested: 26 October 2000 Revision received: 9 March 2001 Accepted: 12 March 2001     

MRI of the marrow in the paediatric skeleton

Magnetic resonance imaging (MRI) has greatly advanced evaluation of marrow diseases of the paediatric skeleton. As with many other aspects of paediatric radiology it is important to recognize the normal variations in the appearance of the marrow that occur in the growing child. These normal variations need to be differentiated from diseases and conditions that affect the marrow. This review describes the normal changes that occur in children with age, and the appearances of the pathological changes seen in infection, infiltration, haematological disorders, transplantation and radiation therapy.     

血液病骨髓MR磁化转移成像初步研究

目的:本实验旨在研究MR磁化转移成像技术(magnetic transfer,MT)与血液病治疗中骨髓的微结构变化的相关性。方法:35例确诊的恶性血液病患者通过MR磁化转移成像及髂嵴穿刺活检进行对照分析,测定骨髓磁化转移率(mag-netic transfer ratio,MTR),细胞构成(cellularity)变化和肿瘤浸润分数(tumor fraction,TF)。同期30例无血液系统疾病患者进行了髂骨的磁化转移成像及MTR测定。对血液病组和对照组分别进行定量均值计算及相关分析。结果:血液病组MTR为0.105±0.034,对照组MTR为0.103±0.059,MTR血液病组与对照组间差异无显著性(P>0.05),血液病组中不同组织学类型的骨髓MTR组间差异亦无显著性(P>0.05);肿瘤复发组与肿瘤缓解组组间MTR差异亦无显著性(P>0.05)但不同细胞构成比MTR组间差异有统计学意义(P<0.05)。结论:血液病骨髓磁化转移的变化可能与骨髓有形细胞数目变化有关。     

颅骨与腰椎骨髓转化的MR定量研究及临床应用

目的 :从定量角度探讨MRI上颅骨与腰椎骨髓转化特点并评估骨髓相对信号强度 (RSI)的诊断价值。方法 :正常组 2 5 7例 ,其中颅骨 10 1例 ,腰椎 15 6例 ;异常组 6例 ,白血病 5例 ,多发性骨髓瘤 1例。MR扫描仪为 0 .5TPhilipsGyroscan。成像序列为TSET1 WI ,测定颅骨和腰椎骨髓的RSI并进行F检验、相关分析及动态分析。结果 :腰椎和颅骨骨髓RSI与年龄呈明显正相关 (P <0 .0 1)。颅骨骨髓RSI的净增量及平均增长速度大于腰椎。正常组颅骨骨髓与腰椎骨髓RSI在不同年龄段之间差异有显著性意义。异常组骨髓RSI值明显低于相应年龄段正常均值。结论 :骨髓RSI在不同年龄段间存在显著性差异 ,颅骨骨髓转化程度、速度均较腰椎显著。RSI对弥漫性骨髓浸润性疾病有较高的敏感性 ,但缺乏特异性。     

Volume (three-dimensional) fast spin-echo imaging of the lumbar spine

RATIONALE AND OBJECTIVES: The purpose of this study was to prospectively evaluate a proton-density-weighted, three-dimensional (3D) volume fast spin-echo (SE) pulse sequence in the assessment of the lumbar spine for suspected spondylosis. MATERIALS AND METHODS: Twenty-eight patients referred for low back or lower extremity pain were imaged with both a two-dimensional (2D) protocol and a proton-density-weighted 3D volume fast SE imaging. The spinal canal, conus medullaris, intervertebral disks, neural foramina, bone marrow, and spinal alignment shown with the 3D volume fast SE pulse sequence were independently assessed by two neuroradiologists. These findings were compared with those of the routine 2D studies. RESULTS: Interpretation of disk protrusions and stenoses of the neural foramina were concordant between both protocols. No instance of cord abnormality was detected with either protocol. CONCLUSION: A 3D volume fast SE proton-density-weighted pulse sequence may provide information comparable to that of routine 2D imaging. Advantages of volume imaging include thinner sections, the capability of reconstruction into any plane, and the potential to decrease imaging time.     

Useful internal standards for distinguishing infiltrative marrow pathology from hematopoietic marrow at MRI

The objective of this study was to establish internal standards on MRI differentiating infiltrative marrow pathology from hematopoietic marrow. The T1-weighted images of 74 patients (51 biopsy-proven; 23 clinical follow-up) were reviewed retrospectively. The relative signal intensity of bone marrow was compared to adjacent skeletal muscle (n = 65) and/or nondegenerated intervertebral disk (n = 53). Twenty foci were hyperintense compared to muscle, of which 17 (85%) cases represented normal red marrow (P < .0001); 45 were isointense or hypointense compared to muscle, of which 44 (98%) represented infiltrative marrow processes (P < .0001). Twelve were hyperintense compared to disk, of which 12 (100%) represented normal red marrow (P < .0001); 41 were isointense or hypointense compared to disk, of which 40 (98%) represented infiltrative marrow processes (P < .0001). On T1-weighted spin-echo MRI, skeletal muscle and intervertebral disk may serve as internal standards for differentiating infiltrative pathology from normal hematopoietic marrow. Marrow lesions that are relatively isointense or hypointense to muscle and/or disk should not be considered normal hematopoietic marrow.     

Regional migratory osteoporosis: a review illustrated by five cases

Regional migratory osteoporosis is an uncommon self-limiting disease characterized by an arthralgia which migrates between the weight-bearing joints of the lower limb. The radiological features of the disease obtained by conventional radiography, CT, MRI and radionuclide scintigraphy are illustrated by means of five case reports. These range from the most common presentation of sequential, proximal to distal spread in the lower limb to the rare intra-articular form, and disease involving the axial skeleton is also recognized. Clinical and radiographical features often overlap with those of diseases such as transient osteoporosis of the hip and transient bone marrow oedema syndrome, which is reflected in confusing terminology. Histological sampling is usually unnecessary; the radiological features are characteristic and the histological findings are not specific. Regional migratory osteoporosis is associated with systemic osteoporosis. This association is probably under-recognized, and has implications for the pathophysiology of the disease and for treatment.     

Bone bruises: MR characteristics and histological correlation in the young pig

PURPOSE: To correlate magnetic resonance (MR) signal characteristics of bone bruises with histological findings. MATERIALS AND METHODS: In 14 tibiae of young pigs, bone bruises were created in the proximal tibial metaphysis. The signal intensity seen on the MR images were correlated with histological findings. The following findings were evaluated: (a) changes of signal intensity on the tibiae; (b) changes of histology on the tibiae; and (c) changes of (a) and (b) on follow-up examinations. RESULTS: We observed three types of injuries on T1-weighted images: focal or diffuse low signal, normal signal and linear low signal intensities. Severe hemorrhagic areas showed low signal intensities on all sequences of MR imaging. Fast spin-echo (FSE) T2-weighted images showed a more distinct low signal intensity than T1-weighted images. FSE short tau inversion recovery (STIR) and FSE fat saturated (FSE-FS) T2-weighted images showed similar signal intensities with FSE T2-weighted images. FS T1-weighted enhanced images showed low signal intensities with variable enhancements. Upon histological examination, hemorrhages and edemas were prominent at the subcortical areas of the contusion sites. The areas of dense, low signal intensities in all imaging sequences showed signs of severe hemorrhage. The areas of diffuse low signal and enhanced areas showed mixed areas of hemorrhages and edemas. Follow-up MR imaging showed evolution of the processes of hemorrhages and edemas with fatty marrow changes. CONCLUSIONS: MR imaging can depict changes in the bone marrow resulting from direct injury to the bone. MR imaging is a useful tool for evaluating the evolution of bone bruises.     

MRI of the spine in cobalamin deficiency: the value of examining both spinal cord and bone marrow

We observed a case of pernicious anaemia in which MRI of the spine demonstrated both intrinsic lesions of the spinal cord and abnormal signal in the bone marrow. The latter resolved with replacement therapy. Only partial recovery of the cord lesions was observed.     

Bone marrow diffusion in osteoporosis: evaluation with quantitative MR diffusion imaging

PURPOSE: To determine the diffusion of vertebral body marrow with quantitative MR diffusion imaging and to examine whether differences exist between subjects with postmenopausal osteoporosis and premenopausal control subjects. MATERIALS AND METHODS: A total of 44 consecutive women (mean age, 70 years) with documented bone mineral density (BMD) measured by dual energy x-ray absorptiometry (T-score) and 20 normal subjects (mean age, 28 years) were examined with echo-planar diffusion imaging at 1.5 T using b values of 0, 20, 40, 60, 80, 100, 200, 300, 400, and 500 seconds/mm2. Extravascular diffusion (D) and apparent diffusion coefficient (ADC) were calculated and results from both groups compared. RESULTS: Both D and ADC values tended to decrease with decreasing BMD. Mean D values were significantly lower in postmenopausal women with reduced BMD (0.42 +/- 0.12 x 10(-3) mm2/second) than normal premenopausal women (0.50 +/- 0.09 x 10(-3) mm2/second). Mean ADC values were significantly lower both in subjects with reduced BMD (0.41 +/- 0.10 x 10(-3) mm2/second) and normal BMD (0.43 +/- 0.08 x 10(-3) mm2/second) compared to normal controls (0.49 +/- 0.07 x 10(-3) mm2/second). CONCLUSION: Accumulation of fatty bone marrow associated with osteoporosis is reflected by a decrease in D and ADC. Diffusion imaging may prove useful in the study of osteoporosis.     

T1-Weighted MR imaging of the brain using a fast inversion recovery pulse sequence

The purpose of this paper was to develop and evaluate a fast inversion recovery (FIR) technique for T1-weighted MR imaging of contrast-enhancing brain pathology. The FIR technique was developed, capable of imaging 24 sections in approximately 7 minutes using two echoes per repetition and an alternating echo phase encoding assignment. Resulting images were compared with conventional T1-weighted spin echo (T1SE) images in 18 consecutive patients. Compared with corresponding T1SE images, FIR images were quantitatively comparable or superior for lesion-to-background contrast and contrast-to-noise ratio (CNR). Gray-to-white matter and cerebrospinal fluid (CSF)-to-white matter contrast and CNR were statistically superior in FIR images. Qualitatively, the FIR technique provided comparable lesion detection, improved lesion conspicuity, and superior image contrast compared with T1SE images. Although FIR images had greater amounts of image artifacts, there was not a statistically increased amount of interpretation-interfering image artifact. FIR provides T1-weighted images that are superior to T1SE images for a number of image quality criteria.     

Diffusion-Weighted Imaging with Sensitivity Encoding (SENSE) for Detecting Cranial Bone Marrow Metastases: Comparison with T1-Weighted Images

Objective

This study was designed to determine whether diffusion-weighted imaging (DWI) with sensitivity encoding (SENSE) could detect bone marrow involvement in patients with cranial bone marrow (CBM) metastases. DWI results obtained were compared with T1-weighted imaging (T1WI) findings.

Materials and Methods

DWI with sensitivity encoding (SENSE; b value = 1,000) was performed consecutively in 13 patients with CBM metastases diagnosed pathologically and radiologically. CBM lesions were dichotomized according to the involved site, i.e., skull base or calvarium. Two radiologists qualitatively evaluated the relative conspicuousness of CBM lesions and image qualities in B0 and in isotropic DWI and in T1WI. According to region of interest analysis of normal and pathologic marrow for these three sequences, absolute signal difference percentages (SD%) were calculated to quantitatively analyze lesion contrast.

Results

All 20 lesions in 13 patients with CBM metastases revealed abnormal DWI signals in areas corresponding to T1WI abnormalities. Both skull base and calvarial lesions provided better lesion conspicuousness than T1WI and B0 images. Although the image quality of DWI was less satisfactory than that of T1WI, relatively good image qualities were obtained. Quantitatively, B0 images (SD%, 82.1 ±7.9%) showed better lesion contrast than isotropic DWI (SD%, 71.4 ±13.7%) and T1WI (SD%, 65.7 ±9.3%) images.

Conclusion

For scan times of less than 30 seconds, DWI with SENSE was able to detect bone marrow involvement, and was superior to T1WI in terms of lesion conspicuity. DWI with SENSE may be helpful for the detection of cranial bone/bone marrow metastases when used in conjunction with conventional MR sequences.     

Bone marrow relaxation times in Gaucher disease before and after enzyme replacement therapy

The aim of this work was to monitor the effectiveness of enzyme replacement therapy on the basis of the changes in T1 relaxation times in Gaucher patients. A total of 26 patients underwent MR before enzyme replacement therapy; of them, 18 have been followed-up. A total of 22 age-matched controls underwent the same MR study. Scans were focused on the femoral neck, and T1 relaxation times were measured by means of a mixed spin-echo inversion recovery sequence. The T1 relaxation times in Gaucher patients were significantly longer than normal (p < 0.05). After enzyme replacement therapy, T1 relaxation times gradually became closer to those of control subjects, and there was also a significant decrease (p < 0.01) with respect to values before therapy, probably due to an increase in the fat/water ratio. Evaluation of T1 relaxation time may supply a useful indication of Gaucher disease regression after enzyme replacement therapy particularly in those cases in which a normal skeletal appearance corresponds to prolonged T1 relaxation times. Received 28 February 1996; Revision received 20 May 1996; Accepted 21 August 1996     

正常股骨中下段骨髓MRI定量及1H-MRS研究

目的探讨正常股骨中下段骨髓磁共振成像（MRI）信号强度和氢质子磁共振波谱（^1H—MRS）随年龄增长的变化特点,为临床评价骨髓病变提供正常参考依据。资料与方法将70名2．30岁正常受检者按年龄分为6组：A组（2—5岁）9例,B组（6-10岁）10例,C组（11—15岁）10例,D组（16—20岁）13例,E组（21。25岁）13例,F组（26—30岁）15例。对股骨中下段分别采用矢状位SE T1WI和单体素激发回波序列（SVS-STEAM）进行MRI扫描和^1H-MRS采集。在T1WI上测量股骨干中段、下段和远侧干骺端骨髓及其相同水平相同层面邻近肌肉的信号强度,并计算各部位骨髓信号强度相对于肌肉的比值;同时分析3个相应股骨部位骨髓的^1H-MRS谱线。结果各年龄组中每一组内股骨干中段和下段骨髓信号强度之间差异无统计学意义（P〉0．05）,上述两个部位在B组与其他各任意年龄组间差异均有统计学意义（P〈0．05）,而在C-F组内任意两组间差异无统计学意义（P〉0．05）,15岁以前骨髓信号强度与年龄呈明显正相关,其后随年龄增长信号强度变化不显著。股骨远侧干骺端骨髓信号强度在c组与A—F组中的任一组之间差异均有统计学意义（P〈0．05）,但在AB两组间和D—F3组内差异无统计学意义（P〉0．05）,25岁以前骨髓信号强度与年龄呈明显正相关。股骨干中下段骨髓的^1H-MRS谱线在A组均为Lip1型,在B和C两组为Lip1型或Lip2型,在D—F组均为up2型。远侧干骺端骨髓的^1H-MRS谱线在所有年龄组为Lipl型,其中F组有up2型并存。结论不同年龄和不同股骨中下段骨髓的MRI信号强度和^1H-MRS的谱线不同,符合骨髓解剖生理学特点和骨髓转化规律,可作为股骨骨髓疾病分析的正常参考依据。     

Dynamic Contrast Enhanced Magnetic Resonance Imaging of Diffuse Spinal Bone Marrow Infiltration in Patients with Hematological Malignancies

Objective

To investigate the significance of the dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) parameters of diffuse spinal bone marrow infiltration in patients with hematological malignancies.

Materials and Methods

Dynamic gadolinium-enhanced MR imaging of the lumbar spine was performed in 26 patients with histologically proven diffuse bone marrow infiltration, including multiple myeloma (n = 6), acute lymphoblastic leukemia (n = 6), acute myeloid leukemia (n = 5), chronic myeloid leukemia (n = 7), and non-Hodgkin lymphoma (n = 2). Twenty subjects whose spinal MRI was normal, made up the control group. Peak enhancement percentage (E_max), enhancement slope (ES), and time to peak (TTP) were determined from a time-intensity curve (TIC) of lumbar vertebral bone marrow. A comparison between baseline and follow-up MR images and its histological correlation were evaluated in 10 patients. The infiltration grade of hematopoietic marrow with plasma cells was evaluated by a histological assessment of bone marrow.

Results

Differences in E_max, ES, and TTP values between the control group and the patients with diffuse bone marrow infiltration were significant (t = -11.51, -9.81 and 3.91, respectively, p < 0.01). E_max, ES, and TTP values were significantly different between bone marrow infiltration groups Grade 1 and Grade 2 (Z = -2.72, -2.24 and -2.89 respectively, p < 0.05). E_max, ES and TTP values were not significantly different between bone marrow infiltration groups Grade 2 and Grade 3 (Z = -1.57, -1.82 and -1.58 respectively, p > 0.05). A positive correlation was found between E_max, ES values and the histological grade of bone marrow infiltration (r = 0.86 and 0.84 respectively, p < 0.01). A negative correlation was found between the TTP values and bone marrow infiltration histological grade (r = -0.54, p < 0.01). A decrease in the E_max and ES values was observed with increased TTP values after treatment in all of the 10 patients who responded to treatment (t = -7.92, -4.55, and 5.12, respectively, p < 0.01).

Conclusion

DCE-MRI of spine can be a useful tool in detecting diffuse marrow infiltration of hematological malignancies, while its parameters including E_max, ES, and TTP can reflect the malignancies'' histological grade.     

Rapid fat/water assessment in knee bone marrow with inner-volume RARE spectroscopic imaging.

An inner-volume modification of a spectroscopic imaging technique based on RARE (rapid acquisition with relaxation enhancement) sequences is shown to provide, in less than 1 minute, spectra suitable for fat/water peak-area integration from selected imaging columns containing more than 1,000 5 x 5 x 1-mm voxels. A limitation is the unavoidable T2 weighting of the spectral peaks, which influences estimations of true fat/water composition from the spectra. Studies obtained in the knees of healthy volunteers demonstrate the ability of the technique to enable characterization of the two major proton peaks in bone marrow. Data collected at two or more effective TEs are suitable for extrapolation of fat/water estimates to zero TE.