7 T MR肾脏成像:初步结果

目的探讨利用8通道传送/接收射频体部线圈获得7TMR肾脏影像的可行性。方法 8名健康志愿者采用7T全身MR系统行非增强MR检查。B0匀场后,采用以下序列:     

Renal imaging at 7 Tesla: preliminary results

Objective

To investigate the feasibility of 7T MR imaging of the kidneys utilising a custom-built 8-channel transmit/receive radiofrequency body coil.

Methods

In vivo unenhanced MR was performed in 8 healthy volunteers on a 7T whole-body MR system. After B₀ shimming the following sequences were obtained: 1) 2D and 3D spoiled gradient-echo sequences (FLASH, VIBE), 2) T1-weighted 2D in and opposed phase 3) True-FISP imaging and 4) a T2-weighted turbo spin echo (TSE) sequence. Visual evaluation of the overall image quality was performed by two radiologists.

Results

Renal MRI at 7T was feasible in all eight subjects. Best image quality was found using T1-weighted gradient echo MRI, providing high anatomical details and excellent conspicuity of the non-enhanced vasculature. With successful shimming, B₁ signal voids could be effectively reduced and/or shifted out of the region of interest in most sequence types. However, T2-weighted TSE imaging remained challenging and strongly impaired because of signal heterogeneities in three volunteers.

Conclusion

The results demonstrate the feasibility and diagnostic potential of dedicated 7T renal imaging. Further optimisation of imaging sequences and dedicated RF coil concepts are expected to improve the acquisition quality and ultimately provide high clinical diagnostic value.     

MR imaging of the knee: preliminary results with a 3DFT GRASS pulse sequence

The knees of 17 patients (18 extremities) with possible meniscal, cruciate ligament, and articular cartilage abnormalities were examined with a three-dimensional Fourier transform (3DFT), gradient-refocused acquisition in a steady state (GRASS) pulse sequence. Arthroscopic confirmation was available in all cases and was the standard for comparison. Thirteen of these extremities were also examined by using a two-dimensional Fourier transform spin-echo pulse sequence with a 2000-msec repetition time and 20- and 80-msec echo time. In these 13 cases, both pulse sequences correctly identified seven of eight meniscal abnormalities. However, interpretation of the 3DFT GRASS images resulted in fewer false-positive meniscal tears (three vs six). Cruciate ligament tears were detected more readily on the 3DFT GRASS images (six vs three with two possible tears on the spin-echo images). These preliminary findings suggest that the overall accuracy of MR imaging of the knee could be improved by including 3DFT gradient-refocused pulse sequences.     

Detection of liver metastases with pulse inversion harmonic imaging: preliminary results

The aim of this study is to evaluate capability of contrast enhanced ultrasonography (US) using pulse inversion harmonic imaging (PIHI) to detect liver metastases in comparison to fundamental B-mode ultrasound and spiral CT. Thirty-six consecutive patients with known malignancies and sonographically proved or suspicious liver metastases have been examined with fundamental B-mode US, with PIHI 2', 4' and 6' after Levovist injection and with four phase spiral-CT. Presence, conspicuity and number of lesions have been evaluated comparing PIHI with fundamental B-mode US and spiral-CT. A strong grey-scale enhancement of the liver parenchyma has been observed 2' and 4' after Levovist injection. The optimum parenchymal enhancement and contrast difference between liver and metastases was observed during the 2' measurements. PIHI revealed more lesions than fundamental B-mode US in 56 % of patients, while in 39 % and in 5 % revealed respectively the same number and fewer lesions. PIHI and spiral-CT were in agreement in 67 % of patients, while in 22 % and 11 % PIHI revealed respectively more and fewer lesions. PIHI accurancy presents restrictions in anterior superficial and in deep liver areas, whereas it may be superior to spiral-CT in studying sub-diaphragmatic liver regions.     

Whole-body diffusion-weighted imaging: technical improvement and preliminary results

PURPOSE: To optimize the free-breathing whole-body diffusion-weighted imaging (WB-DWI) protocol by using the short TI inversion-recovery diffusion-weighted echo-planar imaging (STIR-DWEPI) sequence and the built-in body coil. Additionally, to evaluate the feasibility of tumor screening using high-resolution three-dimensional (3D) maximum intensity projection (MIP) images. MATERIALS AND METHODS: The prescan procedure of STIR-DWEPI was modified using the data from 30 volunteers. During each exam, an optimized center frequency (CF) was used to minimize the slice offsets in consecutive scan stations. Prescan time was reduced from 50 seconds to 20 seconds with improved station profile. Total scan time was 30 minutes for five stations and 1.2 m coverage. A total of 30 patients with histologically-proven malignant disease were scanned under the final protocol using a built-in body coil. The image quality and the degree of background body signal suppression were assessed. RESULTS: Free-breathing WB-DWI was 100% successfully performed in all patients, without slice misregistration, fat contamination, significant distortion, or nonuniformity. The reconstructed 3D-MIP images were adequate to depict malignant lesions in all 30 patients. The results of WB-DWI were found to be comparable to those of single-photon emission computed tomography (SPECT) and positron emission tomography (PET). CONCLUSION: Stable and high-resolution WB-DWI is feasible using the technical improvements described in this study. WB-DWI might have important clinical value for the detection of primary and metastatic malignancies within the whole body. The potential for diagnosis and therapeutic assessment of tumors should be further assessed in a larger patient cohort.     

前列腺癌的MR扩散成像初步研究

目的初步评价MR扩散成像(DWI)对前列腺癌的诊断可行性。方法28例前列腺癌患者及20例前列腺正常的对照组受试者行MR DWI检查,使用回波平面扩散张量成像序列,b值为1000s/mm2。测量正常前列腺外周带及前列腺癌区域的表观扩散系数(ADC)值。同时测量每位受检者膀胱区域的ADC值。结果48例中44例(91.7%)获得前列腺外周带和膀胱的ADC值。24例前列腺癌灶的ADC值为(0.35±0.06)×10-3mm2/s,20例正常前列腺外周带的ADC值为(1·35±0.30)×10-3mm2/s,前列腺癌灶较正常前列腺外周带ADC值低(t=11.99,P=0.00)。前列腺癌患者膀胱的ADC值为(1.27±0.21)×10-3mm2/s,对照组膀胱ADC值为(1.29±0.30)×10-3mm2/s,2组之间差异无统计学意义(t=1.15,P=0.48)。结论MR DWI可用于前列腺的检查。前列腺癌灶与正常前列腺外周带ADC值的差别有可能用于前列腺癌的鉴别诊断。     

Quantitative cerebral MR perfusion imaging: preliminary results in stroke

Purpose:

To demonstrate that OKN007, a disulfonyl derivative of phenyl‐tert‐butyl nitrone (PBN), has anti‐glioma activity in the clinically relevant C6 rat glioma model using multi‐parametric magnetic resonance imaging.

Materials and Methods:

Twenty‐one rats were intracerebrally implanted with C6 cells and administered OKN007 or kept as controls. Animals were monitored with MRI at 7 Tesla (T), using morphologic, diffusion‐weighted and perfusion imaging, followed by histology and Western blots of angiogenesis and inflammatory markers.

Results:

OKN007 was found to decrease tumor volumes and increase survival. The glioma tissues of OKN007‐treated rats were found to have longitudinal apparent diffusion coefficients (ADC_z) of 0.76 ± 0.06 × 10^?3 mm²/s, similar to the contralateral tissue and significantly smaller than untreated gliomas (0.97 ± 0.13 × 10^?3 mm²/s). They had higher perfusion rates (66 ± 4 mL/100 g·min) than untreated gliomas (26 ± 7 mL/100 g·min). All examined molecular markers were decreased in OKN007‐treated rat gliomas, compared with elevated levels in untreated rats.

Conclusion:

MRI assessment was successfully used to monitor a decrease in tumor growth, and corresponding alterations in ADC and perfusion rates in rat C6 gliomas treated with the anti‐glioma agent, OKN007. J. Magn. Reson. Imaging 2010;31:796–806. ©2010 Wiley‐Liss, Inc.

     

Interventional MR imaging with an endospinal imaging coil: preliminary results with anatomic imaging of the canine and cadaver spinal cord

Percutaneous intraspinal navigation (PIN) is a new minimally invasive approach to the subarachnoid space. Using conventional radiographic fluoroscopy, entrance is gained to the lumbar subarachnoid space, allowing navigation throughout the spinal canal. Using an antenna/guidewire introduced via PIN, we performed endospinal MR imaging of the thoracic spinal cord in a cadaver and canine subject. Comparison images were obtained with an optimal surface coil. PIN allows endospinal MR imaging of the spinal cord, providing significant signal-to-noise ratio gains over conventional imaging.     

MR imaging of the brain: preliminary results with a gradient echo sequence after paramagnetic contrast enhancement

In a series of 15 patients with contrast enhancing lesions of the brain, a gradient echo sequence (TR = 400 ms; TE = 10 ms; flip angle 90 degrees, one excitation) after IV administration of a paramagnetic contrast agent provided equal diagnostic information and image quality to conventional T1 weighted spin-echo images. Imaging time for one sequence could be reduced by two thirds to 1 min 45 sec. Susceptibility artifacts caused only slight image degradation in the bitemporal region and the region of the sella turcica. This gradient echo sequence can be useful in combination with paramagnetic contrast enhancement, as a complement to conventional T1 and T2 weighted spin-echo sequences.     

Cardiac imaging using 256-detector row four-dimensional CT: preliminary clinical report

Purpose Along with the increase of detector rows on the z-axis and a faster gantry rotation speed, the spatial and temporal resolutions of the multislice computed tomography (CT) have been improved for noninvasive coronary artery imaging. We investigated the feasibility of the second specification prototype 256-detector row four-dimensional CT for assessing coronary artery and cardiac function. Materials and methods The subjects were five patients with coronary artery disease. Contrast medium (40–60 ml) was intravenously administered at the rate of 3–4 ml/s. The patient's whole heart was scanned for 1.5 s to cover at least one cardiac cycle during breathholding without electrocardiographic gating. Parameters used were 0.5 mm slice thickness, 0.5 s/rotation, 120 Kv, and 350 mA, with a half-scan reconstruction algorithm (temporal resolution 250 ms). Twenty-six transaxial datasets were reconstructed at intervals of 50 ms. Results The assessability of the coronary arteries in AHA segments 1, 2, 3, 5, 6, 7, 9, and 11 was visually evaluated, resulting in 29 of 32 (90.9%) segments being assessable. Functional assessment was also performed using animated movies without banding artifacts in all cases. Conclusions The 256-detector row four-dimensional CT can assess the coronary artery and cardiac function using data during 1.5 s without banding artifacts.     

Salivary gland function evaluated by diffusion-weighted MR imaging with gustatory stimulation: preliminary results

Purpose:

To evaluate the usefulness of diffusion‐weighted MR imaging using a transient gustatory stimulation method in patients with xerostomia.

Materials and Methods:

Ten consecutive patients complaining of xerostomia and 10 healthy volunteers were examined with a 1.5 Tesla (T) MR unit. All study subjects completed a questionnaire, and patients underwent salivary gland scintigraphy and Saxon test. T1‐, T2‐, and diffusion‐weighted MR images were obtained before stimulation. One minute after gustatory stimulation with lemon juice, diffusion‐weighted sequence was repeated 9 times. A radiologist evaluated signal intensities and apparent diffusion coefficients (ADCs) in parotid and submandibular glands. ADC increase rate (IR) and times to maximum ADC (Tmax) were assessed.

Results:

IRs showed a moderate positive correlation with washout rates by scintigraphy for parotid (r = 0.554, P < 0.05) and submandibular (r = 0.617, P < 0.01) glands. Furthermore, Tmax values of parotid and submandibular glands were significantly higher in patients (420 ± 226 and 357 ± 232 s, respectively) than in volunteers (181 ± 68 and 200 ± 75 s, respectively) (P < 0.01).

Conclusion:

Our preliminary results indicate that diffusion‐weighted MR imaging using a transient gustatory stimulation method is potentially useful for evaluating patients with xerostomia. J. Magn. Reson. Imaging 2011;. © 2011 Wiley‐Liss, Inc.     

Diagnosis and quantification of hepatic fibrosis with diffusion weighted MR imaging: preliminary results

PURPOSE: Diagnosis and quantification of hepatic fibrosis are especially important in patients with chronic liver disease. Liver biopsy remains the gold standard for diagnosis of cirrhosis but has several limitations. The purpose of this study was to determine the usefulness of diffusion-weighted MR imaging, for the diagnosis of cirrhosis and quantification of hepatic fibrosis, and to define the best sequence parameters for this evaluation. METHODS AND MATERIALS: Diffusion-weighted imaging using a 1.5 T MR unit was performed in 14 healthy volunteers and 13 cirrhotic patients. Sets of 8 images with different b values (200, 400, 600, and 800 sec/mm2) and different TR (3500 and 5000 ms) were acquired with breath-holding. Apparent diffusion coefficients (ADCs) were calculated. Correlation between Child-Pugh scores, serum hyaluronate concentrations and ADCs were performed. RESULTS: ADCs were significantly lower in cirrhotic patients (2,055 10-3) compared to controls (2,915 10-3) (p<0.05) when the b value was 200 s/mm2 and the TR was 5000 ms. Significant correlations were observed between Child-Pugh scores and ADCs (p<0.05), and between serum hyaluronate concentrations and ADCs (p<0.05), when the b value was 400 sec/mm2 and the TR was 5000 ms. CONCLUSION: Our preliminary study showed that the measurement of ADCs has good potential for diagnosis and quantification of hepatic fibrosis, especially when using b values of 200 sec/mm2 and 400 sec/mm2.     

Magnetization transfer imaging of normal and abnormal testis: preliminary results

Objectives

The aim was to determine the magnetization transfer ratio (MTR) of normal testes, possible variations with age and to assess the feasibility of MTR in characterizing various testicular lesions.

Methods

Eighty-six men were included. A three-dimensional gradient-echo MT sequence was performed, with/without an on-resonance binomial prepulse. MTR was calculated as: (SIo-SIm)/(SIo)?×?100 %, where SIm and SIo refers to signal intensities with and without the saturation pulse, respectively. Subjects were classified as: group 1, 20-39 years; group 2, 40-65 years; and group 3, older than 65 years of age. Analysis of variance (ANOVA) followed by the least significant difference test was used to assess variations of MTR with age. Comparison between the MTR of normal testis, malignant and benign testicular lesions was performed using independent-samples t testing.

Results

ANOVA revealed differences of MTR between age groups (F?=?7.51, P?=?0.001). Significant differences between groups 1, 2 (P?=?0.011) and 1, 3 (P?<?0.001) were found, but not between 2, 3 (P?=?0.082). The MTR (in percent) of testicular carcinomas was 55.0?±?3.2, significantly higher than that of benign lesions (50.3?±?4.0, P?=?0.02) and of normal testes (47.4?±?2.2, P?<?0.001).

Conclusions

MTR of normal testes decreases with age. MTR might be helpful in the diagnostic work-up of testicular lesions.

Key Points

? MTR of normal testes shows age-related changes. ? Testicular carcinomas have high MTR values. ? MTR may be useful in the diagnostic work-up of testicular lesions.

     

Focal lesions of the spleen: preliminary results with fast MR imaging at 1.5 T

Sixteen patients with splenic lymphoma and six with nonlymphomatous splenic lesions underwent magnetic resonance (MR) imaging, ultrasound (US), and dynamic CT. All patients were studied at 1.5 T with gradient echo sequences using a repetition time of 80 ms, echo time of 16 ms, and two pulse angles of 30 and 60 degrees. In 14 patients with lymphomatous lesions fast MR showed circumscribed areas of low signal intensity at both pulse angles. The lesion-to-spleen contrast was better on images acquired with a pulse angle of 30 degrees. For fast MR with pulse angles of 30 degrees, the mean lesion-to-spleen contrast was similar to US and contrast-enhanced CT. However, with fast MR the contrast showed a lower variability and was considerably better than with unenhanced CT. In one patient fast MR showed splenic involvement that was missed on both CT and US. The signal characteristics of lymphomatous, leukemic, and sarcoid involvement and of healed infarcts were similar and indistinguishable on fast MR images. Recent splenic infarctions (three cases) were, however, distinctly different, characterized by regions of high signal intensity at both pulse angles. The results of this preliminary study suggest that fast MR imaging is a promising diagnostic tool for the assessment of splenic disorders.     

Dynamic optical breast imaging: a new technique to visualise breast vessels: comparison with breast MRI and preliminary results

The purpose of our study was to explore and evaluate an innovative imaging approach, which consists on imaging the breast parenchyma by means of photoluminescence detectors (LED) and analysis of dynamic data. Breast magnetic resonance imaging (MRI) was chosen as the reference imaging method, as this is considered to be nowadays the gold standard for breast vascularisation evaluation. Preliminary results reveal a good correlation between breast MRI findings and light images.     

7.0T钠元素MR成像在阿基里斯跟腱炎临床诊断的初步应用

目的为了研究钠元素MR成像诊断阿基里斯跟腱炎的可行性。材料与方法该研究获得医学伦理委员会批准,研究对象为签署知情同意书的20名健康志愿者和8例阿基里斯跟腱炎病人。使用7.0T全身MR扫描设备,15通道钠元素膝部线圈。不仅获得MR影像中跟腱的信噪比(SNR),而     

恶性血液病骨髓动态增强磁共振成像特征的初步研究

目的探讨利用动态增强MR成像技术检测恶性血液病患者骨髓构成的变化，判定其骨髓浸润程度，以减少血液病患者治疗随访过程中穿刺活检的次数。方法25例恶性血液病患者经动态增强MPJ（DCE-MR）及髂嵴穿刺活检，测定骨髓灌注的最大强化率（PER），最大强化斜率值（Slopemax），峰值时间（TTP），平均时间（MT），以及骨髓活检分析细胞构成、肿瘤分数（TF）。结果25例恶性血液病患者骨髓的PER、Slopemax、TTP、MT的中位值分别为0．27、0．21s^-1。、79．08s、84．43s。不同细胞构成（低、正常、高）骨髓的灌注特征性变量的中位数值分别为PER（0．29、0．24、1．15）、Slopemax（0．20s^-1、0．21s^-1、1．28s^-1）、TTP（96．67s、83．49s、25．52s）、MT（77．52s，86．25s，84．34s）。肿瘤浸润组首次灌注值（PER0．32，Slopemax0．28s。）高于肿瘤缓解组，（PER0．20，Slopemax0．20s^-1），而对比剂到达峰值时间（TTP68．66s）低于缓解组（TTP85．85s）。肿瘤浸润组与缓解组骨髓的PER差异有统计学意义（P=0．02），而Slopewmax、TTP、MT差异无统计学意义（P值均＞0．05）。PER（r=0．564，P=0．003）、Slopemax（r=0．478，P=0．016）、MT（r=0．186，P＞0．05）与骨髓细胞构成状态（低、正常、高）呈正相关，而TTP（r=-0．222）与骨髓细胞构成状态呈负相关。PER（r=0．561，P=0．004）、Slopemax（r=0．318，P=0．121）、MT（r=0．207，P＞0．05）与TF呈正相关，而TTP（r=-0．305，P＞O．05）与TF呈负相关。结论动态增强MR成像能够监测恶性血液病骨髓肿瘤细胞浸润和细胞构成的变化。