MR扩散张量成像在膝关节前交叉韧带的初步应用

目的:探讨采用3.0T磁共振对膝关节前交叉韧带进行磁共振扩散张量成像(DTI)及纤维束示踪成像(FT)的可行性.方法:对25名健康志愿者进行膝关节DTI检查,男15例,女10例,年龄21～40岁,平均34.6岁.采用单次激发自旋回波平面成像序列,在工作站进行纤维束示踪三雏模拟成像,计算前交叉韧带的纤维束长度及平均FA值、ADC值,比较不同性别的FA值及ADC值差异,并分析同一操作者在不同时间测量结果的一致性.结果:25名受检者中16例前交叉韧带显示三维纤维束结构,4例显示多束,5例未显示规则的纤维束.所显示的平均纤维长度为(13.79±1.75)～(25.43±3.37)mm..全部受试者前交叉韧带平均FA值为0.457士0.058,平均ADC值为1.419±0.289,无性别差异.比较同一测量者在不同测量时间的FA和ADC测量值,其可信度和组内相关系数均较好.结论:采用3T MR成像系统能成功完成正常前交叉韧带DTI和DTT,并可显示正常前交叉韧带的双束结构.     

冠状动脉搭桥术后磁共振桥血管成像的初步探讨

目的 以ＭＲ成像评价桥血管开通及功能,探讨适用于国人冠状动脉搭桥（ＣＡＢＧ）术后的影像学随访手段,方法 用１．５ＴＭＲ机检查２７例ＣＡＢＧ术后患者的７４支桥血管,行屏气快速场回波（ＦＦＥ）序列扫描观察桥血管的开通。其中１６例４２支桥血管行相位对比磁共振血流成像（ＰＳＭＲＡｆｌｏｗ）,得出血流速度和流量曲线,对桥血管的开通进行再评价。结果 本组桥血管ＦＦＥ成像开通率为８９．２％（６６／７４）。以ＰＳ     

3D 1 HMRSI对外周带前列腺癌鉴别诊断价值的初步研究

目的:探讨3D1HMRSI(three dimensional proton MR spectroscopic imaging)研究外周带前列腺癌(PCa)的代谢特点,及对外周带PCa的鉴别诊断价值。方法:分析18例良性前列腺增生(BPH)和21例PCa的3D MRSI表现。测量外周带PCa体素及BPH外周带体素的(Cho Cre)/Cit及Cho/Cre,并比较它们之间的差异。结果:BPH的外周带波谱主要表现为Cit高耸,Cho次之,Cre最低;PCa波谱主要表现为Cit峰明显下降甚至消失,Cho显著升高,两者波峰可呈现倒置,(Cho Cre)/Cit>0.86。PCa体素的(Cho Cre)/Cit显著高于BPH体素,且两者仅存在小部分重叠,PCa体素的Cho/Cre也显著高于BPH体素,但两者存在较大部分重叠;经ROC曲线分析得出(Cho Cre)/Cit对外周带PCa的鉴别诊断效能高于Cho/Cre,(Cho Cre)/Cit对外周带PCa的最佳诊断阈值为1.16。结论:外周带PCa的3D MRSI表现具有特征性,(Cho Cre)/Cit为诊断外周带PCa的有效指标,以(Cho Cre)/Cit>1.16作为诊断标准,可获得较高的敏感度、特异度和准确度(分别为99.3%、99.2%、99.3%)。     

Penile hemangioma: US and MR imaging demonstration

A case of a penile hemangioma is reported. The mass had hypoechogenicity on ultrasonography (US) and high signal intensity on T2-weighted magnetic resonance (MR) image. MR images clearly demonstrated the extent of the lesion, especially deep extension into the corpus cavernosum.     

Penile hemangioma: US and MR imaging demonstration

A case of a penile hemangioma is reported. The mass had hypoechogenicity on ultrasonography (US) and high signal intensity on T2-weighted magnetic resonance (MR) image. MR images clearly demonstrated the extent of the lesion, especially deep extension into the corpus cavernosum.     

Amide proton transfer MR imaging of prostate cancer: a preliminary study

Purpose:

To evaluate the capability of amide proton transfer (APT) MR imaging for detection of prostate cancer that typically shows a higher tumor cell proliferation rate and cellular density leading to an MRI‐detectable overall elevated mobile protein level in higher grade tumors.

Materials and Methods:

Twelve patients with biopsy‐proven prostate cancer were imaged on a 3 Tesla MR imaging system before prostatectomy. APT‐MR images were acquired by means of a single‐slice single‐shot turbo spin echo sequence with a saturation prepulse preparation using 33 different frequency offsets (?8 to 8 ppm, interval 0.5 ppm). For quantification we used the APT ratio (APTR) based on the asymmetry of the magnetization transfer ratio at 3.5 ppm in respect to the water signal. Tumor and peripheral zone benign regions of interest (ROIs) were delineated based on whole mount pathology slides after prostatectomy.

Results:

APTR in prostate cancer ROIs was 5.8% ± 3.2%, significantly higher than that in the peripheral zone benign regions (0.3% ± 3.2%, P = 0.002).

Conclusion:

APT‐MR imaging is feasible in prostate cancer detection and has the potential to discriminate between cancer and noncancer tissues. J. Magn. Reson. Imaging 2011;33:647–654. © 2011 Wiley‐Liss, Inc.

     

The wrist: a preliminary report on high-resolution MR imaging

Excellent spatial resolution is required to demonstrate the complex region of the wrist, with its diverse structures comprising bone, cartilage, and ligaments. Magnetic resonance (MR) imaging was done with a Magnetom imaging system operating at 1.0 T. Use of a flat surface coil enabled excellent spatial resolution and a section thickness of 4 mm. Twenty-nine patients with navicular nonunion or pseudarthrosis, rheumatoid arthritis, recent fractures, soft-tissue alterations, and bone tumors were examined. All patients had undergone radiography and bone scintigraphy. In this limited sampling, MR was found to detect and characterize marrow and articular alterations more accurately, and earlier, than either of those modalities.     

Evaluation of PROPELLER MR imaging: preliminary experiences

Periodically Rotated Overlapping ParallEL Lines with Enhanced Reconstruction (PROPELLER) MR imaging (MRI) has a unique ability to correct motion artifacts and is expected to be useful in diffusion-weighted MRI. This article describes preliminary experiences with PROPELLER MRI. PROPELLER uses a radial scan variation of the fast spin-echo sequence and it shows much less spatial deterioration than the echo-planar imaging sequence. To determine the optimal parameters of this technique, we calculated the signal intensities of phantoms and brains in various settings. PROPELLER MR examinations were also performed in 66 patients for clinical use. PROPELLER MRI appears to be a promising and useful technique.     

Undescended testis: value of MR imaging

Magnetic resonance (MR) imaging was performed in 32 male patients, 20 with no abnormalities and 12 with clinically suspected undescended testes. The results were compared with ultrasonographic, computed tomographic, clinical, and surgical findings. The undescended testes were unilateral in eight patients (one had testicular duplication) and bilateral in four. Of 16 undescended testes, 15 were correctly identified on MR images. One intraabdominal testis was not seen. Testis-fat contrast at 0.35 T was optimal with a short repetition time (TR) and a short echo time (TE). At 1.5 T, good contrast was achieved with short TR/TE sequences, but the contrast was even more pronounced with even longer TR/TE parameters. In seven patients with unilateral undescended testes, the undescended and contralateral testes showed symmetrical tissue signal intensity on both T1- and T2-weighted images. In three, the undescended testis was of lower signal intensity, suggesting atrophy. MR imaging promises to become an important diagnostic tool in the detection of undescended testes.     

Pituitary adenomas: value of MR imaging

MR imaging has become the imaging modality of choice for diagnosis of pituitary adenomas. In order to optimize MR evaluation, dedicated pulse sequences must be utilized and knowledge of diagnostic pitfalls and normal variants is mandatory. The MRI features of pituitary adenomas may vary based on their volume, but also on their cell-type. Postoperative MR imaging based on a pre-established schedule is useful to detect residual and/or early recurrent tumor.     

Intramuscular myxoma: value of MR imaging

A 58-year-old woman with a large intramuscular myxoma of the left thigh was studied with standard X-rays, ultrasonography, CT, MRI and incisional biopsy. MRI provided the most complete information, giving sufficient data for a correct therapeutic approach. Correspondence to: M. Fontana     

High field body MR imaging: preliminary experiences

Whole-body magnetic resonance (MR) scanners at high field strengths (> or =3 T) have been introduced in expectation of a larger signal-to-noise ratio (SNR), which would decrease the length of scan time or improve the spatial resolution. In this paper, the advantages and disadvantages of the high field MR imaging are discussed. Although the building of the radio frequency (RF) coil, safety and the specific absorption rate (SAR) are issues, the application of high field MR imaging is promising. The optimization of all parameters including injection rate of Gd-DTPA is necessary for high field MR imaging to obtain maximal results; however, we hope that high field MR imaging can be used in routine clinical applications in the future.     

Using diffusion-weighted MR imaging for tumor detection in the collapsed lung: a preliminary study

The usefulness of diffusion-weighted magnetic resonance (MR) imaging (DWI) for differentiating central lung cancer from postobstructive lobar collapse (POC) was investigated. Thirty-three cases suspected of lung cancer and POC on chest bolus computed tomography (CT) underwent thoracic MR imaging examinations. MR examinations were performed using a 1.5-T clinical scanner. Scanning sequences were T1-weighted imaging, T2-weighted imaging (T2WI) and DWI with b = 0, 500 s/mm², four excitations and segmented breath-holding. The densities and signals of cancer and postobstructive collapsed lung were compared on bolus-enhanced CT, T2W and DW images. Statistical analyses were performed with chi-square test, paired t-test, non-parameter test and kappa statistics. Differentiation between cancer and POC was possible on bolus CT, T2W and DW images in 14, 21 and 26 patients, respectively. Eight cases that were impossible to differentiate on T2W images were distinguishable on DWI, demonstrating that DWI is complementary to T2WI. Using a combination of T2W and DW images, 88% (29/33) of cases were differentiated on MR imaging. Thus, a combination of T2W and DW imaging is superior to bolus-CT or T2WI alone. The contrast-to-noise ratio of DWI was significantly higher than that of T2WI. Agreement between two independent observers on the differential ability of lung cancer and POC was higher for DWI (kappa = 0.474) than for T2WI (kappa = 0.339). The degree of consolidation around the cancer was negatively correlated with the degree of artifact and degree of deformation. It is feasible to use DWI to differentiate lung cancer from POC. DWI played a role in confirming and providing complementary information to that obtained from T2WI. Our data indicate that using a combination of the two scanned sequences was the best means of distinguishing between lung cancer and POC.