3D proton MR spectroscopic imaging of prostate cancer using a standard spine coil at 1.5 T in clinical routine: a feasibility study

The objective of this study was to demonstrate the feasibility of 3D proton MR spectroscopic imaging (MRSI) of the prostate using a standard spine instead of a dedicated endorectal coil at 1.5 T. Twenty-eight patients (25 with biopsy proven prostate cancers and three patients with a benign prostate hyperplasia) were examined. MRI and MRSI were conducted with commercial array surface coils at 1.5 T. Ratios of choline (Cho), creatine (Cr) and citrate (Ci) were calculated for tumour, central and peripheral zone retrospectively, based on axial T2 weighed MR images and histology reports. Prostate cancer was characterized by significantly elevated (Cho+Cr)/Ci ratio compared with non-tumourous prostate tissue. The quality of all proton MR spectra was considered to be good or acceptable in 17/28 patients (61%) and poor in 11/28 (39%) examinations. In 20/25 patients with proven malignancy (80%), MRSI was considered to be helpful for the detection of prostate cancer. In 4/25 patients with proven malignancy (16%) who underwent seed implantation, radiotherapy or hormone deprivation before MR examination spectroscopy was of poor and non-diagnostic quality. MRSI of the prostate is feasible within clinical routine using the spine array surface coil at 1.5 T. It can consequently be applied to patients even with contraindications for endorectal coils. However, spectral quality and signal-to-noise ratio is clearly inferior to 3D MRSI examinations with endorectal coils.     

Endorectal surface coil MR imaging of prostatic carcinoma with the inversion-recovery sequence

The value of inversion-recovery (IR) sequences in the diagnosis and staging of prostatic carcinoma with magnetic resonance (MR) imaging was studied. Twenty-six patients with carcinoma of the prostate were imaged at 1.5 T with an endorectal surface coil and with a variety of IR sequences and a set of spin-echo (SE) sequences for comparison. Ex vivo prostate specimens were imaged again at the same field strength. The two images were correlated with histologic sections. Cancer was identified with MR imaging in 96% of patients. Of the tumors more than 4 mm in diameter, 87% were identified on T2-weighted SE images, whereas only 26% were identified on IR images. However, IR images may be more useful in local staging of carcinoma. Gross capsular infiltration was present in only two patients; however, it was detectable (and excluded in five other patients) by means of IR images. It was not detectable on SE images. The high quality of images obtained with the endorectal coil was confirmed. The authors conclude that addition of the IR sequence to MR imaging with the endorectal coil may improve the usefulness of this examination.     

Proton two-dimensional chemical shift imaging for evaluation of prostate cancer: external surface coil vs. endorectal surface coil

PURPOSE: To compare the diagnostic ability of proton magnetic resonance spectroscopy (MRS) using an external surface coil with that using an endorectal surface coil in patients with prostate cancer. MATERIALS AND METHODS: MR imaging (MRI) and two-dimensional chemical shift imaging (2D CSI) were performed in 5 healthy volunteers and in 35 patients with prostate cancer. The receiver coil was the anterior lower part of a phased-array coil or an endorectal surface coil. RESULTS: Receiver-operating characteristic analysis for diagnosing prostate cancer showed no significant difference (P = 0.784) between the area under the curve of phased-array coil CSI and that of endorectal surface coil CSI. CONCLUSION: The phased-array coil CSI could provide comparable detection accuracy to endorectal surface coil CSI. In patients with rectal diseases or patients who could not tolerate the discomfort with insertion of an endorectal surface coil, we recommend the phased-array coil CSI.     

MR imaging of blood vessels with an intravascular coil.

A method for producing high-resolution magnetic resonance (MR) images of blood vessel walls is described. The authors review a theoretical analysis of receiver-coil design and present a coil well suited for intravascular MR imaging. The design is based on two coaxial solenoids separated by a gap region and with current driven in opposite directions. Placement of this receiver coil within the vascular space is shown to provide a substantial increase in sensitivity over that external surface coils. Experimental verification of these predictions was obtained in a vessel phantom in which a 13-cm surface coil was compared with a 3.5-mm-diameter opposed-solenoid intravascular coil. This intravascular coil had a cylindric region of high sensitivity that offered a 10-fold improvement in signal-to-noise ratio over that of an external coil near the vessel wall. The performance of this coil was also tested in the jugular vein of a swine.     

Prostate cancer: comparison of local staging accuracy of pelvic phased-array coil alone versus integrated endorectal–pelvic phased-array coils

To compare the visibility of anatomical details and prostate cancer local staging performance of pelvic phased-array coil and integrated endorectal–pelvic phased-array coil MR imaging, with histologic analysis serving as the reference standard. MR imaging was performed in 81 consecutive patients with biopsy-proved prostate cancer, prior to radical prostatectomy, on a 1.5T scanner. T2-weighted fast spin echo images of the prostate were obtained using phased-array coil and endorectal–pelvic phased-array coils. Prospectively, one radiologist, retrospectively, two radiologists and two less experienced radiologists working in consensus, evaluated and scored all endorectal–pelvic phased-array imaging, with regard to visibility of anatomical details and local staging. Receiver operator characteristics (ROC) analysis was performed. Anatomical details of the overall prostate were significantly better evaluated using the endorectal–pelvic phased-array coil setup (P<0.05). The overall local staging accuracy, sensitivity and specificity for the pelvic phased-array coil was 59% (48/81), 56% (20/36) and 62% (28/45), and for the endorectal-pelvic phased-array coils 83% (67/81), 64% (23/36) and 98% (44/45) respectively, for the prospective reader. Accuracy and specificity were significantly better with endorectal–pelvic phased-array coils (P<0.05). The overall staging accuracy, sensitivity and specificity for the retrospective readers were 78–79% (P<0.05), 56–58% and 96%, for the endorectal–pelvic phased-array coils. Area under the ROC curve (Az) was significantly higher for endorectal–pelvic phased-array coils (Az=0.74) compared to pelvic phased-array coil (Az=0.57), for the prospective reader. The use of endorectal–pelvic phased array coils resulted in significant improvement of anatomic details, extracapsular extension accuracy and specificity. Overstaging is reduced significantly with equal sensitivity when an endorectal–pelvic phased-array coil is used. Financial support: Grant from the Dutch Cancer Society     

MRI快速自旋回波序列和盆腔相控线圈对前列腺癌的诊断价值

评价快速自旋回波序列和盆腔相控线圈在前列腺癌ＭＲＩ诊断的价值。方法１４６例进行前殂朱ＭＲＩ检查,其中２４例应用常规ＳＥＴ２ＷＩ和体线圈;７０例应用ＦＳＥＴ２ＷＩ和体线圈;５２例应用ＦＳＥＴ２ＷＩ和盆腔相控线圈;比较３种扫描方法所获图像质量之间的差异和对前列腺癌诊断的准确性、敏感性、特异性、阳性预测值和阴性预测值。     

Surface coil with variable geometry: a new tool for MR imaging of the spine

A switchable-array surface coil for magnetic resonance (MR) imaging of the spine has been built that enables the user to change the working size of the coil depending on the volume of interest. The prototype has achieved similar image quality to that obtained with conventional coils of equal size. This type of antenna may reduce the number of individual coils necessary for a high-quality MR imaging study.     

Phased-array MRI of canine prostate using endorectal and endourethral coils.

A four-channel phased array consisting of one surface coil, two endorectal coils, and one flexible endourethral loop coil was designed for MRI of the canine prostate. The endorectal coils provide high signal in the posterior region of the prostate, while the endourethral and surface coils are sensitive to the central and anterior regions of the prostate. Gel phantom experiments indicate that the proposed phased-array configuration generates 15 times more signal-to-noise ratio (SNR) than a combination of two surface coils and one endorectal coil within the posterior region of the prostate; the performance of the two configurations is comparable near the anterior prostate surface. Ultimate intrinsic SNR (UISNR) analysis was used to compare the proposed phased array's performance to the best possible SNR for external coils. This analysis showed that the proposed phased array outperforms the best-case external coil within the posterior and central regions of the prostate by up to 20 times. In canine experiments in vivo, high-resolution fast spin-echo (FSE) images of the prostate were obtained with a pixel size of 230 microm obtained in 3 min 12 s. The proposed phased-array design potentially can be used to increase the accuracy of prostate cancer staging and the feasibility of MR-guided prostate interventions.     

Three-dimensional time-of-flight MR angiography with a surface coil: evaluation in 12 subjects.

We compared three-dimensional time-of-flight MR angiograms obtained with head coils and then with surface coils in five patients with intracranial vascular lesions and in seven normal volunteers to determine if imaging of intracranial vascular anatomy could be improved with the use of a surface coil. Visualization of small peripheral vessels was consistently better with a surface coil than with a head coil at identical small fields of view (FOVs). The surface-coil technique allowed small-FOV imaging of peripheral vascular lesions with higher spatial resolution and signal-to-noise ratio similar to that of large-FOV head-coil images. The use of a surface coil introduced the problem of signal falloff; centrally located vessels were visualized as well or better when a standard head coil was used. We conclude that surface-coil MR angiography can serve as a useful adjunct to routine head-coil MR angiography in the evaluation of peripheral vascular abnormalities.     

A solid reusable endorectal receiver coil for magnetic resonance imaging of the prostate: Design,use, and comparison with an inflatable endorectal coil

We have designed a solid endorectal receiver coil for MRI of the prostate. The coil provided an improved signal-to-noise ratio up to 5 cm from its surface when compared with a standard pelvic phased array. This preliminary report describes 16 patients who were imaged using this coil, seven of whom had been examined previously with a balloon-design endorectal coil. Patient tolerance of these coils was compared. The solid coil was easy to insert and quick to set up because it did not require external tuning and matching. It avoided uncomfortable rectal distension experienced with the balloon coil as well as susceptibility artifacts from air in the balloon. In addition, it could be sterilized and reused.     

直肠内线圈MR在前列腺癌诊断中作用:肿瘤位置和分期

目的:利用直肠内线圈MR成像显示前列腺癌及进行临床分期。方法:75例前列腺癌,年龄30~81岁,平均年龄为65岁。均经直肠前列腺穿刺活检术获得病理结果。Philips Intera 1.5T Master超导型临床医用磁共振仪,采用标准直肠腔内线圈。对前列腺包膜显示及是否侵犯,精囊侵犯和淋巴结转移进行了分析。结果:直肠内线圈的应用可显著提高前列腺图像的信噪比,可清晰显示前列腺癌病变、局部解剖、包膜、血管神经丛,并能显示前列腺癌转移及盆腔淋巴结转移途径。结论:直肠内线圈可以确定前列腺癌肿瘤的位置,以及包膜和精囊血管侵犯,并有利于分析前列腺癌淋巴结转移的方式。     

Inflatable surface coil for MR imaging of the prostate

An inflatable surface coil for transrectal magnetic resonance imaging of the prostate was designed. The coil was tested during imaging of an insulated saline phantom and of the prostates of four patients. Phantom images were comparable to those obtained with commercial coils of similar size. High spatial resolution and excellent contrast were noted in coronal images of the prostates. Use of this coil could substantially improve studies of the prostate and cervix.     

中国健康成人前列腺3.0T体线圈磁共振波谱表现

目的探讨采用体线圈行前列腺3.0T磁共振波谱（MRS）检查的可行性,总结3D1H-MRS在正常前列腺中的表现。方法收集20名中老年健康志愿者行3.0T MRI常规检查、扩散加权成像及MRS检查。年龄为41～80岁,平均年龄（56±11）岁。MRS以体线圈为信号接收线圈,用Proseme序列进行扫描,体素分为正常外腺区、正常内腺区。然后工作软件自动计算每个体素的胆碱（Cho）相对值、（胆碱＋肌酸）/枸橼酸盐[（Cho＋Cr）/Cit]的比值。正常前列腺内、外腺分为左、右两侧,每侧由上到下分为底部、中部和尖部3部分,这样每个志愿者测量12个感兴趣区,每个感兴趣区包括0～3个可用体素平均计算。结果20名健康志愿者获得体素201个,其中可用体素170个（84.6%）,不可用体素为31个（15.4%）。20名中老年健康志愿者前列腺外腺区的（Cho＋Cr）/Cit平均值是0.39±0.21,内腺区的（Cho＋Cr）/Cit平均值是0.50±0.17,2组间比较差异有统计学意义（t=3.219,P〈0.01）。结论①用3.0T体线圈可以顺利完成对前列腺的MRS检查,并可以获得用于分析的体素,其在临床实践中具有可行性。②中老年正常前列腺内腺和外腺的代谢物含量是不同的,差异有统计学意义（t=3.219,P〈0.01）,内腺区（Cho＋Cr）/Cit平均值高于外腺区,进一步对其病变进行MRS定量研究时应根据解剖进行分区研究。     

X-ray compatible radiofrequency coil for magnetic resonance imaging.

The range of RF coils that can be used in combined X-ray/MR (XMR) systems is limited because many conventional coils contain highly X-ray attenuating materials that are visible in the X-ray images and potentially obscure patient anatomy. In this study, an X-ray compatible coil design that has minimal X-ray attenuation in the field of view (FOV) of the X-ray image is presented. In this design, aluminum is used for the loop conductor and discrete elements of the coil are eliminated from the X-ray FOV. A surface coil and an abdominal phased array coil were built using the X-ray compatible design. X-ray attenuation and MR imaging properties of the coils were evaluated and compared to conventional coils. The X-ray compatible phased array coil was used to image patients during two interventional procedures in the XMR system. The X-ray compatible coils allowed for fluoroscopic X-ray image acquisition, without degradation by the coil, while maintaining excellent MR imaging qualities.     

Orbit: initial experience with surface coil spin-echo MR imaging at 1.5 T

Fifty-nine cases in which surface coil MR imaging of the orbit was performed were reviewed. MR imaging was performed with spin-echo techniques at 1.5 T with both short repetition time/echo time (TR/TE) and long TR/TE sequences in all cases. In all patients short TR/TE images were obtained with small-diameter surface coils; long TR/TE images were usually obtained with a standard head coil. Surface coil MR appears to be an important adjunct in state-of-the-art orbital imaging. Orbital MR imaging may be most useful, providing information not available on computed tomography (CT), in identifying lesions in the orbital apex, superior orbital fissure, and optic canal; differentiating inflammatory pseudotumor from malignancy in clinically similar patients; characterizing lesions containing hemorrhage or other paramagnetic material; defining the posterior extent of optic pathway gliomas; and detecting abnormal flow in intraorbital vascular structures. CT seems to be superior to MR imaging in the evaluation of small perioptic meningiomas, especially those that are calcified.     

Transrectal probe for 1H MRI and 31P MR spectroscopy of the prostate gland

A transrectal probe for 1H imaging and 31P MR spectroscopy of the prostate gland is described. The probe is covered with plastic and consists of an insectional portion containing an rf coil and a handle containing a tuning and matching circuit. Using this transrectal probe, 1H MR images and the first 31P MR spectra of the in situ canine prostate were obtained. Serial alterations in prostate size and changes in the ratio of phosphomonoesters to ATP ratio following orchiectomy were observed. Transrectal images of the prostate appear to be superior to conventional whole body coil images in the canine. For the first time a device to obtain high signal-to-noise 1H images and 31P spectra of the in situ prostate has been constructed. This will allow the assessment of transrectal imaging and spectroscopy as tools for medical studies of prostate pathophysiology.     

Local staging of prostate cancer using magnetic resonance imaging: a meta-analysis

Our objective was to determine the influence of patient-, study design-, and imaging protocol characteristics on staging performance of MR imaging in prostate cancer. In an electronic literature search and review of bibliographies (January 1984 to May 2000) the articles selected included data on sensitivity and specificity for local staging. Subgroup analyses examined the influence of age, prostate specific antigen, tumor grade, hormonal pre-treatment, stage distribution, publication year, department of origin, verification bias, time between biopsy and MR imaging; consensus reading, study design, consecutive patients, sample size, histology preparation, imaging planes, fast spin echo, fat suppression, endorectal coil, field strength, resolution, glucagon, contrast agents, MR spectroscopy, and dynamic contrast-enhanced MRI. Seventy-one articles and five abstracts were included, yielding 146 studies. Missing values were highly prevalent for patient characteristics and study design. Publication year, sample size, histologic gold standard, number of imaging planes, turbo spin echo, endorectal coil, and contrast agents influenced staging performance ( p=0.05). Due to poor reporting it was not possible to fully explain the heterogeneity of performance presented in the literature. Our results suggest that turbo spin echo, endorectal coil, and multiple imaging planes improve staging performance. Studies with small sample sizes may result in higher staging performance.     

A clinical comparison of rigid and inflatable endorectal-coil probes for MRI and 3D MR spectroscopic imaging (MRSI) of the prostate

PURPOSE: To compare the data quality and ease of use of four endorectal-coil probe setups for prostate MRI. MATERIALS AND METHODS: Four endorectal-coil probe setups were compared: 1) air-inflated probe; 2) perfluorocarbon (PFC)-inflated probe; 3) rigid, smaller prototype coil; and 4) rigid, smaller coil designed for biopsying the prostate. Signal-to-noise ratio (SNR), positioning, shimming, MRI motion artifact, and MR spectroscopic imaging (MRSI) spectral quality were assessed. RESULTS: Rigid coils provided approximately 2.5-fold higher SNR than inflatable coils near the peripheral zone midline. The biopsy probe sensitivity decreased dramatically by the apex. The rigid probes, as compared to the inflatable probes, took longer to place (10 +/- 2 vs. 7 +/- 2 minutes, P < 0.0002), tended to be placed too superiorly, required repositioning more often (73% vs. 20%, P < 0.003), and had higher motion artifacts (P < 0.001). Shimming time was least for the PFC-inflated probe (2 +/- 0.5 minutes, P < 0.05). The air-inflated probe produced larger linewidths (P < 0.01) and tended to have longer shim times (7 +/- 4 minutes) and poorer spectral quality. CONCLUSION: The inflatable coil is a good clinical choice due to ease of use, good coverage, and low motion artifacts. PFC-inflation is recommended as it provided higher quality data than air-inflation. The rigid, smaller probes have higher SNR and produce less tissue distortion and may be preferred for certain applications.     

T2-weighted MR imaging of prostate cancer: multishot echo-planar imaging vs fast spin-echo imaging

The aim of the present study was to assess the performance of pre-biopsy T2-weighted MR imaging using multishot echo-planar imaging (EPI) sequence for visualization of prostate cancer and to compare image quality with that of fast spin-echo (FSE) sequence. Thirty-nine patients with suspected prostate cancer and one healthy male volunteer were examined on a 1.5-T MR scanner equipped with a pelvic phased-array coil. Axial MR images were obtained using multishot EPI sequence with a multishot number of 16 and FSE sequence without fat suppression. Paired EPI and FSE images were independently evaluated by three radiologists. Furthermore, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were compared between EPI and FSE images of 12 pathologically proven lesions of prostate cancer. Delineation of the periprostatic venous plexus, prostate zonal anatomy, and seminal vesicle on EPI was graded to be superior/inferior to FSE in 15.8/0, 14.6/0, and 21.5/4.3% of cases, respectively. On the other hand, delineation of the neurovascular bundle was superior/inferior to FSE in 2.6/13.2% of cases. The SNR and CNR of prostate cancer on EPI were significantly higher than those on FSE (7.99±2.51 vs 3.36±0.58, p<0.0001, and 5.51±2.02 vs 2.21±0.79, p<0.0001, respectively). In conclusion, multishot EPI has higher quality of contrast resolution for imaging of prostate cancer compared with FSE and would have the potential usefulness in the detection of prostate cancer, although these results obtained with a phased-array coil cannot be extrapolated to examinations performed with an endorectal coil.     

Three-dimensional proton MR spectroscopy of human prostate at 3 T without endorectal coil: feasibility

PURPOSE: To evaluate sensitivity and specificity of proton magnetic resonance (MR) spectroscopy of the prostate with external surface coil elements at 3 T for differentiation of cancer from healthy tissue within an acceptable measurement time, by using histopathologic findings as the reference standard. MATERIALS AND METHODS: The study was approved by the institutional review board; informed consent was obtained. Forty-five men (age range, 51-70 years) underwent 3-T MR imaging with external radiofrequency surface coils for signal reception. MR spectroscopy was performed with acquisition-weighted three-dimensional water- and lipid-suppressed point-resolved spectroscopy pulse sequence. Voxels were classified into healthy peripheral zone, central gland, and periurethral zone and cancer tissue. Cancer voxels were classified according to cancer size and certainty in matching histopathologic findings with MR images. After visual inspection of automated fitting of classified voxels, the choline plus creatine-to-citrate (Cho + Cr/Cit) ratio was calculated for all tissues. Area under the receiver operating characteristic curves (A(z)) values were used to assess accuracy of discrimination of cancer from healthy tissues. P < .05 indicated a significant difference. RESULTS: After exclusion of four patients with no voxels that passed visual inspection of the automated fit, a median of 82% of the classified voxels per patient was used in the analysis. Mean Cho + Cr/Cit ratios for healthy tissues were 0.22 +/- 0.12 (standard deviation) for peripheral zone, 0.34 +/- 0.14 for central gland, and 0.36 +/- 0.20 for periurethral area; all were significantly different from that of cancer (P < .001). A(z) for discrimination of probable and definite cancer tissue from healthy tissue for the peripheral zone (0.84) was significantly higher than that for the central gland (0.69) (P < .05). CONCLUSION: Three-dimensional proton MR spectroscopy of the prostate, with a combination of only external radiofrequency surface coils at 3 T, can be used to discriminate cancer from healthy tissue.