Facial surface coil for MR imaging

A local-reception counter-rotating-current coil for magnetic resonance imaging at 1.5 T was developed. It consists of two parallel coaxial racetrack-shaped loops. The planes of the loops are orthogonal to the surface of the body, and the space between the loops is open. The separation between the loops allows the device to fit over the nose and mouth for oral-maxillofacial imaging without the threat of occlusion to the patient's air passages. The sensitivity of this coil is similar to that of conventional surface coils of the same dimensions. The two active current elements conform to other anatomic objects including the eyes and anterior portion of the neck.     

Orbital fractures: surface coil MR imaging

Twenty-six patients with orbital fractures diagnosed with plain radiography and computed tomography were examined with surface coil magnetic resonance (MR) imaging. Fifteen patients had blow-out fractures, and 11 had maxillofacial complex fractures. In all patients with blow-out fractures, the location of the fracture was precisely indicated by the presence of prolapsed orbital fat. Incarceration of the extraocular muscle or orbital fat was correctly diagnosed with MR imaging, which was less sensitive in depicting maxillofacial fractures but was useful in assessment of soft-tissue involvement. Postoperative follow-up MR studies provided valuable information about the cause of motility impairment. While T1-weighted images are useful for the detection of the fracture site, both T1- and T2-weighted images are usually necessary for evaluating soft-tissue lesions. The results of this study indicate that surface coil MR imaging is an important adjunct procedure in the diagnosis and treatment of orbital fractures.     

Tendons: high-field-strength, surface coil MR imaging

High-resolution magnetic resonance (MR) images of the tendons of the hands, wrists, feet, and ankles of six healthy volunteers and six cadavers were obtained using receive-only surface coils and reduced-field-of-view imaging. Normal anatomy was identified and compared with gross anatomic sections of the six cadavers. Experimentally produced tears of the calcaneal (Achilles) tendon in domestic swine were identified on MR images. The hands and feet of 11 patients were examined, and a variety of pathologic lesions were identified, including acute posttraumatic rupture, acute tenosynovitis, chronic tendonitis, and postsurgical complications. MR imaging provides inherently greater soft-tissue contrast than any other currently available imaging modality. With the use of surface coils and reduced-field-of-view imaging to enhance spatial resolution, MR imaging has become a valuable tool for imaging tendons. Advantages over other available modalities include excellent depiction of anatomic detail, superior contrast resolution, and the potential for multiplanar imaging.     

Clinical MR imaging with a Helmholtz-type surface coil

Limited-field-of-view radio-frequency receiver antennas provide improved near-field sensitivity for magnetic resonance imaging by decreasing the antenna volume. The Helmholtz-type surface coil, consisting of two flat rings, is an organ-encompassing antenna that takes advantage of this principle to yield an improved signal-to-noise ratio (S/N). The coil was tested in a group of 50 patients and 16 healthy volunteers. Images obtained with the Helmholtz coil demonstrated quantitatively superior S/N of 2.2-fold or greater than that of comparison body coil images, as well as qualitatively superior anatomic resolution.     

Use of pelvic surface coil MR imaging for assessment of clinically localized prostate cancer with histopathological correlation

We evaluated the ability of magnetic resonance imaging (MRI) operating at 1.0 Tesla with a Helmholz pelvic surface coil to predict the pathological stage of prostate carcinoma. Radiological diagnosis was based on fast spin-echo axial T2-weighted images with and without frequency selective fat-suppression and fast spin-echo coronal T2-weighted images. Thirty-one consecutive patients (mean age 61 years, range 49 to 71 years) underwent pelvic MRI before radical prostatectomy. Correlation with whole-mount step-sections of the surgical specimens showed that the tumours were correctly localized in all but one prostate gland in which the tumour could not be seen on pelvic MRI. The transverse diameter of the visible tumour at pelvic MRI appeared to represent an approximate estimate of the true tumour dimension. Based on histopathologic whole-mount step-sections of the surgical specimens, 22 of 31 patients (71%) had tumours extending beyond the confines of the prostatic capsule. The specificity for MRI to predict capsular penetration and seminal vesicle invasion was relatively high (0.80 and 0.86, respectively). The sensitivity was acceptable for capsular penetration (0.62) but poor for seminal vesicle invasion (0.30).     

MR imaging of the scrotum with a high-resolution surface coil

Magnetic resonance (MR) imaging of the scrotum with a high-resolution surface coil was performed in ten healthy volunteers and 20 patients with scrotal abnormalities demonstrated by high-resolution real-time ultrasound (US). Four patients had an abnormal testis (two tumors, one cyst, one testicular atrophy), and 16 patients had extratesticular abnormalities (four hydroceles, five epididymal cysts, one hernia, and six cases of epididymitis). The normal structures of the scrotum were depicted clearly on MR images. In all cases, the tunica albuginea was easily differentiated from the testis and epididymis. MR imaging enabled one to distinguish intratesticular from extratesticular lesions and to determine whether a lesion was solid or cystic. Complicated and simple fluid collections could also be differentiated. In general, MR imaging and US scanning provided similar information. A potential advantage of MR imaging is in the evaluation of patients with painful scrotal lesions that may limit US evaluation.     

Comparison of surface coil and knee coil for evaluation of the patellar cartilage by MR imaging

PURPOSE: The aim of this work was to compare the knee coil and the surface coil for the visualisation of the patellar cartilage. MATERIALS AND METHODS: In 28 patients (17 women, 11 men) with an average age of 40 years (range 14-76) with knee pain MR was performed. Transverse images were obtained using a fast spin echo proton density weighted sequence on a Philips Gyroscan Intera 1.5 T clinical system. Transverse images were obtained at the level of the patellar cartilage using both the surface and the knee coil. All images were evaluated by consensus of two radiologists. They evaluated a number of quality criteria on a 4-point scale. Criteria for artefacts were also graded on a 4-point scale. RESULTS: For the visualisation of fluid there was no significant difference between the knee coil and the surface coil (P=0.021). For all other criteria regarding image quality and presence of imaging artefacts there was a significant difference between both coils (P<0.001) with the surface coil obtaining the better result. CONCLUSION: The use of the surface coil in the visualisation of the patellar cartilage can be recommended at knee MR.     

Characterization of orbital lesions by surface coil MR imaging

Surface coil MR imaging is an effective technique for evaluating orbital pathology. T1 and T2 weighting provides information not obtainable by CT and results in better characterization of some lesions. MR appears to be most useful for characterizing ocular pathology, specifically for differentiating retinoblastoma from benign diseases (Coat's disease and PHPV). MR can also be used to separate ocular tumors from associated subretinal fluid. With MR imaging, the signal intensities of lymphoma differ from those of benign inflammatory or infiltrative conditions such as pseudotumor or thyroid ophthalmopathy. Mucoceles, too, have a specific signal intensity pattern with T1 and T2 weighting. CT appears to be superior to MR for demonstrating densely calcified lesions or lesions of bone.     

Local staging of prostate cancer with endorectal surface coil MR imaging in a mid-field magnetic system

To investigate the accuracy of endorectal surface coil magnetic resonance imaging (ecMRI) in a 1.0-T magnetic field for the local staging of prostate cancer, 25 patients were studied. In 14 Stages T1 and T2 tumors, 11 were correctly identified and 3 were overstaged. In 11 Stage T3 neoplasms, ecMRI was accurate in 7 cases, and the other 4 were understaged. The overall accuracy of ecMRI in 1.0 T was 72% and that was comparable to the reported accuracy of this technique in high-field systems.     

Prostate: MR imaging with an endorectal surface coil

An endorectal surface coil has been developed to obtain high-resolution magnetic resonance images of the prostate. The probe consists of a surface coil mounted on the inner surface of a balloon. The balloon is concave to ensure tight seating against the prostate. The coil has been used in 15 patients with biopsy-proved prostatic carcinoma and in two healthy volunteers. The axial images were obtained with a 12-16-cm field of view and a 3-mm section thickness. Compared with images obtained with a body coil, the surface coil images better demonstrate prostatic anatomy and pathologic conditions.     

Spine: device to facilitate surface coil MR imaging

A device was constructed to allow rapid adjustment of the position of a surface coil in magnetic resonance (MR) imaging of the spine. The device consists of two sheets of acrylic plastic and a movable sled. The surface coil is placed on the sled and can be precisely moved superiorly or inferiorly with a cord attached to the sled. The device can save approximately 30 minutes during MR imaging of the entire spine and increases patient comfort and cooperation.     

Ankle: surface coil MR imaging at 1.5 T

High-field surface coil magnetic resonance (MR) images were obtained of 12 ankles: two from healthy volunteers, seven from patients, and three from fresh cadavers. The cadaver ankles were sectioned in the coronal, sagittal, and axial planes for direct comparison with the MR images. Plain film confirmation of pathologic conditions was obtained in all patients, and five underwent arthroscopy or surgery, or both. MR imaging provided excellent delineation of ligaments and cartilaginous structures in all cases.     

Ocular and orbital lesions: surface coil MR imaging

Nine lesions, four ocular (three melanomas, one hemangioma) and five orbital (two perioptic meningiomas, one hemangioma, one pseudotumor, one mucocele), were evaluated by magnetic resonance surface coil imaging at 1.5 T. Small ocular lesions with 3.9-4.5-mm-elevation were demonstrated. The use of two different pulse sequences resulted in separation of melanoma from adjacent retinal detachment. Contrast obtained between orbital lesions and the adjacent normal structures was better than that demonstrated with high-resolution computed tomography.     

前列腺癌的MR波谱成像中体线圈与直肠内线圈的比较

目的 比较体线圈(BODY)与直肠内线圈(ERC)MRS对前列腺癌的定性诊断效能,探讨BODY MRS临床应用的可行性.方法 12例取得穿刺病理结果的前列腺外周带癌患者,其中6例为前列腺癌,6例除外了前列腺癌.12例全部完成BODY MRS检查,其中7例同时完成ERC MRS检查.以六分区法对照穿刺结果进行MRS定量分析,分别测量每个区域内癌与非癌区(胆碱+肌酸)/枸橼酸盐[(Cho+Cre)/Cit]的比值,并采用Wilcoxon符号等级检验进行比较,计算BODY MRS对前列腺癌的诊断准确性.结果 (1)癌区与非癌区体素(Cho+Cre)/Cit比较:BODY组(7例)癌区体素比值中位数1.744(0.295～7.998),非癌区中位数0.412(0.112～2.113),两者差异有统计学意义(Z=-9.159,P＜0.01).ERC组(7例)癌区体素比值中位数为1.975(0.479～7.998),非癌区中位数为0.400(0.104～2.232),两者差异有统计学意义(Z=-9.200,P＜0.01).BODY与ERC组间比较:癌区体素组间比较差异无统计学意义(Z=-0.105,P＞0.05),非癌区体素组间比较差异无统计学意义(Z=-0.692,P＞0.05).(2)ROC分析:7例BODY与ERC组曲线下面积(Az值)分别为0.931、0.935,两者比较差异无统计学意义(P=0.851);应用BODY MRS 12例患者组Az值为0.935,敏感度、特异度分别为82.2%和88.2%.结论 BODY与ERC的MRS对前列腺外周带癌定性诊断效能接近,临床应用具有可行性.     

Surface coil for MR imaging of the skin

A strategy for the design of surface coils for the imaging of extended superficial planar anatomic structures including skin and subcutaneous fat is presented. The central concept is to create an array of closely spaced coplanar radiofrequency current filaments parallel to BO, the polarizing field, with opposite current directions in adjacent filaments. A specific coil design with four such filaments for imaging at 1.5 T is presented. It consists of two pairs of counterrotating current (CRC) coils. Phantom images as well as representative images of normal skin are shown.