External Surface Coil Research Articles

A Novel Three-Channel Endorectal Coil for Prostate Magnetic Resonance Imaging at 3T.

The purpose of this work is to develop a 3-channel endorectal coil (ERC-3C) structure to obtain higher signal-to-noise (SNR) and better parallel imaging performance for prostate magnetic resonance imaging (MRI) at 3T. The coil performance was validated by in vivo studies and the SNR, g-factor, and diffusion-weighted imaging (DWI) were compared. A 2-channel endorectal coil (ERC-2C) with two orthogonal loops and a 12-channel external surface coil were employed for comparison. Compared with the ERC-2C with a quadrature configuration and the external 12-channel coil array, the proposed ERC-3C improved SNR performance by 23.9% and 428.9%, respectively. The improved SNR enables the ERC-3C to produce spatial high-resolution images of 0.24 mm × 0.24 mm × 2 mm (0.1152 μL) in the prostate area within 9 minutes. We developed an ERC-3C and validated its performance through in vivo MR imaging experiments. The results demonstrated the feasibility of an ERC with more than two channels and that a higher SNR can be achieved using the ERC-3C compared with an orthogonal ERC-2C of the same coverage.

Implantable NMR Microcoils in Rats: A New Tool for Exploring Tumor Metabolism at Sub-Microliter Scale?

The aim of this study was to evaluate the potential of a miniaturized implantable nuclear magnetic resonance (NMR) coil to acquire in vivo proton NMR spectra in sub-microliter regions of interest and to obtain metabolic information using magnetic resonance spectroscopy (MRS) in these small volumes. For this purpose, the NMR microcoils were implanted in the right cortex of healthy rats and in C6 glioma-bearing rats. The dimensions of the microcoil were 450 micrometers wide and 3 mm long. The MRS acquisitions were performed at 7 Tesla using volume coil for RF excitation and microcoil for signal reception. The detection volume of the microcoil was measured equal to 450 nL. A gain in sensitivity equal to 76 was found in favor of implanted microcoil as compared to external surface coil. Nine resonances from metabolites were assigned in the spectra acquired in healthy rats (n = 5) and in glioma-bearing rat (n = 1). The differences in relative amplitude of choline, lactate and creatine resonances observed in glioma-bearing animal were in agreement with published findings on this tumor model. In conclusion, the designed implantable microcoil is suitable for in vivo MRS and can be used for probing the metabolism in localized and very small regions of interest in a tumor.

PD11-03 IMPACT OF MAGNETIC RESONANCE SPECTROSCOPIC IMAGING ON DIFFERENTIAL DIAGNOSIS OF RENAL TUMORS

You have accessJournal of UrologyImaging/Radiology: Uroradiology II1 Apr 2017PD11-03 IMPACT OF MAGNETIC RESONANCE SPECTROSCOPIC IMAGING ON DIFFERENTIAL DIAGNOSIS OF RENAL TUMORS Masahiro Sumura, Haruki Ajiki, Chiaki Koike, Keita Inoue, Keisuke Nakanishi, Hiroaki Yasumoto, Tsuyoshi Yoshizako, Hajime Kitagaki, and Hiroaki Shiina Masahiro SumuraMasahiro Sumura More articles by this author , Haruki AjikiHaruki Ajiki More articles by this author , Chiaki KoikeChiaki Koike More articles by this author , Keita InoueKeita Inoue More articles by this author , Keisuke NakanishiKeisuke Nakanishi More articles by this author , Hiroaki YasumotoHiroaki Yasumoto More articles by this author , Tsuyoshi YoshizakoTsuyoshi Yoshizako More articles by this author , Hajime KitagakiHajime Kitagaki More articles by this author , and Hiroaki ShiinaHiroaki Shiina More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2017.02.579AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The utility of magnetic resonance imaging (MRI) for diagnosis of a renal tumor is controversial. MR spectroscopy (MRS), a noninvasive method utilized for assessment of biochemical tissue characteristics in vivo, has value for differentiation of tumors in the brain, breast, and prostate. However, there are few reports of MRS examinations of kidneys. Here, we evaluated the diagnostic potential of MRS for renal tumors. METHODS We analyzed 45 renal tumors in 45 patients (age 60-82 years, median 62 years; clinical stage: T1a, n=25; T1b, n=9; T2a, n=1; T2b, n=1; T3a, n=6; T4, n=1). All patients underwent pre-operative MRS examinations with a 1.5 T MR device equipped with a phased array type external surface coil, in which respiratory-triggered single voxel MRS was performed with a point-resolved spectroscopy sequence (TR, 2000 ms; TE, 135 ms). The obtained spectra were analyzed for choline resonances at 3.2 ppm, after normalization for noise outside the diagnostic range. Choline/noise ratio (CNR) values were automatically calculated using the “R” software package, then the CNRs in spectra obtained from both cancerous and benign tumors were compared. Histological results were defined as the standard for reference. RESULTS Of the 45 tumors examined, 41 including 3 cystic tumors were malignant in histological findings, while 2 were histologically diagnosed as angiomyolipoma (AML), 1 as oncocytoma and 1 as tuberculous granuloma (TG). In all cases, the obtained spectra were of sufficient quality for diagnosis. The mean choline CNR value for malignant lesions was 3.4, while that was 1.01 for AML, 1.05 for oncocytoma, and 1.12 for TG. Malignant renal tumors tended to show higher CNR values than benign tumors as well as in tumors with higher grade. CONCLUSIONS Although further studies are necessary, our findings indicate that MRS has potential to differentiate malignant from benign renal tumors. Furthermore, it may be an effective diagnostic tool for cystic renal tumor cases. © 2017FiguresReferencesRelatedDetails Volume 197Issue 4SApril 2017Page: e206 Advertisement Copyright & Permissions© 2017MetricsAuthor Information Masahiro Sumura More articles by this author Haruki Ajiki More articles by this author Chiaki Koike More articles by this author Keita Inoue More articles by this author Keisuke Nakanishi More articles by this author Hiroaki Yasumoto More articles by this author Tsuyoshi Yoshizako More articles by this author Hajime Kitagaki More articles by this author Hiroaki Shiina More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Sensitive enhancement of vessel wall imaging with an endoesophageal Wireless Amplified NMR Detector (WAND).

To improve the imaging quality of vessel walls with an endoesophageal Wireless Amplified NMR Detector (WAND). A cylindrically shaped double-frequency resonator has been constructed with a single metal wire that is self-connected by a pair of nonlinear capacitors. The double-frequency resonator can convert wirelessly provided pumping power into amplified MR signals. This compact design makes the detector easily insertable into a rodent esophagus. The detector has good longitudinal and axial symmetry. Compared to an external surface coil, the WAND can enhance detection sensitivity by at least 5 times, even when the distance separation between the region of interest and the detector's cylindrical surface is twice the detector's own radius. Such detection capability enables us to observe vessel walls near the aortic arch and carotid bifurcation with elevated sensitivity. A cylindrical MRI detector integrated with a wireless-powered amplifier has been developed as an endoesophageal detector to enhance detection sensitivity of vessel walls. This detector can greatly improve the imaging quality for vessel regions that are susceptible to atherosclerotic lesions. Magn Reson Med 78:2048-2054, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

MP78-08 DIAGNOSTIC POTENTIAL OF PROTON MAGNETIC RESONANCE SPECTROSCOPY ON RENAL TUMORS.

You have accessJournal of UrologyKidney Cancer: Epidemiology & Evaluation/Staging II1 Apr 2016MP78-08 DIAGNOSTIC POTENTIAL OF PROTON MAGNETIC RESONANCE SPECTROSCOPY ON RENAL TUMORS. Masahiro Sumura, Naoko Arichi, Shigenobu Nakamura, Hiroaki Yasumoto, Takeshi Yoshizako, Hajime Kitagaki, and Hiroaki Shiina Masahiro SumuraMasahiro Sumura More articles by this author , Naoko ArichiNaoko Arichi More articles by this author , Shigenobu NakamuraShigenobu Nakamura More articles by this author , Hiroaki YasumotoHiroaki Yasumoto More articles by this author , Takeshi YoshizakoTakeshi Yoshizako More articles by this author , Hajime KitagakiHajime Kitagaki More articles by this author , and Hiroaki ShiinaHiroaki Shiina More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2016.02.1964AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES Magnetic resonance spectroscopy (MRS) is a noninvasive method for assessment of biochemical tissue characteristics in vivo and has proven its value for differentiation of tumors in brain, breast, and prostate. However, there are few reports of MRS on kidney, because of respiratory displacement of kidney. This problem could be solved with respiratory-triggered examination in our institution. We evaluate the diagnostic potential of MRS on renal tumors. METHODS 28 renal tumors in 28 patients were enrolled in this study (age 60-82 years-old (median 62 years-old), and clinical stage T1a 15 cases, T1b 5cases, T2a 1 case, T3a 6 cases and T4 1 cases). All patients underwent MRS with 1.5 T MR device and phased array type external surface coil, pre-operatively. A respiratory-triggered single voxel MRS was performed with the point-resolved spectroscopy sequence (TR 2000 ms, TE 135 ms). The spectra were analyzed for choline resonances at 3.2 ppm, that were normalized using the noise outside the diagnostic range of the spectra. The spectra obtained from both tumor and benign tumors were compared. Histological results were defined as the standard of reference. RESULTS 26 tumors in 28 tumors were histologically malignant. Two tumors were histologically diagnosed angiomyolipoma (AML). In all cases, spectrum had sufficient quality to diagnose. Mean choline SNR in malignant lesions was 3.4 and 1.01 in AML. Higher choline SNR were observed in tumors with higher grade. CONCLUSIONS We recognized that further studies were essential, but MRS might have the potential to differentiate the malignant renal tumor from benign. Furthermore, choline could be a biomarker of aggressiveness in malignant renal tumors. © 2016FiguresReferencesRelatedDetails Volume 195Issue 4SApril 2016Page: e1027 Advertisement Copyright & Permissions© 2016MetricsAuthor Information Masahiro Sumura More articles by this author Naoko Arichi More articles by this author Shigenobu Nakamura More articles by this author Hiroaki Yasumoto More articles by this author Takeshi Yoshizako More articles by this author Hajime Kitagaki More articles by this author Hiroaki Shiina More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Three-dimensional proton magnetic resonance spectroscopic imaging with and without an endorectal coil: a prostate phantom study.

Proton magnetic resonance spectroscopic imaging (MRSI) of the prostate has been used with only a combination of external surface coils. The quality of spectral fitting of the (choline + creatine)/citrate ([Cho + Cr]/Cit) ratio at different field strengths and different coils is important for quantitative/semi-quantitative diagnosis of prostate cancer. To evaluate the quality of spectral fitting of the (Cho + Cr)/Cit ratio of a prostate phantom using MRSI at different field strengths and various coils. Experiments were using 1.5-T and 3.0-T MR systems. Measurements were taken on a homemade prostate phantom with different coils: spinal array; abdominal array; and endorectal. The signal-to-noise ratio (SNR) of choline, creatine, and citrate peaks as well as the (Cho + Cr)/Cit ratio in each voxel were compared among groups using multi-way analysis of variance. Magnetic field strength, coils, and plane position had a significant effect on the SNR or (Cho + Cr)/Cit ratio, and there were interactions among groups (all P = 0.000). The 1.5-T (0.228 ± 0.044) exhibited a higher (Cho + Cr)/Cit ratio than the 3.0-T (0.125 ± 0.041) magnetic field strength (F = 3238, P = 0.000). The (Cho + Cr)/Cit ratio of both surface coils (0.183 ± 0.065) and all coils (0.181 ± 0.057) was significantly lower than that of the endorectal coil (0.195 ± 0.077) (both P < 0.05), but significant differences in the mean (Cho + Cr)/Cit ratio were not observed if surface coils and all coils were used (P > 0.05). No significant differences were found among the (Cho + Cr)/Cit ratios of all voxels in the middle planes by the post-hoc analyses (all P > 0.05). Three-dimensional proton MRSI of prostate metabolites in a phantom using surface coils is feasible and reliable, but (Cho + Cr)/Cit ratios acquired at different magnetic fields and coils were different. This difference should be taken into account when calculating this ratio in a field strength-independent way.

Spectro-IRM de prostate avec antennes externes : faisabilité en pratique clinique ?

To determine the clinical feasibility of MR spectroscopy (MRS) of prostate cancer using external multi-channel surface coils at 1.5T. Materials and methods. Retrospective study of 31 patients with prostate cancer who underwent MRS as part of the staging work-up prior to radical prostatectomy. The ratio of the three main metabolites ([choline + creatine]/citrate) were measured along with spectral analysis of different regions of interest (ROI) placed in areas of normal tissue and cancer using the surgical specimen as the standard of reference. One hundred and eighty-three voxels were analyzed. Qualitative visual analysis identified pathological spectra in 88.5% of cancer ROI, 11.7% of normal transitional zone ROI and 1.6% of normal peripheral zone ROI. The ratios of normal prostate tissue were significantly more elevated (p<0.0001) in the transition zone (0.41 +/- 0.24) than in the peripheral zone (0.22 +/- 0.36). Tumor containing voxels had significantly higher ratios (2.84 +/- 2.74) than normal tissue containing voxels of the transition zone (p<0.0001) and peripheral zone (p<0.0001). Prostate MRS using external surface coils appears routinely feasible at 1.5T, even though it presents some limitations.

Three-dimensional Proton MR Spectroscopy of Human Prostate at 3 T without Endorectal Coil: Feasibility

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. 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. 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). 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.

Prostate and Lymph Node Proton Magnetic Resonance (MR) Spectroscopic Imaging with External Array Coils at 3 T to Detect Recurrent Prostate Cancer After Radiation Therapy

In a patient suspected of having recurrent prostate cancer after radiation therapy, we demonstrate the feasibility of noninvasive proton magnetic resonance spectroscopic (1H-MRS) imaging of the prostate and a lymph node at 3 T using a matrix of external surface coils. Written informed consent was obtained from the patient. With 1H-MRS imaging, high choline with low citrate signal was observed in the prostate, and in the lymph node a signal of choline-containing compounds was identified. The tissue level of the compounds in the enlarged lymph node was estimated to be 8.1 mmol/kg water. Subsequent histopathological analysis of systematic transrectal ultrasound-guided prostate biopsy and computed tomography-guided biopsy of the lymph node confirmed the presence of prostate cancer in both.

The development and optimization of high spatial resolution MRI for imaging the oesophagus using an external surface coil

This paper describes the development and optimization of an innovative technique using an external surface coil to obtain high resolution, thin section MR images of the oesophagus using volunteers. T2 weighted fast spin echo sequences were performed with and without cardiac gating. The field of view (FOV), matrix size, slice thickness, number of signal averages (NSA), and repetition time (TR)/echo time (TE) were altered to optimize signal to noise ratio (SNR) whilst maintaining spatial resolution. The effect of cardiac gating was also investigated. Workstation images were evaluated on the ability to visualize: individual oesophageal wall layers; perioesophageal fat; the azygos vein and wall of the descending aorta, giving qualitative assessment of image clarity. The optimum sequence enabled the layers of the oesophageal wall and perioesophageal tissues to be demonstrated in an acceptable scan time of 7.07 min. A FOV of less than 250 mm degraded image quality so that individual oesophageal wall layers could not be depicted and noise within the image impaired visualization of posterior mediastinal structures. The results indicate that high resolution imaging of the oesophagus using an external surface coil can depict anatomic structures clearly and that the use of cardiac gating improves image clarity. The technique offers an alternative, non-invasive method of detailed imaging of the oesophagus.

The appearances of oesophageal carcinoma demonstrated on high-resolution, T2-weighted MRI, with histopathological correlation

This paper describes the spectrum of imaging features of oesophageal adenocarcinoma seen using high-resolution T2-weighted (T2W) magnetic resonance imaging (MRI). Thirty-nine patients with biopsy-proven oesophageal adenocarcinoma were scanned using an external surface coil. A sagittal T2W sequence was used to localise the tumour and to plan axial images perpendicular to the tumour. Fast spin-echo (FSE) T2W axial sequence parameters were: TR/TE, 3,300-5,000 ms/120-80 ms; field of view (FOV) 225 mm, matrix 176x512(reconstructed) mm to 256x224 mm, giving an in-plane resolution of between 1.28x0.44 mm and 0.88x1.00 mm, with 3-mm slice thickness. Thirty-three patients underwent resection and the MR images were compared with the histological whole-mount sections. There were four T1, 12 T2, and 17 T3 tumours. The T2W high-resolution MRI sequences produced detailed images of the oesophageal wall and surrounding structures. Analysis of the imaging appearances for different tumour T stages enabled the development of imaging criteria for local staging of oesophageal cancer using high-resolution MRI. Our study illustrates the spectrum of appearances of oesophageal cancer on T2W high-resolution MRI, and using the criteria established in this study, demonstrates the potential of this technique as an alternative non-invasive method for local staging for oesophageal cancer.

Imagerie de la prostate normale, de l’hyperplasie bénigne et de la pathologie inflammatoire

According to Mc Neal, the prostate gland is characterized by three major glandular compartments: the transition zone, the central zone and the peripheral zone. This zonal anatomy can be identified with endorectal sonography and with MRI. With the later, both endorectal or external surface coils can be used. Internal structure of seminal vesicles and vas deferens is better analyzed with MRI than with sonography. Relationship between these elements is important to know, as well as areas of weakness of the prostatic capsule, mainly in the evaluation of cancer extraprostatic extension. Sonography plays a major role in diagnosis, pre-therapeutic evaluation and follow-up of patients with benign prostatic hyperplasia. The role of imaging in inflammatory disorders is more questionable.

An inductively-coupled, detachable receiver coil system for use with magnetic resonance compatible endoscopes.

To construct an inductively-coupled receiver coil system for use with a magnetic resonance (MR) compatible endoscope, and to evaluate its use in a pilot group of patients with esophageal cancer. An inductively-coupled coil system, comprising a saddle geometry cylindrical receiver coil fitted as a sleeve around the endoscope tip and a pick-up coil housed within a channel of an MR-compatible endoscope, was designed and developed for use at 0.5 T. Twenty-three patients with esophageal cancer were recruited for MR endoscopy. In 17 cases, the endoscopic coil system was used in conjunction with an external surface coil in order to obtain information from the surrounding mediastinum. The examination took 40-50 minutes. MR imaging using the inductively-coupled endoscopic coil was successful in 21 cases (one failed intubation and one artifact from unrelated external source). Image artifact was largely due to respiration and global patient motion in sedated individuals undergoing endoscopy. Inductively-coupled coil systems may be used with endoscopes to allow improved safety through increased patient-system isolation and detachability of coils and electronics for repair or replacement with coils tuned for different frequencies.

Preoperative staging of rectal cancer using magnetic resonance imaging with external phase-arrayed coils.

Rectal cancer can be accurately staged preoperatively by magnetic resonance imaging (MRI) with external phase-arrayed coils. Comparison of MRIs with pathologic staging. University hospital. Twenty-eight consecutive patients with biopsy-proven rectal cancer who did not undergo irradiation. Patients underwent imaging using a 1.5-T MRI scanner with external phase-arrayed surface coils. Streaking of the perirectal fat and disruption of the bowel wall margin were interpreted as transmural invasion. Lymph nodes were defined as metastatic when they had a diameter of at least 0.5 cm. Tumors were staged according to the TNM staging system (American Joint Committee on Cancer guidelines) as confined to the bowel wall (T1-T2) and invading through the bowel wall (T3-T4). Patients underwent anterior resection (n = 15), abdominoperineal resection (n = 11), or local excision (n = 2). Calculation of sensitivity, specificity, and accuracy for invasion through the bowel wall and lymph node status. Sensitivity of MRI in detecting invasion through the bowel wall was 89% (16/18), specificity was 80% (8/10), and accuracy was 86% (24/28). Sensitivity for malignant lymphadenopathy was 67% (8/12), specificity was 71% (10/14), and accuracy 69% (18/26). Although more costly and not as accurate as endoscopic ultrasound, MRI with phase-arrayed coils had excellent sensitivity at detecting transmural penetration of rectal cancer.

In vivo 1H magnetic resonance imaging and spectroscopy of the rat spinal cord using an inductively‐coupled chronically implanted RF coil

An inductively coupled, chronically implanted short-solenoid coil was used to obtain in vivo localized 1H NMR spectra and diffusion-weighted images from a rat spinal cord. A 5 x 8 mm two-turn elliptically shaped solenoid coil was implanted in rats at the site of a T-12 vertebral-level laminectomy. Excitation was achieved solely by a 3 x 3 cm external surface coil, and signal detection was achieved by inductively coupling the external coil to the implanted coil. The image signal-to-noise ratio (SNR) obtained with the inductively-coupled implanted coil was compared with that obtained using a linear or a quadrature external surface coil. The implanted coil provided a gain by over a factor of 3 in SNR. The implanted coil was used to measure localized 1H spectra in vivo at the T13/L1 spinal-cord level within a 1.85 x 1.85 x 4.82 mm (16.5 microL) volume. With 256 averages, a approximately 3-s repetition delay and respiratory gating, a high-quality spectrum was acquired in 13 min. In addition, water translational diffusion was measured in three orthogonal directions using a stimulated-echo imaging sequence, with a short echo time (TE), to produce a quantitative map of diffusion in a rat spinal cord in vivo.

A method for in vivo high resolution MRI of rat spinal cord injury

We have developed an implanted radiofrequency coil to obtain high resolution in vivo MR images at 1.9 Tesla of rat spinal cords that have been injured using a standardized weight drop technique. The signal-to-noise ratio and motion artifact suppression of these images is superior to that achieved in earlier attempts at this field strength using an external surface coil. The high quality and spatial resolution provided by this technique afford the possibility for longitudinal studies of experimental spinal cord injury before and after treatment, as well as detailed correlation of in vivo MRI contrast, histopathological findings, and functional deficit, in a controlled setting.

Magnetic stimulation of the sacral roots.

Magnetic stimulation using an external surface coil induces an electrodynamic field that penetrates various tissues and stimulates peripheral nerves in a similar fashion to conventional electrical stimulation. An 83 mm magnetic surface coil was used to stimulate 11 spinal cord injury (SCI) patients, during which time detrusor activity and evoked potentials of the striated urinary sphincter motor pathways were evaluated. All patients had urodynamic studies and conventional sacral evoked potentials prior to magnetic stimulation. The mean bladder capacity was 337 ml (range 109-590), mean leak point pressure was 50 cm H2O (range 10-80), and mean sacral reflex (afferent-efferent) latency was 37.9 ms (range 25.1-49.3). Eight patients had detrusor-sphincter dyssynergia. Magnetic stimulation over the sacral spine at different bladder volumes was performed. Detrusor and striated sphincter responses were recorded during stimulation. In all patients the technique was easy and the results were reproducible. The mean sacral motor pathway (efferent) latency was 27.9 ms (range 18.7-39.6). Using maximal stimulation, no detrusor response was recorded at bladder volumes < 200 ml. However, a detrusor response was recorded in 7 patients (> 10 cm H2O in 2, < 10 cm H2O in 5) when the bladder volume was > 200 ml. No complications were seen. Sacral evoked potential measurements assess the function and integrity of the sacral arc but it does not distinguish between afferent and efferent pathways. Magnetic stimulation is a safe and effective method to assess the integrity and function of the detrusor and striated sphincter motor (efferent) pathways. When combined with sacral evoked potential studies, the sensory (afferent) pathways can be evaluated indirectly.(ABSTRACT TRUNCATED AT 250 WORDS)

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.

Use of fluorine-19 nuclear magnetic resonance spectroscopy and hydralazine for measuring dynamic changes in blood perfusion volume in tumors in mice.

One method of evaluating the mechanism of action of agents which alter tumor oxygenation is to determine their effects on tumor blood flow. This study tests applicability of a new approach using an emulsion of the inert fluorocarbon perfluorooctylbromide (PFOB) at nontoxic doses as a tracer in fluorine-19 (19F) nuclear magnetic resonance (NMR) spectroscopy to evaluate dynamic changes in vascular perfusion volume in transplanted tumors. The PFOB emulsion (100% wt/vol) was injected into the tail vein in tumor-bearing C3H/He or nu/nu mice immobilized in a magnet interfaced to a spectrometer, either as a single bolus injection of 8 mL/kg body weight or in multiple injections to a total dose of 24 mL/kg. A 7-mm external surface coil was placed over the tumor. Signal from the PFOB in the tumor volume seen by the coil rapidly reached equilibrium and was maintained for at least 2 hours, and multiple doses of PFOB emulsion resulted in a linear increase in 19F signal strength. Since the 19F signal strength was directly proportional to the perfusion volume of the tumor vasculature, reduction of signal intensity should correspond directly to any reduction in volume caused by a change in the tumor blood flow. To investigate this hypothesis, the vasoactive agent hydralazine (5 mg/kg) was injected intravenously after administering the PFOB emulsion to induce changes in tumor blood supply. KHT and RIF-1 murine sarcomas, the HT29 human colon carcinoma, and the HX118 human melanoma tumors were studied. In a comparative analysis of changes in blood flow induced by hydralazine, we studied Xe-133 clearance in KHT murine sarcoma and SCCVII/Ha (SCCVII) murine squamous cell carcinoma. Hydralazine significantly reduced the 19F signal intensity in the murine tumors RIF-1 and KHT and in the HT29 human tumor, with little reduction in the SCCVII/Ha murine and HX118 human tumors. Hydralazine induced a statistically significant 64% decrease in mean clearance rate in the KHT tumor, while SCCVII/Ha tumors showed no significant change, indicating that hydralazine restricted blood flow to a greater extent in the tumor type that showed reduced 19F signal from the PFOB emulsion. These data demonstrate the potential of PFOB emulsion as a tracer in NMR spectroscopy for studying tumor vasculature.