开放式MR引导下颅脑介入手术的护理

目的：探讨开放MR引导下颅脑介入操作的护理措施。方法：总结对10例颅脑活检或治疗患者的术前、术中和术后护理。结果：术中和术后部分患者出现并发症，经相应的对症治疗、护理后均痊愈。结论：开放式MR引导下的颅脑介入手术是一种安全、准确的新技术，但细致、周到的护理措施、严格遵守介入治疗护理常规也是手术成功的重要保障。     

MR-guided liver biopsy within a short, wide-bore 1.5 Tesla MR system

The purpose of this study was to evaluate the diagnostic efficacy of magnetic resonance (MR)-guided biopsy of focal liver lesions within a short, wide-bore 1.5-T MR system and to determine the duration and accuracy of needle placement using MR fluoroscopy guidance in 25 patients. Accuracy of needle placement was evaluated in two orthogonal planes, and the out-of-plane angle of needle deflection was measured. Needle positioning was characterised subjectively as centred, peripheral, or exterior relative to the lesion. Exterior positioning was corrected by a step-by-step procedure. Surgical resection (n = 6), previous histologies (n = 8), or clinical/radiological follow-up (n = 11) served as the ‘gold standard’. The guidance needle could be placed successfully using MR fluoroscopy in 20 of 25 patients (80%). Needle placement was rated as ‘centred’ in 11 and as ‘peripheral’ in nine patients. Median needle deflection was 2.6 degrees, with a median deviation of 3.4 mm. In five patients, the direct approach failed or was rated as ‘exterior’; therefore, repositioning after needle stabilisation with a stainless-steel stylet was necessary. The diagnostic yield of all biopsies was: sensitivity 95.5%, specificity 100.0% and accuracy 96.0%. In conclusion, MR-guided biopsies in a short, wide-bore MR system yielded highly reliable biopsy results, and in most cases the direct approach with MR fluoroscopy guidance proved to be fast and accurate.     

Feasibility of MR imaging-guided breast lumpectomy for malignant tumors in a 0.5-T open-configuration MR imaging system

RATIONALE AND OBJECTIVES: The authors performed this study to develop the technology for and evaluate the utility of a 0.5-T vertical open-configuration magnetic resonance (MR) imaging system for imaging-guided breast lumpectomy of malignant tumors. MATERIALS AND METHODS: Twenty women with breast cancer underwent MR imaging-guided lumpectomy in a 0.5-T vertical open-configuration MR system. During lumpectomy, pre- and postresection images were acquired with and without contrast material. Images were used both for tumor localization and to monitor resection. If residual enhancement was observed, additional resection was performed in an effort to secure negative pathologic margins. RESULTS: The procedure evolved over time with technology innovations and improvements. Specifically, instruments were acquired that were compatible with MR imaging breast procedures, the echo time with the Dixon technique was modified to optimize image quality, contrast material injection was timed for maximum lesion enhancement, breath-hold image acquisition was instituted, and the biopsy cavity was filled with saline and the incision closed before image acquisition. CONCLUSION: All breast lesions were identified despite limited spatial resolution and fat-suppression techniques. The evolved techniques facilitated intraoperative margin evaluation and prompted additional surgical margin resection in five patients, sparing four from an additional surgical procedure. Intraoperative MR imaging has the potential to improve the complete pathologic excision of invasive breast cancer.     

Dynamic contrast-enhanced MR imaging and MR-guided bone biopsy on a 0.23T open imager

Objective:To assess the feasibility of MR-guided bone biopsies.Methods::Thirty-six consecutive patients with known or suspected benign or malignant bone lesions underwent comprehensive MR imaging.A dynamic contrast-enhanced sequence followed by stationary Ti-weighted sequences were obtained and MR-guided bone biopsy of the tumor at the site with fastest enhancement was performed using an open 0.23 T MR imager.Results:All MR-guided bone biopsies samples were estimated to be sufficient by the pathologists.The biopsy specimens were diagnostic in 34 of 36 cases.Conclusion:MR-guided bone biopsies combined with dynamic contrast-enhanced imaging are feasible and safe for the diagnostic investigation of equivocal bone lesions.     

Dynamic contrast-enhanced MR imaging and MR-guided bone biopsy on a 0.23 T open imager

OBJECTIVE: To assess the feasibility of MR (magnetic resonance)-guided bone biopsies. DESIGN AND PATIENTS: Thirty-six consecutive patients with known or suspected benign or malignant bone lesions underwent comprehensive MR imaging. A dynamic contrast-enhanced sequence followed by stationary T1-weighted sequences were obtained and MR-guided bone biopsy of the tumor at the site with fastest enhancement was performed using an open 0.23 T MR imager. RESULTS: All MR-guided bone biopsies samples were estimated to be sufficient by the pathologists. The biopsy specimens were diagnostic in 34 of 36 cases. CONCLUSION: MR-guided bone biopsies combined with dynamic contrast-enhanced imaging are feasible and safe for the diagnostic investigation of equivocal bone lesions.     

MR-guided laser thermoablation of inoperable renal tumors in an open-configuration interventional MR scanner: preliminary clinical experience in three cases.

A minimally invasive technique for performing magnetic resonance (MR)-guided laser interstitial thermoablation (LITT) for inoperable renal tumors is described. Three patients were treated using a percutaneous technique with real-time MR guidance in an open access interventional MR scanner. Laser therapy was delivered using a neodymium-YAG source via a water-cooled applicator system. Thermal lesions were monitored in real time using a color thermometry sequence. All patients were discharged the following day with no complications. Follow-up with gadolinium-enhanced MRI in a conventional high-field system confirmed necrosis in targeted tissue, and further treatment is planned for one patient. We concluded that LITT can be useful in treating inoperable renal malignancy and merits further evaluation. J. Magn. Reson. Imaging 1999;10:545-549.     

MR-guided vacuum-assisted breast biopsy in the management of incidental enhancing lesions detected by breast MR imaging

Purpose

The objective of this study was to determine the clinical value and accuracy of magnetic resonance (MR)-guided vacuum-assisted breast biopsy (VAB).

Materials and methods

We retrospectively analysed 106 incidental breast lesions detected on MR imaging in 98 patients. Patients with nonpalpable suspicious lesions that were only MR visible were referred for MR-VAB performed with a 10-gauge needle. All patients with a VAB diagnosis of infiltrating carcinoma, carcinoma in situ or atypical epithelial hyperplasia were referred for surgery. Histopathology of the surgical specimen was considered the reference standard.

Results

MR-guided VAB was attempted in 29/106 lesions (27%); in 2/29 patients, the procedure could not be performed owing to failure to visualise the lesion. Lesions with clearly malignant features and borderline lesions (atypical ductal hyperplasias) were identified in 12 cases (44%) and benign entities in 15 (56%). Seven of 12 (58%) malignant lesions were <10 mm. Among the 27 successful MR-VAB procedures, VAB yielded one false-negative diagnosis (4%) and underestimation (4%). MR-guided VAB sensitivity and specificity were 92% and 100%, respectively, with a positive predictive value of 100% and a negative predictive value of 93%.

Conclusions

The results of this study indicate that MR-guided VAB offers good accuracy in characterising nonpalpable breast lesions visible on MR imaging alone. Small lesion size (<1 cm) did not prove to be a limitation for the success of the procedure.     

Dynamic MR defecography with an open-configuration, low-field, tilting MR system in patients with pelvic floor disorders

Purpose

This study was undertaken to explore the capabilities of an open-configuration, low-field, tilting, magnetic resonance (MR) system for investigating pelvic floor disorders and to compare the results obtained with the patient in the semiorthostatic and supine positions.

Materials and methods

Eighteen female patients with a diagnosis of pelvic floor disorder (physical examination and conventional defecography) underwent dynamic MR defecography (MRD) with a 0.25-T tilting MR system (G-scan, Esaote). Images were obtained after administration of contrast agent into the rectum, bladder and vagina in both the orthostatic and supine positions. Three-dimensional T2-weighted hybrid contrast-enhanced (HYCE) sequences and dynamic T1-weighted gradient echo (GE) sequences were acquired at rest, during maximal contraction of the anal sphincter, straining and defecation.

Results

Good image quality was obtained in 15/18 patients; three presented severe artefacts due to motion, and three had incontinence, which hampered the functional studies. Better anatomical detail was obtained with MRD compared with conventional defecography. Three prolapses were observed in the semiorthostatic position only, and seven were found to be more severe in the orthostatic than in the supine position.

Conclusions

Dynamic MRD with an open-configuration, low-field, tilting MR system is a feasible and promising tool for studying the pelvic floor. Larger series are necessary to assess its real diagnostic value.     

MRI-guided abdominal biopsy in a 0.23-T open-configuration MRI system

The purpose of this study was to test the hypothesis that when ultrasound (US) guidance is not feasible, abdominal biopsies can be performed safely and accurately under magnetic resonance imaging (MRI) guidance in a low-field environment. MRI-guided abdominal biopsy was performed on 31 consecutive patients, in whom US-guided abdominal biopsy was not possible because the lesion was not visualized in US (n=27) or an US-guided procedure was not considered safe (n=4). The locations of the lesions were liver (n=14), pancreas (n=6), lymph node (n=4), retroperitoneal mass (n=3), adrenal gland (n=3) and spleen (n=1). The average size of the lesion was 2.2 cm (range 1–4 cm) in maximum diameter. All procedures were done by using a 0.23-T open-configuration C-arm-shaped MRI scanner with interventional optical tracking equipment and software. Fine-needle aspiration (FNA) biopsy was performed on all 31 patients; 18 patients underwent both FNA biopsy and cutting needle core biopsy. Procedures were evaluated for diagnostic sensitivity, specificity and accuracy as well as procedure time and complications. The FNA biopsy specimens were adequate for interpretation in 27 (87%) of 31 cases. Two of these proved to be false-negative findings during follow-up or subsequent biopsy. The final diagnosis was malignant in 15 and benign in 16 patients. The sensitivity, specificity and accuracy of FNA biopsy were 71, 100 and 81%, respectively. Of the 18 core-needle biopsies, one was determined false-negative owing to nonrepresentativeness. The sensitivity, specificity and accuracy of histological samples were 90, 100 and 94%, respectively. The needle time was 19 min on average and the mean room time was 1 h 48 min. No immediate or late complications occurred. MRI-guided abdominal biopsy can be performed safely and accurately in a low-field environment in patients for whom an US-guided procedure is not feasible.     

Monitoring and visualization techniques for MR-guided laser ablations in an open MR system

Our purpose was to develop temperature-sensitive MR sequences and image-processing techniques to assess their potential of monitoring interstitial laser therapy (ILT) in brain tumors (n = 3) and liver tumors (n = 7). ILT lasted 2 to 26 minutes, whereas images from T1-weighted fast-spin-echo (FSE) or spoiled gradient-recalled (SPGR) sequences were acquired within 5 to 13 seconds. Pixel subtraction and visualization of T1-weighted images or optical flow computation was done within less than 110 msec. Alternating phase-mapping of real and imaginary components of SPGR sequences was performed within 220 msec. Pixel subtraction of T1-weighted images identified thermal changes in liver and brain tumors but could not evaluate the temperature values as chemical shift-based imaging, which was, however, more affected by susceptibility effects and motion. Optical flow computation displayed the predicted course of thermal changes and revealed that the rate of heat deposition can be anisotropic, which may be related to heterogeneous tumor structure and/or vascularization.     

MR-guided biopsy of musculoskeletal lesions in a low-field system

Thirty magnetic resonance (MR)-guided biopsies were obtained from 20 skeletal and 10 soft-tissue lesions in 31 patients using an open 0.2 T MR system equipped with interventional accessories. The results from aspiration (N = 3), core biopsy (N = 15), and transcortical trephine biopsy (N = 12) were evaluated for accuracy and clinical efficacy. Specimens were successfully obtained from 29 patients. Results were clinically effective in 23 patients, rated definitive in 16, nonconclusive in 9, and unspecific in 2 patients. A false diagnosis due to sampling error occurred in 2 patients, and biopsy sampling was impossible in one case. The best diagnostic yield was achieved from nontranscortical biopsies of osteolytic or soft-tissue masses. Results from transcortical biopsies were less specific due to the predominance of benign lesions. MR fluoroscopy for needle guidance was applied in 13 patients. Complete needle placement inside the magnet could be performed in 16 patients. MR-guided biopsy using an open low-field MR imager is feasible and clinically effective and will become a valuable tool in the management of musculoskeletal lesions. J. Magn. Reson. Imaging 2001;13:761-768.     

Interactive MR-guided percutaneous nephrostomy

Open-configuration MRI systems have been recently introduced and hold promise to allow the performance of a variety of minimally invasive procedures. Experience with MR-guided catheter-based luminal interventions is experimental to date. This is the first case of a successful percutaneous nephrostomy tube placement in a patient in an interventional MR system. The procedure was performed completely under MR guidance, and technical aspects are reviewed and compared with other, established techniques for percutaneous nephrostomy placement.     

Interactive MR-guided biopsies of maxillary and skull-base lesions in an open-MR system: first clinical results

The purpose of this study was to explore the potential of interactive MR-guided biopsies in the maxillary and skull base region using a 0.5-T open-configuration scanner in patients with tumours affecting the maxilla or skull base. Ten patients with cystic or solid tumours affecting the maxillary and skull base regions underwent MR-guided biopsy in a superconducting, open 0.5-T MR system equipped with an optical frameless stereotaxic system. T2-weighted spin-echo images were acquired prior to and following biopsy, which was performed with 18- or 22-G needles using an enoral or percutaneous approach following infiltration of the skin, mucosa and periosteum with local anaesthetics. The position of the needle tip was continuously updated on fast T1-weighted gradient-recalled-echo images (TR 19 ms, TE 7.1 ms, flip angle 30 °, slice thickness 1 cm, field of view 24 × 24 cm) using the frameless stereotaxic system. In addition, the needle was identified based on the associated susceptibility artefact in all three planes. Once the target lesion had been reached, cytology material was aspirated. All ten patients tolerated the interactive MR-guided biopsies well without complications. Vital structures, including the brain, neurovascular bundles, vessels and eyes, were visualized on MR imaging and could be spared. There was no difference in the use of 18- or 22-G non-ferromagnetic needles concerning the susceptibility artefact. Sufficient material for cytological analysis was obtained in nine of ten cases. The mean biopsy time was 15 min. Interactive MR-guided biopsies of the head and neck in an open system are technically feasible and safe. Monitoring of the needle path in multiple planes permits the interactive adjustment of the needle course in near real time. Interactive MR-guided biopsies may well replace open surgical procedures in the maxillary region in selected patients. Received: 26 May 1998; Revision received: 18 August 1998; Accepted: 7 September 1998     

Positional lumbar imaging using a positional device in a horizontally open-configuration MR unit - initial experience

PURPOSE: To evaluate whether positional MR images of the lumbar spine, obtained with a horizontally open-configuration MR unit, demonstrate positional changes of the dural sac, and to assess whether there are significant differences in positional changes between healthy volunteers and patients with chronic low back pain. MATERIALS AND METHODS: The study population consisted of 15 patients with chronic low back pain and 14 healthy volunteers. MR images were obtained using a horizontally open-configuration 0.4-T MR unit. After conventional lumbar MR examinations, images were obtained in the flexion, neutral, and extension positions, using a positioning device. The anteroposterior diameter of the dural sac at the level of each lumbar disk was measured in the three positions and quantitative data were compared. RESULTS: Our MR protocol was tolerated by all patients. In both patients and volunteers, the mean anteroposterior diameter of the dural sac was smaller in the extension positions than in the flexion positions. In the mean rate of change (RC) in the dural sac diameter at the site of the degenerated disks, the difference between the volunteers and patients was significant (P < 0.05). There was no significant difference in the mean RC between patients and volunteers without degenerative disks. CONCLUSION: Using a horizontally open-configuration MR unit, positional MR imaging provided position-dependent change of the dural sac. Positional changes at the site of the degenerated disks may be different in patients with and without chronic low back pain.