A case of hepatocellular carcinoma treated by MR-guided focused ultrasound ablation with respiratory gating.
Focused ultrasound surgery (FUS) is a method of noninvasive focal thermal ablation. Temperature-sensitive phase-difference magnetic resonance (MR) imaging allows monitoring of the focal point and measurement of tissue temperature elevation in real time, ensuring delivery of a therapeutic dose. A newly developed respiratory monitoring system enables us to track liver tumors, which move with respiration. We report our initial experience using MR-guided FUS with respiratory gating in successfully treating a hepatocellular carcinoma 15 mm in diameter. (+info)
The evolving non-surgical ablation of breast cancer: MR guided focused ultrasound (MRgFUS).
MRgFUS (MR guided Focused Ultrasound) being one of the non-surgical ablation techniques. We have already achieved favorable results in the past clinical study of MRgFUS to local treatment. New twenty one cases of invasive/noninvasive ductal carcinoma of the breast were treated by MRgFUS. Core needle biopsy led to the definitive diagnosis. All the patients were positioned prone in the treatment, using the therapeutic apparatus such as Signa Excite 1.5 T for MRI and ExAblate 2000 version 2.6/4.1 for FUS. Irradiation was not applied to all the 21 cases after MRgFUS. Axillary lymph node metastases were examined by dissection or sentinel lymph node biopsy. Recurrence or abnormal area of residual cancer was treated with Re-MRgFUS or ablated by usual surgery. All the 21 cases were from women patients. Median age is 54 years (range: 34-72). Median diameter of tumor is 15 mm (range: 5-50). As for the numbers of treatment, 17 patients were treated once, and 4 patients twice. Median period of observation is 14 months (range: 3-26). One case of recurrence of pure mucinous carcinoma was experienced. No evidences of recurrence were obtained through MRI for the rest of 20 cases. Skin burns were found in 2 cases. The patient had dimple on the skin immediately above tumor. In conclusion, MRgFUS is a good mean as local control of breast cancer, but the indicated case must be selected strictly. And it needs to observe longer the patients who ware treated by MRgFUS alone. (+info)
High-grade MRI bone oedema is common within the surgical field in rheumatoid arthritis patients undergoing joint replacement and is associated with osteitis in subchondral bone.
OBJECTIVES: MRI bone oedema has been observed in early and advanced RA and may represent a cellular infiltrate (osteitis) in subchondral bone. We studied MRI scans from RA patients undergoing surgery, seeking to identify regions of bone oedema and examine its histopathological equivalent in resected bone. METHODS: Preoperative contrast-enhanced MRI scans were obtained in 11 RA patients scheduled for orthopaedic surgery to the hands/wrists or feet. In 9, MRI scans were scored by 2 readers for bone oedema (RAMRIS system). Its distribution with respect to surgical site was investigated. In 4 patients, 7 bone samples were examined for a cellular infiltrate, and this was compared with MRI bone oedema, scored for spatial extent and intensity. RESULTS: Inter-reader intraclass correlation coefficients for bone oedema were 0.51 (all sites) and 0.98 (bone samples for histology). Bone oedema was observed at 60% of surgical sites vs 38% of non-surgical sites. High-grade bone oedema (score >/=50% maximum) was strongly associated with the surgical field (OR 9.3 (3.5 to 24.2), p<0.0001). Bone oedema scores correlated with pain (r = 0.67, p = 0.048) and CRP (r = 0.86, p = 0.01). In 4 of the 7 bone samples, there was concordance between bone oedema and subchondral osteitis. In 3, there was no MRI bone oedema, and osteitis was "slight". CONCLUSION: High-grade MRI bone oedema was common within the field of intended surgery and associated with pain. There was concordance between the presence and severity of MRI bone oedema and osteitis on histology, with an MRI threshold effect due to differences in image resolution. (+info)
"MRI Stealth" robot for prostate interventions.
The paper reports an important achievement in MRI instrumentation, a pneumatic, fully actuated robot located within the scanner alongside the patient and operating under remote control based on the images. Previous MRI robots commonly used piezoelectric actuation limiting their compatibility. Pneumatics is an ideal choice for MRI compatibility because it is decoupled from electromagnetism, but pneumatic actuators were hardly controllable. This achievement was possible due to a recent technology breakthrough, the invention of a new type of pneumatic motor, PneuStep 1, designed for the robot reported here with uncompromised MRI compatibility, high-precision, and medical safety. MrBot is one of the "MRI stealth" robots today (the second is described in this issue by Zangos et al.). Both of these systems are also multi-imager compatible, being able to operate with the imager of choice or cross-imaging modalities. For MRI compatibility the robot is exclusively constructed of nonmagnetic and dielectric materials such as plastics, ceramics, crystals, rubbers and is electricity free. Light-based encoding is used for feedback, so that all electric components are distally located outside the imager's room. MRI robots are modern, digital medical instruments in line with advanced imaging equipment and methods. These allow for accessing patients within closed bore scanners and performing interventions under direct (in scanner) imaging feedback. MRI robots could allow e.g. to biopsy small lesions imaged with cutting edge cancer imaging methods, or precisely deploy localized therapy at cancer foci. Our robot is the first to show the feasibility of fully automated in-scanner interventions. It is customized for the prostate and operates transperineally for needle interventions. It can accommodate various needle drivers for different percutaneous procedures such as biopsy, thermal ablations, or brachytherapy. The first needle driver is customized for fully automated low-dose radiation seed brachytherapy. This paper gives an introduction to the challenges of MRI robot compatibility and presents the solutions adopted in making the MrBot. Its multi-imager compatibility and other preclinical tests are included. The robot shows the technical feasibility of MRI-guided prostate interventions, yet its clinical utility is still to be determined. (+info)
Magnetically-assisted remote control (MARC) steering of endovascular catheters for interventional MRI: a model for deflection and design implications.
Current applied to wire coils wound at the tip of an endovascular catheter can be used to remotely steer a catheter under magnetic resonance imaging guidance. In this study, we derive and validate an equation that characterizes the relationship between deflection and a number of physical factors: theta/sin(gamma-theta) = nIABL/EI(A) where theta is the deflection angle, n is the number of solenoidal turns, I is the current, A is the cross-sectional area of the catheter tip, B is the magnetic resonance (MR) scanner main magnetic field, L is the unconstrained catheter length, E is Young's Modulus for the catheter material, and I(A) is the area moment of inertia, and y is the initial angle between the catheter tip and B. Solenoids of 50, 100, or 150 turns were wound on 1.8 F and 5 F catheters. Varying currents were applied remotely using a DC power supply in the MRI control room. The distal catheter tip was suspended within a phantom at varying lengths. Images were obtained with a 1.5 T or a 3 T MR scanner using "real-time" MR pulse sequences. Deflection angles were measured on acquired images. Catheter bending stiffess was determined using a tensile testing apparatus and a stereomicroscope. Predicted relationships between deflection and various physical factors were observed (R2 = 0.98-0.99). The derived equation provides a framework for modeling of the behavior of the specialized catheter tip. Each physical factor studied has implications for catheter design and device implementation. (+info)
Clinical improvement and shrinkage of uterine fibroids after thermal ablation by magnetic resonance-guided focused ultrasound surgery.
OBJECTIVE: Hysterectomy or myomectomy are the accepted treatments for symptomatic uterine fibroids. Heat ablation of uterine fibroids has been shown to be an effective alternative treatment. The aim of this study was to determine the clinical efficacy of non-invasive thermal ablation by transcutaneous magnetic resonance-guided high-intensity focused ultrasound (MRgFUS) for the treatment of symptomatic uterine fibroids. METHODS: In this prospective study, MRgFUS ablation of uterine fibroids was performed in 35 symptomatic women scheduled for hysterectomy. Clinical symptoms, patient satisfaction and uterine size were determined at 1 month and 6 months after the procedure. RESULTS: This outpatient procedure was very well tolerated by all women. Sixty-nine percent (24/35) of the treated patients reported either significant or partial improvement in symptoms. Treated fibroids decreased in volume by 12% and 15% at 1 and 6 months, respectively. Minor transient side-effects were observed in two women. Six women underwent hysterectomy during the follow-up period. CONCLUSION: This study demonstrates the clinical efficacy of MRgFUS ablation of uterine fibroids. This novel, non-invasive surgical approach may offer an alternative therapy for women with uterine fibroids. (+info)
A magnetic resonance-based seed localization method for I-125 prostate implants.
This study was performed to develop and evaluate a semi-automatic seed localization algorithm from magnetic resonance (MR) images for interstitial prostate brachytherapy. The computerized tomography (CT) and MR images (3 mm-slice thickness) of six patients who had received real-time MR imaging-guided interstitial prostate brachytherapy were obtained. An automatic seed localization method was performed on CT images to obtain seed coordinates, and an algorithm for seed localization from MR images of the prostate was developed and tested. The resultant seed distributions from MR images were then compared to CT-derived distribution by matching the same seeds and calculating percent volume receiving 100% of the prescribed dose and the extent of the volume in 3-dimensions. The semiautomatic seed localization method made it possible to extract more than 90% of the seeds with either less than 8% of noises or 3% of missing seeds. The mean volume difference obtained from CT and MR receiving 100% of the prescribed dose was less than 3%. The maximum extent of the volume receiving the prescribed dose were 0.3, 0.6, and 0.2 cm in x, y, and z directions, respectively. These results indicate that the algorithm is very useful in identifying seeds from MR image for post-implant dosimety. (+info)
Fast and efficient radiological interventions via a graphical user interface commanded magnetic resonance compatible robotic device.
The graphical user interface for an MR compatible robotic device has the capability of displaying oblique MR slices in 2D and a 3D virtual environment along with the representation of the robotic arm in order to swiftly complete the intervention. Using the advantages of the MR modality the device saves time and effort, is safer for the medical staff and is more comfortable for the patient. (+info)