PURPOSE This study systematically investigates artifacts produced by biopsy and ablation needles imaged at various trajectories with respect to the static magnetic field (B0). MATERIALS AND METHODS An acrylic phantom was scanned using a rapid balanced fast field echo sequence (FFE) with 3.0-T MRI. A 15-gauge microwave needle, a 17-gauge cryoneedle and 18-gauge coaxial-biopsy needle were imaged in sagittal and axial planes, in 7 different orientations to B0(0°-15°-30°-45°-60°-75°-90°). For four angles (15°-30°-60°-75°), images were acquired with slice orientation aligned to the angulation of the needle, resulting in the frequency-encoding direction being parallel to the needle long-axis for the sagittal and perpendicular for the axial acquisition. The artifact length at the needle-tip and maximum artifact width were recorded. RESULTS There was no significant difference in mean artifact length for the cryoneedle (13mm, 95%CI 7-19mm) and coaxial-biopsy needle (8mm, 95%CI 5-10, p=0.08). The mean artifact length was significantly smaller for the MWA needle (1mm, 95%CI 0-2, p 15°), the needle tip position can be predicted better from images acquired where the slice orientation is aligned to the needle's angulation.
#1Saikat Sengupta(VUMC: Vanderbilt University Medical Center)H-Index: 8
PURPOSE Artifacts caused by large magnetic susceptibility differences between metallic needles and tissue are a persistent problem in many interventional MRI applications. The signal void caused by the needle can hide procedure targets and prevent accurate image-based monitoring. In this paper, a solution to this problem is presented in the form of an active shim insert inspired from degaussing coils used in naval vessels, that is designed to correct the field disturbance (ΔB0 ) caused by the ne...
Last. Jan Fritz(JHUSOM: Johns Hopkins University School of Medicine)H-Index: 9
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Background Interventional magnetic resonance imaging (MRI) at 3T benefits from higher spatial and temporal resolution, but artifacts of metallic instruments are often larger and may obscure target structures. Purpose To test that compressed sensing (CS) slice-encoding metal artifact correction (SEMAC) is feasible for 3T interventional MRI and affords more accurate instrument visualization than turbo spin echo (TSE) and gradient echo (GRE) techniques, and facilitates faster data acquisition than ...
#1Elena Kaye(MSK: Memorial Sloan Kettering Cancer Center)H-Index: 13
#2Kristin L. Granlund(MSK: Memorial Sloan Kettering Cancer Center)H-Index: 9
Last. Stephen B. Solomon(MSK: Memorial Sloan Kettering Cancer Center)H-Index: 63
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OBJECTIVE. The purpose of this article is to review clinical applications and technologic development of MRI-guided percutaneous interventions performed in closed-bore MRI scanners. CONCLUSION. Interventional MRI has rapidly adapted to the closed-bore environment. New tools are being developed to facilitate the use of MRI-guided procedures, and cost-effectiveness studies are exploring the economics of interventional MRI.
Balanced steady state free precession (balanced SSFP) has become increasingly popular for research and clinical applications, offering a very high signal-to-noise ratio and a T2/T1-weighted image contrast. This review article gives an overview on the basic principles of this fast imaging technique as well as possibilities for contrast modification. The first part focuses on the fundamental principles of balanced SSFP signal formation in the transient phase and in the steady state. In the second ...
Purpose This study was designed to systematically investigate artifacts caused by interventional needles recommended for use in MRI, with focus on field strength, needle/mandrin type, orientation and sequence.
OBJECTIVE. The purpose of this article is to review some of the basic principles of imaging and how metal-induced susceptibility artifacts originate in MR images. We will describe common ways to reduce or modify artifacts using readily available imaging techniques, and we will discuss some advanced methods to correct readout-direction and slice-direction artifacts. CONCLUSION. The presence of metallic implants in MRI can cause substantial image artifacts, including signal loss, failure of fat su...
The recently developed multi-acquisition with variable resonance image combination (MAVRIC) and slice-encoding metal artifact correction (SEMAC) techniques can significantly reduce image artifacts commonly encountered near embedded metal hardware. These artifact reductions are enabled by applying alternative spectral and spatial-encoding schemes to conventional spin-echo imaging techniques. Here, the MAVRIC and SEMAC concepts are connected and discussed. The development of a hybrid technique tha...
We describe a MRI-compatible biopsy needle instrumented with optical fiber Bragg gratings for measuring bending deflections of the needle as it is inserted into tissues. During procedures, such as diagnostic biopsies and localized treatments, it is useful to track any tool deviation from the planned trajectory to minimize positioning errors and procedural complications. The goal is to display tool deflections in real time, with greater bandwidth and accuracy than when viewing the tool in MR imag...
Steady-state sequences are a class of rapid magnetic resonance (MR) imaging techniques based on fast gradient-echo acquisitions in which both longitudinal magnetization (LM) and transverse magnetization (TM) are kept constant. Both LM and TM reach a nonzero steady state through the use of a repetition time that is shorter than the T2 relaxation time of tissue. When TM is maintained as multiple radiofrequency excitation pulses are applied, two types of signal are formed once steady state is reach...
Exact determination of needle tip position is obsolete for interventional procedures under control of magnetic resonance imaging(MRI). Exact needle tip navigation is complicated by the paramagnetism of microsurgical instruments: Local magnetic field inhomogeneities are induced resulting in position encoding artifacts and in signal voids in the surrounding of instruments and especially near their tips. The artifacts generated by the susceptibility of the material are not only dependent on the mat...