Abstract
ObjectivesMRI is of great clinical utility for the guidance of special diagnostic and therapeutic interventions. The majority of such procedures are performed iteratively ("in-and-out") in standard, closed-bore MRI systems with control imaging inside the bore and needle adjustments outside the bore. The fundamental limitations of such an approach have led to the development of various assistance techniques, from simple guidance tools to advanced navigation systems. The purpose of this work was to thoroughly assess the targeting accuracy, workflow and usability of a clinical add-on navigation solution on 240 simulated biopsies by different medical operators.MethodsNavigation relied on a virtual 3D MRI scene with real-time overlay of the optically tracked biopsy needle. Smart reference markers on a freely adjustable arm ensured proper registration. Twenty-four operators – attending (AR) and resident radiologists (RR) as well as medical students (MS) – performed well-controlled biopsies of 10 embedded model targets (mean diameter: 8.5 mm, insertion depths: 17-76 mm). Targeting accuracy, procedure times and 13 Likert scores on system performance were determined (strong agreement: 5.0).ResultsDifferences in diagnostic success rates (AR: 93%, RR: 88%, MS: 81%) were not significant. In contrast, between-group differences in biopsy times (AR: 4:15, RR: 4:40, MS: 5:06 min:sec) differed significantly (p<0.01). Mean overall rating was 4.2. The average operator would use the system again (4.8) and stated that the outcome justifies the extra effort (4.4). Lowest agreement was reported for the robustness against external perturbations (2.8).ConclusionsThe described combination of optical tracking technology with an automatic MRI registration appears to be sufficiently accurate for instrument guidance in a standard (closed-bore) MRI environment. High targeting accuracy and usability was demonstrated on a relatively large number of procedures and operators. Between groups with different expertise there were significant differences in experimental procedure times but not in the number of successful biopsies.
Highlights
Invasive diagnostic and therapeutic procedures are typically performed under image guidance
The described combination of optical tracking technology with an automatic MRI registration appears to be sufficiently accurate for instrument guidance in a standard MRI environment
MRI becomes the method of choice, most often when targets or critical anatomical structures along the access path are only visible by MRI [1]
Summary
Invasive diagnostic and therapeutic procedures are typically performed under image guidance. Established imaging techniques like ultrasound (US) and computed tomography (CT) are widely available and allow for fast or even real-time control of the procedure. MRI becomes the method of choice, most often when targets or critical anatomical structures along the access path are only visible by MRI [1]. The last two decades have seen a number of dedicated MRI systems, in particular open units that provide good access to the patient and have been successfully used for image-guided procedures [2,3,4,5]. Traditional 60-cm bore MRI systems have increasingly been replaced by wide-bore models that offer some more space for operation [8,9,10,11,12]
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