Abstract and Introduction
Abstract
Objective. Freehand ultrasound-guided breast biopsy may present difficulties in needle visualization within the scanning plane of the ultrasound image. Scanning plane and needle misalignment, an unknown needle insertion site (relative to the ultrasound image), needle trajectory before insertion, and physician experience play roles in the difficulty of these biopsy procedures. The objective of our study was to compare the currently used freehand technique with the use of a needle guidance system that limits needle motion to within the ultrasound scanning plane for breast biopsy.
Materials and Methods. We developed a needle guidance system for breast biopsy that is composed of an electronically tracked passive mechanical arm and braking mechanism. The system was attached to an ultrasound transducer, and biopsy needles were inserted through the guidance arm. Both experienced and inexperienced radiologists performed ultrasound-guided biopsy on simulated breast lesions with and without the guidance system. Success rates were scored on the basis of the presence of lesions in the core biopsy samples. The biopsy procedures were analyzed using procedure time and total needle tip travel distance before firing.
Results. The biopsy success rates were greater using the guidance system (p < 0.05) than using the freehand technique. Experienced radiologists and inexperienced radiologists performed biopsy significantly faster using the needle guidance system (p < 0.001). Additionally, needle tip motion was significantly greater when using the freehand technique (p < 0.001) than using the guidance system.
Conclusion. Biopsy using the developed needle guidance system is feasible and its use decreases procedure time and decreases needle motion; thus, it has the potential to reduce patient morbidity. Moreover, less operator experience is required for a successful breast biopsy using the needle guidance system than using the freehand technique.
Introduction
Mammography screening subjects who present with suspicious breast lesions usually undergo imaging-guided biopsy using either stereotactic mammography or ultrasound guidance. Ultrasound guidance is preferred because it provides real-time images, does not require ionizing radiation, and makes use of compact imaging instrumentation Radiologists performing biopsy on suspicious breast lesions by ultrasound use a freehand technique: A needle is guided to the target with one hand while the other hand positions the ultrasound transducer for adequate visualization. Guidance under freehand conditions is challenging and may be time-consuming because of the necessity to align the scanning plane and needle axis. The ultrasound scanning plane must remain coplanar with the needle axis for adequate visualization of the needle tip; thus, the experience of the physician dictates the success of the freehand ultrasound-guided biopsy procedure.
Guidance devices that attempt to overcome the challenges of freehand biopsy by restricting needle motion to varying degrees are available. Fixed-angle insertion is achieved with a needle guide: a plastic clip-on attachment (Ultra-Pro 3, CIVCO Medical Solutions) that permits needle insertion at a static angle relative to the ultrasound transducer scanning surface. With the attachment in place, the needle is limited to angled insertion toward targets located in the center of the ultrasound image, which prevents access to shallow and deep lesions. Han et al. developed a rotary insertion wheel that attaches to the ultrasound transducer and permits angled and parallel insertion to overcome the limitations of fixed-angle insertion. The difficulty with this approach is the inability to insert the needle either close to the lesion or consistently parallel or anterior to the patient's chest wall to avoid potential chest wall or transducer puncture.
Additional solutions have been developed that provide relatively unrestrained biopsy: tracking the magnetic field of the imaging and needle components or displaying a line on the patient's skin corresponding to the ultrasound scanning plane. These unrestrained solutions may be challenging to use because they do not limit the needle to motion within the ultrasound scanning plane, resulting in difficulty aligning the needle and scanning plane similar to the freehand technique.
We developed a mechanical needle guidance system that couples a 2D ultrasound transducer to a needle. The system allows needle insertion at an unrestricted trajectory but constrains the needle to within the ultrasound scanning plane. Additionally, the electronically tracked needle trajectory is displayed as an overlay on real-time ultrasound images before and during needle insertion procedures.
In this article, our objective is to report the results of our study comparing the success rate, procedure time, needle tip travel distance, and physician experience of biopsy procedures in a tissue model. We compared these variables for freehand biopsy and needle-guided biopsy.
With the development of the attached system and visualized pathway, we endeavor to improve biopsy guidance and reduce the time of ultrasound-guided procedures. Additionally, we propose that this device can aid physicians by reducing the amount of experience required to perform a successful biopsy procedure.