Feasibility study of navigated endoscopy for the placement of high dose rate brachytherapy applicators in the esophagus and lung

Abstract

Purpose To evaluate the electromagnetic (EM) tracking of endoscopes and applicators as a method of positioning a high dose rate (HDR) luminal applicator. Method An anatomical phantom consisting of a rigid trachea and flexible esophagus was used to compare applicator placement measurements using EM tracking vs the traditional method using two‐dimensional (2D) fluoroscopy and surface skin markers. The phantom included a tumor in the esophagus and several pairs of optically visible points inside the lumen that were used to simulate proximal and distal ends of tumors of varying lengths. The esophagus tumor and lung points were visible on a computed tomography (CT) image of the phantom, which was used as ground truth for the measurements. The EM tracking system was registered to the CT image using fiducial markers. A flexible endoscope was tracked using the EM system and the locations of the proximal and distal ends of the tumor identified and this position recorded. An EM‐tracked applicator was then inserted and positioned relative to the tumor markings. The applicator path was mapped using the EM tracking. The gross tumor length (GTL) and the distance between the first dwell position and distal edge of tumor (offset) were measured using the EM tracking and 2D fluoroscopy methods and compared to the same measurements on the CT image. Results The errors in GTL using EM tracking were on average −0.5 ± 1.7 mm and 0.7 ± 3.6 mm for esophagus and lung measurements, similar to errors measured using the 2D fluoroscopy method of −0.9 ± 1.2 mm and 3.4 ± 4.4 mm. Offset measurements were slightly larger while using EM tracking relative to the fluoroscopy method but these were not statistically significant. Conclusions Electromagnetic tracking for placement of lumen applicators is feasible and accurate. Tracking of the endoscope that is used to identify the proximal and distal ends of the tumor and of the applicator during insertion generates accurate three‐dimensional measurements of the applicator path, GTL and offset. Guiding the placement of intraluminal applicators using EM navigation is potentially attractive for cases with complex insertions, such as those with nonlinear paths or multiple applicator insertions.

Optical spectroscopy and imaging in surgical management of cancer patients

“…The first is the instrumentation, where a common challenge is accurate spatial co-registration, especially between planar (surface) and volumetric images or between en-face (eg, fluorescence) and crosssectional (eg, OCT) views. Co-registration between preoperative radiological and intra-operative optical techniques is enabled by EM tracking or laser-based triangulation of the intraoperative device [125,126]. Independent of the instrumentation, exogenous contrast can be used either as two different single-modality agents or combined into a single dual-modality agent such as conjugates of a gamma-emitting radionuclide and a fluorophore [123].…”

Stereotactic Ablative Brachytherapy: Recent Advances in Optimization of Radiobiological Cancer Therapy

“…Computed tomography (CT) guidance is mainly used for seed implantation into cancers located at head and neck, thoracic, primary/metastatic liver/adrenal, recurrent/metastatic pelvic cavity, and spinal areas [ 29 , 33 , 43 ]. Recent testing of electromagnetic tracking of endoscopes and BT applicators indicated higher precision of HDR-BT positioning in cases with complex insertions [ 53 ]. MRI guidance is less accessible in the clinic than ultrasound and/or CT guidance, although is regularly used during pre-BT assessments [ 54 ].…”

“…High dose optimization and conformity of ablative BT allow achieving advanced curative effects. For instance, HDR-BT was shown effective in early-stage intra-tracheal [ 53 ] and cervical cancers [ 57 ], while LDR-BT is successfully used in prostate cancers [ 58 ]. Recent retrospective analysis indicated that HDR-BT patients had a lower incidence of acute genitourinary toxicities (grade ≥ 2) [ 59 ].…”

Magnetic Catheter Placement in Neonates: A Handheld Solution to Radiation Exposure and Operational Delays

“…[7] Magnetic tracking systems have been researched by several authors [8][9][10][11][12][13][14][15][16][17] and proposed for multiple surgical operations. [18][19][20][21][22][23][24][25] A magnetic tracking system can provide effective assistance to surgeons or interventional radiologists during procedures performed in a clinical environment. [26] These systems are used to track or localize the position of instruments relative to the patient anatomy.…”