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Design and evaluation of an optically-tracked single-CCD laser range scanner.

ABSTRACT: Acquisition of laser range scans of an organ surface has the potential to efficiently provide measurements of geometric changes to soft tissue during a surgical procedure. A laser range scanner design is reported here which has been developed to drive intraoperative updates to conventional image-guided neurosurgery systems.The scanner is optically-tracked in the operating room with a multiface passive target. The novel design incorporates both the capture of surface geometry (via laser illumination) and color information (via visible light collection) through a single-lens onto the same charge-coupled device (CCD). The accuracy of the geometric data was evaluated by scanning a high-precision phantom and comparing relative distances between landmarks in the scans with the corresponding ground truth (known) distances. The range-of-motion of the scanner with respect to the optical camera was determined by placing the scanner in common operating room configurations while sampling the visibility of the reflective spheres. The tracking accuracy was then analyzed by fixing the scanner and phantom in place, perturbing the optical camera around the scene, and observing variability in scan locations with respect to a tracked pen probe ground truth as the camera tracked the same scene from different positions.The geometric accuracy test produced a mean error and standard deviation of 0.25 ± 0.40 mm with an RMS error of 0.47 mm. The tracking tests showed that the scanner could be tracked at virtually all desired orientations required in the OR set up, with an overall tracking error and standard deviation of 2.2 ± 1.0 mm with an RMS error of 2.4 mm. There was no discernible difference between any of the three faces on the lasers range scanner (LRS) with regard to tracking accuracy.A single-lens laser range scanner design was successfully developed and implemented with sufficient scanning and tracking accuracy for image-guided surgery.

SUBMITTER: Pheiffer TS

PROVIDER: S-EPMC3267792 | biostudies-other | 2012 Feb

REPOSITORIES: biostudies-other

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Project description:Background:For surgical fixation of bone fractures of the human hand, so-called Kirschner-wires (K-wires) are drilled through bone fragments. Due to the minimally invasive drilling procedures without a view of risk structures like vessels and nerves, a thorough training of young surgeons is necessary. For the development of a virtual reality (VR) based training system, a three-dimensional (3D) printed phantom hand is required. To ensure an intuitive operation, this phantom hand has to be realistic in both, its position relative to the driller as well as in its haptic features. The softest 3D printing material available on the market, however, is too hard to imitate human soft tissue. Therefore, a support-material (SUP) filled metamaterial is used to soften the raw material. Realistic haptic features are important to palpate protrusions of the bone to determine the drilling starting point and angle. An optical real-time tracking is used to transfer position and rotation to the training system. Methods:A metamaterial already developed in previous work is further improved by use of a new unit cell. Thus, the amount of SUP within the volume can be increased and the tissue is softened further. In addition, the human anatomy is transferred to the entire hand model. A subcutaneous fat layer and penetration of air through pores into the volume simulate shiftability of skin layers. For optical tracking, a rotationally symmetrical marker attached to the phantom hand with corresponding reference marker is developed. In order to ensure trouble-free position transmission, various types of marker point applications are tested. Results:Several cuboid and forearm sample prints lead to a final 30 centimeter long hand model. The whole haptic phantom could be printed faultless within about 17 hours. The metamaterial consisting of the new unit cell results in an increased SUP share of 4.32%. Validated by an expert surgeon study, this allows in combination with a displacement of the uppermost skin layer a good palpability of the bones. Tracking of the hand marker in dodecahedron design works trouble-free in conjunction with a reference marker attached to the worktop of the training system. Conclusions:In this work, an optically tracked and haptically correct phantom hand was developed using dual-material 3D printing, which can be easily integrated into a surgical training system.

Project description:PurposeTranscranial focused ultrasound (FUS) is increasingly being explored to modulate neuronal activity. To target neuromodulation, researchers often localize the FUS beam onto the brain region(s) of interest using spatially tracked tools overlaid on pre-acquired images. Here, we quantify the accuracy of optically tracked image-guided FUS with magnetic resonance imaging (MRI) thermometry, evaluate sources of error and demonstrate feasibility of these procedures to target the macaque somatosensory region.MethodsWe developed an optically tracked FUS system capable of projecting the transducer focus onto a pre-acquired MRI volume. To measure the target registration error (TRE), we aimed the transducer focus at a desired target in a phantom under image guidance, heated the target while imaging with MR thermometry and then calculated the TRE as the difference between the targeted and heated locations. Multiple targets were measured using either an unbiased or bias-corrected calibration. We then targeted the macaque S1 brain region, where displacement induced by the acoustic radiation force was measured using MR acoustic radiation force imaging (MR-ARFI).ResultsAll calibration methods enabled registration with TRE on the order of 3 mm. Unbiased calibration resulted in an average TRE of 3.26 mm (min-max: 2.80-4.53 mm), which was not significantly changed by prospective bias correction (TRE of 3.05 mm; 2.06-3.81 mm, p = 0.55). Restricting motion between the transducer and target and increasing the distance between tracked markers reduced the TRE to 2.43 mm (min-max: 0.79-3.88 mm). MR-ARFI images showed qualitatively similar shape and extent as projected beam profiles in a living non-human primate.ConclusionsOur study describes methods for image guidance of FUS neuromodulation and quantifies errors associated with this method in a large animal. The workflow is efficient enough for in vivo use, and we demonstrate transcranial MR-ARFI in vivo in macaques for the first time.

Project description:Introduction: Surgery for chronic anal fissure is challenging for every proctologist. Solving the pain by guaranteeing rapid and effective healing is the objective, but what is the price to pay today in functional terms? Though this result is nowadays partially achievable through interventions that include the execution of an internal sphincterotomy among the procedures, it is necessary to underline the high rate of patients who can present faecal incontinence. The aim of this study is to explore the effectiveness of scanner-assisted CO2 laser fissurectomy. Methods: From April 2021 to September 2021, all consecutive patients who affected by chronic anal fissure suitable for surgery, meeting the inclusion and exclusion criteria, were evaluated. All planned data were recorded before surgery, then at 24 h, 1 week, and 1 month follow-up. A scanner-assisted CO2 laser was used in this study to achieve a smooth and dried wound with a minimal tissue thermal damage, to ensure good postsurgical pain control, rapid and functional, elastic and stable healing, and to prevent potential relapses. Paracetamol 1 g every 8 h was prescribed for the first 24 h and then continued according to each patient's need. Ketorolac 15 mg was prescribed as rescue. Results: Mean pain intensity ≤3, considered as the principal endpoint, was recorded in 26 out of the 29 patients who enrolled in the study with a final success rate of 89.7% at 1-month follow-up. Pain and anal itching showed a statistically significant reduction while bleeding, burning, and maximum pain, and REALIS score showed a reduction too at the end of the follow-up period. Reepithelisation proved to be extremely fast and effective: 22 of 29 (75.9%) showed a complete healing and 5 showed a partial reepithelisation at 1-month follow-up. Discussion: Outcomes of this study showed that it is undoubtedly necessary to change the surgical approach in case of anal fissure. The internal sphincterotomy procedure must be most of all questioned, where the availability of cutting-edge technological tools must be avoided and offered only in selected cases. Scanner-assisted CO2 laser showed great results in terms of pain control and wound healing, secondary to an extremely precise ablation, vaporisation, and debridement procedures with minimal lateral thermal damage.

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Design and evaluation of an optically-tracked single-CCD laser range scanner.

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