Head and neck tumors: fractionated frameless stereotactic interstitial brachytherapy-initial experience

Laser Target System in Combination with an Aiming Device for Percutaneous CT-Guided Interventions - An Accuracy Study

RATIONALE AND OBJECTIVES

To evaluate the targeting accuracy of laser-guided punctures in combination with an aiming device for computed tomography (CT) interventions during in vitro experiments. MATERIALS AND METHODS: A total of 600 CT-guided punctures were performed using a laser target system, half of them with the additional help of an aiming device. Conically shaped targets in a plexiglass phantom were punctured. The planning CT data sets were acquired with 1.25, 2.5 and 5 mm slice thickness. Needle placement accuracy, as well as procedural time, was assessed. The Euclidean (ED) and normal distances (ND) were calculated at the target point.

RESULTS

Using the aiming device, the accomplished mean ND at the target for the 1.25, 2.5 and 5 mm slice thickness was 1.76 mm (SD ± 0.92), 2.09 mm (SD ± 1.06) and 1.93 mm (SD ± 1.38), respectively. Without aiming device, the corresponding results were 2.55 mm (SD ± 1.42), 2.7 mm (SD ± 1.43) and 2.31 mm (SD ± 1.64). At a slice thickness of 1.25 mm and 2.5 mm, punctures with the aiming device were significantly more accurate for both the ED and ND as compared to the punctures without aiming device (p < 0.001). The mean time required to complete the procedure, including image acquisition, trajectory planning, the placement of 10 needles, and the control-CT scan was 24.8 min without and 29.8 min with the aiming device.

CONCLUSION

The additional use of the aiming device in combination with the commercially available laser guidance system significantly increased the level of accuracy during this in vitro experiment compared to freehand passes.

Computer assistance for intraoperative navigation in ENT surgery

The intraoperative need for exact orientation during interventions in the paranasal sinuses and the augmented need for navigational aids in lateral skull base surgery have lead to the development of computer-aided tools during the last fifteen years. These tools, which provide the position of a tool or a pointer in the patient's preoperative radiologic imaging, have quickly gained a wide acceptance for revision surgeries and the surgical treatment of complex pathologies in Ear-, Nose- and Throat (ENT-) surgery. Currently, the use of such systems is spreading from academic centers to smaller hospitals and will become a standard tool in the near future. We review the present state of computer-aided surgery (CAS) systems, based on our experience as clinical and research centers with a long experience in the field, provide some technological background information and, based on selected cases, show the merits of this technology. The systems we have been working with cover a wide variety of intraoperative navigational systems in ENT surgery (Easy Guide, MedScan II, MKM, SNN, STN, SurgiGATE ORL, Treon, VectorVision, Viewing Wand, [without claiming completeness]), and virtually the whole area of ENT surgeries: macroscopic, (video-)endoscopic and microscopic procedures. The 3D tracking technologies involved cover mechanical, optical (active and passive), magnetic and robotic principles. The visualization tools used are computer monitors, video monitors, head-up-displays and the microscope's oculars, thus spanning the area from pointer-systems to real navigators and a surgical telepresence demonstrator, implementing the majority of available patient-to-image referencing strategies. Clinically, the systems can be operated with an acceptable accuracy of around 1 mm, whereas in laboratory settings and in cadaver studies application accuracy may be pushed to its limits: the physical resolution of the radiologic imaging used for navigation.

Projector-based augmented reality for intuitive intraoperative guidance in image-guided 3D interstitial brachytherapy

PURPOSE

The aim of this study is to implement augmented reality in real-time image-guided interstitial brachytherapy to allow an intuitive real-time intraoperative orientation.

METHODS AND MATERIALS

The developed system consists of a common video projector, two high-resolution charge coupled device cameras, and an off-the-shelf notebook. The projector was used as a scanning device by projecting coded-light patterns to register the patient and superimpose the operating field with planning data and additional information in arbitrary colors. Subsequent movements of the nonfixed patient were detected by means of stereoscopically tracking passive markers attached to the patient.

RESULTS

In a first clinical study, we evaluated the whole process chain from image acquisition to data projection and determined overall accuracy with 10 patients undergoing implantation. The described method enabled the surgeon to visualize planning data on top of any preoperatively segmented and triangulated surface (skin) with direct line of sight during the operation. Furthermore, the tracking system allowed dynamic adjustment of the data to the patient's current position and therefore eliminated the need for rigid fixation. Because of soft-part displacement, we obtained an average deviation of 1.1 mm by moving the patient, whereas changing the projector's position resulted in an average deviation of 0.9 mm. Mean deviation of all needles of an implant was 1.4 mm (range, 0.3-2.7 mm).

CONCLUSIONS

The developed low-cost augmented-reality system proved to be accurate and feasible in interstitial brachytherapy. The system meets clinical demands and enables intuitive real-time intraoperative orientation and monitoring of needle implantation.

Frameless stereotactic cannulation of the foramen ovale for ablative treatment of trigeminal neuralgia

OBJECTIVE

Ablative neurosurgical treatment of trigeminal neuralgia, including percutaneous radiofrequency thermocoagulation, requires cannulation of the foramen ovale. To maximize patient security and cannulation success, a frameless stereotactic system was evaluated in a phantom study, a cadaveric study, and a preliminary clinical trial.

METHODS

Frameless stereotaxy using an optical navigation system, an aiming device, and a noninvasive vacuum mouthpiece-based registration and patient fixation technique was used for the targeting of a test body based on 1-, 3-, and 5-mm axial computed tomographic slices and of the foramen ovale in three cadavers and 15 patients based on 3-mm axial computed tomographic slices.

RESULTS

The mean normal (x/y) localization accuracy/standard deviation (n = 360) was 1.31/0.67 mm (1-mm slices), 1.38/0.65 mm (3-mm slices), and 1.84/0.96 mm (5-mm slices). Significantly better results were achieved with 1- and 3-mm slices when compared with 5-mm slices (P < 0.001). The foramen ovale (3 x 6 mm) was successfully cannulated at the first attempt in all cadavers and patients, which indicates clinical localization accuracies better than 1.5 mm in the anteroposterior and 3 mm in the medial-lateral directions.

CONCLUSION

Based on the noninvasive Vogele-Bale-Hohner vacuum mouthpiece, there is no need for invasive head clamp fixation. Imaging, real laboratory simulation, and the actual surgical intervention can be separated in time and location. The presented data suggest that frameless stereotaxy is a predictable and reproducible procedure, which may enhance patient security and cannulation success independent of the surgeon's experience.

Image-guided surgery and medical robotics in the cranial area

Surgery in the cranial area includes complex anatomic situations with high-risk structures and high demands for functional and aesthetic results. Conventional surgery requires that the surgeon transfers complex anatomic and surgical planning information, using spatial sense and experience. The surgical procedure depends entirely on the manual skills of the operator. The development of image-guided surgery provides new revolutionary opportunities by integrating presurgical 3D imaging and intraoperative manipulation. Augmented reality, mechatronic surgical tools, and medical robotics may continue to progress in surgical instrumentation, and ultimately, surgical care. The aim of this article is to review and discuss state-of-the-art surgical navigation and medical robotics, image-to-patient registration, aspects of accuracy, and clinical applications for surgery in the cranial area.

Improved targeting device and computer navigation for accurate placement of brachytherapy needles

Successful treatment of skull base tumors with interstitial brachytherapy requires high targeting accuracy for the brachytherapy needles to avoid harming vital anatomical structures. To enable safe placement of the needles in this area, we developed an image-based planning and navigation system for brachytherapy, which includes a custom-made mechanical positioning arm that allows rough and fine adjustment of the needle position. The fine-adjustment mechanism consists of an XYZ microstage at the base of the arm and a needle holder with two fine-adjustable inclinations. The rotation axes of the inclinations cross at the tip of the needle so that the inclinational adjustments do not interfere with the translational adjustments. A vacuum cushion and a noninvasive fixation frame are used for the head immobilization. To avoid mechanical bending of the needles due to the weight of attached tracking markers, which would be detrimental for targeting accuracy, only a single LED marker on the tail of the needle is used. An experimental phantom-based targeting study with this setup demonstrated that a positioning accuracy of 1.4 mm (rms) can be achieved. The study showed that the proposed setup allows brachytherapy needles to be easily aligned and inserted with high targeting accuracy according to a preliminary plan. The achievable accuracy is higher than if the needles are inserted manually. The proposed system can be linked to a standard afterloader and standard dosimetry planning module. The associated additional effort is reasonable for the clinical practice and therefore the proposed procedure provides a promising tool for the safe treatment of tumors in the skull base area.

In vitroaccuracy of a novel registration and targeting technique for image-guided template production

OBJECTIVES

The objective of this study was to evaluate the accuracy of a novel registration and targeting technique for image-guided template production (IGTP) in a preliminary phantom study.

MATERIAL AND METHODS

Registration of four standard dental stone casts with integrated target pellets to the corresponding computed tomography (CT) data was performed via a vacuum mouthpiece and an external reference frame (Medical Intelligence GmbH, Germany). Using the Treon navigation system (Medtronic Inc., Minneapolis, MN, USA) a surgical path with the entry in the centre of the dental crown and the target in the centre of the target pellet was planned on the CT data. An aiming device was adjusted according to the planned trajectory and guided drillings into the dental stone casts. The accuracy was evaluated on postoperative 3D-CT data.

RESULTS

The mean fiducial registration error as given by the registration software was 0.4 mm. One hundred and twelve navigated drillings showed a mean accuracy [xy] of 0.42+/-0.26 mm (maximum 1 mm). For the z-axis, a mean accuracy [z] of 0.25+/-0.12 mm (maximum 0.6 mm) was found.

CONCLUSIONS

Comparing the presented registration technique to existing registration methods in IGTP and burr tracking, no radiographic and registration templates are needed. The procedure is easy and requires only minimal effort. Navigation-controlled drillings could be performed with an accuracy that approaches the intrinsic navigation system's accuracy, a fact that warrants its use for surgical template production. Further accuracy studies of template-guided drillings are necessary before the presented registration technique can be implemented for patient treatment.

Feasibility report for retreatment of locally recurrent head-and-neck cancers by combined brachy-chemotherapy using frameless image-guided 3D interstitial brachytherapy

PURPOSE

Brachytherapy re-irradiation may offer an alternative re-treatment of recurrent head-and-neck cancer even after previous full dose radiation therapy. The purposes of this study were to determine the feasibility and accuracy of frameless image-guided interstitial needle implantation.

METHODS AND MATERIALS

Between January 2000 and March 2003, 14 patients with biopsy-proven locally recurrent head-and-neck-cancer were retreated after previous full dose irradiation with combined external beam-brachytherapy with concomitant chemotherapy. Brachytherapy needle implantation was virtually planned taking into account the surrounding risk structures. Needles were implanted using an adapted frameless navigation system. Chemoradiotherapy was followed by 2-4 courses of chemotherapy every fourth week starting 4 weeks after the end of brachytherapy.

RESULTS

The 1- and 2-year local control rates were 78% and 57%, respectively. Local control was obtained in 8/14 patients. The actuarial 1- and 2-year survival rates were 83% and 64%, respectively. The median survival was 28 months after a median follow-up of 21 months (range, 8-53). Six weeks after brachytherapy, 1 patient developed localized soft tissue necrosis which did not require surgical intervention. No additional grade III or IV late toxicity was seen after re-irradiation. Mean deviation of image-guided needle implantation was 3.4 mm for each needle (SD, 1.9 mm; range, 0.5-14 mm). The mean deviation of all needles of an implant was 4.3 mm (range, 2.3-8.6 mm).

CONCLUSIONS

These data demonstrate that pulsed-dose-rate brachytherapy in combination with sequential chemotherapy is effective and safe in re-irradiation of locally recurrent oropharyngeal carcinomas and can be offered to patients with curative intent. Image guidance allows virtual planning and navigated implantation of brachytherapy needles with regard to optimized needle distribution and risk structures.

Frameless image guidance improves accuracy in three-dimensional interstitial brachytherapy needle placement

PURPOSE

The aim of this work was to adapt a computer-assisted real-time three-dimensional (3D) navigation system for interstitial brachytherapy procedures.

METHODS AND MATERIALS

The 3-D navigation system Surgical Planning and Orientation Computer System (SPOCS; Aesculap, Tuttlingen, Germany) was adapted for use in interstitial brachytherapy. A special needle holder with mounted infrared-emitting diodes (IRED) for 3D navigation-based needle implantation was developed. Measurements were made on a series of different phantoms to study the feasibility and the overall accuracy and precision of the navigation system with regard to single-needle application and volume implants (multiple-needle implantations). In all, 250 single implants and 20 volume implants were performed. Accuracy was measured as the target registration error (TRE) between the preoperatively defined and the achieved target position.

RESULTS

Analyses of the 250 different targets showed a mean TRE for single-needle applications of 1.1 mm (SD +/- 0.4 mm), 0.9 mm (SD +/- 0.3 mm), and 0.7 mm (SD +/- 0.3 mm) in the x, y, and z direction, respectively. The maximal deviation was 2.3 mm. The corresponding TRE in the x, y, and z direction for volume implants was 1.6 mm (SD +/- 0.4 mm), 1.9 mm (SD +/- 0.6 mm), and 1.0 mm (SD +/- 0.4 mm), respectively. The maximum deviation was 2.9 mm.

CONCLUSIONS

The adaptation of a commercially available surgical planning and navigation system to interstitial brachytherapy is feasible. It enables virtual planning and improved accuracy in 3D interstitial needle implantation.

Osteochondral lesions of the talus: computer-assisted retrograde drilling--feasibility and accuracy in initial experiences

The authors developed a minimally invasive method with computer-assisted navigation for retrograde drilling of osteochondral lesions of the talus. Planning of the pathway and adjustment of the targeting device were performed outside the operating room. In 10 cadavers and four patients, accuracy of pin placement was in the range of 1.0-3.5 mm.

Computer-assisted neurosurgery by using a noninvasive vacuum-affixed dental cast that acts as a reference base: another step toward a unified approach in the treatment of brain tumors

OBJECT

The purpose of the study was to evaluate the use of the Vogele-Bale-Hohner (VBH) mouthpiece, which is attached to the patient's upper jaw by negative pressure, for patient-image registration and for tracking the patient's head during image-guided neurosurgery.

METHODS

A dynamic reference frame (DRF) is reproducibly mounted on the mouthpiece. Reference points, optimally distributed and attached to the mouthpiece, are used for registration in the patient's absence on the day before surgery. In the operating room, the mouthpiece and DRF are precisely repositioned using a vacuum, and the patient's anatomical structures are automatically registered to corresponding ones on the image. Experimental studies and clinical experiences in 10 patients confirmed repeated (rigid body) localization accuracy in the range of 0 to 2 mm, throughout the entire surgery despite movements by the patient.

CONCLUSIONS

Because of its noninvasive, rigid, reliable, and reproducible connection to the patient's head, the VBH vacuum-affixed mouthpiece grants the registration device an accuracy comparable to invasive fiducial markers.