Quantifying the impact of optical surface guidance in the treatment of cancers of the head and neck

Surface guided radiation therapy with an innovative open-face mask and mouth bite: patient motion management in brain stereotactic radiotherapy

INTRODUCTION

To guarantee treatment reproducibility and stability, immobilization devices are essential. Additionally, surface-guided radiation therapy (SGRT) serves as an accurate complement to frameless stereotactic radiosurgery (SRS) and stereotactic radiotherapy (SRT) by aiding patient positioning and real-time monitoring, especially when non-coplanar fields are in use. At our institute, we have developed a surface-guided SRS (SG-SRS) workflow that incorporates our innovative open-face mask (OM) and mouth bite (MB) to guarantee a precise and accurate dose delivery.

METHODS

This study included 40 patients, and all patients were divided into closed mask (CM) and open-face mask (OM) groups according to different positioning flow. Cone beam computed tomography (CBCT) scans were performed, and the registration results were recorded before and after the treatment. Then Bland-Altman method was used to analyze the consistency of AlignRT-guided positioning errors and CBCT scanning results in the OM group. The error changes between 31 fractions in one patient were recorded to evaluate the feasibility of monitoring during treatment.

RESULTS

The median of translation error between stages of the AlignRT positioning process was (0.03-0.07) cm, and the median of rotation error was (0.20-0.40)°, which were significantly better than those of the Fraxion positioning process (0.09-0.11) cm and (0.60-0.75)°. The mean bias values between the AlignRT guided positioning errors and CBCT were 0.01 cm, - 0.07 cm, 0.03 cm, - 0.30°, - 0.08° and 0.00°. The 31 inter-fractional errors of a single patient monitored by SGRT were within 0.10 cm and 0.50°.

CONCLUSIONS

The application of the SGRT with an innovative open-face mask and mouth bite device could achieve precision positioning accuracy and stability, and the accuracy of the AlignRT system exhibits excellent constancy with the CBCT gold standard. The non-coplanar radiation field monitoring can provide reliable support for motion management in fractional treatment.

Setup and intra-fractional motion measurements using surface scanning in head and neck cancer radiotherapy- A feasibility study

Background and purpose

Surface-guided radiotherapy (SGRT) is applied to improve patient set-up and to monitor intra-fraction motion. Head and neck cancer (H&N) patients are usually fixated using 5-point thermoplastic masks, that are experienced as uncomfortable or even stressful. Therefore, the feasibility of irradiating H&N patients without a mask by using SGRT was examined.

Material and methods

Nineteen H&N patients were included in a simulation study. Once a week, before the standard treatment, a maskless treatment was simulated, using SGRT for setup and intrafraction motion monitoring. Initial patient setup accuracy and intrafraction motion was determined using ConeBeam CT (CBCT) images as well as SGRT before and after the (simulated) treatment. The clinical target volume to planning target volume (CTV-PTV) margin for intrafraction motion was calculated. Using patient questionnaires, the patient-friendliness H&N irradiation with and without mask was determined.

Results

Maskless setup with SGRT and CBCT was as accurate as with a mask. SGRT showed that intrafraction motion was gradual during the treatment. The CTV-PTV margin correcting for intrafraction motion was 1.7 mm for maskless treatment without interventions, and 1.2 mm if corrected for motions > 2 mm. For 19 % of fractions, the intrafraction motion, as detected by both SGRT and CBCT, was larger than 2 mm in at least one direction. Sixteen patients preferred maskless treatment, while 3 worried they would move too much.

Conclusions

Using SGRT and a standard head rest resulted in a patient-friendly treatment with accurate patient setup and acceptably small intrafraction motion for H&N patients.

Surface-Guided Radiotherapy: Can We Move on from the Era of Three-Point Markers to the New Era of Thousands of Points?

The surface-guided radiotherapy (SGRT) technique improves patient positioning with submillimeter accuracy compared with the conventional positioning technique of lasers using three-point tattoos. SGRT provides solutions to considerations that arise from the conventional setup technique, such as variability in tattoo position and the psychological impact of the tattoos. Moreover, SGRT provides monitoring of intrafractional motion.

PURPOSE

This literature review covers the basics of SGRT systems and examines whether SGRT can replace the traditional positioning technique. In addition, it investigates SGRT's potential in reducing positioning times, factors affecting SGRT accuracy, the effectiveness of live monitoring, and the impact on patient dosage.

MATERIALS AND METHODS

This study focused on papers published from 2016 onward that compared SGRT with the traditional positioning technique and investigated factors affecting SGRT accuracy and effectiveness.

RESULTS/CONCLUSIONS

SGRT provides the same or better results regarding patient positioning. The implementation of SGRT can reduce overall treatment time. It is an effective technique for detecting intrafraction patient motion, improving treatment accuracy and precision, and creating a safe and comfortable environment for the patient during treatment.

Initial clinical evaluation of a novel combined biometric, radio-frequency identification, and surface imaging system

PURPOSE

To evaluate and characterize the overall clinical functionality and workflow of the newly released Varian Identify system (version 2.3).

METHODS

Three technologies included in the Varian Identify system were evaluated: patient biometric authentication, treatment accessory device identification, and surface-guided radiation therapy (SGRT) function. Biometric authentication employs a palm vein reader. Treatment accessory device verification utilizes two technologies: device presence via Radio Frequency Identification (RFID) and position via optical markers. Surface-guidance was evaluated on both patient orthopedic setup at loading position and surface matching and tracking at treatment isocenter. A phantom evaluation of the consistency and accuracy for Identify SGRT function was performed, including a system consistency test, a translational shift and rotational accuracy test, a pitch and roll accuracy test, a continuous recording test, and an SGRT vs Cone-Beam CT (CBCT) agreement test.

RESULTS

201 patient authentications were verified successfully with palm reader. All patient treatment devices were successfully verified for their presences and positions (indexable devices). The patient real-time orthopedic pose was successfully adjusted to match the reference surface captured at simulation. SGRT-reported shift consistency against couch readout was within (0.1 mm, 0.030). The shift accuracy was within (0.3 mm, 0.10). In continuous recording mode, the maximum variation was 0.2 ± 0.12 mm, 0.030 ± 0.020. The difference between Identify SGRT offset and CBCT was within (1 mm, 10).

CONCLUSIONS

This clinical evaluation confirms that Identify accurately functions for patient palm identification and patient treatment device presence and position verification. Overall SGRT consistency and accuracy was within (1 mm, 10), within the 2 mm criteria of AAPM TG302.

Optimizing the Patient Positioning Workflow of Patients with Pelvis, Limb, and Chest/Spine Tumors at an Ion-Beam Gantry based on Optical Surface Guidance

Purpose

Surface-guided radiation therapy (SGRT) has been investigated intensively to ensure correct patient positioning during a radiation therapy course. Although the implementation is well defined for photon-beam facilities, only a few analyses have been published for ion-beam therapy centers. To investigate the accuracy, reliability, and efficiency of SGRT used in ion-beam treatments against the conventional skin marks, a retrospective study of a unique SGRT installation in an ion gantry treatment room was conducted, where the environment is quite different to conventional radiation therapy.

Methods and Materials

There were 32 patients, divided into 3 cohorts-pelvis, limb, and chest/spine tumors-and treated with ion-beams. Two patient positioning workflows based on 300 fractions were compared: workflow with skin marks and workflow with SGRT. Position verification was followed by planar kilo voltage imaging. After image matching, 6 degrees of freedom corrections were recorded to assess interfraction positioning errors. In addition, the time required for patient positioning, image matching, and the number of repeated kilo voltage imaging also were gathered.

Results

SGRT decreased the translational magnitude shifts significantly (P < .05) by 0.5 ± 1.4 mm for pelvis and 1.9 ± 0.5 mm for limb, whereas for chest/spine, it increased by 0.7 ± 0.3 mm. Rotational corrections were predominantly lowered with SGRT for all cohorts with significant differences in pitch for pelvis (P = .002) and chest/spine (P = .009). The patient positioning time decreased by 18%, 9%, and 15% for pelvis, limb, and chest/spine, respectively, compared with skin marks. By using SGRT, 53% of all studied patients had faster positioning time, and 87.5% had faster matching time. Repositioning and consequent reimaging decreased from about 7% to 2% with a statistically significant difference of .042.

Conclusions

The quality of patient positioning before ion-beam treatments has been optimized by using SGRT without additional imaging dose. SGRT clearly reduced inefficiencies in the patient positioning workflow.

Surface-Guided Patient Setup Versus Traditional Tattoo Markers for Radiation Therapy: Is Tattoo-Less Setup Feasible for Thorax, Abdomen and Pelvis Treatment?

Purpose: In this study, patient setup accuracy was compared between surface guidance and tattoo markers for radiation therapy treatment sites of the thorax, abdomen and pelvis.

Methods and materials: A total of 608 setups performed on 59 patients using both surface-guided and tattoo-based patient setups were analyzed. During treatment setup, patients were aligned to room lasers using their tattoos, and then the six-degree-of-freedom (6DOF) surface-guided offsets were calculated and recorded using AlignRT system. While the patient remained in the same post-tattoo setup position, target localization imaging (radiographic or ultrasound) was performed and these image-guided shifts were recorded. Finally, surface-guided vs tattoo-based offsets were compared to the final treatment position (based on radiographic or ultrasound imaging) to evaluate the accuracy of the two setup methods.

Results: The overall average offsets of tattoo-based and surface-guidance-based patient setups were comparable within 3.2 mm in three principal directions, with offsets from tattoo-based setups being slightly less. The maximum offset for tattoo setups was 2.2 cm vs. 4.3 cm for surface-guidance setups. Larger offsets (ranging from 2.0 to 4.3 cm) were observed for surface-guided setups in 14/608 setups (2.3%). For these same cases, the maximum observed tattoo-based offset was 0.7 cm. Of the cases with larger surface-guided offsets, 13/14 were for abdominal/pelvic treatment sites. Additionally, larger rotations (>3°) were recorded in 18.6% of surface-guided setups. The majority of these larger rotations were observed for abdominal and pelvic sites (~84%).

Conclusions: The small average differences observed between tattoo-based and surface-guidance-based patient setups confirm the general equivalence of the two potential methods, and the feasibility of tattoo-less patient setup. However, a significant number of larger surface-guided offsets (translational and rotational) were observed, especially in the abdominal and pelvic regions. These cases should be anticipated and contingency setup methods planned for.

Advances and potential of optical surface imaging in radiotherapy

This article reviews the recent advancements and future potential of optical surface imaging (OSI) in clinical applications as a four-dimensional (4D) imaging modality for surface-guided radiotherapy (SGRT), including OSI systems, clinical SGRT applications, and OSI-based clinical research. The OSI is a non-ionizing radiation imaging modality, offering real-time 3D surface imaging with a large field of view (FOV), suitable for in-room interactive patient setup, and real-time motion monitoring at any couch rotation during radiotherapy. So far, most clinical SGRT applications have focused on treating superficial breast cancer or deep-seated brain cancer in rigid anatomy, because the skin surface can serve as tumor surrogates in these two clinical scenarios, and the procedures for breast treatments in free-breathing (FB) or at deep-inspiration breath-hold (DIBH), and for cranial stereotactic radiosurgery (SRS) and radiotherapy (SRT) are well developed. When using the skin surface as a body-position surrogate, SGRT promises to replace the traditional tattoo/laser-based setup. However, this requires new SGRT procedures for all anatomical sites and new workflows from treatment simulation to delivery. SGRT studies in other anatomical sites have shown slightly higher accuracy and better performance than a tattoo/laser-based setup. In addition, radiographical image-guided radiotherapy (IGRT) is still necessary, especially for stereotactic body radiotherapy (SBRT). To go beyond the external body surface and infer an internal tumor motion, recent studies have shown the clinical potential of OSI-based spirometry to measure dynamic tidal volume as a tumor motion surrogate, and Cherenkov surface imaging to guide and assess treatment delivery. As OSI provides complete datasets of body position, deformation, and motion, it offers an opportunity to replace fiducial-based optical tracking systems. After all, SGRT has great potential for further clinical applications. In this review, OSI technology, applications, and potential are discussed since its first introduction to radiotherapy in 2005, including technical characterization, different commercial systems, and major clinical applications, including conventional SGRT on top of tattoo/laser-based alignment and new SGRT techniques attempting to replace tattoo/laser-based setup. The clinical research for OSI-based tumor tracking is reviewed, including OSI-based spirometry and OSI-guided tumor tracking models. Ongoing clinical research has created more SGRT opportunities for clinical applications beyond the current scope.

Augmented reality-guided positioning system for radiotherapy patients

In modern radiotherapy, error reduction in the patients’ daily setup error is important for achieving accuracy. In our study, we proposed a new approach for the development of an assist system for the radiotherapy position setup by using augmented reality (AR). We aimed to improve the accuracy of the position setup of patients undergoing radiotherapy and to evaluate the error of the position setup of patients who were diagnosed with head and neck cancer, and that of patients diagnosed with chest and abdomen cancer. We acquired the patient's simulation CT data for the three‐dimensional (3D) reconstruction of the external surface and organs. The AR tracking software detected the calibration module and loaded the 3D virtual model. The calibration module was aligned with the Linac isocenter by using room lasers. And then aligned the virtual cube with the calibration module to complete the calibration of the 3D virtual model and Linac isocenter. Then, the patient position setup was carried out, and point cloud registration was performed between the patient and the 3D virtual model, such the patient's posture was consistent with the 3D virtual model. Twenty patients diagnosed with head and neck cancer and 20 patients diagnosed with chest and abdomen cancer in the supine position setup were analyzed for the residual errors of the conventional laser and AR‐guided position setup. Results show that for patients diagnosed with head and neck cancer, the difference between the two positioning methods was not statistically significant (P > 0.05). For patients diagnosed with chest and abdomen cancer, the residual errors of the two positioning methods in the superior and inferior direction and anterior and posterior direction were statistically significant (t = −5.80, −4.98, P < 0.05). The residual errors in the three rotation directions were statistically significant (t = −2.29 to −3.22, P < 0.05). The experimental results showed that the AR technology can effectively assist in the position setup of patients undergoing radiotherapy, significantly reduce the position setup errors in patients diagnosed with chest and abdomen cancer, and improve the accuracy of radiotherapy.