Verification of field match lines in whole breast radiation therapy using Cherenkov imaging

Enhanced Cherenkov imaging for real-time beam visualization by applying a novel carbon quantum dot sheeting in radiotherapy

BACKGROUND

Cherenkov imaging can be used to visualize the placement of the beam directly on the patient's surface tissue and evaluate the accuracy of treatment planning. However, Cherenkov emission intensity is lower than ambient light. At present, time gating is the only way to realize Cherenkov imaging with ambient light.

PURPOSE

This study proposes preparing a novel carbon quantum dot (cQD) sheeting to adjust the wavelength of Cherenkov emission to obtain the optimal wavelength meeting the sensitive detection region of the camera, meanwhile the total optical signal is also increased. By combining a specific filter, this approach might help in using lower-cost camera systems without intensifier-coupled to accomplish in vivo monitoring of the surface beam profile on patients with ambient light.

METHODS

The cQD sheetings were prepared by spin coating and UV curing with different concentrations. All experiments were performed on the Varian VitalBeam system and optical emission was captured using an electron multiplying charge-coupled device (EMCCD) camera. To quantify the optical characteristics and certify the improvement of light intensity as well as signal-to-noise ratio (SNR) of cQD sheeting, the first part of the study was carried out on solid water with 6 and 10 MV photon beams. The second part was carried out on an anthropomorphic phantom to explore the applicability of sheeting when using different radiotherapy materials and the imaging effect of sheeting with the impact of ambient light sources. Additionally, thanks to the narrow emission spectrum of the cQD, a band-pass filter was tested to reduce the effect from environmental lights.

RESULTS

The experimental results show that the optical intensity collected with sheeting has an excellent linear relationship (R²  > 0.99) with the dose for 6 and 10 MV photons. The full-width half maximum (FWHM) in x and y axis matched with the measured EBT film image, with accuracy in the range of ±1.2 and ±2.7 mm standard deviation, respectively. CQD sheeting can significantly improve the light intensity and SNR of optical images. Using 0.1 mg/ml sheeting as an example, the signal intensity is increased by 209%, and the SNR is increased by 147.71% at 6 MV photons. The imaging on the anthropomorphic phantom verified that cQD sheeting could be applied to different radiotherapy materials. The average optical intensity increased by about 69.25%, 63.72%, and 61.78%, respectively, after adding cQD sheeting to bolus, mask sample and the combination of bolus and mask. Corresponding SNR is improved by about 62.78%, 56.77%, and 68.80%, respectively. Through the sheeting, optical images with SNR > 5 can be obtained in the presence of ambient light and it can be improved through combining with a band-pass filter. When red ambient lights are on, the SNR is increased by about 98.85% after adding a specific filter.

CONCLUSION

Through a combination of cQD sheeting and corresponding filter, light intensity and SNR of optical images can be increased significantly, and it shed new light on the promotion of the clinical application of optical imaging to visualize the beam in radiotherapy.

One Year of Clinic-Wide Cherenkov Imaging for Discovery of Quality Improvement Opportunities in Radiation Therapy

PURPOSE

Cherenkov imaging is clinically available as a radiation therapy treatment verification tool. The aim of this work was to discover the benefits of always-on Cherenkov imaging as a novel incident detection and quality improvement system through review of all imaging at our center.

METHODS AND MATERIALS

Multicamera Cherenkov imaging systems were permanently installed in 3 treatment bunkers, imaging continuously over a year. Images were acquired as part of normal treatment procedures and reviewed for potential treatment delivery anomalies.

RESULTS

In total, 622 unique patients were evaluated for this study. We identified 9 patients with treatment anomalies occurring over their course of treatment, which were only detected with Cherenkov imaging. Categorizing each event indicated issues arising in simulation, planning, pretreatment review, and treatment delivery, and none of the incidents were detected before this review by conventional measures. The incidents identified in this study included dose to unintended areas in planning, dose to unintended areas due to positioning at treatment, and nonideal bolus placement during setup.

CONCLUSIONS

Cherenkov imaging was shown to provide a unique method of detecting radiation therapy incidents that would have otherwise gone undetected. Although none of the events detected in this study reached the threshold of reporting, they identified opportunities for practice improvement and demonstrated added value of Cherenkov imaging in quality assurance programs.

Application of Cherenkov radiation in tumor imaging and treatment

Cherenkov radiation (CR) is the characteristic blue glow that is generated during radiotherapy or radioisotope decay. Its distribution and intensity naturally reflect the actual dose and field of radiotherapy and the location of radioisotope imaging agents in vivo. Therefore, CR can represent a potential in situ light source for radiotherapy monitoring and radioisotope-based tumor imaging. When used in combination with new imaging techniques, molecular probes or nanomedicine, CR imaging exhibits unique advantages (accuracy, low cost, convenience and fast) in tumor radiotherapy monitoring and imaging. Furthermore, photosensitive nanomaterials can be used for CR photodynamic therapy, providing new approaches for integrating tumor imaging and treatment. Here the authors review the latest developments in the use of CR in tumor research and discuss current challenges and new directions for future studies.