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. 2021 Apr 1;109(5):1627-1637.
doi: 10.1016/j.ijrobp.2020.11.013. Epub 2020 Nov 20.

Initial Clinical Experience of Cherenkov Imaging in External Beam Radiation Therapy Identifies Opportunities to Improve Treatment Delivery

Lesley A Jarvis  1 , Rachael L Hachadorian  2 , Michael Jermyn  2 , Petr Bruza  2 , Daniel A Alexander  2 , Irwin I Tendler  2 , Benjamin B Williams  3 , David J Gladstone  3 , Philip E Schaner  4 , Bassem I Zaki  4 , Brian W Pogue  2
Affiliations

Initial Clinical Experience of Cherenkov Imaging in External Beam Radiation Therapy Identifies Opportunities to Improve Treatment Delivery

Lesley A Jarvis et al. Int J Radiat Oncol Biol Phys. .

Abstract

Purpose: The value of Cherenkov imaging as an on-patient, real-time, treatment delivery verification system was examined in a 64-patient cohort during routine radiation treatments in a single-center study.

Methods and materials: Cherenkov cameras were mounted in treatment rooms and used to image patients during their standard radiation therapy regimen for various sites, predominantly for whole breast and total skin electron therapy. For most patients, multiple fractions were imaged, with some involving bolus or scintillators on the skin. Measures of repeatability were calculated with a mean distance to conformity (MDC) for breast irradiation images.

Results: In breast treatments, Cherenkov images identified fractions when treatment delivery resulted in dose on the contralateral breast, the arm, or the chin and found nonideal bolus positioning. In sarcoma treatments, safe positioning of the contralateral leg was monitored. For all 199 imaged breast treatment fields, the interfraction MDC was within 7 mm compared with the first day of treatment (with only 7.5% of treatments exceeding 3 mm), and all but 1 fell within 7 mm relative to the treatment plan. The value of imaging dose through clear bolus or quantifying surface dose with scintillator dots was examined. Cherenkov imaging also was able to assess field match lines in cerebral-spinal and breast irradiation with nodes. Treatment imaging of other anatomic sites confirmed the value of surface dose imaging more broadly.

Conclusions: Daily radiation therapy can be imaged routinely via Cherenkov emissions. Both the real-time images and the posttreatment, cumulative images provide surrogate maps of surface dose delivery that can be used for incident discovery and/or continuous improvement in many delivery techniques. In this initial 64-patient cohort, we discovered 6 minor incidents using Cherenkov imaging; these otherwise would have gone undetected. In addition, imaging provides automated, quantitative metrics useful for determining the quality of radiation therapy delivery.

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Conflict of interest statement

B.W.P. and L.A.J. have a financial interest in a company, DoseOptics, which manufactures cameras that were used in the current study. This company is funded by SBIR grants. Both authors have a conflict of interest management plan at Dartmouth College and Dartmouth-Hitchcock Medical Center, which includes an independent review of the research integrity prior to publication. MJ and PB are employees of DoseOptics. In addition, Dr. Pogue has a patent US 10201718 B2 issued to DoseOptics LLC, a patent US 9731150 B2 issued to DoseOptics LLC, and a patent WO 2019/143972 A2 pending to Dartmouth/DoseOptics LLC. Dr. Tender has a patent WO/2019/165196 issued. Dr. Jarvis has a patent Application No. 62/874,124 pending. Dr. Hachadorian has a patent (application no. 62/874,124) pending. Dr. Gladstone has a patent US10,201,718 B2, 2/12/2019 issued. Dr. Bruza has a patent 62/967,302 pending, a patent 62/873,155 pending, a patent PCT/US19/14242 pending, and a patent PCT/US19/19135 pending. Dr. Jermyn has a patent WO 2019/143972 A2 pending to Dartmouth/DoseOptics LLC.

Research data are stored in an institutional repository and will be shared upon request to the corresponding author.

Figures

Figure 1:
Figure 1:
In (a), a visualization of the plan exported from the treatment planning system, rendered onto the patient CT scan surface and shown from the perspective of the Cherenkov camera. Cumulative Cherenkov images are shown from 4 separate fractions, where: (h) treatment was executed well relative to the plan, (b) some dose was inadvertently delivered to the contralateral breast, (c) attempts were made to correct the field, though not entirely successful as slight dose was still observable on the contralateral side, and (d) avoiding the left breast was over-compensated for where more dose was delivered onto the arm/shoulder region. Right column shows the corresponding AlignRT screenshots from each days treatment (c, e, g, i) with a +/− 3mm tolerance margin.
Figure 2:
Figure 2:
In (a), a leg sarcoma patient was imaged to ensure that the treating beam remained clear of the contralateral leg (a common focus point in the treatment of extremities such as legs). High tangents are another common focus point, shown in (b), where it can be seen if the patient were to move his/her head or chin, which has many degrees of freedom and lacks immobilization. When treating a patient with mastectomy using bolus, accommodating the large field sizes can be difficult, which is shown comparing (c), where the LAO field was successfully covered with bolus, whereas the RPO field (d) was not on the medial side. In a less common case where an MLC was accidentally left open during planning (e), the Cherenkov image (f) shows this incident very clearly
Figure 3:
Figure 3:
A sample of a right posterior oblique beam (RPO) Cherenkov image for a patient is shown in (a), which matches the intensity map from the treatment plan (b). The same is shown for the left anterior oblique (LAO) beam (c) which also includes a couch kick, along with its respective cumulative treatment plan image (d). These individual beams illustrate the dose gradient over the surface of the patient, with higher intensity on the entrance side and lower intensity on the exit side, over a gradient. One example of a supraclavicular field is shown in the Cherenkov image (e) and dose image exported from the treatment plan (f). For another patient, the cumulative treatment of both LAO and RPO beams Cherenkov image (g) is shown matching the cumulative treatment dose image (h). In (i), the mean distance to conformity (MDC) relative to the first recorded treatment day is plotted for.all breast patient images, and in (j) this is replotted relative to the treatment plan dose outline as a reference. A dashed gray line indicates where treatment fractions fall within a 3 mm MDC agreement and a red dashed line indicates a 7 mm MDC agreement.
Figure 4:
Figure 4:
In (a) Cherenkov imaging through clear bolus applied to a breast irradiation case and in (b) Cherenkov imaging of the same patient without bolus, showing lower signal resulting from lower surface dose. In (c) imaging of a TSET patient shows Cherenkov from the skin and scintillation from localized dots placed on the skin, with calculated surface dose values. In (d) & (e) surface doses are shown for two different whole breast radiation cases were a single scintillating dot was placed on the breast during Cherenkov imaging. Surface dose values from scintillator and OSLD are reported in blue and green text, respectively.
Figure 5:
Figure 5:
A treatment plan for cerebral-spinal irradiation (CSI) is shown (a), which was characterized by four fields and three isocenters: a right and left lateral whole brain field, an upper spine field and a lower spine field. A technique for stitching together the Cherenkov treatment images was developed by first isolating the lower spine field individually in (b) and upper spine in (c). The result in (d) shows the sum, with biological fiducials used to register the background and Cherenkov images together. Image (d) shows profiles comparing days 1 through 4 of lower and upper spine junction areas, as compared what was seen in the treatment plan. In (e), the supraclavicular cumulative fields treating the axial nodes of a patient are shown. In (f), the four tangent beam images (LAO/RPO 6X/10X) summed together are shown, and added with the supraclavicular field in (g). The match region has a bounding box that isolates the profile intersection region, such that the meeting of the two beams can be analyzed.
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References

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