Dosimetry control and monitoring of selective retina therapy using optical coherence tomography

Kaufmann, Daniel E.; Burri, Christian; Arnold, Patrik; Koch, Volker; Meier, Christoph; Považay, Boris; Justiz, Joern

doi:10.1117/12.2283067

Cited by 5 publications

(8 citation statements)

References 9 publications

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“…Based on this model, using signal changes of SD-OCT M-scans, Kaufmann et al were able to precisely predict RPE lesions post-treatment in ex vivo porcine eyes [27,28]. Furthermore, Kaufmann et al showed that SRT in ramp mode, combined with fast algorithm-based SD-OCT treatment termination, could provide reliable SRT dosing and prevent overtreatment.…”

Section: Introductionmentioning

confidence: 99%

Dynamic OCT Signal Loss for Determining RPE Radiant Exposure Damage Thresholds in Microsecond Laser Microsurgery

et al. 2021

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Optical microsurgery of the retinal pigment epithelium (RPE) requires reliable real-time dosimetry to prevent unwanted overexposure of the neuroretina. The system used in this experiment implements optical coherence tomography (OCT) to detect the intentional elimination of RPE cells. We evaluated the performance of OCT dosimetry in terms of its ability to detect RPE cell damage caused by microsecond laser pulses of varying duration. Therefore, ex-vivo porcine RPE choroid sclera explants were embedded in an artificial eye and exposed to single laser pulses of 2–20 µs duration (wavelength: 532 nm, exposure area: 120 × 120 µm2, intensity modulation factor: 1.3). Simultaneously, time-resolved OCT M-scans were recorded (central wavelength: 870 nm, scan rate: 33 kHz). Post-irradiation, RPE cell damage was quantified using a calcein-AM viability assay and compared with an OCT-dosimetry algorithm. The results of our experiments show that the OCT-based analysis successfully predicts RPE cell damage. At its optimal operating point, the algorithm achieved a sensitivity of 89% and specificity of 94% for pulses of 6 µs duration and demonstrated the ability to precisely control radiant exposure of a wide range of pulse durations towards selective real-time laser microsurgery.

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Section: Introductionmentioning

confidence: 99%

Dynamic OCT Signal Loss for Determining RPE Radiant Exposure Damage Thresholds in Microsecond Laser Microsurgery

et al. 2021

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“…Optical coherence tomography (OCT), which can provide depth-resolved imaging, was also applied for the SRT monitoring. [15][16][17][18][19] The treatments are considered successful when OCT signal variations, i.e., intensity decrease, are detected, and the results show good agreement with the evaluation of lesions by FFA.…”

Section: Introductionmentioning

confidence: 85%

Selective retina therapy monitoring by speckle variance optical coherence tomography for dosimetry control

et al. 2020

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Significance: Selective retina therapy (SRT) selectively targets the retinal pigment epithelium (RPE) and reduces negative side effects by avoiding thermal damages of the adjacent photoreceptors, the neural retina, and the choroid. However, the selection of proper laser energy for the SRT is challenging because of ophthalmoscopically invisible lesions in the RPE and different melanin concentrations among patients or even regions within an eye. Aim: We propose and demonstrate SRT monitoring based on speckle variance optical coherence tomography (svOCT) for dosimetry control. Approach: M-scans, time-resolved sequence of A-scans, of ex vivo bovine retina irradiated by 1.7-μs duration laser pulses were obtained by a swept-source OCT. SvOCT images were calculated as interframe intensity variance of the sequence. Spatial and temporal temperature distributions in the retina were numerically calculated in a 2-D retinal model using COMSOL Multiphysics. Microscopic images of treated spots were obtained before and after removing the upper neural retinal layer to assess the damage in both RPE and neural layers. Results: SvOCT images show abrupt speckle variance changes when the retina is irradiated by laser pulses. The svOCT intensities averaged in RPE and photoreceptor layers along the axial direction show sharp peaks corresponding to each laser pulse, and the peak values were proportional to the laser pulse energy. The calculated temperatures in the neural retina layer and RPE were linearly fitted to the svOCT peak values, and the temperature of each lesion was estimated based on the fitting. The estimated temperatures matched well with previously reported results. Conclusion: We found a reliable correlation between the svOCT peak values and the degree of retinal lesion formation, which can be used for selecting proper laser energy during SRT.

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“…To alter the last applied pulse energy although the maximum energy E max remained fixed, the trigger signal length for the treatment laser was modified to fire either only the first pulse, the first 4, 9, 14, 18, 23 or all 30 pulses (in which case E max was reached). Previous work, in which a pulse repetition rate of 100 Hz was used, has shown that each pulse within one burst can be considered as standalone because no significant cumulative effects take place [52]. The seven different burst lengths correspond to seven different classes and were evaluated as such, as can be seen in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Selective retina therapy enhanced with optical coherence tomography for dosimetry control and monitoring: a proof of concept study

Kaufmann¹,

Burri²,

Arnold³

et al. 2018

Biomed. Opt. Express

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Selective treatment of the retinal pigment epithelium (RPE) by using short-pulse lasers leads to a less destructive treatment for certain retinal diseases in contrast to conventional photocoagulation. The introduction of selective retina therapy (SRT) to clinical routine is still precluded by the challenges to reliably monitor treatment success and to automatically adjust dose within the locally varying therapeutic window. Combining micrometer-scale depth resolving capabilities of optical coherence tomography (OCT) with SRT can yield real-time information on the laser-induced changes within the RPE after a laser pulse or even during treatment with a laser pulse train. In the present study, SRT and OCT were combined to treat ex-vivo porcine eyes demonstrating closed-loop dose-control. We found a reliable correlation of specific signal changes in time resolved OCT images and physiological lesions in the RPE. First experiments, including 23 porcine eyes, prove the feasibility of the novel treatment concept.

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Dosimetry control and monitoring of selective retina therapy using optical coherence tomography

Cited by 5 publications

References 9 publications

Dynamic OCT Signal Loss for Determining RPE Radiant Exposure Damage Thresholds in Microsecond Laser Microsurgery

Dynamic OCT Signal Loss for Determining RPE Radiant Exposure Damage Thresholds in Microsecond Laser Microsurgery

Selective retina therapy monitoring by speckle variance optical coherence tomography for dosimetry control

Selective retina therapy enhanced with optical coherence tomography for dosimetry control and monitoring: a proof of concept study

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