5-ALA based photodynamic management of glioblastoma

Rühm, Adrian; Stepp, Herbert; Beyer, Wolfgang; Hennig, Georg; Pongratz, Thomas; Sroka, Ronald; Schnell, Oliver; Tonn, Jörg‐Christian; Kreth, Friedrich-Wilhelm

doi:10.1117/12.2040268

Cited by 10 publications

(14 citation statements)

References 21 publications

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“…In interstitial photodynamic therapy of brain tumors, several cylindrical diffuser fibers are placed into the tumor . For all fiber pairs, transmission and fluorescence measurements can be performed and the average optical tissue parameters and PpIX fluorescence can be calculated.…”

Section: Discussionmentioning

confidence: 99%

“…A second similar fiber was used as a detection fiber, which was connected to a spectrometer (USB2000+, OceanOptics, Largo, Fl) which incorporates a 657 nm long‐pass filter. The long‐pass filter did not completely block the transmitted laser light, thus enabled the recording of transmitted laser light and PpIX fluorescence simultaneously as is done during clinical iPDT .…”

Section: Methodsmentioning

confidence: 99%

“…In order to monitor photobleaching during interstitial PDT, spectral online monitoring (SOM) was established to assess the average PpIX fluorescence in the tumor volume between adjacent treatment fibers at least prior to and after PDT irradiation . In addition to PpIX fluorescence, the treatment light transmission (at 635 nm) could be monitored between adjacent fibers.…”

Section: Introductionmentioning

confidence: 99%

“…The intraoperative SOM measurements performed in resulted in interesting and unexpected observations regarding the intensity and/or dynamics of the recorded transmitted laser light. For example, occasionally, the transmitted intensity dropped to undetectable levels after PDT.…”

Section: Introductionmentioning

confidence: 99%

“…If cylindrical diffuser fibers are several optical penetration depths apart from each other, the light transmission losses due to even moderate increase in absorption potentiate accordingly. It can be hypothesized that the occasionally observed loss of treatment light transmission between fibers after interstitial PDT with glioma patients may therefore at least partly be caused by the ROS‐induced formation of deoxy‐ and met‐Hb. Therefore, it was the second aim of the present investigation to experimentally assess the dynamics of laser light transmission between one pair of cylindrical diffuser fibers while recording the spectral changes of white light transmission indicating changes in hemoglobin (oxy‐ versus deoxy‐ and met‐Hb).…”

Section: Introductionmentioning

confidence: 99%

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Fluorescence and Treatment Light Monitoring for Interstitial Photodynamic Therapy

Heckl

Aumiller

Rühm

et al. 2020

Photochem & Photobiology

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In interstitial photodynamic therapy, light is distributed to the tumor via light diffusers. The light dose and the related phototoxic effect achieved throughout the target volume critically depend on absorption, scattering and diffuser positioning. Using liquid tissue phantoms, we investigated the dependencies of treatment light transmission and protoporphyrin IX (PpIX) fluorescence on these parameters. This enabled monitoring hemoglobin oxygenation and methemoglobin formation during irradiation (635 nm, 200 mW cm−1 diffuser length). Starting with two parallel cylindrical diffusers at 10 mm radial separation, the light transmitted between the fibers was largely determined by the minimal distance between the diffusers, but rather insensitive to an additional axial displacement or tilting of one fiber with respect to the other. For fixed distance between the diffusor centers, however, tilting up to direct contact resulted in a 10‐fold signal increase. For hemoglobin within erythrocytes, irradiation leads to photobleaching of PpIX without marked change in hemoglobin oxygenation until hemolysis occurs. Afterward, hemoglobin is rapidly deoxygenized and methemoglobin is formed, leading to a dramatic increase in absorption. For lysed blood, these effects start immediately. A comparison of intraoperative monitoring of the signals with the experimental results might help prevent insufficient treatment by reconsidering treatment planning or prolonging irradiation.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Fluorescence and Treatment Light Monitoring for Interstitial Photodynamic Therapy

Heckl

Aumiller

Rühm

et al. 2020

Photochem & Photobiology

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Homogeneously Emitting, Mechanically Stable, and Efficient fs‐Laser‐Machined Fiber Diffusers for Medical Applications

et al. 2020

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Background and Objectives: Light delivery is an essential part of therapy forms like photodynamic therapy (PDT), laser-induced thermotherapy, and endovenous laser therapy. While there are approaches to the light application for all three therapies, there is no diffuser that can be used for all three approaches. This diffuser must meet the following criteria: Homogeneous radiation profile over a length of 40 mm, efficient light extraction in the diffuser area, mechanical breakage resistance as well as thermal stability when applying high power. Study Design/Materials and Methods: An ultrashort pulse laser was used to inscribe inhomogeneities into the core of a fused-silica fiber core while scanning the laser focus within a linear arrangement of cuboids centered around the fiber axis. The manufactured diffuser was optically and mechanically characterized and examined to determine the maximum power that can be applied in a tissue environment. Results: Based on the analysis of all examined diffusers, the manufactured diffuser exhibits an emission efficiency ε = (81.5 ± 5.9)%, an intensity variability of (19 ± 5)% between distal and proximal diffuser end, and a minimum bending radius R b = (15.4 ± 1.5) mm. It was taken advantage of the fact that the outer areas of the fiber core do not undergo any structural changes due to the machining and therefore do not suffer a major loss of stability. Tissue experiments revealed that a maximal power of 15 W was deliverable from the diffuser without harming the diffuser itself. Conclusions: It could be shown that a diffuser manufactured by ultrafast-laser processing can be used for low power applications as well as for high power applications. Further tests have to show whether the mechanical stability is still maintained after the application of high power in a tissue environment. Lasers Surg. Med.

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