Influence of vitamins and food on the fluorescence spectrum of human urine.

OBJECTIVES: Fluorescence spectroscopy of human urine is a method with the potential to gain importance as a diagnostic tool in the medical field, e.g., for measuring Coproporphyrin III (CPIII) as an indicator of cancer and acute types of porphyria. Food can change human urine's color, which could influence the urine fluorescence spectrum and the detection of CPIII in urine. To determine if there is a noticeable influence on the urine fluorescence spectrum or on the detection of CPIII in urine, 16 vitamin supplements, and three food items were tested. Such investigation may also prevent false interpretation of measured data. METHODS: Urine samples were collected before and after (overnight, ca. 8 h) intake of each test substance. Samples were investigated by fluorescence spectrum analysis. At excitation wavelengths from 300 to 500 nm and emission wavelengths from 400 to 700 nm excitation-emission-matrices were measured. Data obtained from urine before intake were compared to the data from overnight urine. Furthermore, the investigation of any interference with the CPIII concentration was performed at an excitation wavelength of 407 ± 3 nm and emission wavelengths of 490-800 nm. RESULTS: Only vitamin B2, but none of the other tested substances, showed noticeable influence on the urine fluorescence spectrum. None of the tested substances showed noticeable interference with the recovery rate of CPIII. CONCLUSIONS: The correct interpretation of measured data by fluorescence spectroscopy is possible with the exception if vitamin B2 supplementation was performed; thus, the consumption of vitamin B2 supplements before fluorescence testing of the patient's urine should be avoided and/or must be requested. CPIII concentrations could reliably be measured in all cases.

Investigations on correlations between changes of optical tissue properties and NMR relaxation times.

BACKGROUND: Accurate light dosimetry is a complex remaining challenge in interstitial photodynamic therapy (iPDT) for malignant gliomas. The light dosimetry should ideally be based on the tissue morphology and the individual optical tissue properties of each tissue type in the target region. First investigations are reported on using NMR information to estimate changes of individual optical tissue properties. METHODS: Porcine brain tissue and optical tissue phantoms were investigated. To the porcine brain, supplements were added to simulate an edema or high blood content. The tissue phantoms were based on agar, Lipoveneous, ink, blood and gadobutrol (Gd-based MRI contrast agent). The concentrations of phantom ingredients and tissue additives are varied to compare concentration-dependent effects on optical and NMR properties. A 3-tesla whole-body MRI system was used to determine T1 and T2 relaxation times. Optical tissue properties, i.e., the spectrally resolved absorption and reduced scattering coefficient, were obtained using a single integrating sphere setup. The observed changes of NMR and optical properties were compared to each other. RESULTS: By adjusting the NMR relaxation times and optical tissue properties of the tissue phantoms to literature values, recipes for human brain tumor, white matter and grey matter tissue phantoms were obtained that mimic these brain tissues simultaneously in both properties. For porcine brain tissue, it was observed that with increasing water concentration in the tissue, both NMR-relaxation times increased, while µa decreased and µs' increased at 635 nm. The addition of blood to porcine brain samples showed a constant T1, while T2 shortened and the absorption coefficient at 635 nm increased. CONCLUSIONS: In this investigation, by changing sample contents, notable changes of both NMR relaxation times and optical tissue properties have been observed and their relations examined. The developed dual NMR/optical tissue phantoms can be used in iPDT research, clinical training and demonstrations.

Interstitial Photodynamic Therapy of Glioblastomas: A Long-Term Follow-up Analysis of Survival and Volumetric MRI Data.

BACKGROUND: The treatment of glioblastomas, the most common primary malignant brain tumors, with a devastating survival perspective, remains a major challenge in medicine. Among the recently explored therapeutic approaches, 5-aminolevulinic acid (5-ALA)-mediated interstitial photodynamic therapy (iPDT) has shown promising results. METHODS: A total of 16 patients suffering from de novo glioblastomas and undergoing iPDT as their primary treatment were retrospectively analyzed regarding survival and the characteristic tissue regions discernible in the MRI data before treatment and during follow-up. These regions were segmented at different stages and were analyzed, especially regarding their relation to survival. RESULTS: In comparison to the reference cohorts treated with other therapies, the iPDT cohort showed a significantly prolonged progression-free survival (PFS) and overall survival (OS). A total of 10 of 16 patients experienced prolonged OS (≥ 24 months). The dominant prognosis-affecting factor was the MGMT promoter methylation status (methylated: median PFS of 35.7 months and median OS of 43.9 months) (unmethylated: median PFS of 8.3 months and median OS of 15.0 months) (combined: median PFS of 16.4 months and median OS of 28.0 months). Several parameters with a known prognostic relevance to survival after standard treatment were not found to be relevant to this iPDT cohort, such as the necrosis-tumor ratio, tumor volume, and posttreatment contrast enhancement. After iPDT, a characteristic structure (iPDT remnant) appeared in the MRI data in the former tumor area. CONCLUSIONS: In this study, iPDT showed its potential as a treatment option for glioblastomas, with a large fraction of patients having prolonged OS. Parameters of prognostic relevance could be derived from the patient characteristics and MRI data, but they may partially need to be interpreted differently compared to the standard of care.

Interstitial photodynamic therapy for newly diagnosed glioblastoma.

PURPOSE: Innovative, efficient treatments are desperately needed for people with glioblastoma (GBM). METHODS: Sixteen patients (median age 65.8 years) with newly diagnosed, small-sized, not safely resectable supratentorial GBM underwent interstitial photodynamic therapy (iPDT) as upfront eradicating local therapy followed by standard chemoradiation. 5-aminolevulinic acid (5-ALA) induced protoporphyrin IX was used as the photosensitizer. The tumors were irradiated with light at 635 nm wavelength via stereotactically implanted cylindrical diffuser fibers. Outcome after iPDT was retrospectively compared with a positively-selected in-house patient cohort (n = 110) who underwent complete tumor resection followed by chemoradiation. RESULTS: Median progression-free survival (PFS) was 16.4 months, and median overall survival (OS) was 28.0 months. Seven patients (43.8%) experienced long-term PFS > 24 months. Median follow-up was 113.9 months for the survivors. Univariate regression revealed MGMT-promoter methylation but not age as a prognostic factor for both OS (p = 0.04 and p = 0.07) and PFS (p = 0.04 and p = 0.67). Permanent iPDT-associated morbidity was seen in one iPDT patient (6.3%). Patients treated with iPDT experienced superior PFS and OS compared to patients who underwent complete tumor removal (p < 0.01 and p = 0.01, respectively). The rate of long-term PFS was higher in iPDT-treated patients (43.8% vs. 8.9%, p < 0.01). CONCLUSION: iPDT is a feasible treatment concept and might be associated with long-term PFS in a subgroup of GBM patients, potentially via induction of so far unknown immunological tumor-controlling processes.

Development of a microstructured tissue phantom with adaptable optical properties for use with microscopes and fluorescence lifetime imaging systems.

OBJECTIVES: For the development and validation of diagnostic procedures based on microscopic methods, knowledge about the imaging depth and achievable resolution in tissue is crucial. This poses the challenge to develop a microscopic artificial phantom focused on the microscopic instead of the macroscopic optical tissue characteristics. METHODS: As existing artificial tissue phantoms designed for image forming systems are primarily targeted at wide field applications, they are unsuited for reaching the formulated objective. Therefore, a microscopy- and microendoscopy-suited artificial tissue phantom was developed and characterized. It is based on a microstructured glass surface coated with fluorescent beads at known depths covered by a scattering agent with modifiable optical properties. The phantom was examined with different kinds of microscopy systems in order to characterize its quality and stability and to demonstrate its usefulness for instrument comparison, for example, regarding structural as well as fluorescence lifetime analysis. RESULTS: The analysis of the manufactured microstructured glass surfaces showed high regularity in their physical dimensions in accordance with the specifications. Measurements of the optical parameters of the scattering medium were consistent with simulations. The fluorescent beads coating proved to be stable for a respectable period of time (about a week). The developed artificial tissue phantom was successfully used to detect differences in image quality between a research microscope and an endoscopy based system. Plausible causes for the observed differences could be derived based on the well known microstructure of the phantom. CONCLUSIONS: The artificial tissue phantom is well suited for the intended use with microscopic and microendoscopic systems. Due to its configurable design, it can be adapted to a wide range of applications. It is especially targeted at the characterization and calibration of clinical imaging systems that often lack extensive positioning capabilities such as an intrinsic z-stage.

Interstitial Photodynamic Therapy Using 5-ALA for Malignant Glioma Recurrences.

Interstitial photodynamic therapy (iPDT) using 5-aminolevulinic acid (5-ALA)-induced protoporphyrin IX (PpIX) as a cytotoxic photosensitizer could be a feasible treatment option for malignant gliomas. In a monocentric cohort of consecutive patients treated between 2006 and 2018, a risk profile analysis of salvage iPDT for local malignant glioma recurrences and associated outcome measures are presented here. It was considered indicated in patients with circumscribed biopsy-proven malignant glioma recurrences after standard therapy, if not deemed eligible for safe complete resection. A 3D treatment-planning software was used to determine the number and suitable positions of the cylindrical diffusing fibers placed stereotactically to ensure optimal interstitial irradiation of the target volume. Outcome measurements included the risk profile of the procedure, estimated time-to-treatment-failure (TTF), post-recurrence survival (PRS) and prognostic factors. Forty-seven patients were treated, of which 44 (median age, 49.4 years, range, 33.4-87.0 years, 27 males) could be retrospectively evaluated. Recurrent gliomas included 37 glioblastomas (WHO grade IV) and 7 anaplastic astrocytomas (WHO grade III). Thirty (68.2%) tumors were O-6-methylguanine-DNA methyltransferase (MGMT)-methylated, 29 (65.9%)-isocitrate dehydrogenase (IDH)-wildtype. Twenty-six (59.1%) patients were treated for their first, 9 (20.5%)-for their second, 9 (20.5%)-for the third or further recurrence. The median iPDT target volume was 3.34 cm3 (range, 0.50-22.8 cm3). Severe neurologic deterioration lasted for more than six weeks in one patient only. The median TTF was 7.1 (95% confidence interval (CI), 4.4-9.8) months and the median PRS was 13.0 (95% CI, 9.2-16.8) months. The 2- and 5-year PRS rates were 25.0% and 4.5%, respectively. The treatment response was heterogeneous and not significantly associated with patient characteristics, treatment-related factors or molecular markers. The promising outcome and acceptable risk profile deserve further prospective evaluation particularly to identify mechanisms and prognostic factors of favorable treatment response.

Interrelation between Spectral Online Monitoring and Postoperative T1-Weighted MRI in Interstitial Photodynamic Therapy of Malignant Gliomas.

In a former study, interstitial photodynamic therapy (iPDT) was performed on patients suffering from newly diagnosed glioblastoma (n = 11; 8/3 male/female; median age: 68, range: 40-76). The procedure includes the application of 5-ALA to selectively metabolize protoporphyrin IX (PpIX) in tumor cells and illumination utilizing interstitially positioned optical cylindrical diffuser fibers (CDF) (2-10 CDFs, 2-3 cm diffusor length, 200 mW/cm, 635 nm, 60 min irradiation). Intraoperative spectral online monitoring (SOM) was employed to monitor treatment light transmission and PpIX fluorescence during iPDT. MRI was used for treatment planning and outcome assessment. Case-dependent observations included intraoperative reduction of treatment light transmission and local intrinsic T1 hyperintensity in non-contrast-enhanced T1-weighted MRI acquired within one day after iPDT. Intrinsic T1 hyperintensity was observed and found to be associated with the treatment volume, which indicates the presence of methemoglobin, possibly induced by iPDT. Based on SOM data, the optical absorption coefficient and its change during iPDT were estimated for the target tissue volumes interjacent between evaluable CDF-pairs at the treatment wavelength of 635 nm. By spatial comparison and statistical analysis, it was found that observed increases of the absorption coefficient during iPDT were larger in or near regions of intrinsic T1 hyperintensity (p = 0.003). In cases where PpIX-fluorescence was undetectable before iPDT, the increase in optical absorption and intrinsic T1 hyperintensity tended to be less. The observations are consistent with in vitro experiments and indicate PDT-induced deoxygenation of hemoglobin and methemoglobin formation. Further investigations are needed to provide more data on the time course of the observed changes, thus paving the way for optimized iPDT irradiation protocols.

Fluorescence and Treatment Light Monitoring for Interstitial Photodynamic Therapy.

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.