Frequent blood donors are therefore at an increased risk of developing iron deficiency. Currently, there is no easy and routinely available method during blood donation to detect iron deficient erythropoiesis (IDE) before the amount of healthy red blood cells drops below normal levels, which is referred to as anemia. An optical technology to detect iron deficiency in a pre-anemic state had been developed. The measurement is performed on the tubing between the donor and the blood collection bag during the donation. The measurement takes about 1 minute and provides an immediate result at very low costs. The evaluation showed a high sensitivity to identify blood donors with advanced iron deficiency before anemia occurs. The method was shown to be more sensitive than the standard assessment of the hemoglobin value. The optical method envisioned the feasibility and diagnostic value to prevent iron deficiency anemia of frequent blood donors by providing an early warning signal. Beyond the health benefit for the blood donor, this might also lead to less rejections of blood donors due to iron deficiency anemia.
Stereotactic interstitial photodynamic therapy using 5 aminolevulinic acid is a more upcoming approach for the treatment of malignant gliomas, whose treatment is remaining a major challenge in brain tumor therapy. The therapeutic outcome of 16 patients who underwent 5-ALA iPDT for newly diagnosed glioblastomas, are presented. In addition to the basic survival analysis, MRI data was analyzed concerning image changes after iPDT and the possibility to use these changes as prognostic factor for therapy response. Overall the iPDT showed a progression-free survival (PFS) of 16.4 months and an overall survival (OS) of 28.0 months. A PFS longer than 2-years was seen for 43.8% of iPDT patients. In contrast to this complete tumor resection with consecutive chemoradiation shows 8.9% 2-year PFS. Standard MRI-related prognostic factors of the tumor resection like necrosis-tumor ratio, tumor volume and post-treatment contrast enhancement are not useful for iPDT prognosis. This shows that the MRI interpretation has to be different compared to conventional tumor therapy. The survival results showed that iPDT is a potential treatment option especially for tumors, where standard therapy is not possible. Further studies are needed.
Hyperspectral imaging has been explored for clinical applications in various medical disciplines. Based on our experiences, the potential of this versatile imaging method as well as pitfalls and limitations of current approaches are discussed. The use of reference samples and simple image modeling strategies are suggested to avoid misinterpretation and achieve a more conclusive image interpretation.
Hyperspectral imaging (HSI) is a new emerging modality for noncontact assessement of tissue perfusion parameters. This study includes investigations on monitoring perfusion changes of the hand during a modified Allen test and cuff occlusion test, on the influence of the skin tones during HSI-measurements and the feasibility of HSI monitoring of intraoral free flaps
5-aminolevulinic acid (5-ALA) mediated interstitial photodynamic therapy (iPDT) is undergoing clinical trials for the treatment of malignant gliomas. 5-ALA iPDT is based on the creation of reactive oxygen species (ROS) via excitation of 5-ALA mediated protoporphyrin IX (PpIX) in the tumor cells and causing a phototoxic reaction. After iPDT local chemo-radiation is performed as adjuvant therapy. 16 newly diagnosed glioblastomas and 44 malignant glioma recurrences treated with 5-ALA iPDT in Munich were retrospectively analyzed for treatment outcome, spectral online monitoring and changes in the MRI. iPDT for newly diagnosed glioblastomas showed a median overall survival (OS) of 28 months, 16.4 months progression free survival (PFS), respectively. 43.8% patients with newly diagnosed glioblastoma experienced a long term PFS > 24 months. In addition, the methylation of the MGMT promotor showed to be a prognostic factor for prolonged survival (p=0.04). In case of recurrent malignant gliomas PFS after iPDT was 7.1 months with 25% >24 months survival after iPDT (17.9% PFS > 24 months). Analysis of spectral online monitoring showed that a measured decrease of the laser light transmission between the cylindrical diffuser fibers, used for the irradiation, can be associated with silent hemorrhages visible in terms of T1-hyperintensity in the MRI after iPDT. Overall 5-ALA iPDT is a promising tool for the treatment of glioblastomas and other malignant gliomas with prolonged survival and minimally invasive surgery.
The perfusion in cutaneous flap transplants needs to be monitored in order to detect vascular problems as early as possible. This can avoid tissue hypoxia and therefore, necrosis of the transplant. Since free flap transplant failures tend to happen more commonly during surgery than at a later onset, a non-contact real-time imaging device would be most advantageous. As hyperspectral imaging (HSI) is a new emerging modality to asses free flap perfusion contactless, this study aimed to investigate whether perfusion data can be interpreted appropriately using HSI, especially in regard to the individual skin tone. Further factors that might alter these HSI-interpretations, such as aging, BMI, different sexes or smoking habits, were also considered. Therefore, a prospective feasibility study was conducted, including 101 volunteers from whom images were taken on 16 different body sites. Skin pigmentation classification was performed using the Fitzpatrick skin type classification questionnaire and the individual typology angle (ITA) acquired from the images. Perfusion indices provided by the camera software were correlated to the possible influencing factors. The results show that a dark skin tone related to a high amount of melanin may influence the HSI-measurements and thus changes the HSI-derived perfusion indices. In addition, certain physiological influencing factors such as age, BMI and sex alter the tissue composition and qualities, thus showing measurement peculiarities within these groups. In conclusion, hyperspectral imaging can be used for perfusion assessment for people with lighter skin tone levels. Further developments are appreciated especially regarding skin pigmentation and the interpretation of indices of greater skin tone levels.
Existing optical tissue phantoms are usually designed for wide field imaging systems and not readily usable for microscopic or endoscopic systems, especially such without any z-stage. Therefore a fs-laser microstructured artificial tissue phantom with adaptable geometric, tissue-optical and localized fluorescence properties enabling comparison and testing of different microscopic/endoscopic systems was designed, characterized and tested.
KEYWORDS: Magnetic resonance imaging, Absorption, Signal detection, Tumors, Photodynamic therapy, Tissue optics, Luminescence, In vitro testing, Diffusion, Data acquisition
Losses in treatment light transmission during interstitial PDT were found to correlate with T1 hyperintensity in post-therapeutic non-contrast-enhanced T1-weighted MRI. This finding might be related to iPDT-induced early formation of methemoglobin.
Interstitial photodynamic therapy (iPDT) is currently being investigated as a light-based treatment option for highly malignant brain tumours (glioblastomas/GBM). To obtain a sufficient irradiation of the tumour, quantitative knowledge about the light propagation in the tissue is required for the light dosimetry calculations underlying the clinical treatment planning. To individualize the light dosimetry calculations, the optical properties of the irradiated tissue need to be determined in-vivo. A novel approach for this purpose is based on the direction-resolved light detection within the tissue, using a rotating optical side-view probe. During measurement, the tissue is irradiated via a separate interstitially placed light applicator, and from the angular dependence of the recorded signal the optical tissue properties are calculated, based on a solution of the radiative transfer equation (RTE). Measurements were performed on liquid tissue phantoms and biological tissue samples. As a result, an over- and underestimation of the calculated optical absorption and scattering coefficients may arise in some situations, but the effective attenuation coefficient remains largely unaffected and corresponds well with literature values.
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