| 1. |
- Ivashchenko, Oleksandra V., et al.
(författare)
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Time-Activity data fitting in molecular Radiotherapy : Methodology and pitfalls
- 2024
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Ingår i: Physica medica (Testo stampato). - : Elsevier. - 1120-1797 .- 1724-191X. ; 117
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Tidskriftsartikel (refereegranskat)abstract
- Absorbed radiation doses are essential in assessing the effects, e.g. safety and efficacy, of radiopharmaceutical therapy (RPT). Patient-specific absorbed dose calculations in the target or the organ at risk require multiple inputs. These include the number of disintegrations in the organ, i.e. the time-integrated activities (TIAs) of the organs, as well as other parameters describing the process of radiation energy deposition in the target tissue (i.e. mean energy per disintegration, radiation dose constants, etc). TIAs are then estimated by incorporating the area under the radiopharmaceutical's time-activity curve (TAC), which can be obtained by quantitative measurements of the biokinetics in the patient (typically based on imaging data such as planar scintigraphy, SPECT/CT, PET/CT, or blood and urine samples). The process of TAC determination/calculation for RPT generally depends on the user, e.g., the chosen number and schedule of measured time points, the selection of the fit function, the error model for the data and the fit algorithm. These decisions can strongly affect the final TIA values and thus the accuracy of calculated absorbed doses. Despite the high clinical importance of the TIA values, there is currently no consensus on processing time-activity data or even a clear understanding of the influence of uncertainties and variations in personalised RPT dosimetry related to user-dependent TAC calculation. As a first step towards minimising site-dependent variability in RPT dosimetry, this work provides an overview of quality assurance and uncertainty management considerations of the TIA estimation.
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| 2. |
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| 3. |
- McNamara, Paul N, et al.
(författare)
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Tissue viability (TiVi) imaging: temporal effects of local occlusion studies in the volar forearm
- 2010
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Ingår i: Journal of Biophotonics. - : John Wiley & Sons. - 1864-063X .- 1864-0648. ; 3:1-2, s. 66-74
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Tidskriftsartikel (refereegranskat)abstract
- Tissue Viability (TiVi) imaging is a promising new technology for the assessment of microcirculation in the upper human dermis. Although the technique is easily implemented and develops large amounts of observational data, its role in the clinical workplace awaits the development of standardised protocols required for routine clinical practice. The present study investigates the use of TiVi technology in a human, in vivo, localized, skin blood flow occlusion protocol. In this feasibility study, the response of the cutaneous microcirculation after provocation on the volar surface of the forearm was evaluated using a high temporal-low spatial resolution TiVi camera. 19 healthy subjects - 10 female and 9 male - were studied after a localized pressure was applied for 5 different time periods ranging from 5 to 25 seconds. Areas corresponding to 100 x 100 pixels (2.89 cm(2)) were monitored for 60 seconds prior to, during and after each occlusion period. Our results demonstrated the removal of blood from the local area and a hyperaemic response supporting the suitability of TiVi imaging for the generation of detailed provocation response data of relevance for the physiological function of the skin microcirculation in health and disease.
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| 4. |
- ODoherty, Jim, et al.
(författare)
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Correcting for possible tissue distortion between provocation and assessment in skin testing: The divergent beam UVB photo-test
- 2013
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Ingår i: Skin research and technology. - : Wiley-Blackwell. - 0909-752X .- 1600-0846. ; 19:4, s. 368-374
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundIn tissue viability imaging (TiVi), an assessment method for skin erythema, correct orientation of skin position from provocation to assessment optimizes data interpretation. Image processing algorithms could compensate for the effects of skin translation, torsion and rotation realigning assessment images to the position of the skin at provocation. less thanbrgreater than less thanbrgreater thanMethodsA reference image of a divergent, UVB phototest was acquired, as well as test images at varying levels of translation, rotation and torsion. Using 12 skin markers, an algorithm was applied to restore the distorted test images to the reference image. less thanbrgreater than less thanbrgreater thanResultsThe algorithm corrected torsion and rotation up to approximately 35 degrees. The radius of the erythemal reaction and average value of the input image closely matched that of the reference images true value. less thanbrgreater than less thanbrgreater thanConclusionThe image de-warping procedure improves the robustness of the response image evaluation in a clinical research setting and opens the possibility of the correction of possibly flawed images performed away from the laboratory setting by the subject/patient themselves. This opportunity may increase the use of photo-testing and, by extension, other late response skin testing where the necessity of a return assessment visit is a disincentive to performance of the test.
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| 5. |
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| 6. |
- O'Doherty, Jim, et al.
(författare)
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Real time diffuse reflectance polarisation spectroscopy imaging to evaluate skin microcirculation
- 2007
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Ingår i: Novel Optical Instrumentationfor Biomedical Applications III. - : SPIE - International Society for Optical Engineering. - 9780819467751 ; , s. 66310O-1-66310O-10
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Konferensbidrag (refereegranskat)abstract
- This article describes the theoretical development and design of a real-time microcirculation imaging system, an extension from a previously technology developed by our group. The technology utilises polarisation spectroscopy, a technique used in order to selectively gate photons returning from various compartments of human skin tissue, namely from the superficial layers of the epidermis, and the deeper backscattered light from the dermal matrix. A consumer-end digital camcorder captures colour data with three individual CCDs, and a custom designed light source consisting of a 24 LED ring light provides broadband illumination over the 400 nm - 700 nm wavelength region. Theory developed leads to an image processing algorithm, the output of which scales linearly with increasing red blood cell (RBC) concentration. Processed images are displayed online in real-time at a rate of 25 frames s(-1), at a frame size of 256 x 256 pixels, and is limited only by computer RAM memory and processing speed. General demonstrations of the technique in vivo display several advantages over similar technology.
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| 7. |
- O'doherty, Jim, et al.
(författare)
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Sub-epidermal imaging using polarized light spectroscopy for assessment of skin microcirculation
- 2007
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Ingår i: Skin research and technology. - : Wiley. - 0909-752X .- 1600-0846. ; 13:4, s. 472-484
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Tidskriftsartikel (refereegranskat)abstract
- Background/aims: Many clinical conditions that affect the microcirculation of the skin are still diagnosed and followed up by observational methods alone in spite of the fact that non-invasive, more user-independent and objective methods are available today. Limited portability, high cost, lack of robustness and non-specificity of findings are among the factors that have hampered the implementation of these methods in a clinical setting. The aim of this study is to present and evaluate a new, portable and easy-to-use imaging technology for investigation of the red blood cell (RBC) concentration in the skin microvasculature based on the method of polarization light spectroscopy using modified standard digital camera technology. Methods: The use of orthogonal linear polarization filters over both the flash source and the detector array removes the polarization-retaining light reflected from the epidermal layer. Only the depolarized light backscattered from the papillary dermal matrix reaches the detector array. By separating the RGB color planes of an image acquired in this manner and applying a dedicated image processing algorithm, spectroscopic information about the chromophores in the dermal tissue can be attained. If the algorithm is based on a differential principle in which the normalized differences between the individual values of the red and green color plane are calculated, tissue components with similar spectral signature in both planes are suppressed, while components with different spectral signatures such as RBCs are enhanced. Results: In vitro fluid models compare well with theory and computer simulations in describing a linear relationship between the imager output signal termed the tissue viability index (TiVi index) and RBC concentration in the physiological range of 0-4% RBC fraction of tissue volume (cc=0.997, n=20). The influence of oxygen saturation on the calculated RBC concentration is limited to within -3.9% for values within the physiological range (70-100% oxygen saturation). Monte Carlo simulations provide information about the sampling depth (about 0.5mm on the average) of the imaging system. In vivo system evaluation based on iontophoresis of acetylcholine displays a heterogeneous pattern of vasodilatation appearing inside the electrode area after about 10min. Topical application of methyl nicotinate and clobetasol propionate further demonstrates the capacity to document the extent and intensity of both an increase (erythema) and a decrease (blanching) in the skin RBC concentration without movement artifact and with compensation for irregularity in pigmentation. Conclusions: Polarization light spectroscopy imaging for assessment of RBC concentration in the skin microvasculature is a robust and accessible technique for the clinical setting. Additionally, the technique has pre-clinical research applications for investigation of the spatial and temporal aspects of skin erythema and blanching as well as a potential role in drug development, skin care product development and skin toxicological assessment.
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| 8. |
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| 9. |
- O'Doherty, Jim, et al.
(författare)
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Tissue viability imaging (TiVi) in the assessment of divergent beam UV-B provocation
- 2011
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Ingår i: Archives of Dermatological Research. - : Springer. - 0340-3696 .- 1432-069X. ; 303:2, s. 79-87
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Tidskriftsartikel (refereegranskat)abstract
- In routine clinical phototesting and in basic research, naked eye dermatological assessment is the "gold standard" for determining the patient's minimal erythemal dose (MED). In UV-B testing with a divergent, radially attenuating beam of characterised dosimetry, laser Doppler perfusion imaging has been previously used to give quantitative description of reactivity to doses above the MED in addition to a "single-dose" objective determination of the MED itself. In the present paper, the recently developed tissue viability imaging (TiVi) technology is presented for the first time as a reliable, easily applicable, high-resolution alternative to LDPI in the divergent beam testing concept. Data obtained after provocation with a range of doses was analysed in order to determine the reaction diameter, which can be related to the MED using field dosimetry. The dose-response features of exposure above the MED and the relationship between naked eye readings and the diameter were determined from the image data. TiVi data were obtained faster than LDPI data and at a higher spatial resolution of 100 μm instead of 1 mm. A tool was developed to centre over the erythema area of the acquired image. Response data could be plotted continuously against dose. Thresholding of processed images compared to naked eye "gold standard" readings showed that the normal skin value +4 standard deviations produced a good fit between both methods. A linear fitting method for the dose-response data provided a further method of determination of the reaction diameter (MED). Erythemal "volume under the surface (VUS)" for the reaction provided a new concept for visualising information. TiVi offers advantages over LDPI in the acquisition and analysis of data collected during divergent beam testing. An increased amount of data compared to traditional phototesting is easily and more objectively obtained which increases applicability in the clinical and research environment.
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