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Reflectance spectrophotometry in the assessment of radiation erythema

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Hamilton, CS (1995) Reflectance spectrophotometry in the assessment of radiation erythema. Research Master thesis, University of Tasmania.

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Abstract

This thesis describes the dose response relationships, qualitative and
quantitative observations of cutaneous erythema in 236 patients treated on
three prospective clinical radiobiological studies, utilising Fractionated Low
Dose Rate (FLDR) and Fractionated High Dose Rates (FHDR) external beam
radiotherapy.
• Patients with incurable, locally advanced head and neck cancer and
bone and soft tissue metastases from a variety of other solid
malignancies, were treated on a modified Caesium 137 teletherapy
unit , at dose rates ranging from 0.8 to 8.2 Gy/hr in 10 fractions over
12 to 14 days (FLDR).
• Patients with bony and soft tissue metastasis from a variety of solid
malignancies were treated on a Clinac 1800 (6 MV photons), utilising
four fractionation schedules (5, 10, 12 and 20) over 5 to 35 days
(FHDR).
• Patients with localised carcinoma of the prostate were treated on a
Clinac 1800 (6 MV photons), in 30 - 32 fractions over 45 to 55 days
(FHDR).
Skin reactions were quantitatively assessed using a reflectance
spectrophotometer and graded qualitatively using a modified EORTC/RTOG
grading scale (FLDR). Qualitative skin scoring was unreliable and subject to
considerable inter- and intra-observer variation. Qualitative scores were over
estimated (relative to reflectance observations) in female patients and at nonUV
exposed anatomical sites. Pre-treatment reflectance readings were
significantly higher in male patients and in anatomical sites which had
previously heavy UV exposure. Pronounced dips in erythema readings during
the second week of therapy and "reciprocal vicinity" effects adjacent to the
treatment field, undetected by the naked eye, were observed in a subset of
patients. Peak erythema values were found to provide the best measure of
radiation effect. Peak erythema was found to depend on biologically effective
skin dose, patient age, sex and treatment site. Considerable inter- and intrapatient
heterogeneity (both before and during treatment) was demonstrated.
No dose-rate effect was seen in the FLDR group and a negative dose
response relationship was demonstrated for 0.8 Gy/hr patients. FHDR data
was under-predicted by the Linear Quadratic model at doses less than 1.5
Gy/fraction. This finding is potentially explained by the "Induced Repair Model"
of Joiner et al. For doses above 2 Gy/fraction a reasonable fit was obtained
giving an a/13 ratio in the range of 4-8 and a repair half time of 0.05- 0.15
hours. This short VA value is not consistent with other reports and may reflect
multi-component cellular repair processes. This study also suggests that
radiation-induced erythema is not exclusively related to basal cell kill.

Item Type: Thesis (Research Master)
Keywords: Erythema, Spectrophotometry, Skin, Erythema, Radiotherapy, Low Dose Rate, High Dose Rate, Reflectance Spectrophotometry, UV radiation, a/β ratio, Repair Kinetics
Copyright Holders: The Author
Copyright Information:

Copyright 1995 the Author - The University is continuing to endeavour to trace the copyright
owner(s) and in the meantime this item has been reproduced here in good faith. We
would be pleased to hear from the copyright owner(s).

Additional Information:

Thesis (M.D.)--University of Tasmania, 1998.

Date Deposited: 09 Dec 2014 00:03
Last Modified: 04 Jul 2017 06:41
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