Repair Kinetics in Mouse Lung: A Fast Component at 1·1 Gy Per Fraction

Fowler, Jack F.; Whitsed, C.A.; Joiner, Michael C.

doi:10.1080/09553008914551501

Cited by 20 publications

(7 citation statements)

References 11 publications

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“…It is interesting that a number of reports of two-compo nent repair in other tissues are appearing in the literature, including very recently [12,17,[20][21][22]29,34,38]. Further, Denham et al [7] have suggested that a continuum of repair rates may be present, for which two components is only a poor approximation, even though attempts to deconvolute more than two components are fruitless because of the wide confidence intervals of published data from all biological experiments.…”

Section: Discussionmentioning

confidence: 99%

“…Several other tissues have also given results interpreted as bi-exponential repair, including human telangiectasia [3], human oropharyngeal mucosa [7], mouse lung [12,20,38], pig skin [22,34], rat kidney cells [21] and mouse lip mucosa [29], The experiments are technically demanding and diffi cult to analyse because too many variables become neces sary [28]. Further, Denham et al [7] have suggested that even two components are only a rough approximation to a range of multiple T l/2 values in reality.…”

Section: Introductionmentioning

confidence: 99%

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Kinetics of repair in the spinal cord of the rat

Landuyt

Fowler

Ruifrok

et al. 1997

Radiotherapy and Oncology

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Purpose: Split dose experiments were carried out with two 2 Gy fractions per day at intervals ranging from 0.5 to 24 h, in order to investigate both the time to complete repair and the detailed kinetics of repair of sublethal damage in the cervical spine of rats.Materials and methods: Male rats of the WAG/Rij strain were irradiated at 2 Gy/min with 18 MV photons to a length of 18 mm of cervical spinal cord. Four hundred twenty-three rats were irradiated without top-up doses to investigate whether repair was complete by 24 h or whether any slow repair or proliferation occurred up to 50 days after irradiation. Three hundred seventy-nine rats were also irradiated in split dose (2 Gy + At + 2 Gy each day) experiments, with intervals of 0.5, 1, 2 ,4 , 8 and 24 h. The split dose irradiations were followed by a single top-up dose of 15 Gy (producing about half the total damage).Results :

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Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Kinetics of repair in the spinal cord of the rat

Landuyt

Fowler

Ruifrok

et al. 1997

Radiotherapy and Oncology

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“…Though there have been several experiments providing repair rates for normal lung tissue, many of which indicate the presence of both a short and long component of repair, similar analyses for lung tumors do not exist. [16][17][18][19][20][21] One study of normal lung tissue in mice showed that the slower component of repair may approach T 1=2 ¼ 4.0 h. 22 As previously stated, although no evidence indicating similar results in lung tumors exists, if T 1=2 does approach 4.0 h for lung tumors, the effectiveness of this present study would greatly diminish. Nevertheless, Fowler and Chappell did indicate a rapid repopulation of NSCLC during radiation therapy which may imply a fast component of sublethal damage repair.…”

Section: Iic Benchmarking the Lpl Modelmentioning

confidence: 57%

Potential increase in biological effectiveness from field timing optimization for stereotactic body radiation therapy

2012

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“…The present result should not be generalised too widely to other normal tissues. It is known that some other tissues might have two components of repair [16,17,25,26,39,41], including human tissues [10,38]* In view of this possibility, and also in view of some early clinical results which showed telangiectasia at earlier times or unexpected necrosis with PDR treatments [30], the previous radiobiological warning to keep within the cautious envelope of small doses per pulse should not be forgotten [7,14]. experiments in this laboratory [22].…”

Section: Discussionmentioning

confidence: 99%

“…Other tissues too have been reported to have a short and a long component of repair, including human telangiectasia [38], human oropharyngeal mucosa and skin [10], mouse lung [16,41], pig skin [26,39], rat kidney cells [24] and mouse lip mucosa [35].…”

Section: Discussionmentioning

confidence: 99%

Is pulsed dose rate more damaging to spinal cord of rats than continuous low dose rate?

Haustermans¹,

Fowler²,

Landuyt³

et al. 1997

Radiotherapy and Oncology

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Background and. purpose: Theoretical calculations suggest that pulsed dose-rate irradiation (PDR) should have approximately the same effectiveness as continuous low dose-rate (CLDR) when the same total dose is given in the same overall time, unless large doses per pulse (> 2 Gy) are used and/or non-exponential or very short half-times of repair (<0*5 h) are present in the irradiated tissues. However, few animal experiments have been reported to test this theory, and some of them gave contradictory results. W e have carded out experiments to determine whether PDR irradiation of 18 mm of cervical spinal cord in the rat was more or less effective than CLDR at 0,5-1 Gy/h, when the overall average dose rate during each day of PDR was close to the overall CLDR average dose rate.Materials and methods: PDR was simulated at a within-pulse dose rate of 4 Gy/h by filtered 18 MV X-rays from a linear accelerator. Two PDR schedules were used, 0.69 Gy at 1 h repetition (9 pulses per day) and 2 Gy at 3 h repetition (4 pulses per day), with overnight intervals of 16 and 15 h, respectively. The CLDR was delivered from iridium-192 wires in two concentric rings around a collar designed to fit the necks of rats so that they could eat and drink during the 72 h that was always the duration of the CLDR, Dose rate was then proportional to total CLDR dose. A range of doses was used to obtain dose response-curves, with a 15 Gy top-up dose (at 2 Gy/min, HDR) given on the day after the end of the PDR or CLDR irradiations. Animals were observed for at least 9 months to see whether fore-limb myelopathy developed. A total of 6-8 rats was irradiated per dose point, in two sets of experiments at an interval of 12 months.Results: A set of 2 Gy fractions (at HDR) given daily, followed by the same top-up dose of 15 Gy at HDR, was available from a previous experiment for planning. Its ED5o was 61,2 Gy. The ED50 values found for the PDR schedules with 2 Gy at 3 h and 0.69 Gy at 1 h were 59.9 and 60.2 Gy, respectively. These were just 2% more effective than the daily HDR fractions, similar to expectations from theory if two components of repair are present. However, the CLDR irradiations resulted in no myelopathy even after doses up to 68 Gy at 0.94 Gy/h.. Thus PDR over 7 days (not at nights) appears to be more effective than CLDR over 3 days, with an effective dose-modifying factor of at least 1.1 to 1.17.Discussion and conclusions: Reasons for this absence of effect with CLDR in these experiments are discussed, the most likely explanation being that a substantial component of repair with very short T (/2 (< 0.5 h) was present in spinal cord of these rats. There is evidence from other experiments elsewhere and in our laboratory for such a fast component of repair.

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Repair Kinetics in Mouse Lung: A Fast Component at 1·1 Gy Per Fraction

Cited by 20 publications

References 11 publications

Kinetics of repair in the spinal cord of the rat

Kinetics of repair in the spinal cord of the rat

Potential increase in biological effectiveness from field timing optimization for stereotactic body radiation therapy

Is pulsed dose rate more damaging to spinal cord of rats than continuous low dose rate?

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