Influence of adjacent low-dose fields on tolerance to high doses of protons in rat cervical spinal cord.

Purpose: The dose-response relationship for a relatively short length (4 mm) of rat spinal cord has been shown to be significantly modified by adjacent low-dose fields. In an additional series of experiments, we have now established the dose-volume dependence of this effect.

Methods And Materials: Wistar rats were irradiated on the cervical spinal cord with single doses of unmodulated protons (150 MeV) to obtain sharp lateral penumbras, by use of the shoot-through technique, which employs the plateau of the depth-dose profile rather than the Bragg peak.

Radioprotective effect of amifostine on parotid gland functioning is region dependent.

Purpose: To investigation the protective ability of amifostine during partial irradiation of the rat parotid gland.

Methods And Materials: Single-dose X-ray irradiation was performed by use of collimators with conformal radiation portals for either the 100% volume (15 Gy) or the 50% cranial/caudal partial parotid gland volumes (30 Gy). Amifostine was administered intraperitoneally at a dose of 250 mg per kg body weight, 25 minutes before irradiation.

Secondary radiation damage as the main cause for unexpected volume effects: a histopathologic study of the parotid gland.

Purpose: To elucidate with a histopathological study the mechanism of region-dependent volume effects in the partly irradiated parotid gland of the rat.

Methods And Materials: Wistar rats were locally X-irradiated with collimators with conformal radiation portals for 100% volume and 50% cranial/caudal partial volumes. Single doses up to 40 Gy were applied.

On the mechanism of salivary gland radiosensitivity.

Purpose: To contribute to the understanding of the enigmatic radiosensitivity of the salivary glands by analysis of appropriate literature, especially with respect to mechanisms of action of early radiation damage, and to supply information on the possibilities of amelioration of radiation damage to the salivary glands after radiotherapy of head-and-neck cancer.

Methods And Materials: Selected published data on the mechanism of salivary gland radiosensitivity and radioprotection were studied and analyzed.

Results: From a classical point of view, the salivary glands should not respond as rapidly to radiation as they appear to do.

Volume effects and region-dependent radiosensitivity of the parotid gland.

Purpose: To detect volume effects and possible regional differences in radiosensitivity of the rat parotid gland.

Methods And Materials: Parotid glands of male albino Wistar rats were locally X-irradiated, with collimators with conformal radiation portals used to supply 100% volume and 50% cranial/caudal partial volumes. High-resolution magnetic resonance imaging was used to provide the outlines of the parotid glands.

Data on dose-volume effects in the rat spinal cord do not support existing NTCP models.

Purpose: To evaluate several existing dose-volume effect models for their ability to describe the occurrence of white matter necrosis in rat spinal cord after irradiation with small proton beams.

Methods And Materials: A large number of dose-volume effect models has been fitted to data on the occurrence of white matter necrosis after irradiation with small proton beams. The fitting was done with the maximum likelihood method.

Regional differences in radiosensitivity across the rat cervical spinal cord.

Purpose: To study regional differences in radiosensitivity within the rat cervical spinal cord.

Methods And Materials: Three types of inhomogeneous dose distributions were applied to compare the radiosensitivity of the lateral and central parts of the rat cervical spinal cord. The left lateral half of the spinal cord was irradiated with two grazing proton beams, each with a different penumbra (20-80% isodoses): lateral wide (penumbra = 1.

Unexpected changes of rat cervical spinal cord tolerance caused by inhomogeneous dose distributions.

Purpose: The effects of dose distribution on dose-effect relationships have been evaluated and, from this, iso-effective doses (ED(50)) established.

Methods And Materials: Wistar rats were irradiated on the cervical spinal cord with single doses of unmodulated protons (150 MeV) to obtain sharp lateral penumbras, using the shoot-through technique, which employs the plateau of the depth-dose profile rather than the Bragg peak. Two types of inhomogeneous dose distributions have been administered: (1) 2 4-mm fields with 8- or 12-mm spacing between the center of the fields (referred to as split-field) were irradiated with variable single doses and (2) cervical spinal cord was irradiated with various combinations of relatively low doses to a large volume (20 mm) combined with high doses to a small volume (4 mm) (referred to as bath and shower).

Comparison of radiosensitivity of rat parotid and submandibular glands after different radiation schedules.

Background And Purpose: To investigate the radiosensitivity of rat parotid and submandibular gland functioning after local single dose, conventional fractionated and accelerated fractionated irradiation.

Methods: The salivary glands of male albino Wistar rats were locally irradiated with a single dose (15 Gy) or a calculated (alpha/beta; 9.6) biological effective dose of fractionated irradiation equal to this, viz.

Dose-volume effects in the rat cervical spinal cord after proton irradiation.

Purpose: To estimate dose-volume effects in the rat cervical spinal cord with protons.

Methods And Materials: Wistar rats were irradiated on the cervical spinal cord with a single fraction of unmodulated protons (150-190 MeV) using the shoot through method, which employs the plateau of the depth-dose profile rather than the Bragg peak. Four different lengths of the spinal cord (2, 4, 8, and 20 mm) were irradiated with variable doses.