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. Single doses of up to 40 Gy were applied, and the effects on saliva secretion, measured with the aid of miniaturized Lashley cups, were followed up to 365 days after the irradiation. RESULTS: Under conditions of equal mean absorbed doses and small variations in dose distribution, a pertinent volume effect was observed for late but not for early radiation damage. The late effects were different for the cranial part as compared with the caudal part of the parotid gland. The reduction in flow rate was much more severe after irradiation in the cranial part. After a single dose of 30 Gy, the reductions in flow rates were approximately 65% and 25% for the cranial and caudal parts, respectively. At that dose, no saliva flow was observed after irradiation of 100% of the gland. CONCLUSION: From the rat model studies presented, it is concluded that late radiation damage after partial irradiation of parotid glands shows region-dependent volume effects. This finding is expected to be relevant to the radiosensitivity of human salivary glands, and it implies that the predictive power of the mean dose concept in radiotherapeutic practice is limited. The finding of region-dependent late radiation damage also challenges the basic assumptions of most current normal tissue complication probability models for parotid gland function.
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. Single doses of up to 40 Gy were applied, and the effects on saliva secretion, measured with the aid of miniaturized Lashley cups, were followed up to 365 days after the irradiation. RESULTS: Under conditions of equal mean absorbed doses and small variations in dose distribution, a pertinent volume effect was observed for late but not for early radiation damage. The late effects were different for the cranial part as compared with the caudal part of the parotid gland. The reduction in flow rate was much more severe after irradiation in the cranial part. After a single dose of 30 Gy, the reductions in flow rates were approximately 65% and 25% for the cranial and caudal parts, respectively. At that dose, no saliva flow was observed after irradiation of 100% of the gland. CONCLUSION: From the rat model studies presented, it is concluded that late radiation damage after partial irradiation of parotid glands shows region-dependent volume effects. This finding is expected to be relevant to the radiosensitivity of human salivary glands, and it implies that the predictive power of the mean dose concept in radiotherapeutic practice is limited. The finding of region-dependent late radiation damage also challenges the basic assumptions of most current normal tissue complication probability models for parotid gland function.
Authors: Molly M McCulloch; Guillaume Cazoulat; Alexandra C Ford; Baher Elgohari; Houda Bahig; Andrew D Kim; Hesham Elhalawani; Renjie He; Jihong Wang; Yao Ding; Abdallah Sr Mohamed; Daniel F Polan; Jason B King; Christine B Peterson; Andrea N Ohrt; Clifton D Fuller; Stephen Y Lai; Kristy K Brock Journal: Phys Med Biol Date: 2020-08-31 Impact factor: 3.609
Authors: Joseph O Deasy; Vitali Moiseenko; Lawrence Marks; K S Clifford Chao; Jiho Nam; Avraham Eisbruch Journal: Int J Radiat Oncol Biol Phys Date: 2010-03-01 Impact factor: 7.038
Authors: Peter van Luijk; Sarah Pringle; Joseph O Deasy; Vitali V Moiseenko; Hette Faber; Allan Hovan; Mirjam Baanstra; Hans P van der Laan; Roel G J Kierkels; Arjen van der Schaaf; Max J Witjes; Jacobus M Schippers; Sytze Brandenburg; Johannes A Langendijk; Jonn Wu; Robert P Coppes Journal: Sci Transl Med Date: 2015-09-16 Impact factor: 17.956