A Dosimetric Comparison Between 3D-Conformal and Intensity-Modulated Co-Planer Radiotherapy Plans for Treatment of Pediatric Posterior Fossa Medulloblastoma.

Abstract

Background:Craniospinal irradiation followed by a boost to the posterior fossa combined with cisplatinbased chemotherapy after maximal safe resection is the standard of care in treatment of pediatric medulloblastoma. Sensorineural hearing loss is one of the most serious positble late effect of this treatment. Material and Method: Five high-risk medulloblastoma pediatric patients were treated by craniospinal irradiation (36 Gy) combined with cisplatin weekly followed by a boost of irradiation (18 Gy) to the posterior fossa by 3D-CRT plan. Dosimetric plans by IMRT were done to the 5 cases to compare between 3D-CRT and IMRT in sparing of the different OARs as well as their coverage of the target. Results: By comparing the mean doses and DVHs for the 3D-CRT and IMRT plans, it was obvious that IMRT plans were able to spare the cochlea more than the 3D-CRT. As the cochlea received 80.5% (43.5 Gy) of the prescribed dose in the IMRT plans compared to 94.5% (51. Gy) of the prescribed dose in the 3D-CRT plans, even the target was better covered by IMRT as it has been shown when comparing the DVHs of the different plans. Conclusion: IMRT increases the conformality of dose of radiation in the target and limiting the dose to the OARs especially the cochlea thus reducing the incidence of sensory hearing loss.

Dosimetric comparison of rapidplan and manually optimized plans for hippocampus avoidance whole brain radiation therapy

“…When the tumor localization and OARs surrounding has been identified, the number of beams and beam boundaries in patient were designed using beam's eye view. For whole brain irradiation, this technique is commonly used right and left parallel opposing fields as presented in figure 2.1 (5) , however, this 3D-CRT plan cannot spare the hippocampus (6) . (7) Intensity-modulated radiation treatment (IMRT) is a sort of asymmetrical radiotherapy in which a linear accelerator is used to deliver an advanced type of high-precision radiotherapy in which the radiation beam is shaped to precisely suit the tumor's area.…”