Fig 1.
Dose distribution with a conformity index of 0.95 (a) for a deeply-seated tumor located in the midline via two lateral 18-MV beams and (b) for a superficial tumor located in the left temporal lobe via a lateral 6-MV beam (from the left) and an 18-MV beam (from the right). Planning Target Volume (PTV) = Clinical Target Volume (CTV) + 1 cm and CTV = Grass Target Volume + 0.6 cm.
Table 1.
Tolerated dose of organs at risk in radiotherapy of head and neck area [32].
Fig 2.
Neutron rem detector including (a) thermal neutron counter BF3, (b) polyethylene modulator and cadmium layer with suitable thickness, and (c) equipped with Eberline’s ASP-2e rate-meter with pulse height analysis capability (2000 V to create an appropriate differential pulse height distribution was adopted).
Table 2.
Position of the center of the organs: Horizontal distance of the organs from the central axis of the beam and the depth of the organs from the phantom surface.
This information is extracted from Howell et al’s study [36] using an Eclipse measuring instrument for an Alderson Radiation Therapy Phantom Female. In this table, the organs are classified into three levels of depth (superficial, middle, and deep).
Table 3.
Neutron absorbed dose reported by d’Errico et al. As a function of the initial neutron energy (0.5 MeV) and the depth in a phantom 30 × 30 × 20 cm3 [38].
Fig 3.
Detector set-up for measurement of neutron ambient dose equivalent at the isocenter under a Source to Surface Distance (SSD) of 95 cm.
A similar procedure was employed also for measurements at the 20 and 60 cm far away from the isocenter.
Table 4.
Neutron ambient dose equivalent, H*(10), in different distances at the patient table under a 10 × 10 cm2 treatment field when 1 Gy photon dose was delivered to the isocenter.
The results also were compared with Zanini et al’s study [40].
Table 5.
Neutron equivalent dose (HT), effective dose, and risk of secondary cancer & genetic effects for a glioma patient undergoing 18-MV radiotherapy when 60-Gy photon dose is delivered to the brain with two lateral 10 × 10 cm2 treatment fields.
Tissue weighting factor (WT) and risk coefficients were employed based on NCRP 116 recommendation [39].
Fig 4.
Contribution of photoneutrons and scattered photons to the total equivalent dose received by several out-of-field organs in glioma patients undergoing 18-MV radiotherapy.