Abstract
Breakthrough whole body energy-specific photoneutron (PN) dosimetry was made in/out-of-field in polyethylene phantom organ surface/depths remote from isocenter of 10 × 10 cm2 field prostate cancer therapy in 18 MV X-rays Varian Clinac 2100C medical linear accelerator for PN tissue-specific second primary cancer (PN-SPC) risk estimation. A novel miniature neutron dosimeter/spectrometer with polycarbonate/10B/cadmium inserts was invented and applied. Each dosimeter determines seven tissue-specific dose equivalent (mSv)/Gy X-ray dose at each measurement point providing seven major energy-specific responses for beam thermal, albedo thermal, total thermal, total epithermal, total fast, sum of totals (thermal + epithermal) and sum of totals (thermal + epithermal + fast) PNs dose equivalents. The neutron dosimeter is simple, efficient, and unique with high spatial resolution and provides matrix of energy-specific PN dose equivalent (mSv)/Gy X-ray dose on surface and organ depths for tissue-specific PN-SPC risk estimation. The dosimeter also performs like a “miniature neutron spectrometer” and is unique for other applications in health physics in particular individual neutron dosimetry, medical physics, space flights, science and technology.
Highlights
Medical linear accelerators produce high-energy electrons and X-rays and have found widespread applications worldwide for patient cancer radiotherapy
Neutrons are high linear energy transfer (LET) particles which produce high-LET secondary charged particles in particular protons when interact with atomic nuclei in human body
Sensitivity to fast, epithermal and thermal PNs from the beam and albedo PNs; high spatial resolution for in-depth tissue-specific dose equivalent determination; insensitivity to high doses of low-LET radiation (X, γ, β) and non-ionizing radiation; little/negligible post-exposure fading; simple and easy to be used in numbers on and in organ depths so that preferably all the dosimeters can be exposed under one single exposure to avoid busy beam time
Summary
Medical linear accelerators produce high-energy electrons and X-rays and have found widespread applications worldwide for patient cancer radiotherapy. A review of in and out-of-field X-rays and neutron dose measurements by solid state dosimeters and ion chambers usually in water tanks has focused on importance of estimating SPC risks from PNs and X-rays[11]. The rationale for assigning correct radiation W T and W R values in radiation protection as well as for estimating accurately tissue-specific PN-SPC risks of patients undergoing high energy X-ray therapy is to have a neutron dosimeter with some specific neutron dosimetry characteristics. Some major studies have been reviewed for in/out-of-field X-rays and neutron dose measurements usually in water tanks for estimating SPC risks by some solid state dosimeters and ion chambers[11]
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