Radiation Physics1) Many old references list "dose" rate in terms of R/hr in air. What is the...

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Radiation Physics1) Many old references list "dose" rate in terms of R/hr in air. What is the conversion factor from R/hr to Sv/s in air and in tissue? (assume Q =1, N = I. (PaMussue, E- Imes, = XXXXXXXXXXcm2/g, and (FiciP)m. E • IMeV = XXXXXXXXXXcm2/82) A 2 cm2 ionization chamber is placed in a radiation field of 100 Pis. The current generated is how many amperes (para XXXXXXXXXXg/ cm)?3) Mad scientist and Medical Physicist wannabe Homer .1. is frustrated by the fact that over the course of experiment his once hot cup of coffee grew cold before he had on opportunity to drink any of it. Not having enough money to buy a new cup, he decides to reheat his cold coffee with a radiation beam. Using the Cobalt machine (Co-60 unit), Homer calculates the dose rate in the middle of his 500 ml coffee cup to be 158 eGy/min. Assuming that the coffee has the same physical properties as water and that the dose rate is constant throughout the coffee, how long will it take to heat his coffee from 20 °C to 90 °C? (for the sake of this calculation, assume the coffee to be held in a perfect insulator so that cooling effects during heating need not be taken into account).4) How many HVI-s are approximately equivalent to three tenth-value layers?- 5) There is a 75% chance that a monoenergetic photon beam will be attenuated by 4 mm of lead. What is the HVL of lead for the photon?

Robert · Accepted Answer

Answers: 
 
1). Let us consider some definitions first. 
Dose (also referred to as absorbed dose) is defined as energy absorbed per unit 
mass of medium. 
Roentgen (R): The roentgen is a unit used to measure a quantity called 
exposure. This can only be used to describe an amount of gamma and X-rays, 
and only in air. One roentgen is equal to depositing in dry air enough energy to 
cause 2.58 x 10-4 coulombs per kg. It is a measure of the ionizations of the 
molecules in a mass of air. The main advantage of this unit is that it is easy to 
measure directly, but it is limited because it is only for deposition in air, and 
only for gamma and x rays. 
Sievert (Sv): The Sievert is a unit used to derive a quantity called equivalent 
dose. This relates the absorbed dose in human tissue to the effective biological 
damage of the radiation. Not all radiation has the same biological effect, even 
for the same amount of absorbed dose. Equivalent dose is often expressed in 
terms of millionths of a Sievert, or micro-Sievert (µSv) or thousandth of a 
Sievert as a milli- Sievert (mSv). One Sievert is equivalent to100 rem. 
In air, 
1 R/hr = 2.78 x 10-6 Sv/s 
And in soft tissue, 
1 R/hr = 3.04 x 10-6 Sv/s
2).

Radiation Physics 1) Many old references list "dose" rate in terms of R/hr in air. What is the conversion factor from R/hr to Sv/s in air and in tissue? (assume Q =1, N = I. (PaMussue, E- Imes, =...

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