University Radiation Protection Homework Assignment

This assignment provides a detailed solution to a radiation protection homework. The first question involves calculating the extra dose absorbed by an OSL left near a Cs-137 source, including decay calculations and dose estimation. The second question focuses on drawing a cell survival curve from experimental data to estimate the mean lethal dose. The third question addresses the storage space required for digital radiographs, considering image dimensions and bit depth. The fourth question involves applying a 5x5 low-pass filter to a noisy digital radiograph to smooth pixels. The final question requires a critical evaluation of radiation protection protocols in a medical clinic, including assessment criteria and recommendations for improvement. The assignment covers core concepts in medical physics, including radiation dosimetry, radiobiology, digital image processing, and radiation safety practices.

Assignment Questions: SET 19
Q1. You work in a nuclear medicine department. One day you mistakenly left your OSL on the
worktable in the hot lab. Next day you found your OSL next to a radioactive source. Now you
must estimate the extra dose absorbed by the OSL and report to RSO for record. To estimate
the dose, you gathered the following information:
The Radioactive source was Cs-137. Its activity was 27 milli Curie 2 year ago. You know Cs-
137 is a gamma emitter and its gamma energy = 661.7 keV, and the half-life is 30.17 years.
You remembered that you left the OSL at around 5:00 pm, got it back at 8:00 am. Your OSL
was 25 cm away from the source.
Calculate the dose absorbed by your OSL. If you need formula find it from your lecture slides
and notes. Show all the steps of your calculations.
Solution:
Stay Time is 15 years. Distance from source is 25 cm.
Absourbance
Q2. You are a radiation worker and interested to know the mean lethal dose of a certain type of
biological cells. To do so you culture the cells in a cell biology lab. You selected five samples
and irradiated them with different doses of x-rays. Then you allowed them to grow for two
weeks. Then you have counted the colonies of cells formed. You gathered the information as
follows:
Sample X-ray Dose (Gy) Number of cell Seeded Number of Colonies
1 0 300 80
2 2 800 144
3 4 2,000 72
4 6 20,000 90
5 8 30,000 80
From these data draw the cell survival curve and estimate the mean lethal dose. You can use
Excel spreadsheet to draw the graph. Then you print the graph and work on that graph to
estimate mean lethal dose.

0 1 2 3 4 5 6 7 8 9
0.001
0.01
0.1
1
Series2
Q3. You work in a radiography department where on average 120 digital radiographs are
processed every week. The average dimension of the radiographs is 22 cm X 32 cm. You
want to preserve all the details in the image to a special resolution of 5 lp/mm. If the
radiographs are 10-bit depth, what will be the minimum space required per week to archive
all digital radiographs on an external hard drive?
Assignment Questions: SET 19
Q4. Digital image enhancement is an integral part of Medical image processing. The following
matrix is representing a small part of a digital radiograph which is somewhat noisy. Apply a
5X5 average low pass filter (given below) to smooth 2 central pixels (positions A & B in the
new matrix) of the given matrix.
198 189 210 135 89 90
88 39 252 133 202 230
178 28 139 240 33 57
192 190 187 243 99 56
101 243 212 221 167 234
230 34 138 167 139 149

The 5x5 low pass filter you will be using is:
0.01 0.03 0.03 0.07 0.01
0.02 0.04 0.04 0.06 0.02
0.03 0.05 0.02 0.05 0.05
0.04 0.06 0.01 0.03 0.06
0.05 0.07 0.04 0.04 0.07
Find the New values of pixels A & B indicated in the following matrix position. Show the detail
calculations.
A = ?
B = ?
A=
A= 264
B= 354.26
Q5. You have recently completed your 2 weeks clinical placement in a medical radiations clinic.
You have experienced the patient management and radiation protection activities in the
clinic.
(a) What specific criteria do you need to make a full assessment of the overall radiation
protection process in the clinic?
(b) Evaluate the overall radiation protection protocols in place in the clinical
department you worked and make necessary recommendations based on the
specific criteria you stated in section (a).