Analysis of Radiation Incidents and Biological Effects

This assignment delves into the analysis of radiation exposure incidents and their biological consequences. It examines two specific cases: a diagnostic radiology incident involving a repeat DTPA scan and a therapeutic treatment error where a patient received an incorrect dosage of radiation. The assignment explores the causes of such incidents, emphasizing the importance of training and regulatory procedures. It then differentiates between alpha and beta particles, discussing their ionization characteristics and linear energy transfer (LET). The core of the assignment focuses on the biological effects of radiation, including direct and indirect DNA damage, single and double-strand breaks, and the resulting cellular responses like deletion of DNA segments and apoptosis. The assignment also covers repair mechanisms and calculates absorbed doses and survival fractions using the linear quadratic equation. Finally, it distinguishes between somatic and genetic injuries, and defines relative biological effectiveness. The analysis is supported by references to relevant literature.

Running head: CELL 1

CELL 2
Radiation and incidents of exposure
Question 1
Part (a): (i),(ii) & (iii)
Diagnostic radiology, imaging
A repeat DTPA scan was required to be done to a patient since the first scan was paused
in error. A pause acquisition button was accidentally touched on the screen and this
produced insufficient data required to produce a diagnostic image. An effective dose
estimated to be 2mSv was administered to the patient.
Part (b): (i), (ii) & (iii)
Therapeutic treatment
A dosage of 7 Gy was administered to a patient who was undergoing a radiation
oncology treatment instead of a dosage of 5.5 Gy which was intended, this was because
the reduced dose was not loaded into the planning system. An addition estimated dose of
1.5 Gy was later given to the patient
Part (a) & (b): (IV)
The radiation accidents such as the ones described above are as a result of lack of
management or shortcoming among those entitled being responsible for proper
implementation of the systems. To prevent these accidents from happening, proper
counseling and further training of individuals can be performed to ensure no such
incidents occur. Also, the regulatory bodies in charge can introduce additional procedures
that will ensure that all checks before, during, and after the treatment are satisfied before
other causes of action follows.
Question 2
Part (a)

CELL 3
The emitted particle in 1 is an electron (beta particle) track as evidenced by the wispy
nature of the pattern which bears evidence of deflections through collisions.
The emitted particle in 2 is an alpha particle which characteristically has a thick and
straight path ionization path
Part b
Radiations are different because each has a characteristic constituent and energy.
Radiations causing heavy ionization in their path are referred to as high LET (linear
energy transfer) radiation (Mayles, Nahum, & Rosenwald, 2007). High LET are most
harmful as compared to low-LET radiations (Mayles, Nahum, & Rosenwald, 2007), this
is because low-LET radiations produce ionizations only sparsely along their track and,
hence, almost homogeneously within the cell (Mayles, Nahum, & Rosenwald, 2007).
Thus, particle 2 has a higher LET as compared to particle 1.
Part c
Part (i)
Ionizations induced by radiation are capable of direct action on tiny particles of
components resembling a cell or act in different ways on water molecules. The latter
forms liquid-derived radicals. Radicals culminate the splitting of chemical bonds or
oxidation because they react with the nearby atoms. (Reisz, Bansal, Qian, Zhao,&
Furdui,2014).DNA breakage results from the interaction. Hence, when DNA breaks one
or both strands also break. However, the latter is much more significant to biology.
(Mayles, 2007)
Due to the aforementioned dual-stranded characteristic of the DNA molecule, a single-
stranded break can be repaired (Reisz, Bansal, Qian, Zhao,& Furdui,2014). The same
cannot be said of dual-stranded breaks since fixing is very challenging and incorrect
reconstruction of the broken ends may result. These disrepairs can trigger changes,
chromosome aberrations, or demise of a cell (Mayles, Nahum, & Rosenwald, 2007).
Part (ii)

CELL 4
Deleting DNA segments is the predominant form of radiation damage in cells that
survive irradiation. The deletion may be due to the disrepair of two separated dual-strand
breaks in the molecule when two outer ends of the strands are joined resulting in loss of
the fragment between the breaks (Reisz, Bansal, Qian, Zhao,& Furdui,2014). During the
process of cleaning of the broken ends before rejoining to repair one dual-strand break,
deletion may also occur (Reisz, Bansal, Qian, Zhao,& Furdui,2014).
Part (d)
The main repair mechanisms are direct reversal and translesion synthesis. The mainly
occur during non-replicative stages of the cell cycle.
Part (e)
Apoptosis is the most common type of cell death that is brought about by the ionizations
Part (f)
Absorbed dose for dish 1 = Mean energy transferred/Mass of substance
= 1.6 x 10-13 j/0.001kg = 1.6 x 10-10 j/kg = 1.6 x 10-10 Gy
Absorbed does for dish 2 = mean energy transferred/mass of substance
= 8.0 x 10-13 j/0.001kg = 8.0 x 10-10 j/kg = =8.0 x 10-10 Gy
Part (g)
Linear quadratic equation S (D) = e-(aD=D2)
For Petri Dish 1, s = e-(0.00625*0.5+0.002462*0.5*0,5) = 1.00
For petri dish 2, s = e-(1.5*0.5+0.05*0.5*0.5) = 0.47
Part (h)
Somatic injury and genetic injury are the kinds of injury that can result from ionizing
radiation. Somatic injury occurs when the cells are exposed to high levels of ionizing
radiation with the exception of reproductive cells. Genetic injury refers to the damage of
inflicted when reproductive cells are subjected to high levels of ionizing radiation.

CELL 5
Part (i)
The ratio of the doses needed by two radiations to cause the same level of effect is
referred to Relative biological effectiveness. The ratio is dependent on the biological
endpoint and the dose.

CELL 6
References
Mayles, P, Nahum, A, & Rosenwald, J. (2007).Handbook of Radiotherapy
Physics: Theory and practice. CRC Press
Reisz, J. A, Bansal, N, Qian, J, Zhao, W, & Furdai, C. M. (2014). Effects of
Ionizing Radiation on Biological Molecules—Mechanisms of Damage and
Emerging Methods of Detection. Antioxidants and Redox Signaling, 21(2). 260-
292