Lecture 5

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Which of the following is an operational classification of radiation damage?

All of the above

What is the characteristic of Lethal Damage?

It is Irreversible and leads to cell death

What is the potential outcome of Potentially Lethal Damage (PLD) repair?

Enhanced cell survival

Which type of radiation damage can be repaired under normal circumstances?

Sublethal Damage (SLD)

Where was PLD repair studied in vitro?

In density-inhibited stationary-phase cell cultures

How can PLD repair in vitro be enhanced?

By remaining in a density-inhibited state for 6 or 12 hours after irradiation

What is the relevance of PLD repair in radiotherapy?

It influences the fraction of surviving cells after irradiation

Which of the following is true about sublethal damage repair (SLD)?

SLD involves three simultaneous processes: prompt repair, reassortment, and repopulation.

What is the effect of dividing the total dose into two equal fractions with a time gap of 1 to 4 hours for X-rays?

It leads to a significant increase in cell survival due to prompt repair of SLD.

What is the effect of dividing the dose into two fractions with a time gap for neutrons?

It has little effect on SLD repair and does not significantly impact cell survival.

What is the dose-rate effect?

Dose rate is a critical factor influencing the biological consequences of absorbed doses from x- or γ-rays.

What is the importance of understanding the dose-rate effect in radiotherapy planning?

It maximizes tumor control while minimizing damage to healthy tissues.

What does the survival curve demonstrate in the dose-rate effect?

The survival curve shows a shoulder due to repeated shoulders in each fraction.

What is the impact of repair times on survival curves at low dose rates?

Repair times can vary among different cell types.

Which type of brachytherapy involves implanting sources directly into tumors and adjacent tissues?

Interstitial Brachytherapy

Which type of brachytherapy is a temporary procedure lasting 1 to 4 days?

LDR Intracavitary Brachytherapy

What is the advantage of Permanent Interstitial Implants?

An operation to remove the implant is not needed.

What is the common use of iodine-125 in brachytherapy?

Delivering a total prescribed dose of 160 Gy.

What is the dose rate of LDR Intracavitary Brachytherapy?

About 50 cGy per hour

What is the potential advantage of HDR techniques in brachytherapy?

Reduced normal tissue exposure for specific cases like cervical carcinoma.

What is the definition of Potentially Lethal Damage Repair (PLD)?

Radiation damage modification post-irradiation.

What is the definition of Sublethal Damage Repair (SLD)?

Increase in survival if radiation dose is split into two fractions separated in time.

What is the effect of reducing the dose rate in radiation therapy?

Reduction in cell killing due to Sublethal Damage Repair (SLD) during prolonged exposure.

Which of the following best describes the dose-rate effect in mouse jejunum crypt cells?

The dose-rate effect in mouse jejunum crypt cells is characterized by a dramatic decrease in cell survival as the dose rate decreases.

Which of the following is true about the repair of sublethal radiation damage (SLD)?

The dose-rate effect is caused by the repair of SLD.

What is the importance of apoptosis in the dose-rate effect?

Apoptosis plays a significant role in the dose-rate effect, with different cell types showing variations in the importance of apoptosis.

What is the inverse dose-rate effect in HeLa cells?

The inverse dose-rate effect in HeLa cells refers to an increase in the efficiency of cell killing with decreasing dose rate.

What is the significance of the G2 phase in the inverse dose-rate effect?

The G2 phase is a radiosensitive phase where cells become arrested at low dose rates, contributing to the inverse dose-rate effect.

What is brachytherapy also known as?

Brachytherapy is also known as intracavitary therapy.

What is the transition in brachytherapy from low dose rate (LDR) to high dose rate (HDR) therapy?

The transition from LDR to HDR therapy in brachytherapy is for specific cases, with a focus on cervical carcinoma.

Test your knowledge on the dose-rate effect in mouse jejunum with this quiz! Explore survival curves for crypt cells irradiated with γ-rays at different dose rates and learn about the correlation with repair of sublethal radiation damage. Understand why cell division plays a dominant role in reducing the number of surviving crypts at lower dose rates. Plus, discover seven examples of the dose-rate effect in vitro.

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