First Long Examination Flashcards by Kathleen Cole Tung

Defined as the quantity of radioactive substance that gives rise to a decay rate of 1 decay per second.

Becquerel (Bq)

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Traditional unit of radioactivity; It is the amount of radioactive substance which gives rise to a decay rate of 3.7 x 1010 decays per second.

Curie (Ci)

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Expresses how much ionization the beam causes in the air through which it travels; It is the quantity of X-rays or gamma-rays such that the associated electrons emitted per kilogram of air at S.T.P produce ions carrying 1 coulomb of electric charge.

Radiation Exposure

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What is the SI unit for radiation exposure?

C/kg

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What is the traditional unit for radiation exposure?

Roentgen

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Defined as the quantity of X- or gamma rays such that the associated electrons emitted per kilogram of air at S.T.P produce ions carrying 2.58 x 10-4 coulombs of electric charge.

Roentgen

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Energy deposited in the absorber when radiation interacts with it.

Absorbed Dose (D)

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What is the SI unit for absorbed dose?

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What is the traditional unit for absorbed dose?

rad

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Defined as the absorption of 1 joule of radiation energy per kilogram of material.

Gray

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Defined as the absorption of 10-2 joules of radiation energy per kilogram of material.

rad

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Based on estimates of the ionization capability of the different types of radiation

Equivalent Dose (H)

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What is the formula for equivalent dose and what factors are considered?

H = WrD

where Wr is the radiation weighting factors and D is the absorbed dose

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Includes radiation weighting factors as well as estimates of the sensitivity of different tissues.

Effective Dose (E)

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What is the formula for effective dose and what factors are considered?

E = ΣWtH

where Wt is the tissue weighting factors and H is the equivalent dose

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Derived unit of ionizing radiation dose in the International System of Units (SI) and is a measure of the health effect of low levels of ionizing radiation on the human body.

Sievert

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Expresses the exposure rate produced by the gamma-rays emitted from a radioisotope; It is defined as the exposure rate per unit activity at a certain distance from a source.

Specific Gamma Ray Constant

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What is the SI unit for specific gamma ray constant?

C/kg/s/Bq at 1 m

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What is the traditional unit for specific gamma ray constant?

R/hr/mCi at 1 cm

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Law on the influence of distance on the intensity of radiation beam; It states that radiation intensity will decrease with the square of the distance from the source

Inverse Square Law

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A very destructive process which occurs in some heavy nuclei which split into 2 or 3 fragments plus some neutrons

Spontaneous Fission

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Which phase of the cell cycle is radioresistant?

S phase

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Which phase of the cell cycle is radiosensitive?

G2 and M phases

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Type of radiation damage wherein photons physically break one or both of the sugar phosphate backbones or break the base pairs of the DNA.

Direct Action or Damage

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Photons are absorbed in the water of an organism causing excitation and ionization in the water molecules

Indirect Action or Damage

Type of break in the sugar phosphate backbone wherein only one of the sugar phosphate backbones is broken; It is readily repaired using the opposite strand as a template; Base pair substitutions and frameshift mutations can still occur

Single Strand Break

Most detrimental lesions in chromosomes; Difficult to repair, they can cause mutations and cell death

Double Strand Breaks

What is the process of DNA repair?

Excision

Enzyme that recognizes damaged DNA

Glycosylase

Enzyme that cuts out damaged DNA

Endonuclease

Enzyme that resynthesizes the original DNA

DNA Polymerase

Enzyme that repairs the sugar phosphate backbone

DNA Ligase

Sequence of Radiation Injury

1) Exposure 2) Latent Period 3) Period of Injury 4) Recovery Period

Factors Affecting Biologic Response to Radiation

1) Tissue Radiosensitivity 2) Dose 3) Duration of Exposure 4) Age of the Patient

Types of Radiation Effects

1) Acute and Late Effects 2) Somatic and Genetic Effects 3) Deterministic and Stochastic Effects

Type of effect wherein the probability of occurrence increases with increasing dose but the severity does not depend on the dose.

Stochastic Effects

Type of effect wherein there is a threshold dose, below which the effect does not occur. However, once the threshold is reached, the severity of an effect increases with dose.

Deterministic Effects

Irradiation of the entire body by a high dose of ionizing radiation in a very short period of time.

Acute Radiation Syndrome (ARS)

What is the major cause of ARS?

Depletion of parenchymal stem cells

What are the stages of ARS?

1) Prodromal Stage 2) Latent Stage 3) Manifest Illness Stage 4) Recovery or Death

Types of Radiotherapy According to Aim

1) Curative 2) Palliative 3) Prophylactic 4) Total Body Irradiation

Type of radiotherapy that prevents possible metastases or recurrences

Prophylactic

Type of radiotherapy that involves ablation of bone marrow in order to suppress the immune system

Total Body Irradiation

Types of Radiotherapy According to Timing

1) Adjuvant Radiotherapy 2) Neoadjuvant Radiotherapy 3) Radiochemotherapy

Radiotherapy given after any kind of treatment modality

Adjuvant Radiotherapy

Radiotherapy given before any kind of treatment modality

Neoadjuvant Radiotherapy

Radiotherapy given concurrently with chemotherapy

Radiochemotherapy

Types of Radiotherapy According to Mode

1) External Beam Radiation Therapy | 2) Internal Beam Radiation Therapy

Type of radiotherapy wherein the radioactive material is placed in the body near the cancer cells

Internal Beam Radiation Therapy

Sealed source of radiotherapy

Brachytherapy

Unsealed source of radiotherapy; Delivered through ingestion or intravenous route

Systemic Radioisotope Therapy

Type of radiotherapy wherein radiation is delivered by a machine outside of the body

External Beam Radiation Therapy

Delivers radiation beams from different directions designed to match the shape of the tumor through the use of 3D anatomical data from CT or MRI; Aim is to apply the maximum dose to the target; Helps to reduce radiation damage to normal tissues.

Three-Dimensional Conformal Radiation Therapy (3D-CRT)

Form of 3D-CRT where imaging (eg CT scan) are done before each treatment; This allows the radiation oncologist to adjust the position of the patient or refocus radiation as needed to hit the tumor; Accounts for target volume changes during RT such as tumor volume decrease or weight loss.

Image-Guided Conformal Radiation Therapy (IGRT)

Similar to 3D-CRT but changes the strength of some of the beams in certain areas, therefore, certain parts of the tumor have higher doses and help lessen damage to nearby normal body tissues.

Intensity Modulated Radiation Therapy (IMRT)

Form of IMRT that delivers radiation inside a large “donut”; Delivers many small beams of radiation at the tumor from different angles around the body

Helical-tomotherapy

Administer large dose of radiation to a small tumor area and is very precisely aimed; Used for brain tumors and other tumors inside the head; Brain imaging are done to determine exact location of the tumor and radiation is sent to the area from many different angles; Given in more than five fractions

Stereotactic Radiotherapy (SRT)

Stereotactic Radiosurgery (SRS)

Administer large dose of radiation to a small tumor area and is very precisely aimed; Used for treatment outside the brain

Stereotactic Body Radiation Therapy (SBRT)

Given directly to the tumor during surgery; Used when tumors cannot be removed completely or risk of cancer recurrence is high; Can give large dose of radiation which limits effects on nearby tissues

Intraoperative Radiation Therapy (IORT)

Radioisotopes used for brachytherapy

1) Ir-192 2) I-125 3) Pd-103

What type of decay does cobalt-60 undergo?

Beta- decay

What energy is emitted by the decay of cobalt-60?

Two gamma emissions

What is the half life of cobalt-60?

5.27 years

What collimator is often used for EBRT?

Multileaf Collimator

What are the 5 R's of Fractionation?

1) Repopulation 2) Repair 3) Redistribution 4) Reoxygenation 5) Radiosensitivity

What are the three types of cell damage caused by ionizing radiation?

1) Lethal Damage 2) Sublethal Damage 3) Potentially Lethal Damage

Gross palpable or visible/demonstrable extent and location of malignant growth

Gross Tumor Volume

Tissue volume that contains demonstrable GTV and/or subclinical microscopic malignant disease, which has to be eliminated; May contain microscopic disease and other areas considered to be at risk and requiring treatment (eg positive lymph nodes)

Clinical Tumor Volume

Consists of the CTV plus an internal margin; Designed to take into account variations in the size and position of the CTV relative to the patient’s frame (e.g. breathing)

Internal Tumor Volume

Geometrical concept defined to select appropriate beam arrangements, taking into consideration the net effect of all geometrical variations, in order to ensure that the prescribed dose is actually absorbed in the CTV

Planning Target Volume

Type of photon beam wherein there is a higher dose near the entrance at the depth of dose maximum.

Single Photon Beams

Requires adjusting the patient such that the skin is at the correct distance from each beam orientation

Fixed SSD Technique

Requires placing the patient such that the target is usually at the isocenter

Isocentric Techniques

This beam combination is well suited to a large variety of treatment sites (eg. lung, brain, head and neck)

Parallel Opposed Beams

Allow for a higher dose in the beam intersection region;

Multiple Coplanar Beams

Isodose curves for two bilateral arcs of 120° each; Produce a relatively concentrated region of high dose near the isocenter but they also irradiate a greater amount of normal tissue to lower doses than fixed-field techniques

Rotational Technique

Most often used for treatments of brain as well as head and neck; Useful to get more adequate critical structure sparing compared to conventional coplanar

Multiple Non-coplanar Beams

Used to evaluate treatment plans along a single plane or over several planes in the patient

Isodose Curves

Most commonly used as a plan evaluation tool and to compare doses from different plans or to structures

Dose-Volume Histogram

First Long Examination Flashcards

(80 cards)