Exam A
The annual effective dose equivalent limits for members of the public (non-occupational workers) for infrequent exposures based on the stochastic effects has a recommended annual limit of ____.
5 mSv (.5 rem) The implied limits are 40 mrem (.4mSv) per month and 10 mrem (.1mSv) per week. The following annual effective dose limits for the deterministic effects for a member of the public are 1500 mrem (15 mSv) for the lens of the eye and 5000 mrem (50mSv) for all other organs including bone marrow, breasts, lungs, skin, extremities, etc.
The dose threshold for radiation myelopathy is normally in the range of ____.
50-60 Gy.
The annual limit of an occupational worker on intake (ALI) for 131I is a total uptake of ____ microcuries.
6.65 Under the current NRC Regulatory guide 8.9, the evaluation level has been reached when the thyroid measurement exceeds .133 microcuries or 2% of the annual limit on intake (ALI). The investigation level is reached when the thyroid gland of an occupational worker exceeds 6.65 microcuries or 10% of the ALI. If the uptake of the individual exceeds 3 microcuries, the individual should avoid the handling of iodine so as not to exceed the ALI limit of 6.65 microcuries.
The percent depth dose for a 4MV photon beam at 100cm SSD and a 10 x 10 cm field for a tumor located at a distance of 3cm is about ____ %.
93%
Radiotherapy treatment simulation is used for: - Verify position that is maintained by immobilization devices. - Checking accuracy of block placement - The delineation of treatment field
All of the above. A treatment simulator is a diagnostic radiographic/fluoroscopic unit that is designed to duplicate the radiation therapy treatment unit in terms of its geometrical, mechanical and optical properties. It is used to display the treatment field to help insure the step-up will adequately cover the desired target volume and the placement of shielding blocks. The advantages of simulation include improved visualization of the field compared with port films, the ability to free up the treatment unit for more important treatment and detect unforeseen problems in the set-up or treatment procedures. A modern simulator can also be used to facilitate the acquisition of patient contours and the formation of tissue compensators and/or boluses. These units are normally equipped with laser lights, contour makers and shadow trays.
The dose distribution of a high-energy beam therapy unit is most often
Because it's not often possible to measure the dose distribution directly in the patient during radiotherapy, the use of values obtained from tissue equivalent phantoms is more often employed to estimate the actual distribution in the patient. These values are often taken from measurements which have been obtained from water or tissue equivalent phantoms that have been embedded with small ionization chambers. Through other detectors such as TLDs, silicon diodes and radiographic films may be used in some situations; the higher precision and smaller energy independence of the ion chamber is normally preferred.
The prescription for treatment should include all of the following EXCEPT: - energy of the unit - total dose planned - MUs actually delivered - depth of tumor
MUs actually delivered The prescription for treatment should include the energy and type of radiation that should be used, the total dose for the therapy, the location and depth of the tumor, and planned fractionation.
The principal advantage of the use of a tissue air ratio is its ability to remove the dependence upon the: - SSD - Field Size - PDD - Back scattered radiation
PDD The TAR at the depth of max dose on the CAX is one of the ways to define the backscatter factor. The TAR is dependent on the beam quality and geometrical field size. At beam energies in the megavoltage range, the TAR builds up to maximum at the depth of max dose before decreasing exponentially with depth.
The value for field flatness of one electron beam over the area confined within 2cm inside the geometric edge of the field of at least 10 x 10 cm should not exceed + or - ____%.
+ or - 5% The field flatness (uniformity) of an electron beam specified at a plane perpendicular to the beam at 1/2 the depth of therapeutic range. This is normally defined as the ratio of the area where the dose exceeds 90% of the CAX to the cross sectional area of a phantom. This value for field flatness of an electron beam over the area confined within 2cm inside the geometric edge of the field of at least 10 x 10cm should not exceed + or - 5%.
Mechanical or electrical interlocks shall be provided on therapy machines above 150 keV to ensure: 1. That the useful beam is directed only toward secondary barriers. 2. That opening a treatment door will terminate the exposure. 3. That a locking device is available to prevent unauthorized use. - 1 & 2 only - 1 & 3 only - 2 & 3 only - 1, 2, & 3
- 1, 2, & 3
According to current recommendations of the DOT, the maximum reading for a package containing radioactive materials at a distance of 1 meter should NOT exceed ____.
- 1,000 mrem per hour All packages that are labeled "radioactive materials" must undergo a visual inspection label and surface to look for any damage. A wipe test is performed to check to ensure that the surface contamination is no greater than 22 disintegrations per minute (dpm) per square centimeter that has been wiped over 300 cm sq. or 6600 dpm or a value of .003 micro curies. After the radionuclides have been removed, the empty package should be tested for residual radioactivity. The internal shielding of the package should be sufficient to reduce the surface rate to less than 200 mrem per hour or 10 mrem per hour at a distance of 1 m. Labels are used to estimate the surface rate of the package. The surface rate for a White-I label is less than .5 mrem per hour, the surface rate for a Yellow-II label is between .5-50 mR per hour and the surface rate for a Yellow-III label is between 200-1,000 mrem per hour.
In the absence of chemotherapeutic agents, the normal maximum tolerance dose to the vasculoconnective tissues of the lung is in the range of ___ to ___ Gy.
- 20-30 Gy When this dose is exceeded, two primary late effects are seen: pneumonitis and pulmonary fibrosis. Lung toxicity can be dramatically increased if alkalating agents or antibiotic therapeutic agents are also given.
It is recommended that the fetus should not exceed a dose equivalent of ____ mSv for the entire gestation.
- 5mSv ... or 0.5mSv (500mrem) per month once a pregnancy is known.
Effective patient immobilization of the H & N is often accomplished by a device called: - a Striker frame - a cervical collar localizer - Crouchfield tongs - A bite block system
- A bite block system During treatments of the tongue or floor of the mouth, it is important for the patient to have their mouth open to reduce the exposure to the maxillary antrum and roof of the oral cavity. Bite blocks are often improved through the placement of a tongue blade and a breathing tube which are based on the patient's dental impressions.
Syncope or fainting is a mild form of neurogenic shock that may occur: - After a highly unpleasant or painful event - Following a sudden change of posture which increases the blood pressure - After the exposure to an air-borne contamination - Following exposure to a pathogen
- After a highly unpleasant or painful event
The increase in the dose enhancement in the soft tissue that occurs on the entrance side of bone-tissue interface with high energy photon beams is primarily related to: - Photoelectron absorption - Pair production electrons - Electron back scattering - Bremmstrahlung x-rays
- Electron back scattering During therapies involving photons in the 2-24 MV range, the soft tissue around the bone will normally experience a dose enhancement of about 8% on the entrance side of high energy photon beam due to electron back scattering.
The beam quality for photon beams below 1 MV should be measured by: - The half-value layer thickness of the beam and the kVp values. - Isodose data that has been obtained from actual patient procedures. - The use of ionization chambers calibrated with low energy sources. - The maximum energy of the electrons before they strike the target.
- The half-value layer thickness of the beam and the kVp values.
Which of the following assumes that the fraction of scatter at a given depth is independent of beam divergence and depends only on the size field and the depth of the overlaying tissues for a beam of a given energy? - Off-axis scatter point ratio - Tissue-air minimum ratio - Tissue-maximum ratio - Total field off-axis ratio
- Tissue-maximum ratio TMR assumes that the fraction of scatter at a given depth is independent of beam divergence and depends only on the size field and the depth of the overlaying tissues for a beam of a given energy.
During a radiation treatment to the upper torso in a patient with kyphosis, the beam must be directed toward the head. This is most often accomplished by: - a 45 degree rotation of the couch and gantry rotation perpendicular to the torso - a rotation of the couch that matches the degree of kyphosis - a 90 degree rotation of the couch and gantry rotation perpendicular to the torso - a gantry rotation that matches the degree of the kyphosis
- a 90 degree rotation of the couch and gantry rotation perpendicular to the torso The angle of the beam as it intersects the patient can be modified by either a change in the rotation of the beam or alteration of the patient's position. This is often dependent upon the pathologic considerations. Patients with kyphosis may not be able to lay flat so the beam must be directed toward the head. In patients that are unable to breath while supine (vena cava obstruction) may require treatment through a single angled field. The major disadvantages of treating patients standing or sitting is the inability to maintain the desired centering and positional reproducibility.
The most common types of cancers arising from the epithelium of the alimentary tract are ____.
- adenocarcinomas The only areas where there is less than 60% is the esophagus. Over 85% of cancers affecting the stomach, small intestines and colon are adenocarcinomas.
The most likely side effect for a 45cGy exposure to a non-gravid female patient is ____.
- an increased genetic risk The amount of x-rays or gamma radiation that is required to cause temporary sterilization in non-gravid females under the age of 35 is about 200cGy. The amt. of radiation required to cause permanent sterility in these females is about 600cGy. An absorbed dose of about 200cGy may cause permanent sterility in women of the age of 40. Menopause was seen in approximately 50% of younger women and 90% of women exposed to doses to the gonads between 150-500cGy.
A common cause of a longitudinal shift between radiation fields during a split field test is: - an incorrectly oriented wedge - a misaligned laser light - asymmetry of the collimator jaws - an irregularity in the scattering foil
- asymmetry of the collimator jaws A longitudinal shift between radiation fields during a split field test may be caused by focal spot displacement, misalignment of the collimator jaws, or misalignments of the collimator or gantry rotational axis. The split field test is accomplished using a plastic covered radiographic film that is exposed by beams which are 180 degrees apart.
The TAR at the depth of maximum dose on the central axis of the beam is termed the ____.
- backscatter factor For a given beam energy, the TAR is related to the depth and size of the field, but is independent of the distance. The BSF is independent of the distance but is dependent on the beam quality and geometrical field size. At beam energies in the orthovoltage range, the BSF can be as high as 1.5 for large fields. In the megavoltage range above 8MV, the BSF approaches a minimal value.
The Clarkston method is useful for the determination of the scatter produced in irregular fields and using scatter-air ratios data to compare this to a: - circular field - rectangular field - triangular field - elliptical field
- circular field Any field is considered irregular if it is not square, rectangular or circular. The Clarkson method uses the concept of the scatter-air ratio (SAR) to estimate the scattered dose in irregular fields. The method divides an irregular field into a number of different sectors that can be considered as a circle. This data is then used to compare the irregular field to SAR values for a circular field.
During the planning of a 3-D conformal radiotherapy, the dose distribution to the tumor and all of its extensions is known as the: - planning target volume - minimum tumor volume - tumor control volume - clinical target volume
- clinical target volume
All of the following are types of ductal carcinoma EXCEPT: - papillary carcinoma - comedocarcinoma - colloid carcinoma - adenocarcinoma
- colloid carcinoma Most breast carcinomas arise from ductal or glandular epithelium of the lobules of the breast. The most common types of ductal carcinomas include papillary carcinoma, comedocarcinoma, scirrhous, and intraductal carcinoma.
The 2 large bones that help to form the majority of the adult pelvis are termed the ____.
- cruciate bones The innominate or coxa bones are the 2 large bones that form the majority of the adult pelvis. During early childhood the innominate bones developed from 3 individual bones that fuse in the mid-teens called the ilium, pubis, and ischial bones. The 2 halves of the pelvis are united anteriorly across the superior rami of the public bones by a fibrocartilage interpublic disc. Posteriorly the innominate bones articulate laterally with the sacrum.
All of the following are reasons for the need of a target volume to be larger than the gross tumor volume EXCEPT: - the dose falloff that occurs at the edges of the beam - inaccuracies that occur in defining the target volume - dose distribution alterations that occur from tumor cell differences - misalignments of the beam that occur from organ or patient motion
- dose distribution alterations that occur from tumor cell differences The GTV and TV are different because there must be a margin around the GTV to account for dose fallout at the edges of the beam, inaccuracies in defining the target volume, and misalignments due to organ or patient motion. A tumor margin of 15mm is normally considered adequate. Improvements in the ability to shape the fields with formed blocks are used to help reduce these margins.
All of the following reactions are likely reactions seen following a fractionated radiation exposure to the skin of 30-40 Gy EXCEPT: - moist desquamation - epistaxis - erythema - epilation
- epistaxis
The highest portion of the normal adult stomach sitting just below the left diaphragm is the ____.
- fundus The fundus extends superiorly to a space under the left hemidiaphragm. The largest portion of the stomach is called the body which narrows into the pylorus. The stomach is lined by a thick mucosal layer that contains numerous folds called rugae. The gastric mucosa contains 3 types of secreting cells: the goblet cell that produces mucus, the chief or zymogenic cells for the digestive enzyme pepsinogen, and the parietal cells which secrete hydrochloric acid. The digestive enzymes and acids produces in the gastric walls and the churning motion provided by the muscles of the stomach assist in both the chemical and mechanical digestive process.
Which of the following consists of the clinical target volume (CTV) and internal margins that are added to compensate for variations in size, shape movements, and position of the target volume? - internal target volume - irradiated volume - gross tumor volume - model target volume
- internal target volume
Because large changes in x-ray energy are required for small changes in the half value layer thickness, the quality of x-ray beams between 2-50 MV should be started in terms of their: - minimum wavelengths of the photons at the skin surface - percentage of penetration through 5cm of lead - maximum energy of the electron beam before striking the target - mass energy equivalence
- maximum energy of the electron beam before striking the target This is related to the fact that the transmission type target and flattening filters in the MV beams have already hardened the beam.
The main components of an electronic portal imaging devices includes all of the following EXCEPT: - microwave generator - metallic fluorescent screen - charged couple device or TV camera - cathode ray tube or TV monitor
- microwave generator The main components of an EPID include a metallic fluorescent screen; charged couple device or TV camera; a tube; a microprocessor; and a cathode ray tube or TV monitor.
Which of the following are all possible sources of light-radiation field incongruence with an MV treatment unit? - misalignment of the collimator mirror - insufficient beam flatness - electron beam contamination
- misalignment of the collimator mirror
The main clinical features of radiation hepatitis include all of the following except: - pernicious anemia - jaundice - heptomegally - ascites
- pernicious anemia The most common type of cancer affecting the liver arise from the parenchymal cells such as hepatocellular cancer and/or intrahepatic ducts. These most often affect adults after the age of 40. The most common treatment is subtotal hepatectomy. Because the tolerance of the liver is in the range of 20-35Gy, adjuvant therapy may cause radiation hepatitis. This syndrome is characterized by hyperemia, congestion of the sinusoid and vena-occlusive lesions often appears within 6 months after the treatment. The main clinical features of radiation hepatitis include heptomegally, ascites and jaundice.
All of the following devices can be employed for the determination of the monthly occupational dose equivalent limit of a Radiation Therapist EXCEPT: - film monitor badge - thermoluminescent dosimeter - proportional detector - optically stimulated luminescent dosimeter
- proportional detector The measurement of an individual's absolute dose is most commonly determined with a device called a dosimeter. Four common types of dosimeters that are currently employed are the pocket dosimeter, TLD, film badge, and OSLD.
The most common treatment for adenocarcinomas of the stomach is: - primary radiation therapy and surgical removal of the tumor - a combination of irradiation and brachytherapy - primary chemotherapy and brachytherapy - surgical removal of the stomach and adjuvant XRT and chemo
- surgical removal of the stomach and adjuvant XRT and chemo Between 90-95% of the cancer affecting the stomach are adenocarcinomas. These most often affect adults between the ages of 50 & 70 years. The most common treatment is a gastroectomy including local node removal, even though the prognosis is considered relatively poor. Radiotherapy and chemo is used as an adjuvant treatment in high risk patients.
The distribution of dose in an isodose chart are often expressed as a percentage of dose as a function of depth as the: - vertical distance from the source - transverse distance from the CAX - beam moves across a point - oblique distance from the CAX
- transverse distance from the CAX The use of isodose curves is the most commonly used technique to determine the volumetric or planar variation in the absorbed dose through a tissue volume. The distribution of the dose in an isodose chart is represented through a series of lines or curves that pass through points associated with the same absorbed dose. These are often expressed as the percentage of dose as a function of depth and and transverse distance from the CAX.
An important document that is used to record details concerning the patient's therapy is termed the: - treatment chart - physician report form - patient chart - medical record
- treatment chart
A computerized verification system that is often incorporated on the control console of a treatment unit is intended to do all of the following except: - verify the delivered dose - verify the size of the treatment field - verify the position of the gantry - verify the couch angles
- verify the delivered dose Computerized verification systems are now frequently used to only deliver treatments when the field size, gantry position, couch angles and block, wedge and dose parameters have been verified.
Hot and cold spots are common problems associated with: - rotational therapies - wedge-pair techniques - four field technique - arc therapies
- wedge-pair techniques The main disadvantage of wedge-pair techniques is the production of hot spots under the thin edges of the wedges that occur in larger field ends and at larger wedge angles.
The most common type of bone marrow found within the bones of the adult skeletal system is ____ bone marrow.
- yellow bone marrow By adulthood, the majority of the red bone marrow is replaced with the fat, rich, yellow bone marrow that is used for the storage of extra energy.
The coefficient of equivalent thickness (CET) is based on the assumption that the attenuation of missing thickness of tissue can be estimated by its atomic number compared to the electron density of water. The average CET value for the lung is most often taken as ____.
.5 CET is used for the correction of large inhomogeneities based on the assumption that the attenuation of missing thickness of tissue can be estimated by its atomic number compared to the electron density of water. Based on this principle, the electron density for compact bone would provide a value of 1.65 and a value of .50 for air-filled lungs. Small inhomogeneities create an even greater problem because of a change in electron scatter behind the edges which creates a cold spot behind the lesion and a hot spot at the edges of the tissue.
Convulsive seizures may be associated with: 1. hyperthermia 2. epilepsy 3. high intracranial pressure
all of the above Although epilepsy is by far the most common cause of seizures, high intracranial pressure, toxins, infection, fever, tetanus, uremia, and low oxygen levels can also trigger seizures.
Which of the following areas is normally irradiated using an irregular treatment field? 1. mediastinum 2. whole pelvis 3. bronchopulmonary
1. mediastinum 2. whole pelvis 3. bronchopulmonary
The Rs of radiobiology include which of the following? 1. redistribution 2. repopulation 3. repair
1. redistribution 2. repopulation 3. repair The 4th "R" is reoxygenation.
Which of the following is one of the probable causes of death to occur during the CNS syndrome? 1. vasculitis 2. meningitis 3. high intracranial pressure
1. vasculitis 2. meningitis 3. high intracranial pressure The acute radiation syndrome associated with the CNS is only seen at extremely high radiation dose levels above 5000cGy. At these levels death is assured within 24 hours from vasculitis, meningitis, and a dramatic increase in the intracranial pressure.
The collection of fluids or gasses in the pleural space may lead to a lung collapse. This condition may be referred to as: - pneumothorax - hydrothorax - hemothorax
all of the above. The presence of excessive fluids in the pleural cavity increases intrathoracic pressure which collapses the lung. The resulting conditions are often named for the type of agent present in the pleural spaces: blood (hemothorax), fluid (hydrothorax), or air (pneumothorax).
Q 63: Which of the following is normally classified as a type of vehicle that spreads infections? - mosquito bite - contaminated blood - coughing - spitting
coughing??? contaminated blood??? Vehicle routes of transmission spread include water, food, medications, and contaminated blood.
After radiotherapy that exceeds 50 Gy for a pituitary adenoma, a patient complains of headaches and visual defects; a probable cause is ____.
empty sella syndrome This is related to destruction of the pituitary gland, which is located in the sella turcica. Because of the proximity to the optic chiasm, large doses can lead to blindness. Decreased pituitary function should be given hormone replacement therapy.
The most important screening procedure for gastric cancers is ____.
fiberoptic endoscopy
Radiation surveys using a device that is able to detect rates as low as .1 millirem per hour is required daily in areas where the: 1. Radionuclides are delivered 2. Radiopharmaceuticals are administered 3. Radiopharmaceuticals are prepared
2. Radiopharmaceuticals are administered 3. Radiopharmaceuticals are prepared Radiation surveys should be accomplished using a survey type ionization meter that is able to detect rates as low as .1mrem per hour. These evaluations are required daily in areas where the radiopharmaceuticals are administered or prepared. This will include the imaging room, stress lab, and hot lab. Weekly surveys (wipe tests) should be performed in an area used to store radioactive wastes and where radiopharmaceuticals are prepared, stored, and administered.
A split field test is performed to check the alignment of ____.
opposed fields A split field test is also known as a multiple beam alignment. The misalignment of the field may be caused by focal spot displacement, misalignment of the collimator jaws or misalignments of the collimator or gantry rotational axis. The split field test is accomplished using a plastic covered blocked radiographic film that is exposed by beams which are 180 degrees apart.
The breakdown of the RBCs' hemoglobin into bilirubin is principally the function of the ____.
spleen. The phagocytic bacteria present in the spleen break down worn out RBCs and platelets, converting the released hemoglobin into a green-colored fluid called bilirubin. The bilirubin passes into the splenic vein and is carried to the liver. This substance is extracted by the liver and converted into bile.
The normal severe complication associated with excessive irradiation of the liver will normally be first seen when doses are in the range of ____Gy.
20-35 Gy The most common type of cancer affecting the liver arise from the parenchymal cells such as hepatocellular cancer and/or intrahepatic ducts. These most often affect adults after the age of 40. The most common treatment is subtotal hepatectomy. Because the tolerance of the liver is in the range of 20-35 Gy, adjuvant therapy may cause radiation hepatitis. This syndrome which is characterized by hyperemia, congestion of the sinusoid and veno-occlusive lesions often appears within 6 months after the treatment. The main clinical features of radiation hepatitis include heptomegally, ascites and jaundice.
During external beam radiotherapy of carcinomas of the prostate, doses in excess of 70 Gy can be delivered without causing acute toxicity due to the development of ____.
3-D conformal radiation therapy The improvement is due to better delineation of the radiation fields.
What is the usual range of dose that is used to attempt a cure in Hodgkin's disease?
40-50 Gy
A treatment designed to be given at 120cm SSD is mistakenly given at 100cm SSD. What is the error in dose delivered?
44% overdose
During cardiopulmonary resuscitation, the rate of cardiac compressions to assisted respirations should normally be about ____ : ____.
4:1 The ratio between the normal heart rate of 72 bpm and normal respiration rate of 18 breaths per minute is called the vital sign ratio. This ratio is also useful in determining the correct compression to breathing rate that should be employed during cardiopulmonary resuscitation.