Exam B – Flashcard
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An increase in geometrical field size for a given beam energy is normally associated with a: - reduced skin sparing effect - reduction in the PDD - higher dose in the buildup region - reduction in the amount of scattered radiation
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- higher dose in the buildup region The size of the treatment field can be defined in terms of its geometry or dosimetry. The geometrical field size refers to a plane perpendicular to the axis of the beam at the center of the distal end of the collimator, or more simply, the field delineated by the light localizer at the front of the source at a given SSD or SAD. The dosimetric field is the distance intercepted by the 50% isodose at a stated distance on a plane perpendicular to the axis of the beam. An increase in the geometrical field size is normally associated with an increase in the amount of scattered radiation, a greater PDD, and a higher dose in the buildup region. An increase in the geometrical field size is also dependent upon the energy of the photon beam. Because of the forward direction of scatter at higher energies, the PDD is less field size dependent higher energies.
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The treatment of bulky and highly proliferative neoplasms with chemotherapy is sometimes complicated by the: - vena cava syndrome - multihemorrhage syndrome - tumor lysis syndrome - empty sella syndrome
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- tumor lysis syndrome With many fast growing neoplasms such as Burkitt's, lymphoblastic lymphomas, and acute lymphoblastic leukemia, there is a rapid cytoreduction that liberates large amounts of intracellular urates, phosphates, and potassium into the circulation. This cannot be removed rapidly enough and results in hyperkalemia, hyperuricemia, and hyperphosphatemia.
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Which of the following tissues is most likely to receive the highest dose at a bone-tissue interface? - the bone in the medullary cavity at low beam energies - the blood vessels in the bony canals at low beam energies - the bone marrow in the medullary cavity at high beam energies - the blood vessels in the bone canals at high beam energies
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- the bone in the medullary cavity at low beam energies Because bone contains both a medullary cavity and a series of canals which carry blood vessels (Haversian and Volkmans), there may be a dose distribution in homogeneity related to a bone-tissue interface. When the spaces in the bone are small it may be considered a Bragg-gray cavity and will have little effect on the dose distribution of the soft tissue. When a larger space is present within the bone, the dose in the soft tissue may increase by as much as 5 times with low energy (20 keV) photon beams. The dose increase in the megavoltage range is normally less than 1.1 times. In the low energy range, this is the result of electrons produced from photoelectric events in the megavoltage range due to the pair production process.
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Which of the following is NOT one of the signs or symptoms associated with laryngeal carcinoma? - persistent hoarseness - cervical lymphadenopathy - xerostomia - leukoplakia of the mucosa
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- xerostomia Signs/symptoms of laryngeal carcinoma include persistent hoarseness, sore throat, lymphadenopathy, and leukoplakia of the mucosa.
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Whole body casts are an effective means of controlling patient movement during the treatment of: - total body irradiations - craniospinal irradiations - lung irradiations - head ; neck irradiations
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- craniospinal irradiations
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The symptoms of acute radiation enteritis and infraction necrosis will typically appear in the dose range of ___ to ___ Gy.
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50-60 Gy
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In the event of a minor radiation spill, all of the following procedures are required EXCEPT: - immediate confinement of the spill - immediate notification of the RSO - rapid isolation of the area - reduction of air flow into the area
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- immediate notification of the RSO
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A minor spill is classified as one that is less than ___.
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1 millicurie
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A major spill is classified as one that is over ____.
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1 millicurie
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The operating console of a linac must contain indicators for all of the following EXCEPT: - dose monitor - position of the iso - energy of the beam - activation of the beam
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- dose monitor
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A specialized arterial structure in the brain that helps in the prevention of irreparable damage in cases of arterial blockage is called the: - Circle of Willis - Loop of Henle - Plantar arch - Cerebral sinus
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- Circle of Willis
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A bolus is NOT employed during electron therapies for which of the following: - to reduce the effect of Bremmstrahlung photons in the beam - filling in for missing tissues to eliminate surface irregularities - to reduce the penetration of electrons in portions of the treatment field - to increase the dose at the surface of the skin
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- to reduce the effect of Bremmstrahlung photons in the beam
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During a bladder treatment, the curvature of the patient's external surface in the lateral field must be compensated for with 45 degree wedges to avoid excessive doses to the: 1. anterior regions of the field 2. posterior regions of the field 3. lateral regions of the field - 1 only - 2 only - 3 only - 1, 2, & 3
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- 1 only
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A positive indication of possible leakage of a radionuclide from a package is a surface rate that exceeds: - 6600 dpm of removable contamination - 660 dpm of removable contamination - 66 dpm of removable contamination - 6.6 dpm of removable contamination
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- 6600 dpm of removable contamination When a leak test is performed on a package or potentially contaminated surface, a level of removable contamination that exceeds 22 disintegrations per minute (dpm) per square centimeter that has been wiped over 300 square centimeters or 6600 dpm or a value of .003 microcuries is considered above normal.
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The extent of prostate involvement and metastatic dissemination are best obtained by the use of: 1. bone scintigraphy 2. transurethral ulrasonography 3. intravenous urography - 1 only - 2 only - 3 only - 1, 2, & 3
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- 1 only The diagnosis for both prostate involvement and metastatic dissemination will usually include bone scintography, chest radiography, and MRI.
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A special ready packed film without screens that can tolerate exposures of up to 2 Gy taken with the actual treatment machine are called: - real time images - beam's eye images - verification images - post production images
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- verification images
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To check the accuracy of the gantry digital readouts, the radiation therapist should: - close the collimator shutters - use a spirit level at 45 degree angulations - use a breast bridge at 90 degree angulations - use a split field test at 180 degree angulations
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- use a spirit level at 45 degree angulations
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The process that converts ultrasound energy from electrical energy and vice-versa is the: - auger effect - piezoelectric effect - modulation transfer effect - van de graf effect
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- piezoelectric effect The ultrasonic waves used in the imaging process are produced from a ceramic crystal that has been exposed to an electric current. The electric current causes the crystal to contract and expand at a given frequency known as the piezoelectric effect. Because the reverse is also true, the crystals will also produce an electric signal when struck by an ultrasonic wave. The transducer in a modern ultrasonographic unit consists of a piezoelectric crystal such as lead zirconate titanate (PZT) and the matching layers and dampening materials that are used to ensure a more uniform high quality sound beam.
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Distance indicators are required on all high energy treatment units to help verify: - shifts in the position of the source - distance to the edge of the treatment volume - distance to the treatment table - size of the treatment field
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- distance to the treatment table
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An overhead sagittal laser light is useful in aligning the sagittal axis of the patient with the axis of the: - collimator rotation - gantry rotation - table rotation - tumor rotation
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- gantry rotation
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The unlawful touching of a person without their consent is called: - assault - battery - invasion of privacy - negligence
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- battery Personal injury law suits may involve 1) assault - the threat of touching a person in an injurious way, 2) battery - the unlawful touching of a person, 3) false imprisonment - detaining a patient against their will, 4) invasion of privacy - failure to maintain the patient's right to privacy, and 5) negligence - failure to use reasonable care or caution.
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The principal change that takes place in the breast after menopause is the: - atrophy of glandular tissue - fibrous replacement of fatty tissue - loss of the mammary ducts - increased vascularity of the tissue
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- atrophy of glandular tissue After menopause there is a degeneration or atrophy of glandular tissue and fibroglandular tissue that is associated with a decrease in the overall physical density of the breast tissue and an increase in amount of adipose tissue. This process is called involution. The senescent breast consists of mainly ducts and dense connective tissue. The reduction in the size or thickness in the elderly is associated with a loss of adipose tissue in the breast.
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The most common type of cancer affecting the kidneys in adults are: - squamous cell carcinomas - renal sarcomas - adenocarcinomas - medulloblastomas
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- adenocarcinomas The most common type of cancer affecting the kidneys are adenocarcinomas such as renal cell carcinoma. These most often affect adults between the ages of 50 and 70 years. The most common treatment is radical nephrectomy including local node removal. Radiotherapy is used as an adjuvant treatment in high risk patients.
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The main disadvantage with SSD techniques as they related to parallel opposed fields is: - the center of both fields cannot be accurately located - the SSD will be different in the AP and PA fields - the energy of the beam will be different in the AP and PA fields - small errors in the SSD are not balanced out when the patient is moved
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- small errors in the SSD are not balanced out when the patient is moved
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The ratio of the dose for a given field size at the depth of maximum dose to the dose rate for a standard field size at the same depth is termed the: - phantom build-up factor - phantom absorption factor - tissue phantom equivalent factor - phantom scatter factor
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- phantom scatter factor This value is used to evaluate the amount of scatter that originates within the phantom related to different sized fields.
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The field that consists of the primary tumor, metastatic lymphadenopathy and other metastases is called the: - internal target volume - GTV - irradiated tumor volume - model target dose
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- GTV
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If pressure is NOT maintained on a vein immediately after the removal of the needle, a collection of blood may result called a: - hemolysis - hemorrhage - hematoma - diaphoresis
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- hematoma This can usually be avoided by the removal of the tourniquet prior to the administration of fluids and by applying 1 minute of direct pressure over the injection site after the needle is removed.
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Hematogenous metastasis from the breast are most likely to spread by cells entering the: 1. axillary veins 2. pulmonary veins 3. pectoralis veins - 1 only - 2 only - 3 only - 1, 2 & 3
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- 3 only (pectoralis veins)
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The evaluation of PDD assumes the variation of beam intensity along the: - horizontal axis of the beam - isocenter of the beam - central axis of the beam - all axes of the beam
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- central axis of the beam
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The most common type of catheter placed in the pulmonary artery to monitor pulmonary disorders and heart function is a: - Miler-Abbott tube - Greenfield tube - Fowler's catheter - Swan-Ganz catheter
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- Swan-Ganz catheter
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Which of the following is NOT an advantage of electronic portal imaging? - faster image access - reduced equipment costs - the ability to provide real time corrections - lower patient exposures
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- reduced equipment costs
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Which of the following items in the O.R. are usually considered free of all microorganisms? 1. surgical instruments 2. O.R. table 3. suction device - 1 only - 2 only - 3 only - 1, 2, ; 3
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- 1 only (surgical instruments) Sterilization is only possible on relatively small items which can tolerate heat and chemical agents. Suction devices, O.R. tables, mobile x-ray units, and the patients themselves can only be disinfected, not sterilized.
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Any response noted in the absence of a stimulus is called the: - causative response - latent response - threshold response - ambient response
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- ambient response
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Mets to the brain and spinal cord frequently occur from all of the following EXCEPT: - melanomas - lymphomas - breast cancers - osteosarcomas
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- osteosarcomas Mets to the brain and spinal cord frequently occur from melanomas, lung, breast, kidney, gastrointestinal carcinomas, and lymphomas.
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Preservation of reproductive function in a male when large pelvic irradiation is unavoidable can be accomplished by: - the use of external organ shields - the use of internal organ shields - the surgical relocation of the gonads - the placement of a bolus over the gonads
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- the surgical relocation of the gonads
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In general the death resulting from a total body irradiation of between 4.5-10 Gy is most closely related to the: - CNS - respiratory system - GI tract - hematopoietic system
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- hematopoietic system
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The first biological effects of radiation in man to doses of approximately 250 millisievert are changes seen in the: - blood cell count - skin - sperm count - eyes
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- blood cell count 250 millisievert -- WBCs 1 Sievert -- WBCs, RBCs, & platelets
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An effect which increases in severity as the dose increases above a threshold limit is the main characteristic of a: - latent effect - stochastic effect - chronic effect - deterministic effect
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- deterministic effect A stochastic effect is a radiation-induced injury that is assumed to have no dose threshold. Stochastic effects are normally limited to cancer and genetic effects that are considered all or nothing responses. A deterministic effect, formerly called a non-stochastic effect, is defined as a somatic effect that increases in severity as a radiation dose increases above the dose threshold. Deterministic effects may be early (e.g. erythema) or late (e.g. lens opacification, decreased fertility, or organ atrophy).
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The limits for gaseous effluents is now based on Derived Air Concentrations (DACs). This is defined as the concentration of an air borne radionuclide that when inhaled by a reference man for one year would result in the intake of: - 1 annual effective dose value - 1 internal exposure dose limit - 1 annual limit on intake - 1 internal to absorbed dose limit
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- 1 annual limit on intake If the measurement of gaseous effluents is less than 20% of the limit, no routine monitoring of these agents is required.
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A total dose equivalent of 200 millisievert during a one year period of time would most likely increase the likelihood of developing which of the following disorders? 1. pyloric stenosis 2. epilation 3. leukemia - 1 only - 2 only - 3 only - 1, 2, ; 3
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- 3 only (leukemia) Pyloric stenosis and epilation require at least 2000 millisievert.
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Contour irregularities can be compensated for by all of the following EXCEPT: - an internal shield to alter the dose distribution across the field - a bolus used to fill in for the missing mass - wedge filters that are used to tilt the isodose curves - compensating C-wedges to fill in for the missing mass
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- an internal shield to alter the dose distribution across the field When the surface can be approximated as a straight line, a compensating wedge (C-wedge) may be employed. Wedge filters may be used to tilt the isodose curves or a bolus can be placed directly on the skin surface to reduce contour irregularities.
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Fainting (syncope) is caused by an insufficient blood supply to the brain. A patient experiencing this sensation should be instructed to: - stand quietly - stand and walk - sit in a chair - lay supine
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- lay supine
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The most common complication associated with Hodgkin's disease radiotherapies is: - temporary bone marrow suppression - permanent sterilization - hyperthyroidism - pancarditis
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- temporary bone marrow suppression
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The probable energy of an electron beam should be within about: - +.05 MeV of the nominal energy displayed on the operator console - +.5 MeV of the nominal energy displayed on the operator console - +1.5 MeV of the nominal energy displayed on the operator console - +5 MeV of the nominal energy displayed on the operator console
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- +.5 MeV of the nominal energy displayed on the operator console
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Exudates that are the result of tumor cells found on either layer of the pleura or the impairment of the lymphatic drainage by a mediastinal tumor are called: - obstructive parapleural lesions - pleural tamponades - transpleural exudates - malignant pleural effusions
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- malignant pleural effusions Over 75% of these are related to metastatic breast cancer, lung cancer, and lymphomas. If these effusions are substantial, they can restrict ventilation and lead to respiratory insufficiency. Upright chest radiography is often diagnostic showing fluid levels. Cytologic evaluation of fluids obtained from a thoracentesis most often confirms the condition. Treatment usually involves close chest drainage and sclerosis agents such as bleomycin, doxycycline, or talc.
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Shielding blocks that are used with beams having a small focal spot should be tapered to reduce: - edge cutoff - beam shadowing - side-scattering - transmission penumbra
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- transmission penumbra When shielding blocks are used for the protection of vital organs, it is important to consider the effect on the skin and buildup of dose in the subcutaneous tissues. The majority of shielding blocks are made of lead or Lipowitz metal having a thickness that enables a primary beam transmission factor of no more than 5%. This is most easily accomplished by using blocks with an equal thickness of 4.5 - 5 HVL. In the MV range, these blocks are normally placed in a transparent shadow tray that is located at least 15 cm above the surface of the skin. The blocks should be tapered to follow the geometric divergence of the beam to minimize block transmission penumbra.
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Any radiation survey meter will need to be repaired or replaced if the readings are not within: + or = 1% of the actual value + or - 5% of the actual value + or - 10% of the actual value + or - 20% of the actual value
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+ or - 20% of the actual value The calibration of a Cutie Pie or Geiger-Mueller type survey meter should be performed at least once each year using a long-lived gamma NIST traceable source such as Cs137. The radiation survey meter will need to be repaired or replaced if the readings are not within + or - 20% of the actual values, based on calibration graph.
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Which of the following cancers is likely to have a curative dose above 80 Gy? - oro-nasal cancer - retinoblastoma - prostate cancer - embryonal cancer
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- prostate cancer
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The backscatter factor is dependent on: 1. the size of the field 2. the distance from the source 3. the energy of the beam - 1 & 2 only - 1 & 3 only - 2 & 3 only - 1, 2, & 3
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- 1 & 3 only The TAR at the depth of the maximum dose on the central axis is one of the ways to define the backscatter factor. 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 MV range above 8 MV, the BSF factor approaches a minimal value.
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Blood is returned to the heart by way of two major trunk veins that empty into the: - right atrium - right ventricle - left atrium - left ventricle
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- right atrium
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A pregnant radiation therapist receives a monthly badge report showing 4 mSv for the badge worn at waist level. The approximate dose equivalent to the fetus is ___ mSv.
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- 1.2 mSv The fetal dose equivalent is estimated at 30% of the exposure received by the waist badge.
