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Treatment Planning

Treatment Prescription, Geometric Parameters & Dose Calculations

QuestionAnswer
Find the total tumor dose with the given information. Given dose = 250 cGy, PPD = 93.3. 233.25 cGy Reference: Principles and Practice of Radiation Therapy, 2010, pg. 504
What is the total tumor dose when the PDD is 71.7 and the given dose is 300 cGy. 215.1 cGy Reference: Principles and Practice of Radiation Therapy, 2010, pg. 504
What is a patient’s fractionation schedule if they are receiving daily treatment at 200 cGy with a total dose of 5000 cGy? 25 fractions Reference: Principles and Practice of Radiation Therapy, 2010, pg. 79
How many fractions will Sarah receive if she is undergoing a daily treatment of 180 cGy with a total dose of 5760 cGy? 32 fractions Reference: Principles and Practice of Radiation Therapy, 2010, pg. 79
What type of radiation has a negative charge and a mass 2000 times smaller than a proton? Electrons Reference: Principles and Practice of Radiation Therapy, 2010, pg. 551
What type of radiation is a positive, heavily charged particle with a very sharp falloff, which serves a great advantage for treatment? Protons Reference: Principles and Practice of Radiation Therapy, 2010, pg. 324
What type of radiation consists of a “packet” of energy traveling through space at the speed of light, but has no mass and no charge? Photons Reference: Principles and Practice of Radiation Therapy, 2010, pg. 283
What is GTV (gross tumor volume)? The volume that indicates the gross palpable or visible tumor Reference: Principles and Practice of Radiation Therapy, 2010, pg. 445
What is CTV (clinical target volume)? The volume that indicates the GTV and a surrounding volume of tissue that may contain subclinical or microscopic disease Reference: Principles and Practice of Radiation Therapy, 2010, pg. 445
What is PTV (planned target volume)? the volume that indicates the CTV plus margins for geometric uncertainties, such as penumbra and patient motion Reference: Principles and Practice of Radiation Therapy, 2010, pg. 445
What are parallel opposed portal (POP) fields? The most basic multi-field technique that uses fields with a hinge angle of 180 degrees Reference: Principles and Practice of Radiation Therapy, 2010, pg. 174
What are tangential fields? Treatment technique for curved surfaces, such as the breast and ribs, where the hinge angle between the fields may vary slightly from 180 degrees Reference: Principles and Practice of Radiation Therapy, 2010, pg. 174
What type of field technique often requires the use of wedges to achieve homogeneity? Three-field technique Reference: Principles and Practice of Radiation Therapy, 2010, pg. 175
What is the purpose in using 6 or more treatment fields? It allows the target dose to be increased while producing a sharp fall off to surrounding tissues Reference: Principles and Practice of Radiation Therapy, 2010, pg. 175
What is rotational therapy (arc therapy)? Radiation is delivered as the gantry continues to move in rotation creating a continuous sequence of individual overlapping treatment portals Reference: Principles and Practice of Radiation Therapy, 2010, pg. 175
What is dynamic MLC IMRT? The MLC leaves move through one beam on/off sequence. (Also called sliding window technique) Reference: Principles and Practice of Radiation Therapy, 2010, pg. 178
What is the field weighting if the right lateral field receives 25 cGy, the left lateral field receives 25 cGy, the AP receives 100 cGy, and the PA receives 50 cGy? 1:1:4:2 Reference: Principles and Practice of Radiation Therapy, 2010, pg. 515
What is the field weighting if the left lateral receives 100 cGy, the right lateral receives 50 cGy, and the AP receives 50 cGy 2:1:1 Reference: Principles and Practice of Radiation Therapy, 2010, pg. 515
What is Grenz-Ray therapy? An x-ray tube with a lithium borate window with a low-energy range of 10-15 kVp Reference: Principles and Practice of Radiation Therapy, 2010, pg. 134
What is Grenz-Ray therapy effective at treating? Inflammatory diseases involving Langerhans’ cells, Bowens disease, patchy-stage mycosis fungoides, and herpes simplex Reference: Principles and Practice of Radiation Therapy, 2010, pg. 135
What was contact therapy primarily used to treat? Superficial skin lesions Reference: Principles and Practice of Radiation Therapy, 2010, pg. 135
Why has contact therapy significantly decreased since the mid 1970’s? Spontaneous involutions of strawberry angiomas (hemangioma simplex) occurred in 95% of patients several years after treatment Reference: Principles and Practice of Radiation Therapy, 2010, pg. 135
What type of treatment is delivered with x-ray production in the range of 50-150 kV? Superficial therapy Reference: Principles and Practice of Radiation Therapy, 2010, pg. 135
What type of treatment is delivered with x-ray production in the range of 150-500 kV? Orthovoltage Reference: Principles and Practice of Radiation Therapy, 2010, pg. 136
X-ray beams of 1 MV or greater are classified as what? Megavoltage Reference: Principles and Practice of Radiation Therapy, 2010, pg. 136
What does linear accelerator mean? That the charged particles travel in straight lines as they gain energy from an alternating electromagnetic field Reference: Principles and Practice of Radiation Therapy, 2010, pg. 136
What type of pattern do the particles in a cyclotron travel in? Spiral pattern Reference: Principles and Practice of Radiation Therapy, 2010, pg. 136
What type of pattern do the particles in a betatron travel in? Circular pattern Reference: Principles and Practice of Radiation Therapy, 2010, pg. 136
What is the advantage of superficial and orthovoltage treatment machines over linear accelerators? They are extremely reliable and are free of electromechanical problems, which allows for less downtime Reference: Principles and Practice of Radiation Therapy, 2010, pg. 135
What beam modifying device is used to interact with the radiation beam and mimic tissue? Bolus Reference: Principles and Practice of Radiation Therapy, 2010, pg. 170
List three types of bolus material. Superflab, paraffin wax, Vaseline gauze, wet gauze, wet towels, and water bags Reference: Principles and Practice of Radiation Therapy, 2010, pg. 170
What is the purpose of compensators? They are positioned inside the head of the treatment unit and are used to modifying the radiation beam to accommodate the contour of the patient Reference: Principles and Practice of Radiation Therapy, 2010, pg. 171
What is the necessity of a wedge? Wedges are designed to change the angle of the isodose curve relative to the beam axis at a specified depth within the patient Reference: Principles and Practice of Radiation Therapy, 2010, pg. 171
What is the purpose of transmission filters? They allow the transmission of a predetermined percentage of the treatment beam to a portion of a treatment field Reference: Principles and Practice of Radiation Therapy, 2010, pg. 172
What is field size? It is the dimension of the treatment field at the isocenter, represented by length x width Reference: Principles and Practice of Radiation Therapy, 2010, pg. 445
What is a patient’s thickness if the AP SSD is 89 cm and the PA SSD is 92 cm? 19 cm Reference: Principles and Practice of Radiation Therapy, 2010, pg. 494
What is the AP SSD if the patient’s thickness is 23 cm isocentrically? 88.5 cm Reference: Principles and Practice of Radiation Therapy, 2010, pg. 494
What is the typical SAD on Colbalt-60 machines? 80 cm Reference: Principles and Practice of Radiation Therapy, 2010, pg. 494
What is the typical SAD on linear accelerator machines? 100 cm Reference: Principles and Practice of Radiation Therapy, 2010, pg. 494
What is the Dmax depth for 6 MV? 1.5 cm Reference: Principles and Practice of Radiation Therapy, 2010, pg. 496
What is the Dmax depth for 10 MV? 2.5 cm Reference: Principles and Practice of Radiation Therapy, 2010, pg. 496
What is the Dmax depth for 18 MV? 3.5 cm Reference: Principles and Practice of Radiation Therapy, 2010, pg. 496
What is Sterling’s formula and what is it used to calculate? Sterling’s formula is (4 x Area)/ Perimeter; the equation is used to find the equivalent square Reference: Principles and Practice of Radiation Therapy, 2010, pg. 498
What is the equivalent square for a field dimension of 5 cm x 10 cm? ES = 6.67 Reference: Principles and Practice of Radiation Therapy, 2010, pg. 498
What is the equivalent square for a field dimension of 7 cm x 9 cm? ES = 7.86 Reference: Principles and Practice of Radiation Therapy, 2010, pg. 498
What is the skin gap for a patient with 15 cm and 10 cm field both at a depth of 3 cm with an SSD reading of 100 cm? 0.375 cm Reference: Principles and Practice of Radiation Therapy, 2010, pg. 516
What is the effective field size (EFS) equivalent square used to determine? The phantom scatter factor (Sp) and tissue absorption factors, such as PPD, TAR, or TMR Reference: Principles and Practice of Radiation Therapy, 2010, pg. 499
What is the PPD if 167 is the absorbed dose at depth and 182 is the absorbed dose at Dmax? 91.8% Reference: Principles and Practice of Radiation Therapy, 2010, pg. 499
PPD has a direct relationship with what? energy, field size, and SSD (PPD and depth have an indirect relationship) Reference: Principles and Practice of Radiation Therapy, 2010, pg. 499
TAR has a direct relationship with what? energy and field size (TAR has an indirect relationship with depth) Reference: Principles and Practice of Radiation Therapy, 2010, pg. 500
What is the TAR if the dose in air is 87 and the dose in tissue is 99? 1.14 Reference: Principles and Practice of Radiation Therapy, 2010, pg. 500
What is the TMR if the dose in tissue is 162 and the dose in phantom is 173? 0.94 Reference: Principles and Practice of Radiation Therapy, 2010, pg. 501
If the dose rate is 0.84 cGy/MU at 90 cm, what is the dose rate at 110 cm? 0.56 cGy/MU Reference: Principles and Practice of Radiation Therapy, 2010, pg. 497
Will the output factor be greater than or less than 1.00 when the field size is smaller than 10 cm x 10 cm less than 1.00 Reference: Principles and Practice of Radiation Therapy, 2010, pg. 496
When the Mayneord Factor is needed for extended distance, does the depth or the distance change? The depth is constant (Dmax), but the distance changes Reference: Principles and Practice of Radiation Therapy, 2010, pg. 506
What type of treatment technique is SAD? isocentric treatment Reference: Principles and Practice of Radiation Therapy, 2010, pg. 510
What is the wedge factor on a 6 MV linear accelerator when a 30 degree wedge is used? 0.714 Reference: Principles and Practice of Radiation Therapy, 2010, pg. 525
What is the factor if a 2mm brass compensator is used on an 18 MV accelerator? 0.927 Reference: Principles and Practice of Radiation Therapy, 2010, pg. 525
Is IMRT forward planning or inverse treatment planning? Inverse treatment planning (3D CRT is forward planning) Reference: Principles and Practice of Radiation Therapy, 2010, pg. 333
What is a dose volume histogram (DVH)? It is a plot of target or normal structure volume as a function of dose and illustrates a distribution of structures & the relative dose those structures will receive Reference: Principles and Practice of Radiation Therapy, 2010, pg. 542
What is penumbra? It is the area at the edge of the radiation beam where the dose rate changes rapidly Reference: Principles and Practice of Radiation Therapy, 2010, pg. 153
Does the linear accelerator or Colbalt-60 produce a sharper field edge resulting in a decrease in penumbra? Linear Accelerators result in decreased penumbra and sharper edges Reference: Principles and Practice of Radiation Therapy, 2010, pg. 153
Why is the record and verify system important in the field of radiation therapy? It validates parameters from the treatment plan to the treatment setup and delivery by elaborating on the setup, shifts, technique, MU’s, rotational settings, and much more Reference: Principles and Practice of Radiation Therapy, 2010, pg. 160
What is IMRT step and shoot? The MLC leaves are positioned; the beam is turned on, then turned off before the MLC leaves move again (Also called segmental IMRT) Reference: Principles and Practice of Radiation Therapy, 2010, pg. 177
Created by: kimberlymarie