Dose Mock Test Flashcards

Question

If half-life of parent is longer than that of daughter, after a certain time, a condition of equilibrium will be achieved. (The ratio of daughter activity to parent activity becomes constant.) _______________ is when the half life of the parent is much greater than the daughter. A. transient equilibrium B. Secular equilibrium C. stable equilibrium D. radioactive decay

Answer 1

The correct answer is 'B' https://nucmedtutorials.com/wp-content/uploads/2016/12/radionuclide-generators.pdf

Answer 2

C. Bremsstrahlung contamination (xray contamination)

Answer 3

D. 6mm minimum thickness of lead = E/2 in mm of lead, where E is the beam energy in MeV Remember it’s in mm

Answer 4

A bolus/beam spoiler brings surface dose to at least 90% of the prescribed TBI dose. It's a 1-2 cm acrylic screen placed as close as possible to patient surface to increase skin dose to treat blood vessels in the skin

Answer 5

B. increasing frequency Explanation: The energy of a photon is directly proportional to its frequency, meaning that as the frequency increases, the energy also increases. This relationship is described by the equation E = hf, where E is energy, h is Planck's constant, and f is frequency.

Answer 6

D. Pencil Beam Tier A-Monte Carlo- "Gold Standard" most accurate, but slow Tier B-Acuros (Eclipse) -Collapsed Cone (Pinnacle)--superposition convolution -based on Monte Carlo - math tricks to make calculation times faster, while maintaining good accuracy Tier C- Pencil Beam Algorithm (Brain Lab, Radcalc) -simpler, faster, less sophisticated algorithm - over-predicts measured dose in lung Tier D- Hand Calculations (no heterogeneity corrections) -assumes treatment through water -the OG, quick, least accurate

Answer 7

The correct answer is C. The dose to a pacemaker should be kept below 2 Gy. Recommendations: Use 6 MV photons whenever possible. Avoid 10 MV and higher energies (though recent reports consider 10 MV acceptable; avoid 15 MV and above). Important information to gather: Determine whether the patient is pacemaker-dependent. Facilitate communication between dosimetry, physics, and the physician to ensure proper planning.

Answer 8

A. greater than Remember the graph https://radiologykey.com/quantification-and-measurement-of-dose/

Answer 9

B. flattening filter Flattening Filters are cone-shaped pieces of metal commonly used to normalize the dose distribution laterally. These filters are designed to attenuate the central axis of the beam leaving a very uniform dose distribution at a given depth, usually 10cm. Shallower than this depth, the lateral region will have the highest dose rate which appear as "horns" on the dose distribution. Beyond 10cm depth, the dose distribution again becomes forward peaked.

Answer 10

C. GTV,CTV, ITV, PTV Treated Volume ,Irradiated Volume The radiation therapy volumes, from smallest to largest, are: GTV (Gross Tumor Volume): The smallest volume, which is the visible, palpable, or demonstrably diseased area. It represents the known extent of the tumor. CTV (Clinical Target Volume): The GTV plus a margin for potential microscopic disease that cannot be detected by imaging. The CTV is a purely clinical concept. ITV (Internal Target Volume): An optional volume used in some treatment plans. The ITV is the CTV plus an internal margin to account for physiological tumor motion (e.g., due to breathing or digestion). PTV (Planning Target Volume): A geometrical volume designed to ensure the CTV (or ITV, if used) receives the prescribed dose. It includes the CTV and margins for patient setup errors and geometric uncertainties. Treated Volume: The volume of tissue that actually receives the dose considered significant for cure or palliation. It is generally larger than the PTV. Irradiated Volume: The largest volume, representing all tissue that receives a dose considered significant relative to normal tissue tolerance. It is larger than the treated volume and depends on the treatment technique used.

Answer 11

C 1.5 cm X/75=25/127 X =1.48

Answer 12

D Pencil Beam This answer is correct. Tier A is Monte Carlo- "Gold Standard" most accurate but slow Tier B -Acuros (Eclipse) Collapsed Cone--superposition convolution base on Monte Carlo. Math tricks to make calculation run faster while maintaining good accuracy Tier C Pencil Beam Algorithm (Brain Lab, Radcalc) --simpler, faster, less sophisticated algorithm -over-predicts measured dose in lung Tier D-Hand Calculations (no heterogeneity corrections)- -assumes treatment through water quick, least accurate

Answer 13

D liver For metastatic colorectal cancer patients, the most common sites of metastasis were the liver (70% in colon cancer/70% in rectal cancer) and the thorax (32%/47%). In colon cancer, the third most common site was the peritoneum (21%) whereas in rectal cancer it was the bone (12%).

Answer 14

C.1.5 Take 2.5 know shift devided by known distance 127 = x unknown divided by 75 known distance of target to block 2.5/127=x/75 X= 2.5*75/127 X=1.48

Answer 15

D. Pencil Beam Tier A-Monte Carlo- "Gold Standard" most accurate, but slow Tier B-Acuros (Eclipse) -Collapsed Cone (Pinnacle)--superposition convolution -based on Monte Carlo - math tricks to make calculation times faster, while maintaining good accuracy Tier C- Pencil Beam Algorithm (Brain Lab, Radcalc) -simpler, faster, less sophisticated algorithm - over-predicts measured dose in lung Tier D- Hand Calculations (no heterogeneity corrections) -assumes treatment through water -the OG, quick, least accurate

Answer 16

D. Liver For metastatic colorectal cancer patients, the most common sites of metastasis were the liver (70% in colon cancer/70% in rectal cancer) and the thorax (32%/47%). In colon cancer, the third most common site was the peritoneum (21%) whereas in rectal cancer it was the bone (12%).

Answer 17

C. daily bladder filling in treatment of prostate cancer

Answer 18

D. 500 mSv Remember the Occupational Exposures (Annual) Effect dose-equivalent limit (stochastic effects) -50mSv non-stochastic: lens of eye -150 mSv extremities -500 mSv cumulative exposure- 10 mSv x age (in years)

Answer 19

A. M/G2 Remember the Definition and Phases of Cell CycleThe M-phase (mitosis), and the G2 phase of the cell cycle are generally considered the most sensitive phases to radiation damage, with cells in these stages being more vulnerable to DNA damage due to condensed chromosomes and the reduced ability to repair damage, leading to cell death or genetic instability.

Answer 20

C. maintain target coverage and OAR sparing despite range uncertainty and setup variation

Answer 21

B. the distance between the ends of the radioactive material

Answer 22

C. 12MeV R90 = E/2.8

Answer 23

B +/- 5 HU

Answer 24

C. TMR x BSF Because TMR=TAR/BSF U will find all the explanation here https://oncologymedicalphysics.com/dose-calculation-hand-methods/

Answer 25

A. photon side The electron isodose curves bulge outward, and overlap with the photon field at a certain depth, depending on electron energy used. The hotspot will be on the photon side

Answer 26

D The dose the reduces surviving fraction to 37% https://www.astro.org/ASTRO/media/ASTRO/AffiliatePages/arro/Yuan%20Lecture%20PDFs/Chapter3_Lecture2.pdf Initial slope (D1) – Dose to lowers SF to 37% of its previous value on initial portion of the curve Final slope (D0) – Dose to lovers ̄ SF to 37% of its previous value on straight line portion of the curve Quasi-threshold dose (Dq) – Almost a threshold dose, dose below which radiation purportedly has no effect

Answer 27

D seminoma

Answer 28

C microwaves Non-Ionizing vs. Ionizing Radiation •Non-ionizing radiation DOES NOT have enough energy to remove electrons from atoms. For example, microwave radiation heats food. •Ionizing radiation, like x-rays and gamma rays, have enough juice to remove electrons from atoms. We use ionizing radiation to treat cancer.

Answer 29

A any angle Compton-scattered electrons can only be emitted at 0-90 degree angles with respect to the direction of the incident photon. Photons can be emitted from any angle.

Answer 30

B decrease Switching from a 100 cm SSD setup to an isocentric setup means that the patient is closer to the gantry. If no changes were made, the patient would be overdosed. To deliver the same dose, you would need to decrease the MU.

Answer 31

B. Lower Unlike photons, higher electron energies have higher surface dose. So, 9 MeV has a lower surface dose than 16 MeV

Answer 32

A seminoma

Answer 33

B. 5cm The energy loss rate of electrons in water is 2 MeV per 1 cm. So the practical range is about E/2 so 10MeV/2=5

Answer 34

D. 1.65 g/cc

Answer 35

D. Multiple noncoplanar beam arrangement is optimal for dose conformality.

Answer 36

C After nearing spinal cord tolerance, use an off-cord beam arrangement to limit spinal cord dose A traditional lung/mediastinal technique in dosimetry was off-cord AP/PA. The patient was planned to receive a certain number of fractions AP/PA, and once the spinal cord was near tolerance, the remaining fractions would be delivered in an off-cord plan.

Answer 37

A. 2 cm superior to the external cervical os (or cervical end of the tandem) and 2 cm lateral to the cervical canal •doses to 4 points: point A, point B, a bladder point, and a rectum point o Point A: the point of dose prescription  2 cm superior to the external cervical os (or cervical end of the tandem) and 2 cm lateral to the cervical canal  represents the location where the uterine vessels cross the ureter.  believed that the tolerance of these structures is the main limiting factor in the irradiation of the uterine cervix o Point B: 3 cm lateral to point A o Bladder Point  localized by using a Foley catheter, with the balloon filled with a contrast material  On the frontal radiograph, the bladder point is marked at the center of the balloon; on the lateral radiograph, the bladder point is obtained on a line drawn anteroposteriorly through the center of the balloon, at the posterior surface o Rectal Point  identified on the frontal radiograph at the midpoint of the ovoid sources (or at the lower end of the intrauterine source)  On the lateral radiograph, the rectal point is located on a line drawn from the middle of the ovoid sources, 5 mm behind the posterior vaginal wall https://www.aapm.org/meetings/05SS/program/MANCHESTER_SYSTEM_FOR_GYNECOLOGICAL_APPLICATIONS_sharma.pdf

Answer 38

C. 3-4 Gy whole body

Answer 39

C. pyloric sphincter

Answer 40

B. Digital Imaging and Communications in Medicine

Answer 41

B. small cell lung cancer

Answer 42

D. obstruction of surface can reduce the ability to track an external target Say you are tracking an abdomen surface. If the patient is obstructed by a blanket, then the tracking will not be accurate.

Answer 43

A. astrocytoma

Answer 44

D. wall should act as an effective filter, attenuating low energy X-rays •a spherical volume of air with an air cavity in the center •shell wall is solid and air equivalent (atomic number is the same as air) •wall is thick enough for electronic equilibrium to occur inside the cavity •wall is about 1 mm, but sometimes a build-up cap (plastic) is needed to bring the wall thickness up to maintain electronic equilibrium https://radiologykey.com/ionization-chamber/

Answer 45

C. parallel-plate chamber https://oncologymedicalphysics.com/ionization-chamber-design-and-operation/

Answer 46

D. development of cancer https://www.nrc.gov/docs/ML1117/ML111711087.pdf#:~:text=Hereditary%20effects%20and%20cancer%20incidence%20are%20examples,which%20a%20threshold%20is%20believed%20to%20exist.

Answer 47

B. NIST (National Institute of Standards and Technology)

Answer 48

C. 3-4 Gy whole body

Answer 49

B. underdose Lung is about 1/3 the density of soft tissue, so traveling through 9 cm of lung is equivalent to about 3 cm of tissue. With the heterogeneity correction, the beam travels through 3 cm of soft tissue + 9 cm/3 = 6 cm total

Answer 50

D. actively mitotic, undifferentiated, long mitotic cycle Law of Bergonie and Triboneau: cells are most sensitive when they are 1. actively mitotic 2. undifferentiated 3. long mitotic cycle

Answer 51

C isobars Isobars have the same mass number, but different numbers of protons. Isobars are atoms of different elements, meaning they have different atomic numbers (the number of protons) but the same total number of protons and neutrons. Here's a breakdown of the terms: Isotopes -: Atoms of the same element (same number of protons) but with different numbers of neutrons, leading to different mass numbers. Isobars- : Atoms of different elements that have the same mass number but different numbers of protons. isomers differ in their atom arrangement, leading to different physical or chemical properties Atomic Number (Z) : The number of protons in the nucleus of an atom. Mass Number (A) : The total number of protons and neutrons in an atom's nucleus.

Answer 52

B. Bremsstrahlung rays

Answer 53

D. gamma rays

Answer 54

B. critical absorption energy

Answer 55

B. different tissues have different atomic numbers (Z values), Compton interactions are not affected by Z, but Photoelectric interactions are

Answer 56

B. an increase in monitor units to achieve the same dose

Answer 57

C. wedge angle

Answer 58

B. electron density

Answer 59

B. decreases The geometric penumbra is given by the equation: P_geometric = s * (SSD + d – SDD) / SDD. Factors influencing geometric penumbra width Source Size (S): A larger source size increases the geometric penumbra. Source-to-Skin Distance (SSD): A larger SSD (distance from the source to the patient's skin) increases the penumbra. Depth (d): The geometric penumbra of interest increases with depth in the patient. Source-to-Collimator Distance (SCD): A smaller SCD (distance from the source to the collimator) reduces the penumbra.

Answer 60

A. field symmetry

Answer 61

C. Gray; Sievert Activity-Curie (Ci) -Becquerel (Bq) Absorbed dose-rads-Gray (Gy) Exposure-Roentgen, Coulomb/kg (C/kg) Equivalent Dose-rem -Sievert (Sv)

Answer 62

C. recalculate the monitor units

Answer 63

B. sparing a strip of skin to prevent lymphedema

Answer 64

C. Differential DVH Explanation Differential DVH (Option C): A differential DVH is a frequency histogram that plots the volume of a structure receiving a dose within a specific dose interval or bin. The height of each bar or column on the graph indicates the volume that received that exact range of dose. By adding up the volumes of the bins that cover your desired dose range, you can determine the total volume that received a dose within that range. Cumulative DVH (Option B): A cumulative DVH plots the volume of a structure receiving a dose greater than or equal to a certain dose. It is most useful for finding the volume that receives at least a certain dose threshold (e.g., V20 for the lungs, which is the volume receiving 20 Gy or more). However, a cumulative DVH cannot directly show the volume within a specific dose range. Integral DVH (Option A): This is another term for a cumulative DVH. It plots the integral of the differential DVH. Conformity Index (Option D): A conformity index is a single number that describes how well the shape of the prescription isodose line conforms to the shape of the target volume. It does not provide information about the volume receiving a specific dose range.

Answer 65

A. shift the dmax towards the surface

Answer 66

D. feather the junctions periodically

Answer 67

A. brachytherapy

Answer 68

D. normal liver

Answer 69

D. dose would scatter off the wedge onto the contralateral side

Answer 70

C. protons https://physics.stackexchange.com/questions/169665/dose-depth-curve-of-photons-vs-protons

Answer 71

C. 294 cGy Dtotal= R0*T 1/2 /ln2 Step 2: Convert units T1/2= 17 days *24h/1 day=408 h D total= 0.5 cGy/hr * 408h/ .693 D total= 294 cGy

Answer 72

B. 4 mR/hr Er=A*£*(1/d^2) A=200mCi £= 1.9 Rcm2 / mCi-hr d= 3m=300cm A= 200mCi * 1.9Rcm2/ mCi-hr (1/300cm^2) 380 cm2/hr * (1/90 000cm) A=0.004 R/hr- the answer in in mili R so 0.004 R/hr * 1000m/1R= 4 mR/hr

Answer 73

B. 2.8 min

Answer 74

A. 8.3 Gp=S(SSD+d-SDD) / SSD 2 (100+3-20)/ 20= 8.3

Answer 75

C. Gray; Sievert

Answer 76

C. 0.005 R/hr

Answer 77

C. 223 Tangent < = 180• + < - 2 tan^-1(1/2 *F width/100) =180+57-2 tan^-1 (1/2*24/100) =180+57-13.7 =223

Answer 78

A. collimator: 7.4 degrees Here's how to calculate this: Determine the beam width difference: The PA spine port is 26 cm long, while the lateral brain ports are 12 cm long. The difference in length is 26 cm - 12 cm = 14 cm. Calculate half the difference: Half of the difference is 14 cm / 2 = 7 cm. Calculate the table rotation: The table needs to be rotated by an angle where 7 cm represents the arc length at a given distance. In this case, the table is rotated by 7 degrees, resulting in a larger portion of the field. Calculate the collimator rotation: The remaining 4 cm needs to be accounted for, which comes from a 4-degree collimator rotation and the field shape. The collimator must be rotated by approximately 11.4 degrees to account for the remaining portion of the field.

Answer 79

C. 2.4 cm L1/2 x d/SSD + L2/2x d/SSD 30/2 x 8/100 + 30/2 x 8/100 =1.2+1.2=2.4

Answer 80

C. 309 MU MU=250cGy/0.88 x 0.92

Answer 81

C. 15x15 (2x12x20)/ (12+20)=480/32=15

Answer 82

B. 171 cGy 200 cGy/Ddmax = D(4 cm) = .949 Ddmax = 210.75 D(7 cm)/210.75 = .862 D(7 cm) = 181.7 cGy *add inverse square component. D(7 cm) is farther away than D(4 cm) so (100/103)^2 = .942 181.7 x .942 = 171 cGy

Answer 83

D. can function independently of collimator angle

Answer 84

B. 64.7 Gy

Answer 85

B. 2.8 min

Answer 86

A. 0.88 cm

Answer 87

B. 2.8 min

Answer 88

B. 171 cGy 200 cGy/Ddmax = D(4 cm) = .949 Ddmax = 210.75 D(7 cm)/210.75 = .862 D(7 cm) = 181.7 cGy *add inverse square component. D(7 cm) is farther away than D(4 cm) so (100/103)^2 = .942 181.7 x .942 = 171 cGy

Answer 89

B. 64.7 Gy

Answer 90

B. tongue and groove

Answer 91

A. 191 cGy

Answer 92

D. Monte Carlo

Answer 93

B. <2 Gy for the entire treatment

Answer 94

C. Reduce variation of contours between users

Answer 95

C. ROM Read only memory Ram random access memory MIPS can stand for either "Million Instructions Per Second parallel processing refers to a technique where multiple processors or cores in a system work together to execute different parts of a computational task simultaneously

Answer 96

C. 333 cGy To calculate 300x 0.9= 333

Answer 97

C. Photoelectric Effect

Answer 98

B. 10 cm speed of light = wavelength x frequency Don't forget to convert the MHz into Hz.

Answer 99

B. will have decreased average energy planning with a 10X FFF beam (flattening filter free) vs. a regular 10X beam. -The FFF beam will deliver dose faster (more photons getting through to the patient), which is nice for that 3000 MU SBRT plan that takes forever to deliver -An FFF beam will have decreased average energy and decreased dmax depth (penetration) because there's no filter to remove the lower energy photons -Again, filters are like sports tryouts! If you cut out the weakest players, your remaining team is higher quality overall

Answer 100

C. number of protons and electrons

Answer 101

C. Ir-192 The decay constant = .693 / half life. The half life is about 74 days. so it's Ir-192.

Answer 102

D. free air ionization chamber

Answer 103

C. The MU will increase for both fields In order to deliver the same prescription dose, 3000 cGy in this case, you must INCREASE the MU because your new SSD setup puts the patient farther from the source. You can think of it as the machine needing more "juice" to deliver dose to the patient. The dose to the patient should not change.

Answer 104

D. Skin cancer

Answer 105

C. full arc VMAT

Answer 106

A. sharper • MLCs vs. Cones • The MLC has many advantages for cranial radiosurgery, namely that there are no field size or shape limitations for use of a single isocenter, and there is more flexibility in the technique (static, dynamic, conformal arc, IMRT, VMAT) • cones collimate the beam closer to the patient's head, they have a sharper geometric penumbra

Answer 107

C. 30 V20 < 30%

Answer 108

B. pressure is less than 760 mmHg and temperature is greater than 22 degrees celsius

Answer 109

C. central nervous system Hematopoietic -2-3 Gy whole body-Survival months Gastrointestinal-5-12 Gy whole body-1 week Central Nervous System > 12 Gy 1 day

Answer 110

B. 56.3: 168.7: 75

Answer 111

C. Clarkson method Isodose Distribution of an Irregular Field •The dose to an irregular field can be calculated using the Clarkson Method. It's basically like dividing the irregular field into easy-to-solve jigsaw pieces and adding it together. You do not have to know the math behind it, just be aware of the existence of this technique.

Answer 112

C. does not give information on beam quality.

Answer 113

C. the mean dose Because the lesion is located in the upper lobe, the maximum dose will still be delivered to the upper lobe and will not be affected if the inferior portion of the lung is excluded. The V5 and V20 values will also remain relatively consistent, since they represent the percentage of lung volume receiving a specific dose or higher. However, the mean lung dose will be the least accurate if part of the lung is excluded, as it depends on the total lung volume.

Answer 114

C. 4x20 The 4x20 is an elongated field. The equivalent square is least accurate for this field because of off axis factors and inverse square. You should measure this output separately!

Answer 115

D. all of the above can be used to obtain information about patient contours This answer is correct. Below are methods to find body contour (What's the patient separation?) and internal structures (How big are our organs at risk? Where are they?) 1. CT 2. Conventional CT o block positions determined by anatomical landmarks visible on radiographs (bony structures or lead wire clinically placed on the surface of the patient). o scouts o Determination of patient treatment position with fluoroscopy  set beam geometry, fields, isocenter  acquire contours -Lead wire: shaped to the patients contour and the shape is then transferred to a sheet of graph paper. Some reference to the room coordinate system marked on the contour in order to relate the position of the beam geometry to the patient -caliper measurements for separation (AP/PA) -pantograph apparatus (rod moved over patient's skin then placed on paper for contour drawing) -electromechanical rod motion, sensing device, transferred to an X-Y recorder

Answer 116

B. near misses

Answer 117

D. fingernails

Answer 118

B. away from; away from??

Answer 119

C. electron density

Answer 120

0-90 degrees Remember The Compton PHOTON can be scattered at any angle, but the Compton ELECTRON is emitted at an angle limited to 0-90 degrees with respect to the direction of the incident photon.

Answer 121

C. The monitor chamber is removed

Answer 122

C. 3,1,5,4,2

Answer 123

B. Higher for 6 MV than for 15 MV

Answer 124

B. Lower for electron treatment than for photon treatment

Dose Mock Test Flashcards

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