ST:2 Flashcards

Question

Whole-body imaging with [131I]sodium iodide is optimally performed how long after tracer administration? (a)12 hr (b) 48-72 hr (c) 96 hr (d) 128 hr (e) greater than 128 hr

Answer 1

(b) Although 131I whole-body imaging may be performed as early as 24 hr post-administration, optimum images are obtained at 48-72 hr after tracer administration.

Answer 2

(c) A seizure patient may experience a warning that a seizure is about to occur. The technologist should assist the patient to the floor and away from objects that may injure the patient during the seizure. A pillow will cushion the patient's head from the floor.

Answer 3

(a) Because the purpose of 111In-pentetreotide imaging is to visualize the unknown primary site of the cancer or demonstrate the extent of the disease, anterior and posterior whole-body images should be performed.

Answer 4

(c) Red blood cells labeled with [99mTc]pertechnetate are used for demonstrating intermittent lower gastrointestinal (GI) bleeding. The area between the xiphoid and symphysis pubis must be included in the field of view to visualize bleeding in the lower GI tract.

Answer 5

(e) Any high-flux radiopharmaceutical that is not trapped in the lungs could be used to perform a first-pass cardiac function study. However, if stress and rest examinations are to be performed, it would be best to perform the two studies in as short a time interval as possible. Therefore, a radiopharmaceutical that clears the blood quickly and does not concentrate in areas that would interfere with the second first-pass study is indicated. Of the tracers listed, only [99mTc]pentetate meets these criteria.

Answer 6

(d) There is no patient preparation for breast imaging with [99mTc]sestamibi except explanation of the procedure to the patient.

Answer 7

(c) The schilling test is used to measure the absorption of vitamin B12 in patients with unexplained anemia. The absorption of vitamin B12 depends on the secretion of intrinsic factor by the stomach. Pernicious anemia is a vitamin B12 deficiency resulting from lack of intrinsic factor.

Answer 8

(d) The arrow indicates tracer returning prematurely to the lungs, an indication of a left-to-right cardiac shunt. Some of the blood on the left side of the heart is being directed back to the right side of the heart, returning to the lungs rather than being ejected out of the left ventricle into the systemic circulation.

Answer 9

(e) Subcutaneous injections are needed for a lymphoscintigraphy to determine the sentinel lymph node.

Answer 10

(e) The hematocrit represents the portion of the blood made up of cellular components, and the plasmacrit represents the fluid portion. Together, they comprise the total blood volume. Thus, the sum of the hematocrit and the plasmacrit, each expressed in decimal form, is equal to 1.

Answer 11

(a) Sequestration sites for red blood cells include the liver and spleen. Cardiac counts are used as a standard. Renal areas are not counted.

Answer 12

(c) There is leakage of the labeled albumin from the vascular system. The multiple blood samples provide the information needed to estimate the leakage rate and determine the plasma counts before any leakage occurred. The plasma counts at zero-time are extrapolated from the graph.

Answer 13

(c) Propylthiouracil (PTU) interferes with the organification of iodide by the thyroid gland and is one of the antithyroid drugs available to decrease thyroid hormone production.

Answer 14

(d) Injection of about 0.5 mL of heparin is sufficient to maintain the patency of the infusion set tubing used during a red cell mass determination.

Answer 15

(e) Gastric emptying studies involve combining [99mTc]sulfur colloid with eggs.

Answer 16

(d) [111In]pentetreotide binds to somatostatin receptors in certain tumors. In the case of suspected insulinoma, there is a potential for inducing severe hypoglycemia. For this reason, an intravenous infusion of glucose should be readily available.

Answer 17

(b) Structures normally visualized on an image performed with [18F]FDG include the brain, myocardium, liver, spleen, intestines, kidneys, and urine in the bladder.

Answer 18

(c) The [14C]urea breath test is used to detect the presence of Helicobacter pylori bacteria. All patients with duodenal ulcers and 80% of patients with non-drug-induced gastric ulcers are infected with H. pylori. the test may be used to initially diagnose the presence of infection, as well as for follow-up after treatment.

Answer 19

(d) In this instance, the capsule that is administered to the patient is first counted as the standard. The counts in the patient's thyroid are compared with the counts in the standard to determine the percent of radioiodine uptake. Because the patient's thyroid is not counted until 6 hr after the measurement of the capsule, the capsule counts collected at 0900 must be decay-corrected for 6 hr. It will be assumed that room background remains about the same over the 6-hr period. To decay-correct the capsule counts' multiply the capsule counts by the 6-hr decay factor for 123I: 216,789 cpm x 0.73 = 158,256 cpm Then, calculate the thyroid uptake using the following formula: % thyroid uptake = (thyroid cpm - thigh cpm) x 100 /(Standard cpm - bkg cpm) = (94,954 cpm - 521 cpm) x 100 / (158,256 cpm - 92 cpm) =94,433 cpm x 100 / 158,164 cpm =60%

Answer 20

(b) Elution efficiency is expressed as the percentage of 99mTc on the column that is eluted. elution efficiency = 99mTc activity eluted x 100 / 99mTc activity on column Thus. 99mTc activity eluted = elution efficiency x 99mTc activity on column = 0.96 x 11.7 MBq = 11.2 MBq

Answer 21

(a) For a dry-column generator, the eluate volume is equal to the saline volume used to elute the generator. In this example: concentration = 863 mCi / 5 mL = 172.6 mCi/mL Using an evacuated vial with a volume larger than the saline volume causes air to be pulled over the column, completely removing any saline, hence the name dry-column generator.

Answer 22

(b) Loss of vacuum from the elution vial is most likely the cause of this problem and the easiest to rule out. checking the tubing may cause increased radiation exposure to the technologist because the column shielding meets only U.S. DOT requirements for shipping radioactive materials - additional shielding is usually required around the generator to decrease radiation exposure to individuals in its vicinity. Also, changing tubing is not practical, because it will compromise the sterility of the generator components. Adding more saline probably will not force the first saline volume from the column. A vacuum is needed to draw the liquid from the column. Contacting the manufacturer first may delay resolution of an easily solvable problem.

Answer 23

(c) The NRC requires that records of 99Mo concentration in 99mTc eluates be retained for 3 years.

Answer 24

(b) Aluminum is a chemical impurity and not subject to regulation by the NRC. Free pertechnetate is [99mTc]pertechnetate that is not bound to another compound. 99mTc is eluted from a generator as [99mTc]pertechnetate. 99Mo is a radionuclidic impurity, a radionuclide other than the desired one, in 99mTc eluate. According to NRC regulations, its concentration must be determined in the first elution of a 99Mo/99mTc generator.

Answer 25

(a) The technologist does not have to order or prepare [99mTc]macroaggregated albumin, the agent used to perform perfusion lung imaging. A renal function study may be performed with [99mTc]mertiatide, bone imaging with [99mTc]medronate, Meckel's diverticulum localization with [99mTc]pertechnetate, and a hepatobiliary study with [99mTc]mebrofenin.

Answer 26

(b) The NRC requires that records of written directives be maintained for three years.

Answer 27

(c) [99mTc]pentetate is the renal agent used to determine glomerular filtration rate because it is handled by the kidneys solely by glomerular filtration. It is neither bound to protein nor secreted by the renal tubules as are other renal agents.

Answer 28

(d) The maximum activity that can be prepared from this kit is equal to: maximum reconstituting volume x 99mTc concentration maximum activity = 2 mL x 75.5 mCi/mL = 226.5 mCi To calculate the concentration of the kit, note that the reaction vial contains lyophilized reagents with no appreciable volume. Hence, the total volume in the kit is the sum of the [99mTc]pertechnetate volume and the volumes in the two syringes: concentration = total activity in preparation / total vol in preparation = maximum activity to be prepared / (99mTc vol + vol to be prepared in syringes I + II) =226.5 mCi / (3 mL + 1.6 mL +1.6 mL) = 36.5 mCi/mL

Answer 29

(b) Heating is required for the preparation of [99mTc]mertiatide, [99mTc]sestamibi, and [99mTc]sulfur colloid. The preparation of [99mTc]bicisate requires 30-min incubation at room temperature.

Answer 30

(b) Generator yield - amount of 99mTc that may be eluted from a 99Mo/99mTc generator - is calculated by using decay equations that determine the amount of 99mTc formed from the decay of 99Mo at any given time. The sequence for calculating the generator yield is as follows: 1. Determine the time elapsed between calibration of the 99Mo activity and generator elution. 2. Calculate the amount of 99Mo activity in the generator at the time of elution by decay correcting the initial 99Mo activity. 3. Determine how much 99Tc activity is in the generator by calculating how much has formed from the decay of 99Mo. 4. After elution, measure the amount of 99mTc activity (with a dose calibrator) collected from the generator. 5. Calculate the generator yield, or elution efficiency, by comparing the measured activity of 99mTc eluted from the generator to the 99mTc activity calculated to be in the generator in step 3.

Answer 31

(c) The Rf value is the distance traveled by a given radiochemical component compared with the solvent front: Rf = distance from origin to radiochemical component / distance from origin to solvent front In this instance, the Rf value for the hydrolyzed-reduced 99mTc is: Rf = 2.5 cm / 12.6 cm = 0.20

Answer 32

(b) Specific activity is defined as the amount of radioactivity per unit mass of a radionuclide or labeled compound and is expressed in units of radioactivity per mass. Megabecquerels per mole (MBq/mole), Ci/g, and uCi/mg are units of specific activity. Kilobecquerels per milliliter (kBq/mL) is an expression of concentration, the amount of radioactivity per unit volume.

Answer 33

(a) The elapsed time between calibration and dose calculation is three days (May 18-21). In this instance, the radiopharmaceutical is being used before the calibration time. Tehrefore, the initial concentration on May 18 is the unknown, and the known concentration is divided by the decay factor. The concentration on May 21 is 1.0 mCi/mL (3.0 mCi/3.0 mL): C(0) x 0.480 = 1.0 mCi/mL C(0) = 1.0 mCi/mL / 0.480 = 2.1 mCi/mL Then, determine the required volume: volume = activity required / C(t) = 1.0 mCi / 2.1 mCi/mL = 0.48 mL

Answer 34

(e) Calculate the total activity to be administered to the patient based on body weight: 15.5 kg x 25 uCi/kg = 387.5 uCi None of the options match this answer unless it is expressed in millicuries. Thus, 387.5 uCi x mCi / 1000 uCi = 0.39 mCi

Answer 35

(e) 925 MBq = 25mCi 925 MBq x mCi / 37 MBq = 25 mCi The prescribed dosage is expressed as a range, +-10% of 925 MBq or 25 mCi: 0.10 x 25 mCi = 2.5 mCi Therefore, the prescribed range is 22.5 mCi (25 mCi - 2.5 mCi) to 27.5 mCi (25 mCi + 2.5 mCi). Any dose calibrator reading between 22.5 mCi and 27.5 mCi verifies that the prescribed activity was withdrawn into the syringe.

Answer 36

(b) Reconstructed stannouse pyrophosphate must be administered first. This step, sometimes referred to as "pretining," permits [99mTc]pertechnetate to enter the red blood cells

Answer 37

(e) Because the total activity to be prepared is known, it is easiest to calculate the volume of [99mTc]pertechnetate. The volume of [99mTc]pertechnetate is equal to Activity desired / concentration of 99mTc = 20mCi / 20mCi/mL = 1.0 mCi Then, determine the volume of succimer reagent needed. If 1.0 mL = 2 parts, then 1 part must equal half of that, or 0.5 mL.

Answer 38

(d) Material that has passed its expiration date should not be used with patients. In the case of venipuncture materials, the sterility of the materials may be compromised.

Answer 39

(a) Records of 99Mo concentration measurements must contain the ration of 99Mo to 99mTc, time and date of the measurement, and name of the individual making the measurement.

Answer 40

(d) According to the NRC, a written directive is required for any dosage of [131I]sodium iodide greater than 30 uCi or for any therapy dosage of an unsealed byproduct material.

Answer 41

(b) If 99mTc eluate needs to be diluted to prepare other 99mTc-labeled products, the correct diluent is preservative-free isotonic saline. Preservatives may act as oxidizing agents that reverse the effect of reducing agents in kits. The reducing agents are necessary to make 99mTc more chemically active so it will bind to the compound being labeled.

Answer 42

(b) Decay-correct the total activity for 24 hr (July 9, 0800, to July 10, 0800 = 24 hr(: 5 mCi x 0.808 = 4 mCi Determine the concentration: concentration = total activity / total volume = 4.0 mCi / 2.6 mL = 1.54 mCi/mL Determine the volume that will contain the required activity and will have to be retained in the syringe: volume = activity required / concentration = 3.0 mCi / 1.54 mCi/mL = 1.9 mCi/mL

Answer 43

(c) The elution efficiency of a generator is expressed as a percentage of the estimated amount of [99mTc]pertechnetate on the generator column compared to what is actually collected in the elution vial. (198 mCi / 268 mCi) x 100% = 74%

Answer 44

(b) The volume of a solution in a syringe is measured at the edge of the plunger's stopper, where the calibration mark aligns with the edge of the stopper.

Answer 45

(c) The U.S. Department of Transportation (DOT) regulates the packaging and transport of radioactive materials. NRC regulations follow DOT requirements.

Answer 46

``` (d) The label types and exposure rate limits for packages containing radioactive materials are: Label category - At surface - At 1 meter Category I (white) - <=0.5 - No detectable radiation Category II (yellow) - <=50 - <= 1.0 Category III (yellow) - <=200 - <= 10 ```

Answer 47

``` (e) Use the inverse square law: (I1)(D1)^2 = (I2)(D2)^2 where I1 = intensity at original distance (D1) and I2 = intensity at new distance (D2). In this example: (36 mR/hr)(0.5 m)^2 - (18 mR/hr)(D2)^2 Isolate the unknown and solve: (D2)^2 = (36 mR/hr)(0.5 m)^2 /18 mR/hr = 0.5 m^2 Take the square root of each side: D2 = 0.7 m ```

Answer 48

(a) If 1.25 cm of lead is one HVL, then twice that thickness (2 x 1.25 cm) is two HVL. Each HVL absorbs 50% of the photons and allows 50% to be transmitted through the shield. Number of HVLs - 0 - 1 - 2 - 3 Photon intensity (%) 100 - 50 - 25 - 12.5 % absorbed 0 - 50 -75 - 87.5 % transmitted 100 - 50 - 25 - 12.5

Answer 49

(e) The NRC requires a written directive before administration of 131I in quantities greater than 30 mCi and any other unsealed byproduct material that is used for therapy. [32P]sodium phosphate and [89Sr]chloride are used for therapy, whereas [18f]FDG is used for diagnostic purposes.

Answer 50

(e) According to the NRC, the annual occupational dose limit to any organ or tissue, other than the eye, is 50 Rem or 500 mSv.

Answer 51

(a) According to NRC regulations, only patient excreta are exempt from any limits when discarded into the sewage system. Disposal limits for other radioactive waste are based on the solubility and rate of waste water discharge from a facility.

Answer 52

(a) To ensure that the batteries are functional, a battery check should be performed immediately before taking any measurements with a survey meter.

Answer 53

(d) The needle will register 5 for a full-scale deflection on this meter. The maximum scale is 10. The maximum exposure rate that could be measured is the product of the number at full deflection and the maximum scale. Thus, 5 mR/hr x 10 = 50 mR/hr

Answer 54

(d) the exposure rate of the packing material is approximately the same as room background, so the carton may be disposed of in the regular trash after any radiation symbols are removed or obliterated.

Answer 55

(c) NRC regulations require facilities to use facility design and procedures that will minimize the potential for contamination to the extent practicable. Rooms in which radioxenon is used should be tested to determine the amount of time required for evacuation of gas from the room after a gas spill. A negative air pressure exhaust system would be necessary to draw the xenon out of the room without spreading it to adjacent areas.

Answer 56

(c) According to NRC regulations, a unit dosage can be calibrated before administration by one of the following methods: direct calibration using a dose calibrator, or application of a decay factor to the original activity if the dosage has not been manipulated (adjusted) after it was originally prepared and calibrated.

Answer 57

(b) Patients should be given instructions to follow for 3-7 days that will minimize spread of contamination and radiation exposure to others.

Answer 58

(a) For each half-life that passes, the activity decreases to half of the previous activity. In this case, four half-lives are required for the activity to drop to the specified level. If each half-life is 6 hr, the total time required is 24 hr.

Answer 59

(d) If a person is hospitalized after administration of a therapeutic dosage of 131I, the door of the room must have signage that indicates the length of time a visitor may stay.

Answer 60

(c) NRC regulations state that the NRC Operations Center must be notified of a medical event (error, misadministration) no later than the next calendar day.

Answer 61

(e) NRC regulations state that written instructions for precautions must be provided to the patient or the patient's parent or guardian if any individual is likely to exceed 0.1 Rem (1 mSv) exposure from the therapy patient.

Answer 62

(e) To ensure that the shields will give accurate results, the decay method must be performed at the same time the shields are first used.

Answer 63

(a) The NRC requires that dose calibrators be tested for proper functioning according to nationally recognized standards. The standard of practice requires the measured value to be within +-10% of the calculated value. In this example, the measured values for 57Co, 99mTc, and 123I are within that limit. The measured value for 201Tl, however, varies by more than 10% of the calculated value. 0.10 (53.5 uCi) = 5.35 uCi The measured value at the 201Tl setting could vary from 48.15 uCi to 58.85 uCi and be within the prescribed limit. However, the measured value is outside this range.

Answer 64

(d) The full width at half maximum (FWHM) is defined as the width of the photopeak, expressed in keV, at one-half of the maximum or peak counts. This value is used to determine the energy resolution of a scintillation counter. The FVVI-IM is determined by calculating 50% of the highest count obtained. In this example, 50% of 15,000 cpm is 7,500 cpm. Then, a horizontal line is drawn from one side of the photopeak to the other at the 50% point. At the two places on each side of the graph where the horizontal intersects with the graph, a vertical line is dropped to the x-axis. the FWHM is calculated by subtracting the larger value from the smaller. In this example, the width of the photopeak is 50 keV (705-655 keV).

Answer 65

(e) After the long-lived reference is read on its setting, the same source should be used to obtain a reading on each commonly used radionuclide setting. 99mTc, 201Tl, 123I, and 131I are commonly used radionuclides, whereas 125I is used infrequently. 57Co and 137Cs are reference standards that are counted only on a daily basis.

Answer 66

(b) The linearity/resolution image was obtained with an orthogonal-hole phantom.

Answer 67

(b) The standard of practice for performing a dose calibrator accuracy test calls for the use of at least two long-lived reference sources. The measured value should be within +-10% of the calculated value. If the instrument fails to meet this standard, it should be repaired or replaced.

Answer 68

(a) The ramp filter is a high-pass filter; that is, it permits high frequencies to pass through while altering the lower frequencies. This suppresses the star artifact created during filtered backprojection and increase resolution. However, it has little effect on statistical noise, so a low-pass filter, such as Butterworth, Hanning, or Parzen, must be used to eliminate some of this noise, thereby smoothing the image.

Answer 69

(b) The UFOV is first determined by measuring the diameter of the largest area that can be inscribed within the collimated field of view. Then, the CFOV is defined as a circle with a diameter that is 75% of the UFOV diameter.

Answer 70

(a) If the patient's heart rate is 95 beats per minute, then each heart beat or R-R interval is: 60 sec / 95 beats = 0.63 sec/beat

Answer 71

(d) the following calculation is used when using the point source or line source method for pixel calibration: pixel size = distance between sources / number of pixels between activity profile peaks In this example: 15 cm / 45 pixels = 0.33 cm

Answer 72

(d) With activities in the millicurie range and sometimes much lower, photons are striking the well counter crystal at very short intervals. The instrument is in deadtime while many photons are interacting with the crystal. These photons will not be counted and are therefore "lost."

Answer 73

(e) The 95% confidence level is most commonly used in nuclear medicine. To determine the minimum counts (N) needed to assure a maximum given percent error, the following equation is used: % error = (2)(100%) / ((N)^(1/2)) In this example: 2% = (2)(100%) / ((N)^(1/2))

Answer 74

(a) When the decay factor for a desired time is not available, a combination of decay factors can be used to obtain the correct one. In this case, the 2-year decay factor is multiplied by itself to obtain the 4-year decay factor. The original activity is then multiplied by the decay factor to obtain the expected activity of the source. 0. 955 x 0.955 x 200 uCi = 182.4 uCi

Answer 75

(c) First, the source activity must be decay-corrected for 35 days. When the specific decay factor is not available, a combination of decay factors can be used. To obtain the 35-day decay factor, multiply the 30-days factors by the 5-days factor: 0.926 x 0.987 = 0.914 Determine the decay-corrected source activity by multiplaying the original activity by the calculated decay factor: 325.8 uCi x 0.914 = 297.8 uCi According to the accepted limits for dose calibrator constancy, the measured activity of the source should be within +-10% of the calculated or expected activity. Determine the +-10% range: 297.8 uCi x 0.1 = 29.8 uCi 297.8 uCi +- 29.8 = 268.0 x 327.6 uCi If the dose calibrator reading falls within this range, it meets the standard of practice for dose calibrator constancy.

Answer 76

(c) When the geometric variation varies from the expected by more than 10%, a correction factor must be calculated and applied whenever that configuration and activity range are measured. To apply a correction factor: true activity = actual activity reading x correction factor In this example: 26.2 mCi x 1.15 = 30.1 mCi

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ST:2 Flashcards

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