NM Flashcards
All spills and contaminations of ____should be considered major spills.
radium 226
NRC anual dose limits for radiation workers (Troy and Mat) 1) Whole body total effective dose: ? 2) Dose to the lense of the eye: 3) Shallow dose equivalent to the skin and dose to the internal organs:
Dose in (Sv) .05 .15 .5
A written directive must be dated and signed by an authorized user before the administration of 131I sodium iodide greater than
1.11 MBq (30 µCi), any therapeutic dose of unsealed byproduct material, or any therapeutic dose of radiation from byproduct material other than 131I sodium iodide. This appears also to apply to the newer alpha-emitter therapies.
If the total effective dose equivalent to any other individual from exposure to the released individual is not likely to exceed ____ the individual can be released
5 mSv
physiologic distribution of radiopharmaceutical within the gray matter of the brain, lymphoid and glandular tissues of the neck, myocardium, liver, and GI and GU systems. Radiotracer?
F-18FDG
collimators are used for small organs such as thyroid.
Pinhole
collimators are used when the target organ is smaller than the size of the detector
Converging
collimators are used for most examinations and are considered the workhorse of the nuclear medicine department.
Parallel
Increasing the thickness of gamma camera crystals will result in… inc or dec sensitivity and resolution?
increased sensitivity decreased resolution.
organ visualized with excessive aluminum in the Tc-99m sulfur colloid kit
Lung
sensitive handheld instruments that are used to detect small amounts of radioactive contamination. - gas filled - high dead time
Geiger-Mueller counters
used to measure low or high exposure rates. -gas or air filled - short dead time
Ionization chamber
type of ionization chamber used to assay the amount of activity in vials/syringes from a known radiopharmaceutical.
Dose calibrators
composed of NaI crystals with a hole in them to place the sample resulting in the ability to detect very small quantities of radioactivity.
Well counters. Used for the wipe test.
Quality assurance that tests whether correct measurements are obtained regardless of sample size or geometry. uses diff syringe sizes of Tc-99m.
Geometry
is the fraction of emitted radioactivity that falls on the detector. Surrounding the well in scintillator crystals achieves this.
Geometric efficiency
the ability of the calibrator to accurately measure radioactivity at all clinically applicable low to high levels.
Linearity Using various activity levels of Tc99m
refers to the ability of the calibrator to accurately assay samples with all clinically applicable radionuclide energies (low, medium, and high). No matter what isotope I look at are my average readings at the bulls-eye? checked?
Accuracy quarterly-annualy
measures the instrument’s precision and is intended to show the reproducibility of measurements.
Constancy using Cesium 137
Quality assurance tests
CLAG constancy, linearity, accuracy and geometry. daily, quarterly, annually and after recalibration, usage etc.
quality assurance is being performed when the nuclear pharmacist assays a high activity vial of Tc-99m using calibrated lead shields to simulate lower levels of radioactivity?
Linearity This can be evaluated by one of two following methods: (1) Assay a high activity vial of Tc-99m over an 80-hour period, or (2) assay a high-activity vial of Tc-99m using calibrated lead shields to simulate lower levels of radioactivity.
peripheral crescent-shaped defect on the flood image, this is classic for a nonfunctioning
photomultiplier tube.
Center of rotation (COR) errors are seen on
SPECT images. Tested monthly
The maximal uncorrected COR error allowable is
0.5 pixels
Bar phantoms are used to evaluate
spatial resolution (ability to resolve the lines) and linearity (are the lines straight or wavy) on a weekly basis.
Checked by doing flood images daily to correct field inhomogeneities
Extrinsic uniformity (COLLIMATOR ON) tested with cobalt 57
Can be Used to Assess Contrast, Uniformity, Resolution, Attenuation and COR
jaszczak phantom (overall system performance) tested quarterly
Delivered dose must be within ___ of prescribed dose Good Practice say dose should be within ___.
20%, 10%.
Systems are more susceptible to non-uniformities High Count Floods ( > 40 million counts)
SPECT
Light collection is more efficient at the _____ of the PMT
center
____ is tested by doing a high count rate flood.
Collimator integrity
How often should the uniformity flood images be acquired?
Daily - to evaluate both the intrinsic function of the camera and the extrinsic function of the collimators.
How often should spatial resolution be tested?
Weekly
the ability of the crystal, photomultiplier tube detector, and accompanying electronics to record the exact location of the light pulse on the sodium iodide crystal.
Inherent spatial resolution
Overall spatial resolution can be tested with __ or ___.
bar phantoms or with full width at half maximum.
the width of a spectrum curve measured between those points on the y-axis which are half the maximum amplitude.
FWHM
What is the maximum allowable molybdenum-99 breakthrough? What is it measured with?
0.15 μCi per 1 mCi of Tc-99m microCurie, milliCurie. Measured with dose calibrator with lead shield surrounding the sample
What is the max allowed exposure to public from a pt who received an outpatient I-131 therapy?
5 mSv
typically evaluated with a three-phase bone scan and would demonstrate increased or decreased periarticular uptake on the delayed images depending on the stage
Reflex sympathetic dystrophy (RSD) or complex regional pain syndrome (CRPS)
equivalent dose to the embryo/fetus during the entire pregnancy from the occupational exposure
5 mSv (0.5 rem)
What is the occupational whole body dose limit?
50 mSv (5 rems)
annual limits to the lens
150mSv (15 rems (0.15 Sv))
annual limits to the skin (whole body)
500mSv 50 rem (0.5 Sv)
To decreasing beam hardening artifact
Increase tube current but you increase patient dose.
wavy appearance of the image
Moire interference
What is the annual institutional limit for the amount of radioactivity that can be disposed of in the “hot sink”?
1 Ci / year for all liquid wastes for the entire institution. Includes pts shit.
Contaminated waste/trash/clothing is kept until it has decayed back to background or ______ if the physical half-life of the radioactive material is ____days.
10 half-lives, <120
Free pertechnetate would be seen as increased uptake in
salivary glands, thyroid, stomach and renal collecting system
Energy of photons emitted by PET (including F18 and Rubidium)
511 keV
Energy of photons emitted on bone scan
140 keV
Diffuse liver uptake on a bone scan is abnormal and most likely do to
aluminum contamination (aluminum breakthrough in eluate) and subsequent colloid formation.
Thin-layer chromatography is used to determine labeling efficiency also known as
radiochemical purity CHromatography, CHemical
allowable limit of aluminum breakthrough in molybdenum-99/technetium-99m generator?
10 μg/mL of Tc99m eluate micrograms/mL
Too much aluminum causes technetium–aluminum particles to form, which can be seen as uptake in the _____
liver
Label: White I surface radiation, at 1 m ?
< 0.5 mrem / hr, N/A
Label: White II surface radiation, at 1 m ?
< 50mrem / hr, < 1 mrem / hr
Label: White III surface radiation, at 1 m ?
50-200 mrem / hr, 1-10 mrem/ hr
highest radiation level at 1 m from the surface of the package
transport index (TI)
Limulus amebocyte lysate at a pH of 7. What does the formation of gel after 30 minutes of incubation indicate?
presence of pyrogens. The thicker the gel the greater # of pyrogens.
Maximum buildup of Tc-99m activity occurs at __ hours after elution.
23
For TI of 2, what should be the max dose rate?
Radiation level at 1 m should be no more than 2 mrem/h.
adjustment of the differential absorption of signal from tissues deeper in the body compared to the periphery
Attenuation correction
one of the most common causes of altered biodistribution of MIBG….
Medications Known interfering medications with MIBG include the following: Antihypertensives: Labetalol and calcium channel blockers (i.e., diltiazem, nifedipine, verapamil) Tricyclic Antidepressants: amitriptyline, imipramine, doxepin, etc. Sympathomimetics (i.e., cold medications): phenylephrine, pseudoephedrine, ephedrine, etc. Cocaine
What is responsible for the increased detection of counts with positron emission tomography (PET) compared to single photon emission tomography (SPECT)?
Electronic collimation
What happens to the amount of I-124 contamination in an I-123 dose over time?
Increases with time. This is why I-123 doses should be used as soon as possible after their receipt. I124 has longer half life and gives higher energy photons.
Main source of radiation is from close proximity to the breast. As a result, some authors suggest patient to suspend breast-feeding for __ hours after the FDG injection.
8
Full width at half-maximum of a photopeak is a measurement of a system’s…
energy resolution. and should be performed anualy.
The _____________ is measured daily by checking a radionuclide photopeak.
energy spectrum
What happens when one uses a low-energy collimator to image a medium-energy isotope?
decreased resolution bc of increased septal penetration (thinner septa w lower energy collimators).
Uptake in lacrimal glands, nasal mucosa, liver, kidneys, bowel, and bone marrow. NOT SPLEEN.
Ga-67
Ga 67 energy photopeaks
93,185,200 ~100,200,300
Low-energy collimators are generally used to image energy up to
150 keV
medium-energy collimators have a maximum suggested energy of about
400 keV
I-123 MIBG is typically imaged with what collimator?
medium-energy parallel-hole collimator.
High-energy collimator is used to image
I-131
Low-energy, high-resolution collimator or a low-energy, all-purpose collimator can be used to image
Tc-99m-labeled agents.
critical organ for Tl-201
Kidneys
critical organ for Tc-99m-labeled myocardial perfusion agents (tetrofosmin and sestamibi)
Gallbladder
For myocardial perfusion agents, if intense activity is seen in the liver _____. If renal excretion ______.
Tetrofosmin or Sestamibi; TI-201
Only pharmaceuticals w distribution to the skeleton and renal collecting system.
bone scintigraphy agents Tc-99m MDP or Tc-99m HDP.
Liver and spleen are part of the physiologic distribution of
Ga-67, Tc-99m sulfur colloid, tagged leukocytes, and F-18 FDG.
pharmaceuticals w physiologic distribution of nasopharynx, salivary glands, thyroid, stomach, bladder, and bowel.
I-123 and I-131
Physical Half life of TI-201
3d
Physical Half life of Tc-99m
6h
Physical Half life of I-123
13.2h
Physical Half life of Ga-67
3.2d
Physical Half life of In-111
2.8d
Physical Half life of I-131
8d
Physical Half life of Xe-133
5.2d
Principal photon energy, keV of TI-201
69-83 (Hg xrays)
Principal photon energy, keV of Tc 99m
140
Principal photon energy, keV of I-123
160
Principal photon energy, keV of Ga 67
90,200,300,400
Principal photon energy, keV of In III
170, 245
Principal photon energy, keV of I-131
364
Principal photon energy, keV of Xe-133
81
spleen > liver > bone marrow
In III
used for the detection of beta amyloid plaques in the diagnosis of Alzheimer disease by PET imaging
F-18 Florbetaben
myocardial perfusion imaging agents that bind to the cytoplasmic mitochondria and are excreted through the liver by the hepatobiliary system.
Tc-99m tetrofosmin and Tc-99m sestamibi
a K+ analogue that localizes within the cytoplasm of the myocardial cells by sodium potassium ATPase pump and excreted by the kidneys
Thallium-201
radiolabeled analog of choline, a precursor essential for the biosynthesis of cell membrane phospholipids; it has been approved by the FDA to evaluate prostate cancer.
C-11 choline
Radiopharmaceutical used for the detection of hypoxia in tumor
F-18 fluoromisonidazole (FMISO) and Cu-64 ATSM
Radiopharmaceutical is a marker of cell proliferation
F-18 fluorothymidine (FLT)
radiopharmaceuticals used to image apoptosis, mainly in tumors to evaluate early response to therapy.
Tc-99m annexin V
a somatostatin receptor binding agent, mainly used in the evaluation of neuroendocrine tumors.
Ga-68 DOTA
measures the fraction of total radioactivity that is present in the form of the undesired radionuclide. In the Tc-99m case, it is measured in the form of ratio of Mo-99 to Tc-99m.
Radionuclide impurity.
Mo-99 is the most important radionuclide contaminant in the Tc-99m based radiopharmaceutical. Its ______ and _________ result in a very high radiation dose.
long half-life; beta emission
What is being measured when Mo-99/Tc-99m generator eluate is placed on a special test paper that changes color?
Chemical impurity
maximum allowable limit for alumina breakthrough in the generator eluate in the case of Tc-99 is …
10 μg/mL of eluate. Detected with paper strip test.
What is being measured when the radiopharmacist performs thin-layer chromatography on Tc-99m MDP?
Radiochemical impurity
An example would be fraction of the free Tc-99m pertechnetate and insoluble colloids in a Tc-99m MDP dose prepared for bone scintigraphy.
Radiochemical impurity, tested with thin layer chromatography.
Effective half-life =
(physical HL × biologic HL)/(physical HL + biologic HL)
I-131 destroys the thyroid follicular cells by what particulate emission during its radioactive decay?
Beta
Iodine-123 (I-123) decays by
electron capture
radiopharmaceuticals is trapped by the thyroid follicular cells but NOT organified?
Tc-99m pertechnetate. As such, it can gradually wash out of the thyroid gland, requiring imaging at 20 minutes after IV administration.
radiopharmaceuticals organified in the thyroid follicular cells …
I-123 and I-131 are organified into T3 and T4 and stored in the colloid-filled follicular lumen. Antithyroid medication such as propylthiouracil and methimazole block this organification process.
What three “devices” utilize crystal-based scintillation detectors (NaI, CdZnTe, etc.) coupled to a photomultiplier tube for radiation detection?
Scintillation probes, well counters, and gamma cameras
highly sensitive device used to detect a very small amount of radioactivity (up to 1 mCi) such as those of wipe tests or in vitro studies (GFR, shillings test, etc.).
well counter
are typically used to measure high exposure rates (range from 0.1 mR to 100 R) such as those from the patients receiving radioiodine therapy for cancer.
Ionization chambers
The typical 24-hour RAIU of 50% to 80%.
Graves
The typical 24-hour RAIU of 20-30%
TMNG & toxic autonomously functioning nodule
Normal %RAIU is 4-15% at and 10-30%
4 to 6 hours at 24 hours.
Absent or poor visualization of thyroid gland and decreased RAIU are seen with
Hypothyroidism, acute phase of subacute thyroiditis, amiodarone tox, exposure to excess iodine (contrast, amiodarone) or suppression from exogenous thyroid hormone.
Antithyroid peroxidase antibodies are typically seen with
Hashimoto’s thyroiditis.
I-131 dose to treat the patients with Graves disease
5 to 20 mCi Symptomatic improvement is usually noted by 3 weeks with full therapeutic effect typically in 3 to 6 months.
I-131 dose to treat the patients with MNG
20 to 30 mCi. More resistant than graves and lower RAIU.
lactating women undergoing I-131 therapy should be asked to stop breast-feeding for…
that child. May resume for next child.
How long after administration of I-123 radioiodine can the patient resume breast-feeding?
48 hours. Unlike 131 this has short half life and no beta emission.
How long after administration of Tc-99 radioiodine can the patient resume breast-feeding?
24 hours
most accurate tumor marker to detect recurrence of a well-differentiated thyroid carcinoma (papillary and follicular)
Serum thyroglobulin (Tg)
Thyroid hormone undergoes conversion from T4 to T3 by type I iodothyronine deiodinase within the ____. Thus, presence of uptake there suggests evidence of functioning thyroid tissue elsewhere in the body.
liver
Serum TSH value greater than what level is desirable to ensure maximal effect of the ablation?
30 mIU/L is desirable, and a level greater than 50 mIU/L is optimal. Synthroid should be stopped 4 weeks before study.
radiopharmaceutical of choice for the evaluation of substernal goiter.
I-123. better target to background ratio, better tissue penetration, and improved specificity (compared to pertechnetate) as well as ability to perform SPECT–CT images (compared to I-131).