nuclear medicine imaging and therapies Flashcards
wha are 4 imaging techniques in nuclear medicine
static
dynamic
wholebody
SPECT
static, dynamic, whole body are planar imaging techniques
explain how radiation dose and exposure time must be compromised in nuclear medicine
- low-level radiation can be used with increased exposure time vice versa
describe how exposure time correlates with resolution in nuclear med
longer exposure time the greater the resolution
how long are marker images usually
30 seconds
how long do diagnostic images take
2-10 mins
how can the time acquired be decided upon
either by a set time or dependant on counts
What is a DMSA scan
Dimercaptosuccinic acid
- scan used to assess function and location of kidneys
what is IV bolus
the administration of a concentrated dose of medication or fluid directly into a vein
describe the administration/prep procedure for nuclear med scan for the kidneys
- IV bolus off 80 MBq Tc99m DMSA given 2-4 hrs before scan
DMSA scan can provide quantification values, e.g mean percentage of each kidney function
what are counts in nuclear med
the number of events detected, but dose rate relates to the amount of ionising energy deposited in the sensor of the radiation detector
how do you quantify anatomical structure in nuclear med
compare the counts between structures
what is a HIDA scan
hepatobiliary iminodiacetic acid (HIDA) scan
- is an imaging procedure used to diagnose problems of the liver, gallbladder and bile ducts
why would you choose radionuclide renographyh over intravenous urogram
- to asses the physiological function of the kidneys
- renography offers quantitation of both impaired clearance and subsequent effect on renal function
-
why is checking quantitation beneficial
useful for follow up comparison i.e pre and post operation
what is the effective dose of a MAG-3 renogram
0.7 mSv
what is the difference between absorbed, equivilant and effective dose
absorbed = Absorbed dose is the amount of energy deposited by radiation in a mass.
equivalent = absorbed dose to an organ, adjusted to account for the effectiveness of the type of radiation.
effective = ddition of equivalent doses to all organs, each adjusted to account for the sensitivity of the organ to radiation.
how can dehydration effect a nuclear med scan
- delayed peak activity
- delayer parenchymal clearance
- election of excretion slope
how much water should you drink for nuclear med scan
1 l
patient must empty bladder immediately prior to scan
for a renogram, midway or at the start of scan, an intravenous dose of diuretic is given. what is this and type and what dosage is given
- medicines that help reduce fluid buildup in the body.
- frusemide
- 20-40mg administered
what range of fluid production by kidney indicated a form of obstruction by either stone or sedimen
under 5ml per min
what filters/clears out the radionuclide substance in the body
- glomerular filtration and tubular secretion in kidney
what percentage of the radionuclide is excreted within 30 mins
70%
what type of graph is generated by the computer to analyse kidney function
- computer plots curve of activity against time for each region
- curve shape determines how kidneys are behaving
what is stasis
slow urine flow leads to build of debris (stone) or potentiates infection
what is the output efficincy of the kidneys in percentage to be considered obstructed or not
output efficincy of kidneys over 78% = no obstruction
under 70% = obsturction
why are patients asked to go toilet before scan
- intense uptake in urine can obscure views of hips/pelivs and legs
how does patient size affect image quality
increasing size decreases resolution due to more attenuation
how does motion affect image quality
- reduced spacial resolution
be aware of indirect contamination of camera detector, floors, skin, beds from patient, also urine leak from renogram
artefacts can be caused by issues with the gammea camera for example?
- wrong energy window, doesnt receive incoming rays
- flood not flat
- damage to crystals
if the uniformity are within limits but the visual image looks abnormal, what can this indicate an issue of
Photomultiplier tube off-peak artifactual apperance
uniformity map needs recalibrating
why is iodine 131 used in nuclear med for thyroid issues
- it gets in blood stream and deposits in functioning thyroid tissueh
what ion is taken up into thyrocytre and via what
I- ion taken up into thyrocyte via sodium-iodide symporter
what dose of iodine 131 required the patient to be isolated in hospital
over 800 MBq
not all radioactivity administered is taken up by thyroid, some excreted, urine, sweat, saliva
how can you ensure accumulation of the radionuclide is in the correct place
attach it to a pharmaceutical which has an affinity to the target area
length of stay depends on activity given and how quickly individual excretes the radiation
