Nuclear Med Revision Flashcards
What generator do they use?
Technician -99m
What happens after delivery of T-99m?
Collect the technician generator from delivery bay
Measure the external dose rate - if it’s above limit may indicate damaging leakage
And delivery details on database. All radioactive deliveries must be recorded when they arrive.
What is used for a constancy check on the radionuclide assay calibrator ?
Caesium -137 source
What is used to sterilise the isolator?
Hydrogen peroxide gas
How do they get the elute out from the generator?
An evacuated vial is placed onto the generator which draws saline through the ion exchange column. This creates a solution of of t-99m in the form of Pertechnetate anions
What is the hottest radiation source on any given day and what is it used for?
The solution of pertechnetate anions
They are used to prepare different radiopharmaceuticals
What is done at the start of sessions to monitor the environment?
Agar plates are opened in various locations
What happens to the eluted T-99m ?
It’s measured and entered onto the data base along with the volume of the solution. The volume is controlled by the evacuated vial
This vial is put into a tungsten sheild
What is the typical Monday eluted activity?
110 GBq
How are the different radiopharmaceuticals formed?
They come in the form of cold kits to which the pertechnate is added.
The kit vial contains everything needed for the T-99m to be reduced from the pertechnetate to form an oxidation state to bind with the desired molecule
What determines the volume of pertechnetate added to each cold kit?
The radioactive concentration of the pertechnetate
How much radiation does their fingers receive in a session?
1mS
What happens at the end of a session?
• plates are closed and prepared kits passed into the support room
• the kits must be checked by another staff member - product release
They check the appearance, radioactivity level and volume
Also the lot number matches
What is the molybdenum breach through test?
The first elution is checked for molybdenum-99 breakthrough.
To measure this the elute is put into a lead pot. This completely attenuates the T-99m gamma radiation but will allow a higher energy game rays form Molybdenum to pass through
Why is it important that there is no M-99 in the kit vial?
Excess M-99 in the kit will affect the chemistry of the labelling
As it has a 1/2 life of 2.7 days - it will give unnecessary radiation dose to the patient well beyond the scan time
What is the Aluminium break through test?
The first elute is also checked for Aluminium breakthrough.
The elute is spotted onto an indicator paper alongside an aluminium, standard solution. The spot turns pink in the presence of aluminium ions.
The eluate passes the test if there’s no pink colour or the intensity is less than that standard .
Why is it important that there is no aluminium breakthrough?
Aluminium ions in the kit file will affect labelling chemistry and cause particulate injections to clump together which will impair the in vivo behaviour.
What is the threshold for the accepted radioactivity?
Within 10%
How are QC checks completed on the gamma camera?
Uniformity test - checks the camera is imaging a uniform source of radioactivity as a uniform image
A flat source of Colbalt-57 is placed on the camera head
Difference betweeen hottest and coldest should be no more than 3%
What is the definition of Eluate?
Neat pertechnetate taken directly from the elution which is used to create Technegas for lung ventilation imaging
What is Technescan HDP?
HDP (hydroxydiphosphonate) a bone scanning agent
What is nanoscan?
Nanocolloid used to image lymphatic flow
What is pulmonic (MAA)?
MAA ( macroaggregrated albumin) a particle suspension used to image blood flow in the lung
What is involved in a sentinel node scan?
They are injected with 10MBq of T-99m nano scan intradermally in the same quadrant as their breast tumour
They are then imaged to track the lymphatic drainage of the injection to the sentinel, lymph node
The scans are carefully coordinated with theatre .
How is the sentinel node scan used in theatre?
The images and the use of a radiation probe guides the surgeon to which node to be removed
The note is examined for signs of metastatic cancer cells
If the node is clear, and there’s no need to remove any further notes
The patient can be spared, impaired lymphatic drainage and swollen arm .
What is used for nuclear medicine bone scans for breast cancer?
T-99m
What to do in the event of a spill of radioactive substance?
~ after a spill take care that nobody steps on the floor where the spill occurred
~ clean up starts by absorbing the spill onto a dry wipe that’s placed into a shielded waste bin
~ The area is monitored to measure contamination in Bq per cm^2
~ after clean up with detergent and dry wipes the level is above 30 bqcm^-2
Which is above the limit for T-99m
This amount is not an exposure hazard but a contamination hazard so its covered with waterproof plastic and left to decay
What must patients have prior to a v/Q scan?
A CXR to rule out gross changes that explain symptoms
What happens to produce the gas’s for the ventilation part of the V/Q scan?
The technegas generator is prepared
0.14 ml of perechenetate solution is added to the carbon crucible
This is then headed to boil off the water solvent - simmering
Just before inhalation - the gas is created by heating the crucible to 2750 degrees c in an inert argon atmosphere to generate the T-99m labelled carbon particles
During the Ventilation part of the V/Q scan how does the patient inhale the gas?
The patient inhales through a one- way filtered mouthpiece with a nose clip on.
They have a chance to practice before the scan
The patient will inhale the gas over a camera which monitors the lung activity until the correct count rate is reached
They are then scanned using SPECT to get 3D representation of the lungs
What happens during the perfusion part of a V/Q scan?
Th pt is given IV injection of 100mMBq of T-99m MAA
This is also given with the person over a camera to ensure the activity is at least 4x that of the technegas
They then are scanned using SPECT to create a 3 D representation of blood flow in the lungs
What SPECT images are acquired?
At derriford - head/thorax , thorax/abdo, abdo/pelvis
Most of the UK - Anterior and posterior planar whole body scan
What are the +/- of spect?
It offers greater sensitivity and specificity
It take twice as long
What is the level considered safe for T-99m
30 Bq per cm squared
