NM QC Flashcards
What is NM QA?
The overarching nuclear medicine system which ensures quality of outcome
Includes:
Education
Medicines / radiopharmacy
Equipment
What is QC?
Specification, assessment, optimisation and maintenance of a particular aspect – e.g. equipment
What are the principles of QC?
Establish: critical parameters, methods, action levels, frequency, sys of work
Carry out: action response, carry out protocols, reactive action, investigations
Critical Imaging parameter planar:
Resolution: Spatial/Energy
Uniformity, linearity, sens, leakage
Critical Imaging parameter SPECT:
Coll hole angulation, uniformity, CoR, SPECT res, overall quality
SPECT CT: CT QC + Registration
Acceptance and routine tests
NEMA, elec, safety establish QC program
Daily SPECT
Photo peak position
Intrinsic uniformity flood - vis and quant
Monthly SPECT
Uniformity (higher count) Sensitivity Resolution Centre of rotation Tomographic performance with phantom
Uniformity measures (6)
System - Flood Intrinsic - Point source Integral - CoV / min/max - UFOV / CFOV Differential SPECT Whole body - different isotopes
How is daily uniformity tested?
1 Remove collimator
2 Use point source with about 0.6 MBq positioned between detector heads
64x64 matrix
3 Acquire 10 million count acquisition
4 Calculate integral and differential non uniformity
Create via corr matrix
Resolution tests
•System Line source Phantom •Intrinsic Line source Phantom •Quantitative •Qualitative •Planar •SPECT
PET Acceptance tests (EANM)
- Physical inspection
- Computer clock
- Sensitivity
- Uniformity
- Spatial resolution
- Count rate performance
- Image quality
Example PET routine tests
Daily: Physical inspection, Background count rate, Detector check
Weekly: Energy resolution
Monthly: Calibration
Quarterly: Spatial resolution, Sensitivity, Image quality
Annual: Uniformity
Types of PET events
All coincidences have to be within energy acceptance window and time co-incidence window
True events: due to a single event on a line between the two point of detection
Scattered events: incorrectly placed as one or both photon are scattered prior to detection
Random coincidences: arise from 2 separate events
What is the noise equivalent count rate?
Count rate to obtain the same SNR in the absence of scatter and randoms
Scatter fraction: The fraction of total co-incidences in the photo-peak window that have been scattered.
Scatter / Count testing process PET
Cylindrical phantom with a small tube containing F18 which is allowed to decay and make repeated measurements
Sensitivity measurement process PET
Nema method
- Use a line source with a series of concentric aluminium sleeves.
- Measure counts which each sleeve successively added and then extrapolate back to theoretical position of no attenuating material
- This method is required as material is required for annihilation
Image quality testing PET
Phantom with series of hot and cold spheres
Requirements of routine QC
- Simple and sensitive
- Impact - able to be promptly reviewed
- Documented - procedure and results recorded and tracked
What is two bed testing?
Using the Ge68 phantom this is a quick full-system test (8 mins)
Position the phantom on the bed and align it so that two bed positions will be required to image its full extent
Images may be reviewed visually or an offline software analysis:
- PET CT alignment
- PET uniformity, inc atten and scatter corr
- Consistency of quantification
- Bed position stitching artefacts
What is SUV?
Standardized uptake value, used for pharmo modelling
The SUV is the ratio of the image derived radioactivity concentration cimg and the whole body concentration of the injected radioactivity
SUV errors: incorr act records, air bubbles in phantom, ct/pet sys errors, calib perf
issues: no sens to patient weight, physio uptake, tissue inj error
What is CCCF ?
Cross Calibration Correction factor. It relates the sensitivity to Ge68 phantom measured on the scanner to the sensitivity of F18 measured in the calibrator
Req when new QC phantom intro’d by resetting CCCF
Potential PET measurement sources of error
Patient scales Calibrator Blood glucose monitor CT scanner Processing software Data transfer Display station Safety equipment
