Linearity of Capintec CRC-15R systems Richard Fernandez1, Laura Wherity2 1. Dept. of Nuclear Medicine Guy’s & St Thomas’ NHS Foundation Trust, London 2. Dept. of Medical Physics, King’s College London NHS Foundation Trust Nuclear Medicine - Overview GSTT – busy teaching hospital Nuclear Medicine – cross site Radiopharmacy Supply to GSTT & satellite hospitals Dedicated therapy isolation suite Inpatient therapy facilities Treat up to 4 patients per week Thyroid Ca. (3700–7400 MBq I-131) Neuro-endocrine (11000 MBq I-131 MIBG) Nuclear Medicine - Overview GSTT – busy teaching hospital Nuclear Medicine – cross site Radiopharmacy Supply to GSTT & satellite hospitals Dedicated therapy isolation suite In-vitro investigations (GFR, RCM) Diagnostic imaging Diagnostic imaging GSTT: 7 gamma-cameras … Stress Fracture Stress Fracture Radionuclide calibrators Measured activity Radionuclides Tc-99m, I-131, In-111, Ga-67, I-123, Cr-51, Cs-137, Y-90, P-32, Sr-89, … Maximum: 30 GBq Tc-99m Minumum: <1MBq Tc-99m Q. Do we really measure over such a large range? High activity limit Lower activity limit SPECT-CT ALIGNMENT GSTT Radionuclide calibrators Nuclear Medicine: Medical Physics, PET Satellite (UHL, PRUH…) TOTAL 9 3 3 15 RC Guidelines: GPG 93 Recommend for linearity… Measured annually Over activity range used Measured for each radionuclide used ! Calibrator linearity ‘Decaying source’ method used Tc-99m only High activity source in vial Measured at intervals over 3-4 days (~12 halflives) Log-linear graph of results obtained, straight line fitted in ‘linear’ region (range 1000-50 MBq), extrapolated Obtain % difference between measuredcalculated activity Tolerance: Field instrument <5% Linearity results Calibrator linearity: Problems # of calibrators Logistical complications e.g. Radiopharmacy isolators, production run Labour intensive task prioritise scientific support, cross-site cover Operator finger dose Potential for contamination Source positioning error, timing error Clinical error – wrong factor selected Trial of NPL software Developed by John Keightley (NPL) LabVIEW ver8 Windows GUI, XP compatible Direct communication with CRC-15R Automated ! Æ overcome logistical disadvantages, minimise dose, contamination, errors Trial of NPL software Software uploaded to laptop CSV files created Æ imported to Excel Tested on 3 CRC-15R calibrators… I. Background measurement Investigate background fluctuation Measured on calibrator in I-131 therapy suite – adjacent to Radiopharmacy Measurement interval Friday 15:00 Æ 9:00 Monday Activity (MBq) -0.05 -0.1 -0.15 -0.2 -0.25 10 SATURDAY 11:00 0 SATURDAY 09:00 0 SATURDAY 06:00 Tim e of reading (hours) 20 30 40 50 60 MONDAY 07:00 Linearity measurements of I-131 lab calibrator - Background reading 70 II. Linearity: I-131 Suite % Difference in Actual and Measured Activity Measured Activity versus Time % Difference (Predicted - Measured)/ Predicted Measured Activity (MBq) 2.5 30000 2.0 True 25000 1.5 Predicted Expon. (True) 1.0 20000 0.5 15000 0.0 100000 -0.5 5000 10000 15000 20000 25000 30000 5000 -1.0 -1.5 0 -2.0 0 16 32 48 Time (hours) Activity (MBq) 64 80 % Difference in Actual and Measured Activity 2.5 II. I-131 Suite % Difference (Predicted - Measured)/ Predicted 2.0 1.5 1.0 0.5 0.0 9 10 11 12 13 14 15 -0.5 -1.0 -1.5 -2.0 12 MBq Activity (MBq) % Difference in Actual and Measured Activity 1.0 2.0 0.9 1.5 1.0 0.5 0.0 1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000 -0.5 -1.0 % Difference (Predicted - Measured)/ Predicted % Difference (Predicted - Measured)/ Predicted % Difference in Actual and Measured Activity 2.5 0.8 11,900 MBq 0.7 0.6 0.5 0.4 0.3 0.2 0.1 -1.5 1,700 MBq -2.0 Activity (MBq) 0.0 11500 11700 11900 12100 Activity (MBq) 12300 12500 III. Linearity: Radiopharmacy Support Measured Activity versus Time Measured Activity (MBq) 20000 18000 True 16000 Predicted Expon. (True) 14000 12000 10000 8000 6000 4000 2000 0 0 16 32 48 Time (hours) 64 80 % Difference in Actual and Measured Activity 4.0 12 MBq III. Radiopharmacy Support % Difference (Predicted - Measured)/ Predicted 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 -0.5 10 11 12 13 14 15 -1.0 Activity (MBq) % Difference in Actual and Measured Activity % Difference in Actual and Measured Activity % Difference (Predicted - Measured)/ Predicted 1.4 1,700 MBq 1.2 1.0 0.8 0.6 0.4 0.2 % Difference (Predicted - Measured)/ Predicted 0.4 11,900 MBq 0.4 0.3 0.3 0.2 0.2 0.2 0.1 0.1 0.0 0.0 1500 1550 1600 1650 1700 1750 1800 1850 1900 1950 2000 Activity (MBq) 0.0 11500 11700 11900 12100 Activity (MBq) 12300 12500 Linearity results Auto-ranging 12 MBq, 1700 MBq, 11900 MBq Consistent across CRC-15Rs Æ repeat with Tc-99m for other calibrators, Æ repeat with other radionuclides ? Anomalous result on Radiopharmacy CRC-15R … Radiopharmacy Support Æ anomalous result? %% Difference Difference (Predicted (Predicted - Measured)/ - Measured)/ Predicted Predicted Measured Activity (MBq) % Difference in Actual and Measured Activity 12.0 20000 11.0 18000 10.0 10.0 16000 9.0 8.0 14000 8.0 Measured Activity versus Time True Predicted Expon. (True) 12000 7.0 6.0 10000 6.0 8000 5.0 4.0 4.0 6000 3.0 4000 2.0 2.0 2000 1.0 0.0 0 0.0 0 0 -2.01475 5000 16 32 10000 48 1525 Time (hours) Activity (MBq) (MBq) Activity 15000 64 20000 80 1575 Conclusions Software offers highly practicable solution to inherent problems in performing linearity measurements on CRC-15R calibrators Issues Æ data handling in Excel Further work… Expand to testing of all calibrators Investigate radionuclides other than Tc-99m Radiopharmacy sterility • Remote data-logging ÆBluetooth communication?
© Copyright 2024 Paperzz