What validation tests can be done by the clinical medical physicist while waiting for the standardization of quantitative SPECT/CT imaging?

OBJECTIVE: The aim of the study was to assess the accuracy of quantitative SPECT/CT imaging in a clinical setting and to compare test results from two nuclear medicine departments. METHODS: Phantom studies were carried out with two gamma cameras manufactured by GE Healthcare: Discovery NM/CT 670 and NM/CT 850, used in two nuclear medicine departments. The data were collected using a cylindrical uniform phantom and a NEMA/IEC NU2 Body Phantom, filled with 99mTc-pertechnetate. RESULTS: The convergence of activity concentration recovery was validated for the two gamma cameras operating in two medical centers using the cylindrical uniform phantom. The comparison of results revealed a 5% difference in the background calibration factor Bg. cal; 6% difference in COV, and a 0.6% difference in total activity deviation ∆Atot. Recovery coefficients (RCmax) for activity concentration in spheres of the NEMA/IEC NU2 Body Phantom were measured for different image reconstruction techniques. RCmax was in the range of 0.2-0.4 for the smallest sphere (ϕ 10 mm), and 1.3-1.4 for the largest sphere (ϕ 37 mm). Conversion factors for SUVmax and SUVmean for the gamma camera systems used were 0.99 and 1.13, respectively. CONCLUSIONS: (1) Measurements taken in our study confirmed the clinical suitability of 5 parameters of image quality (Bg. cal-background calibration factor, ∆Atot-total activity deviation, COV-coefficient of variation used for image noise assessment, QH-hot contrast, AM-accuracy of measurements, or RC-recovery coefficient) for the validation of SPECT/CT system performance in terms of correct quantitative acquisitions of images. (2) This work shows that absolute SPECT/CT quantification is achievable in clinical nuclear medicine centers. Results variation of quantitative analyses between centers is mainly related to the use of different reconstruction methods. (3) It is necessary to standardize the technique of measuring the SUV conversion factor obtained with different SPECT/CT scanners.

SHOULD PERSONNEL OF NUCLEAR MEDICINE DEPARTMENTS USE PERSONAL DOSIMETERS FOR EYE LENS DOSE MONITORING?

Staff at nuclear medicine departments receive doses of ionising radiation higher than the staff of radiotherapy and radiology departments, with the exception of interventional radiologists. Due to the updated lower occupational exposure limit for the lens of the eye, we measured eye exposure in workers of the Nuclear Medicine Department, Pomeranian Medical University in Szczecin, Poland. EYE-D™ dosimeters were used for 3 months by 10 employees working with sources of ionising radiation. Personal dosimeters also measured the exposure of the whole body and hands. The 3-month dose equivalents for the lens of the eye in the employees was 0.20-0.72 mSv. Staff at NMD PMU do not require regular routine eye lens dose monitoring. Eye lens doses were well within the new annual limit of 20 mSv. Doses to the whole body may be used as an indicator of the eye lens doses in the monitored department.

Radiation doses of employees of a Nuclear Medicine Department after implementation of more rigorous radiation protection methods.

The appropriate radiation protection measures applied in departments of nuclear medicine should lead to a reduction in doses received by the employees. During 1991-2007, at the Department of Nuclear Medicine of Pomeranian Medical University (Szczecin, Poland), nurses received on average two-times higher (4.6 mSv) annual doses to the whole body than those received by radiopharmacy technicians. The purpose of this work was to examine whether implementation of changes in the radiation protection protocol will considerably influence the reduction in whole-body doses received by the staff that are the most exposed. A reduction in nurses' exposure by ~63 % took place in 2008-11, whereas the exposure of radiopharmacy technicians grew by no more than 22 % in comparison with that in the period 1991-2007. Proper reorganisation of the work in departments of nuclear medicine can considerably affect dose reduction and bring about equal distribution of the exposure.

Occupational exposure at the Department of Nuclear Medicine as a work environment: A 19-year follow-up.

BACKGROUND: This study assessed the radiation safety at Nuclear Medicine Department being a work environment. Ionizing radiation exposure of the employees in the last 19 years and the effects of legislative changes in radiological protection were analyzed. MATERIAL/METHODS: All employees of the investigated department were regularly and individually monitored using chest badges equipped with Kodak film type 2. Overall, 629 annual doses of the employees of nuclear medicine department, registered in the period 1991-2009, were analyzed statistically. RESULTS: Technicians were found to be the largest exposed professional group, whereas nurses received the highest annual doses. Physicians received an average annual dose at the border detection methods. Ancillary and administration staff occasionally received doses above the method detection limit (MDL). The average annual dose for all dosimetry records was 0.7 mSv, and that for dosimetry records equal and higher than MDL was 2.2 mSv. CONCLUSIONS: There was no case of an exceeded dose limit for a worker. Furthermore, improvement of radiological protection had a significant impact on the reduction of doses for the most exposed employees.