Supervisors info:
Παντελής Καραϊσκος, Καθηγητής, Ιατρική Σχολή, ΕΚΠΑ, Επιβλέπων
Μαρίνος Μεταξάς, Ειδικός Λειτουργικός Επιστήμονας Β', ΙΙΒΕΑΑ
Ελευθερία Καρίνου, Ειδική Λειτουργική Επιστήμονας Α', ΕΕΑΕ
Summary:
This experimental work was prepared at the Biomedical Research Foundation of the Academy of Athens (BRFAA) and specifically in the PET-CT laboratory in collaboration with the Hellenic Atomic Energy Committee. The BRFAA has a large workload with an average of about ten patients per day being administered for diagnosis. At the same time, from 2018, the laboratory uses a 68Ge- 68Ga generator, except for the FDG. This new radiopharmaceutical has led to the recording of the dose limit in the finger dosimeter of the Radiophysicist of the specific laboratory.
This, of course, requires the immediate adoption of measures to optimize techniques for better radiation protection of personnel, but it also raised questions about whether the dose recorded by the finger dosimeter (at the point of placement) during diagnostic practices, represents the maximum dose absorbed in the hands.
Already, according to the international literature, studies are published documenting that the estimate of the equivalent skin dose for the hand is underestimated based on the usual placement position (3rd phalanx of the dominant upper extremity index) of the individual finger dosimeter. It is also estimated that the highest doses in the upper extremities are located in the fingertips while (in index and middle fingers), the maximum is recorded in the 1st phalanx of the non-dominant hand for FDG [36], [37], [38].
In addition, based on new recommendations from the ICRP to reduce the dose limit in the eyes of exposed workers, better monitoring of the dose absorbed by the eye lenses is required. For some practices, therefore, the purpose of this dissertation is to map the dose absorbed in the hands (along the fingers, palm and wrist of the inner and outer side of the hands) but also an estimate of the dose absorbed by ocular lenses with the use of both drugs.
For this purpose, TLDs were placed on reusable gloves for measurements on the upper extremities and for the lenses of the eyes, respectively, TLDs were supported on an elastic band. For each of the two radiopharmaceuticals, the outer and inner sides of the upper limbs and the eyes were measured for selected procedures.
The results showed that indeed for both FDG and Ga the indication of the finger dosimeter is 3.3 and 6.7 times smaller than the points where the maximum dose is recorded for each of the two radiopharmaceuticals. Maximum dose points are different. For FDG it is confirmed that it corresponds to the first inner phalanx of the index of the non-dominant upper extremity, while for 68Ga it corresponds to the first inner phalanx of the dominant upper extremity.
The outer relative to the outer side of the upper extremities receives an average of 20% less dose.
In total, the estimated annual reference dose for both radiopharmaceuticals is 485.73 ± 43.86 mSv and the maximum dose is 3.5 times higher in the first phalanx of the non-dominant upper extremity. In addition there are many points where the recorded dose exceeds the limit (500mSv).
Also on both the outer and outer sides of the upper extremities, 68Ga delivers an average of 8 and 9 times higher doses per unit of activity (μSv / MBq), respectively.
For ocular lenses the total maximum annual equivalent dose, Hp (3), calculated is 8.06 ± 0.97 mSv, a value over 50% below the limit (20mSv). For the FDG it is 7.76 ± 0.75 mSv while for the 68Ga it is 0.49 ± 0.19 in different but different points. Corresponding to the results of the measurements for the upper extremities, the dose per unit of activity (μSv / MBq) for 68Ga is on average 3 times higher than the FDG.
In conclusion, for each new radiopharmaceutical and each new technique introduced in a Nuclear Medicine laboratory should be systematically checked for the dose it can deliver to the points measured and timely measures should be taken to protect workers.
Keywords:
Equivalent dose for hands' skin, Hp (0.07), Hp (3), Equivalent dose for ocular lenses, Diagnostic Nuclear Medicine, Exposed worker
