Purpose:
Measuring the effect of patient hydration on PET-CT image quality using qualitative and semi-quantitative analysis.
suggesting a method to decrease external radiation dose rate before patient discharge after PET/CT scan.
Materials and methods:
60 Patients over the age of 18 who came to the nuclear medicine department, National Cancer Institute, Cairo university. to undergo 18F-FDG PET-CT for different indications and were willing to participate in our study were selected.

Results:
60 patients who came to undergo 18F-FDG PET-CT were randomly divided into 2 groups (30 patients each). Group A receives a hydration while group B did not receive any form of hydration.
External radiation dose rate at 1 m distance of group A and group B at different times were as follows: post-injection measurement (measurement 1) was 28.8±5.8 μSv/h and 38.5±9.8 μSv/h, post-voiding 1 measurement (measurement 2) was 20.1±5.4 μSv/h and 24.8 ±7.1 μSv/h, post-scan measurement (measurement 3) was 16.8±4.5 μSv/h and 20.4±5.8 μSv/h, post-voiding 2 measurement (measurement 4) was 15.2±4.2 μSv/h and 18.6±5.6 μSv/h respectively (P value <0.05)
The Qualitative analysis showed a total of 3 patients (5%) with poor image quality, of these 3 patients, 1 patient (3.3%) in group A and 2 (6.6%) were in group B. A total of 20 patients (33.3%) with fair image quality, of whom 3 patients (10%) were among group A and 17 (56.7%) among group B. A total of 37 patients (61.7%) with good image quality, 26 (86.7%) of whom were among group A and 11 (36.7%) among group B (P value < 0.001).
Conclusion:
The patient's hydration helps reduce the external radiation dose rate, enhances image quality by qualitative analysis, however, it does not affect other parameters of the semi-quantitative analysis.