A dynamic renal phantom for nuclear medicine studies

Abstract

Dynamic radionuclide renal study (renography) provides functional and structural information of the kidney and urinary tract noninvasively. Our purpose in this study is to describe the construction and test results of a dynamic renal phantom with different clinical features of radionuclide renography. The phantom consisted of five pieces of different shaped Plexiglas boxes: Two kidneys, one liver, two square shaped boxes (one heart and one bladder). The bladder was internally divided into two compartments in order to collect each kidney output separately. The dynamic circulation of the phantom was maintained under a hydrostatic pressure approximately equal to 13.3 kPa (average human blood pressure). The standard dose distribution among different organs and different renographic parameters were calculated from series of normal patients study (91 with 99mTc-DTPA, 68 with 99mTc-EC). All the studies were performed with same camera (Siemens Orbiter Digitrac 7500) equipped with LEAP (low energy all purpose) collimator using ADAC Pegasys II analytic package program under the same clinical procedure. Different regions of interest (ROIs) were drawn for concerning organs and counts per second (CPS) were collected for each ROI. The series of renogram curves were generated by phantom-studies with different flow rates for left kidney (LK) and right kidney (RK). The renal index (RI) for an individual study was calculated as the product of two indexes: "Relative Renal Function" (RRF) (water-volume of LK/RK) and "Relative Renal Time" (RRT) (Tmax of LK/RK). The most significant correlation was found in total CPS for LK and RK between the EC group and phantom studies (p < 0.001). The calculated RI values were used to simulate the patients' study with different clinical features. The dynamics were found reproducible. The phantom is suitable for using in calibration and quality control protocols of the renogram procedure used in Nuclear Medicine.