Tc-99m HDP image interpretation
In the image analysis of Tc-99m HDP (n = 18) with 10 mg of UDCA, buttock Radioactivity and Radioactivity/ID (%) were lower in the UDCA group at the 4 h time point (buttock, Radioactivity, Control : UDCA = 19.943 ± 1.542 kBq : 15.207 ± 2.035 kBq, P = 0.019, Fig. 4a, Radioactivity/ID, Control : UDCA = 0.050 ± 0.010% : 0.039 ± 0.007%, P = 0.031, Fig. 4b). Rate of change (%) of liver activity was different at 2 h – 30 min and 4 h – 30 min and liver activity in the UDCA group decreased more substantially (liver, Rate of change at 2 h – 30 min, Control : UDCA = -31.083 ± 2.181% : -34.525 ± 2.627%, P = 0.011, Rate of change at 4 h – 30 min, Control : UDCA = -46.010 ± 3.402% : -50.761 ± 4.314%, P = 0.024, Fig. 4c). There was a statistically significant difference in Rate of change by section (%) at 2 h – 1 h in the liver and buttock (buttock, Rate of change by section at 2 h – 1 h, Control : UDCA = -5.679 ± 4.770% : -22.857 ± 8.471%, P = 0.040).
Similar effects were found in the Tc-99m HDP experiment with 5 mg of UDCA (n = 18). The Rate of change (%) of buttock radioactivity was significantly different between the 2 groups at 3 h – 30 min and 4 h − 30 min and the buttock showed a greater decrease in radioactivity in the UDCA group (buttock, Rate of change at 3 h – 30 min, Control : UDCA = -47.468 ± 7.073% : -57.312 ± 5.729%, P = 0.008, Rate of change at 4 h – 30 min, Control : UDCA = -56.19 5 ± 4.881% : -64.825 ± 7.452%, P = 0.024, Fig. 4d). Use of 10 mg of UDCA was not associated with greater radioactivity excretion from soft tissue compared to 5 mg of UDCA. The 4 imaging parameters of ROIs in the lumbar spine and the right shoulder were not significantly different between the 2 groups in either the 5 mg or 10 mg of UDCA experiments.
Tc-99m pertechnetate image interpretation
In the image analysis of Tc-99m pertechnetate (n = 12), Radioactivity of the buttock was greater in the Control group at 1, 3, and 4 h (buttock, Radioactivity at 1 h, Control : UDCA = 404.225 ± 22.393 kBq : 316.572 ± 8.279 kBq, P = 0.026, Radioactivity at 3 h, Control : UDCA = 230.214 ± 13.232 kBq : 187.146 ± 5.079 kBq, P = 0.009, Radioactivity at 4 h, Control : UDCA = 197.654 ± 13.032 kBq : 138.158 ± 23.372 kBq, P = 0.015, Fig. 5a). The Rates of change (%) in the buttock also differed at 1 h – 30 min, 3 h – 30 min, and 4 h – 30 min and activity in the UDCA group decreased more substantially (buttock, Rate of change at 1 h – 30 min, Control : UDCA = -14.992 ± 4.912% : -32.191 ± 3.880%, P = 0.004, Rate of change at 3 h – 30 min, Control : UDCA = -51.392 ± 5.152% : -60.041 ± 4.455%, P = 0.015, Rate of change at 4 h – 30 min, Control : UDCA = -58.177 ± 3.024% : -70.230 ± 2.866%, P = 0.009, Fig. 5b). Rate of change by section (%) significantly differed at 1 h – 30 min in the buttock. Radioactivity/ID (%) in the buttock was lower in the UDCA group at 4 h (buttock, Radioactivity/ID at 4 h, Control : UDCA = 0.409 ± 0.033% : 0.305 ± 0.024%, P = 0.041, Fig. 5c).
Rate of change (%) in the thyroid gland was different at 1 h – 30 min and 4 h – 3 0 min and radioactivity decreased more substantially in the UDCA group (thyroid gland, Rate of change at 1 h – 30 min, Control : UDCA = -20.558 ± 4.958% : -28.698 ± 2.536%, P-value = 0.041, Rate of change at 4 h – 30 min, Control : UDCA = -64.947 ± 2.860% : -71.165 ± 4.181%, P = 0.026, Fig. 5d). Radioactivity/ID (%) in the thyroid gland at 30 min also significantly differed (thyroid gland, Radioactivity/ID at 30 min, Control : UDCA = 1.064 ± 0.044% : 1.285 ± 0.098%, P = 0.041), such that Radioactivity/ID (%) of the UDCA group was higher at the early time point of 30 min.
The 4 imaging parameters showed no differences between the Control and the UDCA groups in the stomach ROI.
Tc-99m DMSA image interpretation
In the image analysis of Tc-99m DMSA (n = 12), while the Radioactivity of the kidney in the Control group showed little decrease at 1 h – 30 min, that in the UDCA group increased (kidney, Rate of change at 1 h – 30 min, Control : UDCA = -0.787 ± 0.531% : 4.335 ± 1.144%, P = 0.002, Fig. 6). These findings suggest accumulation of radiotracer into the kidneys in the UDCA group earlier in the experiment. Radioactivity of the buttock decreased more in the UDCA group at 3 h – 30 min (buttock, Rate of change at 3 h – 30 min, Control : UDCA = -32.456 ± 2.826% : -43.164 ± 3.470%, P = 0.065).
Net injection dose and total body radioactivity measured by dose calibrator
Net injection dose (Net ID) was calculated by subtracting the radioactivity that remained in the syringe after injection from the radioactivity of the radiotracer as prepared. Time correction was applied based on the injection time to calculate the net injection dose. Net ID was not statistically different between the Control and the UDCA groups in all radiopharmaceutical experiements (Table 1). Total body radioactivity (TBA) measured just after radiotracer injection was similar between the Control and the UDCA groups in all experiments. The TBAs after all 5 image acquisition time points were generally lower in the UDCA group, except in the Tc-99m DMSA experiment. However, there were no significant differences between the 2 groups (Fig. 7 and Table 1).
Table 1
Net injection dose (Net ID) and total body radioactivity (TBA) measured by dose calibrator after image acquisition
| Group | UDCA dose (mg) | Net ID* (kBq) | TBA† (kBq) |
Tc-99m HDP | Control | 0 | 75.887 ± 4.366 | 23.754 ± 3.441 |
UDCA | 5 | 75.500 ± 6.142 | 21.238 ± 2.516 |
Tc-99m HDP | Control | 0 | 68.672 ± 7.289 | 19.573 ± 4.958 |
UDCA | 10 | 68.833 ± 7.067 | 19.129 ± 3.885 |
Tc-99m pertechnetate | Control | 0 | 74.958 ± 5.772 | 32.227 ± 3.709 |
UDCA | 10 | 74.178 ± 5.180 | 29.822 ± 3.848 |
Tc-99m DMSA | Control | 0 | 64.010 ± 6.586 | 34.780 ± 3.922 |
UDCA | 10 | 65.305 ± 5.883 | 35.076 ± 4.070 |
* ID : injection dose † TBA : total body radioactivity |
Tc-99m MAG3 image interpretation
Time-activity curves of radioactivity in the kidneys in the 2 groups were drawn and compared. Because renal function may differ between the 2 kidneys in the same animals, whole-kidney radioactivity was used to draw the time-activity curve. Time to peak renal activity (Tmax) and half-time of renal activity (T1/2) were shorter in the UDCA group (Tmax = 3.430 min; T1/2 = 17.432 min) than in the Control group (Tmax = 4.134 min; T1/2 = 23.321 min). Tmax and T1/2 are shown on the kidney time-activity curve (Fig. 8).
Radioactivity and Radioactivity/TBA (%) of soft tissue, both kidneys, and the bladder were compared at the time points of 2, 5, 10, 15, 20, 25, and 30 min.
At 2 min, Radioactivity and Radioactivity/TBA (%) of the kidney were greater in the UDCA group than in the Control group, which suggested early accumulation of Tc-99m MAG3 in the kidneys in the UDCA group similar to Tc-99m DMSA experiment (Tc-99m MAG3 kidney Radioactivity, Control : UDCA = 16.361 ± 1.456 MBq : 19.000 ± 1.477 MBq, P = 0.014), (kidney Radioactivity/TBA(%), Control : UDCA = 33.639 ± 3.000% : 36.882 ± 1.515%, P = 0.035).
At the 5 and 10 min time points, Radioactivity/TBA (%) of the soft tissue in the UDCA group was lower than that of the Control group (5 min, Control : UDCA = 52.907 ± 3.292% : 48.215 ± 1.063%, P-value = 0.001), (10 min, Control : UDCA = 40.051 ± 4.344% : 36.066 ± 2.529%, P = 0.022).
At the 15 min time point, Radioactivity/TBA (%) of the soft tissue in the Control group was higher than that of the UDCA group, however, the P-value was 0.051 (15 min, Control : UDCA = 32.793 ± 3.986% : 29.532 ± 2.793%, P = 0.051).
At the 20, 25, and 30 min time points, there was no difference between the 2 groups in Radioactivity and Radioactivity/TBA of soft tissue, both kidneys, and the bladder. Figure 9 demonstrates Radioactivity/TBA (%) curves of the soft tissue and bladder. An asterisk (*) indicates statistical significance.
Net ID and peak radioactivity of the kidney did not differ between the 2 groups (net ID, Control : UDCA = 51.282 ± 1.998 MBq: 52.392 ± 1.110 MBq, peak radioactivity of the kidney, Control : UDCA = 19.729 ± 3.279 MBq: 22.036 ± 3.008 MBq).