Are the simplified methods to estimate K_i in ~(18)F-FDG PET studies feasible in clinical routine? Comparison between three simplified methods

摘要

BACKGROUND: The aim of this study was to verify the feasibility, in clinical practice, of three simplified methods (Hunter, Sadato and another one proposed by our group) to calculate Ki and MR_(glu) of ~(18)F-FDG, comparing the results with those derived by the linear regression (LR) method (considered the golden standard), and also with SUV.METHODS: Forty-five patients (32males, mean age 69±9years) with non-small-cell-lung cancer prospectively enrolled, underwent dynamic ~(18)F-FDG PET-CT over the thorax. K_i was estimated as follows: from a static acquisition and performing one venous blood sampling using the Hunter method; multiplying the SUV for the average plasma clearance rate (k_P(T)) and for the initial distribution volume (V_(Obw)) without performing any blood sampling using the Sadato method; multiplying the SUV for a factor F (which encompasses the mean value of haematocrit and plasma volume, both according to patient's sex) without performing any blood sample using ours method. Wilcoxon signed rank and coefficient of determination (R~2) were used for statistical analysis.RESULTS: No significant difference was observed between the K_i and MR_(glu) estimated by all three simplified methods and the K_i and MR_(glu) estimated by LR. The highest P values and the lower values of mean differences were observed with our method compared with LR: K_i =0.0392±0.0178 min~(-1) vs. K_i=0.0392±0.0202 min~(-1) (P=0.897, MD=0.0001 min~(-1)), respectively; MR_(glu)= 4.47±2.23 ml/min/100g vs. MR_(glu)= 4.43±2.38 ml/min/100g (P=0.839, MD= -0.0373 mL/min/100g), respectively. The highest correlation was observed between the K_i estimated by both Hunter and our methods and the K_i estimated by LR: R~2=0.87, R~2=0.86, respectively. A good correlation (R2=0.83) was observed between SUV and K_i estimated by LR.CONCLUSIONS: These three simplified methods represent a valid alternative to the more invasive and complex full kinetic analysis. Their "pros" are: the non-invasiveness, the feasibility, the good correlation with the golden standard; their "cons" is that full kinetic analysis provides highest accuracy in K_i determination. Therefore, in clinical oncology routine, the nuclear physicians can choose among different simplified methods especially for monitoring the response to treatment, for tumour grading, and for prognostic stratification, letting the full kinetic analysis to specific centre/studies.