Enhancing PET/CT target assessment with porous 3D printed grids: a pilot study

Phantom experiments are widely used for standardisation in positron emission tomography (PET), but current practices do not necessarily reflect clinical reality and require meticulous phantom preparation for repeatability. 3D printing can reduce these limitations by optimizing preparatory methods and improving phantom features. This work proposes employing 3D-printed porous grids as an alternative mechanism to emulate targets with contrast. Acrylonitrile butadiene styrene (ABS) cubic grids (4 cm/side) with varying design characteristics and targets were printed. Grids were immersed in a [¹⁸F]FDG solution with soap within a conventional phantom. Five consecutive acquisitions were repeated on five different days (Day 0, 1, 4-6) using a Discovery MI PET/CT. Target representation index (TRI) (analogous to recovery coefficient) and dilution coefficient (DC) were the metrics used for the analysis. Friedman test was utilized for statistical inference across days. PET images resulted in clear demarcation of various contrast regions produced by the dilution grid. Quantitative metrics showed consistent results across trials, confirming robustness. Dilution coefficient achieved (mean ± std. dev.) were 0.55 ± 0.05, 0.41 ± 0.06, and 0.33 ± 0.03 versus 0.5, 0.4 and 0.3 (theoretical), falling within 10% threshold. Observed TRI_{max, mean} were in range of 0.4-1.2. Correlation across days was strong for TRI_{max, mean} (p-values ≥ 0.67) but the DC_max (p-values ~ 0.03) values denoted minor bias in generated contrast due to noise. 3D-printed grids offer a reliable, reproducible alternative for PET/CT assessment. 27 hot targets with varying contrasts and size were produced with a single tracer administration and the metrics stayed stable across different acquisitions.