Absolute radiotracer concentration measurement using whole-body solid-state SPECT/CT technology: in vivo/in vitro...

Area of Science:

• Nuclear Medicine
• Medical Imaging
• Quantitative Analysis

Background:

• Quantitative clinical software is crucial for accurate medical imaging analysis.
• Solid-state Cadmium-Zinc-Telluride (CdZnTe) SPECT/CT cameras offer advanced imaging capabilities.
• Validating software accuracy with in vivo and in vitro measurements is essential.

Purpose of the Study:

• To determine the accuracy of recently approved quantitative clinical software for solid-state SPECT/CT.
• To compare in vivo measurements from SPECT/CT with in vitro measurements from urine samples.
• To assess the reliability of quantitative software in measuring radiotracer concentration in the urinary bladder.

Main Methods:

• Performed Bone SPECT/CT on 16 patients using technetium-99m methylene diphosphonic acid.
• Collected urine samples for in vitro radiopharmaceutical concentration measurement.
• Used quantitative software (Q.Metrix, GE Healthcare) to measure in vivo radiotracer concentration and Standardized Uptake Value (SUV) in the bladder from SPECT/CT images.
• Employed linear regression to validate in vivo/in vitro relations.

Main Results:

• Thirteen in vivo/in vitro pairs were analyzed after excluding outliers.
• All linear regressions showed strong identity relations (R² ≥ 0.85, P < 0.0001).
• Average SUV measurements across users yielded a slope of 0.99 ± 0.25 and intercept of 0.14 ± 5.15 g/mL, with an average residual difference < 20%.

Conclusions:

• Solid-state SPECT/CT imaging reliably quantifies in vivo urinary bladder radiotracer concentrations with approximately 20% accuracy.
• The quantitative software demonstrates accuracy in measuring radiotracer uptake.
• This non-invasive in vivo quantification method holds potential for improved diagnosis and treatment response assessment.