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Single-photon transmission measurements in positron tomography using 137Cs
1Department of Nuclear Medicine, McMaster University Medical Centre, Hamilton, Ontario, Canada.
Physics in Medicine and Biology
|July 1, 1995
Summary
This study introduces a new method for positron emission tomography transmission measurements using cesium-137 (137Cs) in singles mode. This approach enhances statistical accuracy and reduces costs compared to traditional methods, enabling more precise radioisotope distribution quantification.
Area of Science:
- Nuclear medicine
- Medical imaging physics
- Radiochemistry
Background:
- Positron tomographic techniques require accurate transmission measurements for quantifying in vivo radioisotope distributions.
- Traditional transmission measurements using coincidence mode limit source selection to positron emitters.
- Increased count rates in singles mode operation significantly improve statistical accuracy of transmission data.
Purpose of the Study:
- To propose and validate Cesium-137 (137Cs) as a suitable radioisotope for transmission measurements in singles mode for positron emission tomography (PET).
- To demonstrate the economic advantages and technical feasibility of using 137Cs compared to Germanium-68 (68Ge).
- To develop methods for extrapolating attenuation coefficients and performing scatter correction for 137Cs transmission measurements.
Main Methods:
- Utilized singles mode photon detection for transmission measurements, bypassing coincidence mode limitations.
- Employed 137Cs as the transmission source, evaluating its cost-effectiveness and half-life advantages over 68Ge.
- Developed a simple extrapolation method to convert 662 keV attenuation coefficients to 511 keV and applied a dual-energy-window technique for scatter correction.
Main Results:
- 137Cs offers a more economical alternative to 68Ge due to its longer half-life and lower cost.
- Transmission measurements using 137Cs in singles mode achieved comparable spatial resolution to annihilation photons without tomograph recalibration.
- Measured linear attenuation coefficients using the developed methods showed agreement with predicted values.
Conclusions:
- Cesium-137 is a viable and cost-effective isotope for transmission measurements in PET using singles mode operation.
- The proposed extrapolation and scatter correction techniques enable accurate attenuation coefficient determination for 137Cs.
- This advancement offers improved statistical accuracy and flexibility in transmission scanning for in vivo radioisotope quantification.