CPET - Automated Input Measurement

(Phase II - non-invasive approach)

15O Arterial Time Activity Curve (TAC)

Questions about this project should be addressed to: Brian Murphy - brian@petnet.buffalo.edu. The data here is preliminary (put up as we take it) and this page is primarily for internal communication within the department as this project develops.

Purpose

Design a non-invasive detector system to replace the arterial line methodology we currently use for the quantitation of a 15O input function. Motivation: Ed Bednarczyk who used a similar system in Cleveland. Detector/Shielding design and initial data: Joe Vilani.

In brief: A small 511 keV detector/PMT placed approximately 15[cm] below the acquisition bed and directed at the paitent's lung field.

1st Data (7/15/97): This is an overlay of a curve from our current MCS system and the new system acquired from a subject. The new system's data was arbitrarily amplitude scaled and time shifted to get its peak to coincide with the MCS peak.

• GAM = counts from new system. GAM counts collected at 0.1[sec] have been summed into [0.5]sec bins to match the time base for the BET data.
• BET = counts from old system
• 1st graph is raw data (synchronized time base);
• 2nd graph is raw data with the GAM curve shifted and scaled to best co-register the small saw-tooth like pattern at the peak's top
• Note the regular patter in the GAM tail with a period of just over 5 sec.(breathing?).

• MCS (blue)= current arterial line method
• a*BED(t+s) (red)= time shifted and amplitude scaled signal from the new detector system (signal is noisier in part because acquisition intervals were 100[ms] for this system, and 500[ms] for the MCS system).
• BG (grey) = new system - old system .... approximation of background on the new system (assuming that's where the additional signal is coming from. This needs to be verified).

Other sites and their solutions

coincidence detector - R. Paul Maguire; PET Program, Paul Scherrer Institute

Future Work

• reduce acceptance angle on the new system in an attempt to reduce background signal in the tail.
• move detector over to the existing MCS electronics
• obtain a deadtime curve for the new system
• calibrate the new system
• develop a mechanism for making attenuation corrections in the new system (since these will likely vary with patient size).
• compare to our current gold standard (MCS).