Effects of patient movement on measurements of myocardial blood flow and viability in resting 15O-water PET studies

Abstract

BackgroundPatient movement has been considered an important source of errors in cardiac PET. This study was aimed at evaluating the effects of such movement on myocardial blood flow (MBF) and perfusable tissue fraction (PTF) measurements in intravenous 15O-water PET.MethodsNineteen 15O-water scans were performed on ten healthy volunteers and three patients with severe cardiac dysfunction under resting conditions. Motions of subjects during scans were estimated by monitoring locations of markers on their chests using an optical motion-tracking device. Each sinogram of the dynamic emission frames was corrected for subject motion. Variation of regional MBF and PTF with and without the motion corrections was evaluated.ResultsIn nine scans, motions during 15O-water scan (inter-frame (IF) motion) and misalignments relative to the transmission scan (inter-scan (IS) motion) larger than the spatial resolution of the PET scanner (4.0 mm) were both detected by the optical motion-tracking device. After correction for IF motions, MBF values changed from 0.845 ± 0.366 to 0.780 ± 0.360 mL/minute/g (P < .05). In four scans with only IS motion detected, PTF values changed significantly from 0.465 ± 0.118 to 0.504 ± 0.087 g/mL (P< .05), but no significant change was found in MBF values.ConclusionsThis study demonstrates that IF motion during 15O-water scan at rest can be source of error in MBF measurement. Furthermore, estimated MBF is less sensitive than PTF values to misalignment between transmission and 15O-water emission scans.

A tale of two phases: Can the worst of scans become the best of scans with motion correction?

“…While users can mitigate many technical factors, one that will arguably always be present in one degree or another is patient motion; the impact of which on MBF calculation has been investigated by several authors. 6,7 These studies demonstrate the need for universal access to robust motion correction methods for routine use, in much the same way that myocardial perfusion SPECT has had for many years to adjust raw projection data prior to reconstruction.…”

“…Alternative automated correction techniques may use external markers or monitoring. 6,11 Current commercial implementations of motion compensation focus on periodic respiratory motion and usually involve reconstructing data during the quiet breathing phase. Such data is summed over all breathing cycles during the acquisition, hence is not applicable to more random patient motion that has no regular temporal pattern.…”

Moving towards a better understanding of potential pitfalls in quantitative PET myocardial blood flow

“…10 In addition to these concerns, patient motion can also dramatically impact data acquisition and the fidelity of quantitative PET MBF. 11,12 In contrast to SPECT, where cine raw projection images are available for routine evaluation of patient motion, a conventional clinical PET protocol (static and gated imaging) does not provide the clinician a comparable cine image from which to evaluate patient motion. However, dynamic PET is ''4D imaging'' with a series of tomographic frames, and inter-frame motion of the heart is visible.…”

A Study of the Prevalence of Patient Body Motion and Its Subsequent Correction by Projection Consistency Conditions

“…[43,44,173] The accuracy of MBF quantification is reduced due to these motion effects. [60] A review of motion correction techniques was presented in chapter 1.2. Primarily, motion correction can be performed by applying a tracking protocol using external radioactive, optical markers, cross correlation algorithms in the late time frames or manual realignment.…”