A moving liver phantom in an anthropomorphic thorax for SPECT MP imaging

Abstract

Cranio-caudal respiratory motion and liver activity cause a variety of complex myocardial perfusion (MP) artifacts, especially in the inferior myocardial wall, that may also mask cardiac defects. To assess and characterise such artifacts, an anthropomorphic thorax with moving thoracic phantoms can be utilised in SPECT MP imaging. In this study, a liver phantom was developed and anatomically added into an anthropomorphic phantom that also encloses an ECG beating cardiac phantom and breathing lungs’ phantom. A cranio-caudal respiratory motion was also developed for the liver phantom and it was synchronised with the corresponding ones of the other thoracic phantoms. This continuous motion was further divided into isochronous dynamic respiratory phases, from end-exhalation to end-inspiration, to perform SPECT acquisitions in different respiratory phases. The new motions’ parameters and settings were measured by mechanical means and also validated in a clinical environment by acquiring CT images and by using two imaging software packages. To demonstrate the new imaging capabilities of the phantom assembly, SPECT/CT MP acquisitions were performed and compared to previous phantom and patients studies. All thoracic phantoms can precisely perform physiological motions within the anthropomorphic thorax. The new capabilities of the phantom assembly allow to perform SPECT/CT MP acquisitions for different cardiac-liver activity ratios and cardiac-liver proximities in supine and, for first time, in prone position. Thus, MP artifacts can be characterised and motion correction can be performed due to these new capabilities. The impact of artifacts and motion correction on defect detection can be also investigated.

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“…Therefore, the developed simulation models can be used to validate new types of tools or to learn surgical techniques. These consist of thoracic-and organ phantoms [3][4][5][6][7][8], tissue phantoms [9][10][11][12] and head and brain phantoms [13][14][15][16][17][18][19], which are especially signi cant for neurosurgery. This also includes neurovascular phantoms that re ect the anatomy of the vessels inside the brain.…”

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“…Cardiac phantoms have been developed by many groups to address the costs and impracticalities of current commercially available phantoms [3] and to create myocardial left ventricle phantoms with a variety of defects to assess image quality for different pathology-mimicking scenarios [4]. A moving 3D printed liver phantom was designed to characterise the effect of liver motion and impact on defect detection in myocardial perfusion imaging at various liver-tomyocardial proximities [5].…”

Phantoms to simulate gastrointestinal artefact in MPI

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We thank Panagi et al [1] for their thoughtful approach to constructing a liver phantom for myocardial perfusion imaging (MPI). There are a number of sources within the gastrointestinal system which may be responsible for artefacts in MPI (in terms of motion, scatter and attenuation).

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