Imaging simulations of an “OpenPET” geometry with shifting detector rings

Self Cite

121

The OpenPET geometry is our new idea to visualize a physically opened space between two detector rings. In this paper, we developed the first small prototype to show a proof-of-concept of OpenPET imaging. Two detector rings of 110 mm diameter and 42 mm axial length were placed with a gap of 42 mm. The basic imaging performance was confirmed through phantom studies; the open imaging was realized at the cost of slight loss of axial resolution and 24% loss of sensitivity. For a proof-of-concept of PET image-guided radiation therapy, we carried out the in-beam tests with (11)C radioactive beam irradiation in the heavy ion medical accelerator in Chiba to visualize in situ distribution of primary particles stopped in a phantom. We showed that PET images corresponding to dose distribution were obtained. For an initial proof-of-concept of real-time multimodal imaging, we measured a tumor-inoculated mouse with (18)F-FDG, and an optical image of the mouse body surface was taken during the PET measurement by inserting a digital camera in the ring gap. We confirmed that the tumor in the gap was clearly visualized. The result also showed the extension effect of an axial field-of-view (FOV); a large axial FOV of 126 mm was obtained with the detectors that originally covered only an 84 mm axial FOV. In conclusion, our initial imaging studies showed promising performance of the OpenPET.

Section: Phantom Experimentsmentioning

confidence: 93%

“…Our previous reports have shown feasibility of OpenPET imaging through numerical simulations (Yamaya et al 2008a(Yamaya et al , 2009b(Yamaya et al , 2009c. In this paper, therefore, we develop the first small prototype to show a proof-of-concept of OpenPET imaging.…”

Section: Introductionmentioning

confidence: 98%

Development of a small prototype for a proof-of-concept of OpenPET imaging

Yamaya¹,

Yoshida²,

Inaniwa³

et al. 2011

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121

“…We have proposed the OpenPET geometry which can provide an accessible open space to the patient during positron emission tomography (PET) scanning (Yamaya et al 2008, 2009a, 2009b, 2011and Yoshida et al 2010. The OpenPET has mainly three types of possible applications: (1) integration of treatment and diagnosis; (2) simultaneous multimodal imaging and (3) entire-body PET with a limited number of detector rings.…”

Section: Introductionmentioning

confidence: 99%

A single-ring OpenPET enabling PET imaging during radiotherapy

Tashima¹,

Yamaya²,

Yoshida³

et al. 2012

Self Cite

We develop an OpenPET system which can provide an accessible open space to the patient during PET scanning. Our first-generation OpenPET geometry which we called dual-ring OpenPET consisted of two separated detector rings and it could extend its axial field of view (FOV) therefore enabling imaging the gap region in addition to the in-ring region. However, applications such as dose verification by in-beam PET measurement during particle therapy and real-time tumor tracking by PET require sensitivity focused onto the gap rather than on the wide FOV. In this paper, we propose a second-generation OpenPET geometry, single-ring OpenPET, which can provide an accessible and observable open space with higher sensitivity and a reduced number of detectors than the earlier one. The proposed geometry has a cylinder shape cut at a slant angle, in which the shape of each cut end becomes an ellipse. We provided a theoretical analysis for sensitivity of the proposed geometry, compared with the dual-ring OpenPET and a geometry where the conventional PET was positioned at a slant angle against the patient bed to form an accessible open space, which we called a slant PET. The central sensitivity depends on the solid angle of these geometries. As a result, we found that the single-ring OpenPET has a sensitivity 1.2 times higher than the dual-ring OpenPET and 1.3 times higher than the slant PET when designed for a 600 mm bed width with 300 mm accessible open space and about 200 detector blocks, each with a front area of 2500 mm². In addition, numerical simulation was carried out to show the imaging property of the proposed geometry realized with the ellipsoidal rings and these results indicate that the depth-of-interaction detector can provide uniform resolution even when the detectors are arranged in an ellipsoidal ring.

“…We are developing an open-geometry PET scanner, OpenPET, which has axially separated detector rings and a physically opened field of view (Yamaya et al 2008, 2009a, 2009b, 2009c, 2011, Yoshida et al 2010, Tashima et al 2012a. The OpenPET geometry can reduce patient stress due to claustrophobia during PET brain imaging.…”

Section: Introductionmentioning

confidence: 99%

An OpenPET scanner with bridged detectors to compensate for incomplete data

Tashima¹,

Yamaya²,

Kinahan³

2014

Self Cite

We are developing an open-type PET 'OpenPET' geometry. One possible geometry is a dual-ring OpenPET, which consists of two detector rings separated by a gap for entrance of a radiotherapy beam or for inserting other modalities. In our previous simulations and experiments the OpenPET imaging geometry was shown to be feasible by applying iterative reconstruction methods. However, the gap violates Orlov's completeness condition for accurate tomographic reconstruction. In this study, we propose a solution for the incompleteness problem by adding bridge detectors to fill in parts of the gaps of the OpenPET geometry; we call this bridged OpenPET. Although this geometry was considered previously, its analytical property was not discussed. Therefore, we applied the direct Fourier method as an analytical reconstruction method to the bridged OpenPET, dual-ring OpenPET and conventional cylindrical PET for comparison. Numerical simulations showed that the additional bridge detectors compensate for the incompleteness of the OpenPET by covering one direction perpendicular to the transaxial slices of the imaging subjects.