Physics of Medical Imaging

Development and validation of a segmentation-free polyenergetic algorithm for dynamic perfusion computed tomography

[+] Author Affiliations
Yuan Lin

Carestream Health Inc., Division of Research and Innovations, 1049 Ridge Road West, Rochester, New York 14615, United States

Ehsan Samei

Duke University, Carl E. Ravin Advanced Imaging Lab, 2424 Erwin Road, Suite 302, Durham, North Carolina 27705, United States

J. Med. Imag. 3(3), 033503 (Aug 23, 2016). doi:10.1117/1.JMI.3.3.033503
History: Received April 3, 2016; Accepted August 5, 2016
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Abstract.  Dynamic perfusion imaging can provide the morphologic details of the scanned organs as well as the dynamic information of blood perfusion. However, due to the polyenergetic property of the x-ray spectra, beam hardening effect results in undesirable artifacts and inaccurate CT values. To address this problem, this study proposes a segmentation-free polyenergetic dynamic perfusion imaging algorithm (pDP) to provide superior perfusion imaging. Dynamic perfusion usually is composed of two phases, i.e., a precontrast phase and a postcontrast phase. In the precontrast phase, the attenuation properties of diverse base materials (e.g., in a thorax perfusion exam, base materials can include lung, fat, breast, soft tissue, bone, and metal implants) can be incorporated to reconstruct artifact-free precontrast images. If patient motions are negligible or can be corrected by registration, the precontrast images can then be employed as a priori information to derive linearized iodine projections from the postcontrast images. With the linearized iodine projections, iodine perfusion maps can be reconstructed directly without the influence of various influential factors, such as iodine location, patient size, x-ray spectrum, and background tissue type. A series of simulations were conducted on a dynamic iodine calibration phantom and a dynamic anthropomorphic thorax phantom to validate the proposed algorithm. The simulations with the dynamic iodine calibration phantom showed that the proposed algorithm could effectively eliminate the beam hardening effect and enable quantitative iodine map reconstruction across various influential factors. The error range of the iodine concentration factors (HU·ml/mg) was reduced from [8.01,14.77] for filtered back-projection (FBP) to [0.05,0.08] for pDP. The quantitative results of the simulations with the dynamic anthropomorphic thorax phantom indicated that the maximum error of iodine concentrations can be reduced from 1.1  mg/cc for FBP to less than 0.1  mg/cc for pDP, which suggested that the proposed algorithm could not only effectively eliminate beam hardening artifacts but also significantly reduce the influence of the metal artifacts and accurately reconstruct the iodine map regardless of the influential factors. A segmentation-free polyenergetic dynamic perfusion imaging algorithm was proposed and validated via simulations. This method can accurately reconstruct artifact-free iodine maps for quantitative analyses.

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© 2016 Society of Photo-Optical Instrumentation Engineers

Citation

Yuan Lin and Ehsan Samei
"Development and validation of a segmentation-free polyenergetic algorithm for dynamic perfusion computed tomography", J. Med. Imag. 3(3), 033503 (Aug 23, 2016). ; http://dx.doi.org/10.1117/1.JMI.3.3.033503


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