Model‐based image reconstruction for four‐dimensional PET

Abstract

Positron emission tonography (PET) is useful in diagnosis and radiation treatment planning for a variety of cancers. For patients with cancers in thoracic or upper abdominal region, the respiratory motion produces large distortions in the tumor shape and size, affecting the accuracy in both diagnosis and treatment. Four-dimensional (4D) (gated) PET aims to reduce the motion artifacts and to provide accurate measurement of the tumor volume and the tracer concentration. A major issue in 4D PET is the lack of statistics. Since the collected photons are divided into several frames in the 4D PET scan, the quality of each reconstructed frame degrades as the number of frames increases. The increased noise in each frame heavily degrades the quantitative accuracy of the PET imaging. In this work, we propose a method to enhance the performance of 4D PET by developing a new technique of 4D PET reconstruction with incorporation of an organ motion model derived from 4D-CT images. The method is based on the well-known maximum-likelihood expectation-maximization (ML-EM) algorithm. During the processes of forward- and backward-projection in the ML-EM iterations, all projection data acquired at different phases are combined together to update the emission map with the aid of deformable model, the statistics is therefore greatly improved. The proposed algorithm was first evaluated with computer simulations using a mathematical dynamic phantom. Experiment with a moving physical phantom was then carried out to demonstrate the accuracy of the proposed method and the increase of signal-to-noise ratio over three-dimensional PET. Finally, the 4D PET reconstruction was applied to a patient case.

Application of Partial Volume Effect Correction and 4D PET in the Quantification of FDG Avid Lung Lesions

“…enabling to account for all information acquired to reduce the noise [8,9]. In addition, breathing irregularities can significantly reduce the quantification accuracy of 4D PET images and results in FDG uptake values that lie between the true (stationary) and non-gated values [13,16,36].…”

“…One of the most commonly used techniques is respiratory gating, which consists in dividing a PET dataset into distinct phases of the respiratory cycle [8,9]. Respiratory cycle information may be obtained with the use of external devices (pressure sensor belts or spirometry systems) or by internal, data-driven methods [10,11].…”

Phased Versus Midventilation Attenuation-Corrected Respiration-Correlated PET for Patients with Non-Small Cell Lung Cancer

“…To overcome this shortcoming, several techniques such as respiration-correlated acquisitions have been proposed (10)(11)(12)(13)(14)(15)(16)(17). In respiration-correlated PET (RCPET)/CT (RCCT), the patient's respiratory signal is recorded during the acquisition of the data.…”

Attenuation Correction Strategies for Positron Emission Tomography/Computed Tomography and 4-Dimensional Positron Emission Tomography/Computed Tomography

“…Model-based image reconstruction can also be applied to 4-dimensional PET, 86 based on the tumor motion from 4-dimensional CT, to deform/register the multiple phases of PET data to a single motion freeze PET data set to reduce the noise in 4-dimensional PET data and to improve PET quantification. 89 …”