Optimization of dual-energy imaging systems using generalized NEQ and imaging task

Journal Article · Mon Jan 15 04:00:00 EST 2007 · Medical Physics

DOI:https://doi.org/10.1118/1.2400620· OSTI ID:20853903

Richard, S; Siewerdsen, J H ^[1]

---

1. Department of Medical Biophysics, University of Toronto, Ontario, M5G 2M9 (Canada)

Dual-energy (DE) imaging is a promising advanced application of flat-panel detectors (FPDs) with a potential host of applications ranging from thoracic and cardiac imaging to interventional procedures. The performance of FPD-based DE imaging systems is investigated in this work by incorporating the noise-power spectrum associated with overlying anatomical structures (''anatomical noise'' modeled according to a 1/f characteristic) into descriptions of noise-equivalent quanta (NEQ) to yield the generalized NEQ (GNEQ). Signal and noise propagation in the DE imaging chain is modeled by cascaded systems analysis. A Fourier-based description of the imaging task is integrated with the GNEQ to yield a detectability index used as an objective function for optimizing DE image reconstruction, allocation of dose between low- and high-energy images, and selection of low- and high-kVp. Optimal reconstruction and acquisition parameters were found to depend on dose; for example, optimal kVp varied from [60/150] kVp at typical radiographic dose levels ({approx}0.5 mGy entrance surface dose, ESD) but increased to [90/150] kVp at high dose (ESD{approx}5.0 mGy). At very low dose (ESD{approx}0.05 mGy), detectability index indicates an optimal low-energy technique of 60 kVp but was largely insensitive to the choice of high-kVp in the range 120-150 kVp. Similarly, optimal dose allocation, defined as the ratio of low-energy ESD and the total ESD, varied from 0.2 to 0.4 over the range ESD=(0.05-5.0) mGy. Furthermore, two applications of the theoretical framework were explored: (i) the increase in detectability for DE imaging compared to conventional radiography; and (ii) the performance of single-shot vs double-shot DE imaging, wherein the latter is found to have a DQE approximately twice that of the former. Experimental and theoretical analysis of GNEQ and task-based detectability index provides a fundamental understanding of the factors governing DE imaging performance and offers a framework for system design and optimization.

• OSTI ID: 20853903
• Journal Information: Medical Physics, Journal Name: Medical Physics Journal Issue: 1 Vol. 34; ISSN 0094-2405; ISSN MPHYA6
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
DOSIMETRY
IMAGE PROCESSING
IMAGES
NOISE
OPTIMIZATION
PERFORMANCE
RADIATION DOSES
SYSTEMS ANALYSIS