TH‐A‐103‐08: System Optimization of Spectral Breast CT Based On An Energy‐Resolved Photon‐Counting Si Strip Detector: A Simulation Study

Abstract

Purpose: To determine the optimal design parameters for a high resolution spectral breast CT system based on an energy‐resolved photon counting Si strip detector for breast imaging. Methods: A simulation package was developed for a spectral breast CT system. The focal spot size (100 to 300 μm), magnification (1.1 to 1.4), motion blurring and detector pixel size (intrinsic pixel pitch and 4×4 pixel binning) were considered to optimize the system design. Simulations were conducted using single slice fan beam geometry at 60 kVp with 2 mm Al filter. The system modulation transfer functions (MTFs) were calculated from reconstructed image of a 10 μm diameter tungsten wire. The performance of the system with optimal design parameters was evaluated with a simulated breast phantom. A 14 cm diameter cylindrical phantom made of breast tissue with 20% glandularity was used to simulate an average‐sized breast. The soft tissue lesions and microcalcifications were simulated with spheres of glandular tissues (1,2, and 4 mm in diameter) and hydroxyapatite (100 to 250 μm in diameter), respectively. Results: The spatial frequencies at 10 % of the maximum MTF was calculated to be 1.6 lp/mm and 6.4 lp/mm with and without a 4 x 4 pixel binning, respectively. The optimal system magnification was estimated to be 1.2. There was minimal improvement in system MTF when the x‐ray tube focal spot size was changed from 300 to 100 μm. In the simulated breast phantom image, 100 μm microcalcifications can be clearly identified and the soft tissue contrast‐to‐noise ratio was improved with separate image processing, where 4×4 pixel binning was used at a dose level of 6 mGy. Conclusion: The simulation results show that the proposed system can potentially detect micro‐calcifications and soft tissue lesions with a dose level equivalent to that of a standard two‐view mammography.

Quantification of airway dimensions using a high‐resolution CT scanner: A phantom study

“…AAPM Report Task Group 71 reports on the formalism for calculating monitor units. 1 AAPM Task Group 114 reports on methods and requirements for verification of data for conformal external beam plans. 2 The need for monitor unit verification programs was identified early in the adoption of IMRT treatment planning and delivery techniques.…”

“…Alteration of airway function is associated with airflow obstruction and inflammation in patients with chronic obstructive pulmonary disease (COPD) and asthma 1–6 . Advanced computed tomography (CT) techniques have enabled noninvasive quantitative structural measurements of airway dimensions in the clinical settings for improving management of airway diseases 7–10 .…”

“…[7][8][9][10] The CT-based quantification of airway in the segmental and sub-segmental airways has allowed better evaluation of the relationship between lumen narrowing and airflow impairment. 1,3 Despite accurate CT assessments of larger airways with thicker walls, the cross-sectional pathological features in small airways with internal diameters of less than 2 mm have shown to be more critical to airway function. 9,[11][12][13][14] Due to the spatial resolution limitations of CT techniques in the clinical setting, partial volume effects reduce measurement accuracy for both lumen diameters and wall thicknesses.…”

“…12 Hence, the assessment of small airway dimensions up to the 6th generation (~2.5 mm in inner diameter) or higher generations remains challenging. 1,15 Previous investigators have used paired inspiratory and expiratory CT lung scans as imaging biomarkers to allow for the assessment of functional small airways functions in patient with COPD. 16 However, motion artifacts are the major limitation of the subtraction technique when applied with a voxel-by-voxel basis image co-registration method.…”

“…Advanced computed tomography (CT) techniques have enabled noninvasive quantitative structural measurements of airway dimensions in the clinical settings for improving management of airway diseases 7–10 . The CT‐based quantification of airway in the segmental and sub‐segmental airways has allowed better evaluation of the relationship between lumen narrowing and airflow impairment 1,3 …”