A general method for cupping artifact correction of cone-beam breast computed tomography images.

Purpose: Cone-beam breast computed tomography (CBBCT), a promising breast cancer diagnostic technique, has been under investigation for the past decade. However, owing to scattered radiation and beam hardening, CT numbers are not uniform on CBBCT images. This is known as cupping artifact, and it presents an obstacle for threshold-based volume segmentation.

A dual-view digital tomosynthesis imaging technique for improved chest imaging.

Purpose: Digital tomosynthesis (DTS) has been shown to be useful for reducing the overlapping of abnormalities with anatomical structures at various depth levels along the posterior-anterior (PA) direction in chest radiography. However, DTS provides crude three-dimensional (3D) images that have poor resolution in the lateral view and can only be displayed with reasonable quality in the PA view. Furthermore, the spillover of high-contrast objects from off-fulcrum planes generates artifacts that may impede the diagnostic use of the DTS images.

Radiation doses in volume-of-interest breast computed tomography--A Monte Carlo simulation study.

Purpose: Cone beam breast computed tomography (breast CT) with true three-dimensional, nearly isotropic spatial resolution has been developed and investigated over the past decade to overcome the problem of lesions overlapping with breast anatomical structures on two-dimensional mammographic images. However, the ability of breast CT to detect small objects, such as tissue structure edges and small calcifications, is limited. To resolve this problem, the authors proposed and developed a volume-of-interest (VOI) breast CT technique to image a small VOI using a higher radiation dose to improve that region's visibility.

Reduction of ring artifacts in CBCT: detection and correction of pixel gain variations in flat panel detectors.

Purpose: In using flat panel detectors (FPD) for cone beam computed tomography (CBCT), pixel gain variations may lead to structured nonuniformities in projections and ring artifacts in CBCT images. Such gain variations can be caused by change in detector entrance exposure levels or beam hardening, and they are not accounted by conventional flat field correction methods. In this work, the authors presented a method to identify isolated pixel clusters that exhibit gain variations and proposed a pixel gain correction (PGC) method to suppress both beam hardening and exposure level dependent gain variations.

Cone beam breast CT with a high pitch (75 μm), thick (500 μm) scintillator CMOS flat panel detector: visibility of simulated microcalcifications.

Purpose: To measure and investigate the improvement of microcalcification (MC) visibility in cone beam breast CT with a high pitch (75 μm), thick (500 μm) scintillator CMOS/CsI flat panel detector (Dexela 2923, Perkin Elmer).

Methods: Aluminum wires and calcium carbonate grains of various sizes were embedded in a paraffin cylinder to simulate imaging of calcifications in a breast. Phantoms were imaged with a benchtop experimental cone beam CT system at various exposure levels.

Effects of exposure equalization on image signal-to-noise ratios in digital mammography: a simulation study with an anthropomorphic breast phantom.

Purpose: The scan equalization digital mammography (SEDM) technique combines slot scanning and exposure equalization to improve low-contrast performance of digital mammography in dense tissue areas. In this study, full-field digital mammography (FFDM) images of an anthropomorphic breast phantom acquired with an anti-scatter grid at various exposure levels were superimposed to simulate SEDM images and investigate the improvement of low-contrast performance as quantified by primary signal-to-noise ratios (PSNRs).

Methods: We imaged an anthropomorphic breast phantom (Gammex 169 "Rachel," Gammex RMI, Middleton, WI) at various exposure levels using a FFDM system (Senographe 2000D, GE Medical Systems, Milwaukee, WI).

High resolution dual detector volume-of-interest cone beam breast CT--Demonstration with a bench top system.

Purpose: In this study, we used a small field high resolution detector in conjunction with a full field flat panel detector to implement and investigate the dual detector volume-of-interest (VOI) cone beam breast computed tomography (CBCT) technique on a bench-top system. The potential of using this technique to image small calcifications without increasing the overall dose to the breast was demonstrated. Significant reduction of scatter components in the high resolution projection image data of the VOI was also shown.

Radiation doses in cone-beam breast computed tomography: a Monte Carlo simulation study.

Purpose: In this article, we describe a method to estimate the spatial dose variation, average dose and mean glandular dose (MGD) for a real breast using Monte Carlo simulation based on cone beam breast computed tomography (CBBCT) images. We present and discuss the dose estimation results for 19 mastectomy breast specimens, 4 homogeneous breast models, 6 ellipsoidal phantoms, and 6 cylindrical phantoms.

Methods: To validate the Monte Carlo method for dose estimation in CBBCT, we compared the Monte Carlo dose estimates with the thermoluminescent dosimeter measurements at various radial positions in two polycarbonate cylinders (11- and 15-cm in diameter).

Comparison of scatter rejection and low-contrast performance of scan equalization digital radiography (SEDR), slot-scan digital radiography, and full-field digital radiography systems for chest phantom imaging.

Purpose: To investigate and compare the scatter rejection properties and low-contrast performance of the scan equalization digital radiography (SEDR) technique to the slot-scan and conventional full-field digital radiography techniques for chest imaging.

Methods: A prototype SEDR system was designed and constructed with an a-Se flat-panel (FP) detector to improve image quality in heavily attenuating regions of an anthropomorphic chest phantom. Slot-scanning geometry was used to reject scattered radiation without attenuating primary x rays.

Scan equalization digital radiography (SEDR) implemented with an amorphous selenium flat-panel detector: initial experience.

It is well recognized in projection radiography that low-contrast detectability suffers in heavily attenuating regions due to excessively low x-ray fluence to the image receptor and higher noise levels. Exposure equalization can improve image quality by increasing the x-ray exposure to heavily attenuating regions, resulting in a more uniform distribution of exposure to the detector. Image quality is also expected to be improved by using the slot-scan geometry to reject scattered radiation effectively without degrading primary x-rays.

Reduction in x-ray scatter and radiation dose for volume-of-interest (VOI) cone-beam breast CT--a phantom study.

With volume-of-interest (VOI) cone-beam computed tomography (CBCT) imaging, one set of projection images are acquired with the VOI collimator at a regular or high exposure level and the second set of projection images are acquired without the collimator at a reduced exposure level. The high exposure VOI scan data inside the VOI and the low exposure full-field scan data outside the VOI are then combined together to generate composite projection images for image reconstruction. To investigate and quantify scatter reduction, dose saving and image quality improvement in VOI CBCT imaging, a flat panel detector-based bench-top experimental CBCT system was built to measure the dose, the scatter-to-primary ratio (SPR), the image contrast, noise level, the contrast-to-noise ratio (CNR) and the figure of merit (FOM) in the CBCT reconstructed images for two polycarbonate cylinders simulating the small and the large phantoms.

Dual resolution cone beam breast CT: a feasibility study.

Purpose: In this study, the authors investigated the feasibility of a dual resolution volume-of-interest (VOI) cone beam breast CT technique and compared two implementation approaches in terms of dose saving and scatter reduction.

Methods: With this technique, a lead VOI mask with an opening is inserted between the x-ray source and the breast to deliver x-ray exposure to the VOI while blocking x rays outside the VOI. A CCD detector is used to collect the high resolution projection data of the VOI.

Use of intra-arterial chemotherapy and embolization before limb salvage surgery for osteosarcoma of the lower extremity.

We report our experience with the use of intra-arterial chemotherapy and embolization before limb salvage surgery in patients with osteosarcoma of the lower extremity. We evaluated the effect of this procedure on the degree of tumor necrosis and on the amount of blood loss during surgery. We reviewed the medical records of all patients who received intra-arterial chemotherapy and embolization before undergoing limb salvage surgery for osteosarcoma of the lower extremity at our institution between January 2003 and April 2008.

Feasibility of volume-of-interest (VOI) scanning technique in cone beam breast CT--a preliminary study.

This work is to demonstrate that high quality cone beam CT images can be generated for a volume of interest (VOI) and to investigate the exposure reduction effect, dose saving, and scatter reduction with the VOI scanning technique. The VOI scanning technique involves inserting a filtering mask between the x-ray source and the breast during image acquisition. The mask has an opening to allow full x-ray exposure to be delivered to a preselected VOI and a lower, filtered exposure to the region outside the VOI.

Scatter rejection and low-contrast performance of a slot-scan digital chest radiography system with electronic aft-collimation: a chest phantom study.

Anti-scatter grids have been widely used to reject scatter and increase the perceptibility of low-contrast object in chest radiography; however they also attenuate the primary x-rays, resulting in a substantial degradation of primary information. Compensation for this degradation requires the use of higher exposure technique hence higher dose to the patient. A more efficient approach to reject scatter is the slot-scan imaging technique which employs a narrow scanning x-ray fan beam in conjunction with a slit or slot shaped solid state detector or an area detector used with an aft-collimator.

Spatial resolution properties in cone beam CT: a simulation study.

This work is intended to investigate the spatial resolution properties in cone beam CT by estimating the point spread functions (PSFs) in the reconstructed 3D images through simulation. The point objects were modeled as 3D delta functions. Their projections onto the detector plane were analytically derived and blurred with 2D PSFs estimated and used to represent the detector and focal spot blurring effects.

Comparison of two detector systems for cone beam CT small animal imaging - a preliminary study.

To compare two detector systems - one based on the charge-coupled device (CCD) and image amplifier, the other based on a-Si/CsI flat panel, for cone beam computed-tomography (CT) imaging of small animals.A high resolution, high framing rate detector system for the cone beam CT imaging of small animals was developed. The system consists of a 2048x3072x12 bit CCD optically coupled to an image amplifier and an x-ray phosphor screen.

Dedicated cone-beam breast CT: feasibility study with surgical mastectomy specimens.

Objective: The purpose of this study was to investigate the feasibility of diagnostic breast imaging using a flat-panel detector-based cone-beam CT system.

Conclusion: Imaging of 12 mastectomy specimens was performed at 50-80 kVp with a voxel size of 145 or 290 microm. Our study shows that cone-beam breast CT images have exceptional tissue contrast and can potentially reduce examination time with comparable radiation dose.

Visibility of microcalcification in cone beam breast CT: effects of X-ray tube voltage and radiation dose.

Mammography is the only technique currently used for detecting microcalcification (MC) clusters, an early indicator of breast cancer. However, mammographic images superimpose a three-dimensional compressed breast image onto two-dimensional projection views, resulting in overlapped anatomical breast structures that may obscure the detection and visualization of MCs. One possible solution to this problem is the use of cone beam computed tomography (CBCT) with a flat-panel (FP) digital detector.

Cone Beam Breast CT with a Flat Panel Detector- Simulation, Implementation and Demonstration.

This paper describes our experiences in the simulation, implementation and application of a flat panel detector based cone beam computed tomography (CT) imaging system for dedicated 3-D breast imaging. In our simulation study, the breast was analytically modeled as a cylinder of breast tissue loosely molded into cylindrical shape with embedded soft tissue masses and calcifications. Attenuation coefficients for various types of breast tissue, soft tissue masses and calcifications were estimated for various kVp's to generate simulated image signals.

Comparison of full-field digital mammography and screen-film mammography for detection and characterization of simulated small masses.

Objective: The two objectives of this study were to create an ex vivo phantom model that closely mimics human breast cancer for detection tasks and to compare the performance of full-field digital mammography with screen-film mammography in detecting and characterizing small breast masses in a phantom with a spectrum of complex tissue backgrounds.

Materials And Methods: Sixteen phantom breast masses of varying sizes (0.3-1.

Receiver operating characteristic analysis for the detection of simulated microcalcifications on mammograms using hardcopy images.

The aim of this study was to compare mammography systems based on three different detectors--a conventional screen-film (SF) combination, an a-Si/CsI flat-panel (FP)-based detector, and a charge-coupled device (CCD)-based x-ray phosphor-based detector--for their performance in detecting simulated microcalcifications (MCs). 112-150 microm calcium carbonate grains were used to simulate MCs and were overlapped with a slab phantom of simulated 50% adipose/50% glandular breast tissue-equivalent material referred to as the uniform background. For the tissue structure background, 200-250 microm calcium carbonate grains were used and overlapped with an anthropomorphic breast phantom.

Visibility of simulated microcalcifications--a hardcopy-based comparison of three mammographic systems.

Full-field digital mammography systems are currently available for clinical use. These digital systems offer improved image quality, flexible image processing, display, storage, retrieval, and transmission. These systems employ a variety of different x-ray detectors based on storage phosphors (in computed radiography), charge-coupled devices (CCDs), or amorphous silicon flat panels (FPs).

Microcalcification detectability for four mammographic detectors: flat-panel, CCD, CR, and screen/film).

Amorphous silicon/cesium iodide (a-Si:H/CsI:Tl) flat-panel (FP)-based full-field digital mammography systems have recently become commercially available for clinical use. Some investigations on physical properties and imaging characteristics of these types of detectors have been conducted and reported. In this perception study, a phantom containing simulated microcalcifications (microCs) of various sizes was imaged with four detector systems: a FP system, a small field-of-view charge coupled device (CCD) system, a high resolution computed radiography (CR) system, and a conventional mammography screen/film (SF) system.