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Biomedical subjects

John M Boone

Publications and source records attributed to John M Boone.

At least 19 recordsLinked to original sources
PubMed2006

Computed tomography for imaging the breast.

Despite the success of screening mammography contributing to the reduction of cancer mortality, a number of other imaging techniques are being studied for breast cancer screening. In our laboratory, a dedicated breast computed tomography (CT) system has been developed and is currently undergoing patient testing. The breast CT system is capable of scanning the breast with the woman lying prone on a tabletop, with the breast in the pendant position. A 360 degrees scan currently requires 16.6 s, and a second scanner with a 9-second scan time is nearly operational. Extensive effort was placed on computing the radiation dose to the breast under CT geometry, and the scan parameters are selected to utilize the same radiation dose levels as two-view mammography. A total of 55 women have been scanned, ten healthy volunteers in a Phase I trial, and 45 women with a high likelihood of having breast cancer in a Phase II trial. The breast CT process leads to the production of approximately three hundred 512 x 512 images for each breast. Subjective evaluation of the breast CT images reveals excellent anatomical detail, good depiction of microcalcifications, and exquisite visualization of the soft tissue components of the tumor when contrasted against adipose tissues. The use of iodine contrast injection dramatically enhances the visualization of tumors. While a thorough scientific investigation based upon observer performance studies is in progress, initial breast CT images do appear promising and it is likely that breast CT will play some role in breast cancer imaging.

Breast↗
PubMed2006

An improved method for flat-field correction of flat panel x-ray detector.

In this Technical Note, the effects of different flat-field techniques are examined for a cesium iodide flat panel detector, which exhibited a slightly nonlinear exposure response. The results indicate that the variable flat-field correction method with the appropriate polynomial fit provides excellent correction throughout the entire exposure range. The averaged normalized variation factor, used to assess the nonuniformity of the flat-field correction, decreased from 30.76 for the fixed correction method to 4.13 for the variable flat-field correction method with a fourth-order polynomial fit for the 60 kVp spectrum, and from 16.42 to 3.97 for the 95 kVp spectrum.

Cesium↗
PubMed2006

Quality control for digital mammography: part II. Recommendations from the ACRIN DMIST trial.

The Digital Mammography Imaging Screening Trial (DMIST), conducted under the auspices of the American College of Radiology Imaging Network (ACRIN), is a clinical trial designed to compare the accuracy of digital versus screen-film mammography in a screening population [E. Pisano et al., ACRIN 6652-Digital vs. Screen-Film Mammography, ACRIN (2001)]. Part I of this work described the Quality Control program developed to ensure consistency and optimal operation of the digital equipment. For many of the tests, there were no failures during the 24 months imaging was performed in DMIST. When systems failed, they generally did so suddenly rather than through gradual deterioration of performance. In this part, the utility and effectiveness of those tests are considered. This suggests that after verification of proper operation, routine extensive testing would be of minimal value. A recommended set of tests is presented including additional and improved tests, which we believe meet the intent and spirit of the Mammography Quality Standards Act regulations to ensure that full-field digital mammography systems are functioning correctly, and consistently producing mammograms of excellent image quality.

Breast↗
PubMed2006

A geometric calibration method for cone beam CT systems.

Cone beam CT systems are being deployed in large numbers for small animal imaging, dental imaging, and other specialty applications. A new high-precision method for cone beam CT system calibration is presented in this paper. It uses multiple projection images acquired from rotating point-like objects (metal ball bearings) and the angle information generated from the rotating gantry system is also used. It is assumed that the whole system has a mechanically stable rotation center and that the detector does not have severe out-of-plane rotation (<2 degrees). Simple geometrical relationships between the orbital paths of individual BBs and five system parameters were derived. Computer simulations were employed to validate the accuracy of this method in the presence of noise. Equal or higher accuracy was achieved compared with previous methods. This method was implemented for the geometrical calibration of both a micro CT scanner and a breast CT scanner. The reconstructed tomographic images demonstrated that the proposed method is robust and easy to implement with high precision.

Algorithms↗
PubMed2006

Breast CT: potential for breast cancer screening and diagnosis.

Although screening mammography has been shown to be effective in reducing breast cancer mortality, a new technique called breast computed tomography (CT) is being studied in the hope that breast cancer can be detected even earlier. A prototype unit has been designed, fabricated and tested at the University of California, Davis, USA, and is currently being used in a Phase II clinical trial to study the feasibility of breast CT for breast cancer detection and diagnosis. A total of 46 volunteers and patients have been imaged, and the breast CT images show impressive anatomical detail of the breast that is not appreciated in mammography. The radiation dose levels needed to produce excellent image quality are equal to two-view mammography. Further study of breast CT is needed to better understand its potential role in breast cancer screening and diagnosis.

Breast↗
PubMed2005

Evaluation of x-ray scatter properties in a dedicated cone-beam breast CT scanner.

The magnitude of scatter contamination on a first-generation prototype breast computed tomography (CT) scanner was evaluated using the scatter-to-primary ratio (SPR) metric. The SPR was measured and characterized over a wide range of parameters relevant to breast CT imaging, including x-ray beam energy, breast diameter, breast composition, isocenter-to-detector distance, collimated slot thickness, and grid ratio. The results demonstrated that in the absence of scatter reduction techniques, the SPR levels for the average breast (e.g., 14 cm diameter 50/50 composition cylindrical phantom) are quite high (approximately 0.5 at the center of the phantom for 80 kVp in true cone-beam CT geometry), and increases as the diameter of the phantom is increased (to approximately 1.0 at the center of a 18 cm diameter 50/50 phantom). The x-ray beam energy and the phantom compositions had only minimal impact on the measured SPR. When an ideal bowtie filter was used, the SPRs at the central axis of the 14 and 18 cm cylindrical phantoms were reduced while the SPRs at the edge of the phantoms were increased. Lastly, collimation in the vertical direction had a significant impact on the SPRs at the central axis of the phantoms. These high SPR levels might lead to cupping artifacts and increased noise in the reconstructed CT images, and this suggests that efficient scatter rejection and/or correction techniques may be required to improve the quality and accuracy of cone beam CT images.

Female↗
PubMed2005

Technique factors and their relationship to radiation dose in pendant geometry breast CT.

The use of breast computed tomography (CT) as an alternative to mammography in some patients is being studied at several institutions. However, the radiation dosimetry issues associated with breast CT are markedly different than in the case of mammography. In this study, the spectral properties of an operational breast CT scanner were characterized both by physical measurement and computer modeling of the kVp-dependent spectra, from 40 to 110 kVp (Be window W anode with 0.30 mm added Cu filtration). Previously reported conversion factors, normalized glandular dose for CT-DgN(ct), derived from Monte Carlo methods, were used in concert with the output spectra of the breast scanner to compute the mean glandular dose to the breast based upon different combinations of x-ray technique factors (kVp and mAs). The mean glandular dose (MGD) was measured as a function of the compressed breast thickness (2-8 cm) and three different breast compositions (0%, 50%, and 100% glandular fractions) in four clinical mammography systems in our institution. The average MGD from these four systems was used to compute the technique factors for breast CT systems that would match the two-view mammographic dose levels. For a 14 cm diameter breast (equivalent to a 5 cm thick compressed breast in mammography), air kerma levels at the breast CT scanner's isocenter (468 mm from the source) of 4.4, 6.4, and 9.0 mGy were found to deliver equivalent mammography doses for 0%, 50%, and 100% glandular breasts (respectively) at 80 kVp. At 80 kVp (where air kerma was 11.3 mGy/100 mAs at the isocenter), 57 mAs (integrated over the entire scan) was required to match the mammography dose for a 14 cm 50% glandular breast. At 50 kVp, 360 mAs is required to match mammographic dose levels. Tables are provided for both air kerma at the isocenter and mAs for 0%, 50%, and 100% glandular breasts. Other issues that impact breast CT technique factors are also discussed.

Biophysical Phenomena↗
PubMed2005

X-ray imaging physics for nuclear medicine technologists. Part 2: X-ray interactions and image formation.

The purpose is to review in a 4-part series: (i) the basic principles of x-ray production, (ii) x-ray interactions and data capture/conversion, (iii) acquisition/creation of the CT image, and (iv) operational details of a modern multislice CT scanner integrated with a PET scanner. In part 1, the production and characteristics of x-rays were reviewed. In this article, the principles of x-ray interactions and image formation are discussed, in preparation for a general review of CT (part 3) and a more detailed investigation of PET/CT scanners in part 4.

Nuclear Medicine↗
PubMed2004

A comparison of x-ray detectors for mouse CT imaging.

There is significant interest in using computed tomography (CT) for in vivo imaging applications in mouse models of disease. Most commercially available mouse x-ray CT scanners utilize a charge-coupled device (CCD) detector coupled via fibre optic taper to a phosphor screen. However, there has been little research to determine if this is the optimum detector for the specific task of in vivo mouse imaging. To investigate this issue, we have evaluated four detectors, including an amorphous selenium (a-Se) detector, an amorphous silicon (a-Si) detector with a gadolinium oxysulphide (GOS) screen, a CCD with a 3:1 fibre taper and a GOS screen, and a CCD with a 2:1 fibre taper and both GOS and thallium-doped caesium iodide (CsI:Tl) screens. The detectors were evaluated by measuring the modulation transfer function (MTF), noise power spectrum (NPS), detective quantum efficiency (DQE), stability over multiple exposures, and noise in reconstructed CT images. The a-Se detector had the best MTF and the highest DQE (0.6 at 0 lp mm(-1)) but had the worst stability (45% reduction after 2000 exposure frames). The a-Si detector and the CCD with the 3:1 fibre, both of which used the GOS screen, had very similar performance with a DQE of approximately 0.30 at 0 lp mm(-1). For the CCD with the 2:1 fibre, the CsI:Tl screen resulted in a nearly two-fold improvement in DQE over the GOS screen (0.4 versus 0.24 at 0 lp mm(-1)). The CCDs both had the best stability, with less than a 1% change in pixel values over multiple exposures. The pixel values of the a-Si detector increased 5% over multiple exposures due to the effects of image lag. Despite the higher DQE of the a-Se detector, the reconstructed CT images acquired with the a-Si detector had lower noise levels, likely due to the blurring effects from the phosphor screen.

Algorithms↗
PubMed2004

Automated recognition of lateral from PA chest radiographs: saving seconds in a PACS environment.

Images acquired in a two-view digital chest examination are frequently not electronically distinguishable. As a result the lateral and posterioanterio (PA) images are often improperly positioned on a PACS work station. A series of 1998 chest radiographs (999 lateral, 999 PA or AP) were used to develop a neural network classifier. The images were down-sampled to 16 x 16 matrices, and a feed-forward neural network was trained and tested using the "leave-one-out" method. Using five nodes in the hidden layer, the neural network correctly identified 987 of the 999 test cases (98.8%) (average of six runs). The simple architecture and speed of this technique suggests that it would be a useful addition to PACS work station software. The accumulated time saved by correctly positioning the lateral and PA chest images on the work station monitors in accordance with each radiologist's hanging protocols was estimated to be about 1 week of radiologist time per year.

Electronic Data Processing↗
PubMed2004

Small-animal X-ray dose from micro-CT.

The use of micro-CT in small animals has increased in recent years. Although the radiation levels used for micro-CT are generally not lethal to the animal, they are high enough where changes in the immune response and other biological pathways may alter the experimental outcomes. Therefore, it is important to understand what the doses are for a specific imaging procedure. Monte Carlo simulation was used to evaluate the radiation dose to small animals (5-40 mm in diameter) as a result of X-ray exposure. Both monoenergetic (6-100 keV) and polyenergetic (15-100 kVp) X-ray sources were simulated under typical mouse imaging geometries. X-ray spectral measurements were performed on a mouse imaging X-ray system using a commercially available X-ray spectrometer, and spectra from high-energy systems were used as well. For a typical X-ray system with 1.0 mm of added Al at 40 kVp, the dose coefficients (dose to mouse per air kerma at isocenter) were 0.80, 0.63, 0.52, and 0.44 mGy/mGy for mouse diameters of 10, 20, 30, and 40 mm, respectively. A number of tables and figures are provided for dose estimation over a range of mouse imaging geometries.

Animals↗
PubMed2003

Determination of height, weight, body mass index, and body surface area with a single abdominal CT image.

Techniques for estimation of an individual's height, weight, body mass index (BMI), and body surface area (BSA) with a single abdominal computed tomographic (CT) image were developed. Eighty-seven abdominal CT examinations performed in adult humans were analyzed. Anatomic structures were outlined on the CT section that included L1. Multiple linear regression analysis was used to derive sex-specific predictive equations. Correlation for height was good (r > 0.65). Relationship between predicted weight and actual weight was good (r > 0.93). For BMI and BSA, r was greater than 0.893 and greater than 0.895, respectively. In this study, predictive equations for height, weight, BMI, and BSA were generated.

Body Height↗
PubMed2003

Dose reduction in pediatric CT: a rational approach.

PURPOSE: To determine size-dependent technique factors for pediatric computed tomography (CT) by using physically measured objective data. MATERIALS AND METHODS: Six phantom cylinders (10-32 cm in diameter) were scanned with a clinical multi-detector row CT scanner. CT noise was statistically characterized for CT technique factors from 80 to 140 kVp and from 10 to 300 mAs. Dose measurements were performed with each phantom. Dilute iodine and tissue contrast were determined with computer calculations validated with measured data. The dose, noise, and contrast data were computer fit, and pediatric CT technique factors (milliampere seconds) necessary to maintain the contrast-to-noise ratio (CNR) were computed. RESULTS: As compared with that in a reference cylindric adult abdomen of 28 cm in diameter, CNR was maintained at a constant level in pediatric patients of 25, 20, and 15 cm in diameter, respectively, when milliampere second values of 0.557, 0.196, and 0.054 of the adult milliampere second values were used. The corresponding doses were reduced to 0.642, 0.287, and 0.090 of the 28-cm-diameter adult dose, respectively. CT techniques for examination of pediatric heads measuring 15 and 13 cm, respectively, can involve the use of milliampere second values of 0.572 and 0.366 of those used for examination of a standard 17-cm-diameter adult head. CONCLUSION: CT technique charts for pediatric abdominal and head examinations were produced on the basis of physically measured data; use of these tables will enable pediatric radiation dose to be reduced while CNR is preserved.

Adult↗
PubMed2002

Normalized glandular dose (DgN) coefficients for arbitrary X-ray spectra in mammography: computer-fit values of Monte Carlo derived data.

Normalized glandular dose (DgN) values have been reported by several investigators for specific spectra, however for unconventional or unanticipated x-ray spectra considered for use in mammography, practical methods are not available for DgN computation. In this study, the previously validated SIERRA Monte Carlo code was used to compute the normalized glandular dose coefficients for monoenergetic energies from 8 keV to 50 keV. The overall mammography geometry used was a 65 cm source to image distance, a 1.2 cm air gap between the breast and the detector, and breast thicknesses ranging from 2 to 9 cm. A 4 mm layer of skin was also modeled, and semicircular breast radii of 8.5 cm and 10.0 cm were studied. Breast compositions of 0% glandular, 50% glandular, and 100% glandular were evaluated. The Monte Carlo derived DgN results demonstrated coefficients of variation less than 0.3%. The monoenergetic DgN values, DgN(E), were computer fit using commercial software and the best fit equations are reported. All fits resulted in r2 values of 0.9999 or better. The computer fit equations, along with easy to use spectral modeling routines, are available electronically on the web.

Biophysical Phenomena↗
PubMed2002

Grid and slot scan scatter reduction in mammography: comparison by using Monte Carlo techniques.

PURPOSE: To evaluate a comprehensive array of scatter cleanup techniques in mammography by using a consistent methodology. MATERIALS AND METHODS: Monte Carlo techniques were used to evaluate the Bucky factor (BF) and the contrast improvement factor (CIF) for linear and cellular grids and for slot scan and scanning multiple-slot assembly (SMSA) systems. RESULTS: For a 28-kVp molybdenum anode-molybdenum filter spectrum with a standard detector and a 6-cm-thick 50% adipose-50% glandular breast phantom, slot scan techniques delivered an ideal BF. For slot widths greater than 4 mm, however, the CIF was lower than that achieved by the high-transmission cellular grid with a grid ratio of 3.8:1. A tungsten-septa air-interspaced cellular grid with a 4:1 grid ratio outperformed the high-transmission cellular grid in both BF and CIF. The SMSA was shown to be efficacious when 4-mm-wide slots were separated by at least 20 mm. In comparison with the literature, 3.6% agreement was achieved with other Monte Carlo studies, 3.3% with an experimental study that used a digital detector, and 13%-29% agreement was demonstrated in comparison to film-based experimental studies. CONCLUSION: With use of consistent methods for comparison, cellular grids were shown to substantially outperform linear grids but have slightly higher BFs compared with that of slot scan geometries at the same CIF.

Mammography↗
PubMed2002

Pulmonary embolism in pregnant patients: fetal radiation dose with helical CT.

PURPOSE: To calculate mean fetal radiation dose from helical chest computed tomography (CT) by using maternal-fetal geometries obtained from healthy pregnant women and to compare the calculated CT doses with the fetal doses reported with scintigraphy. MATERIALS AND METHODS: Maternal-fetal geometries were determined in 23 pregnant women with varying body mass index and fetal gestational age. Monte Carlo techniques were used to estimate the dose that would be received by each fetus from CT scanning performed with the following parameters: 120 kVp; 100 mA; scanning time, 1 second per section; collimation, 2.5 mm; pitch of 1. Craniocaudal extent of the scan was 11 cm, with the most caudal section edge being 5 mm inferior to the xiphoid process. RESULTS: For helical CT, estimated mean fetal doses in micrograys at varying gestational ages were as follows: 3.3-20.2 microGy, first trimester; 7.9-76.7 microGy, second trimester; and 51.3-130.8 microGy, third trimester. These values were all less than mean fetal doses reported with scintigraphy, with 37-74 MBq of macroaggregates of human serum albumin labeled with technetium 99m. If 200 mAs (pitch of 1.8) was used, the mean fetal doses were still less than those with scintigraphy. CONCLUSION: The average fetal radiation dose with helical CT is less than that with ventilation-perfusion lung scanning during all trimesters.

Adult↗