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Determination of mass attenuation coefficient of polylactic acid using gamma densitometry in 50-1000 keV energy range. Radiat Phys Chem Oxf Engl 1993 2020. [DOI: 10.1016/j.radphyschem.2020.109097] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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2
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Soares L, Gobo M, Poletti M. Measurement of the linear attenuation coefficient of breast tissues using polienergetic x-ray for energies from 12 to 50 keV and a silicon dispersive detector. Radiat Phys Chem Oxf Engl 1993 2020. [DOI: 10.1016/j.radphyschem.2019.03.030] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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3
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Measurement of attenuation coefficients and CT numbers of epoxy resin and epoxy-based Rhizophora spp particleboards in computed tomography energy range. Radiat Phys Chem Oxf Engl 1993 2018. [DOI: 10.1016/j.radphyschem.2018.04.001] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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Zeman KL, Wu J, Donaldson SH, Bennett WD. Comparison of 133 xenon ventilation equilibrium scan (XV) and 99m technetium transmission (TT) scan for use in regional lung analysis by 2D gamma scintigraphy in healthy and cystic fibrosis lungs. J Aerosol Med Pulm Drug Deliv 2013; 26:94-100. [PMID: 23421899 DOI: 10.1089/jamp.2012.0982] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
BACKGROUND Quantification of particle deposition in the lung by gamma scintigraphy requires a reference image for location of regions of interest (ROIs) and normalization to lung thickness. In various laboratories, the reference image is made by a transmission scan ((57)Co or (99m)Tc) or gas ventilation scan ((133)Xe or (81)Kr). There has not been a direct comparison of measures from the two methods. METHODS We compared (99m)Tc transmission scans to (133)Xe equilibrium ventilation scans as reference images for 38 healthy subjects and 14 cystic fibrosis (CF) patients for their effects on measures of regional particle deposition: the central-to-peripheral ratio of lung counts (C/P); and ROI area versus forced vital capacity. Whole right lung ROI was based on either an isocontour threshold of three times the soft tissue transmission (TT) or a threshold of 20% of peak xenon ventilation counts (XV). We used a central ROI drawn to 50% of height and of width of the whole right lung ROI and placed along the left lung margin and centered vertically. RESULTS In general, the correlation of normalized C/P (nC/P) between the two methods was strong. However, the value of nC/P was significantly smaller for the XV method than the TT method. Regression equations for the relationship of nC/P between the two methods were, for healthy subjects, y=0.75x+0.61, R(2)=0.64 using rectangular ROIs and y=0.76x+0.45, R(2)=0.66 using isocontour ROIs; and for CF patients, y=0.94x+0.46, R(2)=0.43 and y=0.85x+0.42, R(2)=0.41, respectively. CONCLUSIONS (1) A transmission scan with an isocontour outline in combination with a rectangular central region to define the lung borders may be more useful than a ventilation scan. (2) Close correlation of nC/Ps measured by transmission or gas ventilation should allow confident comparison of values determined by the two methods.
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Affiliation(s)
- Kirby L Zeman
- Center for Environmental Medicine, Asthma and Lung Biology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599, USA
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6
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Freed M, Badal A, Jennings RJ, de las Heras H, Myers KJ, Badano A. X-ray properties of an anthropomorphic breast phantom for MRI and x-ray imaging. Phys Med Biol 2011; 56:3513-33. [PMID: 21606556 DOI: 10.1088/0031-9155/56/12/005] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The purpose of this study is to characterize the x-ray properties of a dual-modality, anthropomorphic breast phantom whose MRI properties have been previously evaluated. The goal of this phantom is to provide a platform for optimization and standardization of two- and three-dimensional x-ray and MRI breast imaging modalities for the purpose of lesion detection and discrimination. The phantom is constructed using a mixture of lard and egg whites, resulting in a variable, tissue-mimicking structure with separate adipose- and glandular-mimicking components. The phantom can be produced with either a compressed or uncompressed shape. Mass attenuation coefficients of the phantom materials were estimated using elemental compositions from the USDA National Nutrient Database for Standard Reference and the atomic interaction models from the Monte Carlo code PENELOPE and compared with human values from the literature. The image structure was examined quantitatively by calculating and comparing spatial covariance matrices of the phantom and patient mammography images. Finally, a computerized version of the phantom was created by segmenting a computed tomography scan and used to simulate x-ray scatter of the phantom in a mammography geometry. Mass attenuation coefficients of the phantom materials were within 20% and 15% of the values for adipose and glandular tissues, respectively, which is within the estimation error of these values. Matching was improved at higher energies (>20 keV). Tissue structures in the phantom have a size similar to those in the patient data, but are slightly larger on average. Correlations in the patient data appear to be longer than those in the phantom data in the anterior-posterior direction; however, they are within the error bars of the measurement. Simulated scatter-to-primary ratio values of the phantom images were as high as 85% in some areas and were strongly affected by the heterogeneous nature of the phantom. Key physical x-ray properties of the phantom have been quantitatively evaluated and shown to be comparable to those of breast tissue. Since the MRI properties of the phantom have been previously evaluated, we believe it is a useful tool for quantitative evaluation of two- and three-dimensional x-ray and MRI breast imaging modalities for the purpose of lesion detection and characterization.
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Affiliation(s)
- Melanie Freed
- Division of Imaging and Applied Mathematics, Office of Science and Engineering Laboratories, Center for Devices and Radiological Health, U.S. Food and Drug Administration, 10903 New Hampshire Avenue, Silver Spring, MD 20993-0002, USA.
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7
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Experimental determination of linear attenuation coefficient of normal, benign and malignant breast tissues. RADIAT MEAS 2010. [DOI: 10.1016/j.radmeas.2010.08.008] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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8
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Wang Z, Heymsfield SB, Chen Z, Zhu S, Pierson RN. Estimation of percentage body fat by dual-energy x-ray absorptiometry: evaluation by in vivo human elemental composition. Phys Med Biol 2010; 55:2619-35. [PMID: 20393230 PMCID: PMC2921899 DOI: 10.1088/0031-9155/55/9/013] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Dual-energy x-ray absorptiometry (DXA) is widely applied for estimating body fat. The percentage of body mass as fat (%fat) is predicted from a DXA-estimated R(ST) value defined as the ratio of soft tissue attenuation at two photon energies (e.g., 40 keV and 70 keV). Theoretically, the R(ST) concept depends on the mass of each major element in the human body. The DXA R(ST) values, however, have never been fully evaluated by measured human elemental composition. The present investigation evaluated the DXA R(ST) value by the total body mass of 11 major elements and the DXA %fat by the five-component (5C) model, respectively. Six elements (i.e. C, N, Na, P, Cl and Ca) were measured by in vivo neutron activation analysis, and potassium (i.e. K) by whole-body (40)K counting in 27 healthy adults. Models were developed for predicting the total body mass of four additional elements (i.e. H, O, Mg and S). The elemental content of soft tissue, after correction for bone mineral elements, was used to predict the R(ST) values. The DXA R(ST) values were strongly associated with the R(ST) values predicted from elemental content (r = 0.976, P < 0.001), although there was a tendency for the elemental-predicted R(ST) to systematically exceed the DXA-measured R(ST) (mean +/- SD, 1.389 +/- 0.024 versus 1.341 +/- 0.024). DXA-estimated %fat was strongly associated with 5C %fat (24.4 +/- 12.0% versus 24.9 +/- 11.1%, r = 0.983, P < 0.001). DXA R(ST) is evaluated by in vivo elemental composition, and the present study supports the underlying physical concept and accuracy of the DXA method for estimating %fat.
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Affiliation(s)
- ZiMian Wang
- Obesity Research Center, St. Luke's-Roosevelt Hospital, Columbia University, College of Physicians and Surgeons, New York, NY, USA.
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9
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Branski LK, Norbury WB, Herndon DN, Chinkes DL, Cochran A, Suman O, Benjamin D, Jeschke MG. Measurement of body composition in burned children: is there a gold standard? JPEN J Parenter Enteral Nutr 2009; 34:55-63. [PMID: 19884353 DOI: 10.1177/0148607109336601] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
BACKGROUND Maintaining lean body mass (LBM) after a severe burn is an essential goal of modern burn treatment. An accurate determination of LBM is necessary for short- and long-term therapeutic decisions. The aim of this study was to compare 2 measurement methods for body composition, whole-body potassium counting (K count) and dual x-ray absorptiometry (DEXA), in a large prospective clinical trial in severely burned pediatric patients. METHODS Two-hundred seventy-nine patients admitted with burns covering 40% of total body surface area (TBSA) were enrolled in the study. Patients enrolled were controls or received long-term treatment with recombinant human growth hormone (rhGH). Near-simultaneous measurements of LBM with DEXA and fat-free mass (FFM) with K count were performed at hospital discharge and at 6, 9, 12, 18, and 24 months post injury. Results were correlated using Pearson's regression analysis. Agreement between the 2 methods was analyzed with the Bland-Altman method. RESULTS Age, gender distribution, weight, burn size, and admission time from injury were not significantly different between control and treatment groups. rhGH and control patients at all time points postburn showed a good correlation between LBM and FFM measurements (R(2) between 0.9 and 0.95). Bland-Altman revealed that the mean bias and 95% limits of agreement depended only on patient weight and not on treatment or time postburn. The 95% limits ranged from 0.1 +/- 2.9 kg for LBM or FFM in 7- to 18-kg patients to 16.3 +/- 17.8 kg for LBM or FFM in patients >60 kg. CONCLUSIONS DEXA can provide a sufficiently accurate determination of LBM and changes in body composition, but a correction factor must be included for older children and adolescents with more LBM. DEXA scans are easier, cheaper, and less stressful for the patient, and this method should be used rather than the K count.
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Affiliation(s)
- Ludwik K Branski
- Department of Surgery, University of Texas Medical Branch, Galveston, Texas, and Shriners Hospitals for Children, Galveston, Texas 77550, USA
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10
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Ayres FJ, Zuffo MK, Rangayyan RM, Boag GS, Filho VO, Valente M. Estimation of the tissue composition of the tumour mass in neuroblastoma using segmented CT images. Med Biol Eng Comput 2004; 42:366-77. [PMID: 15191083 DOI: 10.1007/bf02344713] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Neuroblastoma is the most common extra-cranial, solid, malignant tumour in children. Advances in radiology have made possible the detection and staging of the disease. Nevertheless, there is no method available at present that can go beyond detection and qualitative analysis, towards quantitative assessment of the tissue composition of the primary tumour mass in neuroblastoma. Such quantitative analysis could provide important information and serve as a decision-support tool to the radiologist and the oncologist, result in better treatment and follow-up and even lead to the avoidance of delayed surgery. The problem investigated was the improvement of the analysis of the primary tumour mass, in patients with neuroblastoma, using X-ray computed tomography (CT) images. A methodology was proposed for the estimation of the tissue content of the mass: it comprised a Gaussian mixture model for estimation, from segmented CT images, of the tissue composition of the primary tumour. To demonstrate the potential of the method, the results are presented of its application to ten CT examinations of four patients. The method provides quantitative information, and it was observed that the tumour in one of the patients reduced from 523 cm3 to 81 cm3 in volume, with an increase in calcification from about 20% to about 88% of the tumour volume, in response to chemotherapy over a period of five months. Results indicate that the proposed technique may be of considerable value in assessing the response to therapy of patients with neuroblastoma.
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Affiliation(s)
- F J Ayres
- Department of Electrical & Computer Engineering, University of Calgary, Calgary, Alberta, Canada
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Hakulinen MA, Saarakkala S, Töyräs J, Kröger H, Jurvelin JS. Dual energy x-ray laser measurement of calcaneal bone mineral density. Phys Med Biol 2003; 48:1741-52. [PMID: 12870580 DOI: 10.1088/0031-9155/48/12/305] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
In dual energy x-ray absorptiometry (DXA) the photon attenuation is assumed to be similar in soft tissue overlying, adjacent to and inside the measured bone. In the calcaneal dual energy x-ray laser (DXL) technique, this assumption is not needed as attenuation by soft tissues at the local bone site is determined by combining DXA and heel thickness measurements. In the present study, 38 subjects were measured with DXL Calscan, Lunar PIXI and Lunar DPX-IQ DXA instruments and Hologic Sahara ultrasound instrument, and the performance and agreement of the instruments were analysed. Furthermore, numerical simulations on the effect of non-uniform fat-to-lean tissue ratio within soft tissue in heel were conducted. In vivo short-term precision (CV%, sCV%) of DXL Calscan (1.24%, 1.48%) was similar to that of Lunar PIXI (1.28%, 1.60%). Calcaneal areal bone mineral densities (BMD, g cm(-2)) measured using DXL Calscan and Lunar PIXI predicted equally well variations in BMD of femoral neck (r2 = 0.63 and 0.52, respectively) or lumbar spine (r2 = 0.61 and 0.64, respectively), determined with Lunar DPX-IQ. BMD values measured with DXL Calscan were, on average, 19% lower (p < 0.01) than those determined with Lunar PIXI. Interestingly, the difference in BMD values between instruments increased as a function of body mass index (BMI) (r2 = 0.17, p < 0.02) or heel thickness (r2 = 0.37, p < 0.01). Numerical simulations suggested that the spatial variation of soft tissue composition in heel can induce incontrollable inaccuracy in BMD when measured with the DXA technique. Theoretically, in contrast to DXA instruments, elimination of the effect of non-uniform soft tissue is possible with DXL Calscan.
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Affiliation(s)
- M A Hakulinen
- Department of Applied Physics, University of Kuopio, Kuopio, Finland.
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12
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Testolin CG, Gore R, Rivkin T, Horlick M, Arbo J, Wang Z, Chiumello G, Heymsfield SB. Dual-energy X-ray absorptiometry: analysis of pediatric fat estimate errors due to tissue hydration effects. J Appl Physiol (1985) 2000; 89:2365-72. [PMID: 11090591 DOI: 10.1152/jappl.2000.89.6.2365] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Dual-energy X-ray absorptiometry (DXA) percent (%) fat estimates may be inaccurate in young children, who typically have high tissue hydration levels. This study was designed to provide a comprehensive analysis of pediatric tissue hydration effects on DXA %fat estimates. Phase 1 was experimental and included three in vitro studies to establish the physical basis of DXA %fat-estimation models. Phase 2 extended phase 1 models and consisted of theoretical calculations to estimate the %fat errors emanating from previously reported pediatric hydration effects. Phase 1 experiments supported the two-compartment DXA soft tissue model and established that pixel ratio of low to high energy (R values) are a predictable function of tissue elemental content. In phase 2, modeling of reference body composition values from birth to age 120 mo revealed that %fat errors will arise if a "constant" adult lean soft tissue R value is applied to the pediatric population; the maximum %fat error, approximately 0.8%, would be present at birth. High tissue hydration, as observed in infants and young children, leads to errors in DXA %fat estimates. The magnitude of these errors based on theoretical calculations is small and may not be of clinical or research significance.
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Affiliation(s)
- C G Testolin
- Department of Pediatrics, San Raffaele Hospital, 20132 Milano, Italy
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13
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Abstract
In vivo methods used to study human body composition continue to be developed, along with more advanced reference models that utilize the information obtained with these technologies. Some methods are well established, with a strong physiological basis for their measurement, whereas others are much more indirect. This review has been structured from the methodological point of view to help the reader understand what can be examined with each technique. The associations between the various in vivo methods (densitometry, dilution, bioelectrical impedance and conductance, whole body counting, neutron activation, X-ray absorptiometry, computer tomography, and magnetic resonance imaging) and the five-level multicompartment model of body composition are described, along with the limitations and advantages of each method. This review also provides an overview of the present status of this field of research in human biology, including examples of reference body composition data for infants, children, adolescents, and adults.
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Affiliation(s)
- K J Ellis
- Body Composition Laboratory, United States Department of Agriculture/ARS Children's Nutrition Research Center, Department of Pediatrics, Baylor College of Medicine and Texas Children's Hospital, Houston, Texas, USA.
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Pietrobelli A, Wang Z, Formica C, Heymsfield SB. Dual-energy X-ray absorptiometry: fat estimation errors due to variation in soft tissue hydration. THE AMERICAN JOURNAL OF PHYSIOLOGY 1998; 274:E808-16. [PMID: 9612238 DOI: 10.1152/ajpendo.1998.274.5.e808] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Dual-energy X-ray absorptiometry (DXA) is rapidly gaining acceptance as a reference method for analyzing body composition. An important and unresolved concern is whether and to what extent variation in soft tissue hydration causes errors in DXA fat estimates. The present study aim was to develop and validate a DXA physical hydration model and then to apply this model by simulating errors arising from hypothetical overhydration states. The DXA physical hydration model was developed by first linking biological substance elemental content with photon attenuation. The validated physical model was next extended to describe photon attenuation changes anticipated when predefined amounts of two known composition components are mixed, as would occur when overhydration develops. Two overhydration models were developed in the last phase of study, formulated on validated physical models, and error was simulated for fluid surfeit states. Results indicate that systematic errors in DXA percent fat arise with added fluids when fractional masses are varied as a percentage of combined fluid + soft tissue mass. Three independent determinants of error magnitude were established: elemental content of overhydration fluid, fraction of combined fluid + soft tissue as overhydration fluid, and initial soft tissue composition. Small but systematic and predictable errors in DXA soft tissue composition analysis thus can arise with fluid balance changes.
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Affiliation(s)
- A Pietrobelli
- Obesity Research Center, St. Luke's-Roosevelt Hospital, Columbia University, College of Physicians and Surgeons, New York 10025, USA
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15
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al-Bahri JS, Spyrou NM. Photon linear attenuation coefficients and water content of normal and pathological breast tissues. Appl Radiat Isot 1996; 47:777-84. [PMID: 8828159 DOI: 10.1016/0969-8043(96)00066-8] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Normal and pathological breast tissue samples were scanned using a Photon Transmission Tomography (PTT) technique in order to determine their averaged photon linear attenuation coefficients (mu). Subsequent to being freeze-dried the samples were examined, using a high purity germanium detector (HPGe) and the gamma-rays of energy 59.5 keV from an americium source, and the results were corrected for the water reduction by the use of the Mixture Rule. The ratio of our experimental findings to the published data for mu for various breast tissues were 88, 96 and 88% for adipose, glandular and tumour tissues, respectively. The mean accuracy in our study, investigated relative to standard chemical compounds, was about 3%. The water content of each tissue type was determined as the weight loss during the freeze drying process. This work was initiated in order to evaluate the suitability of new tissue substitute materials for mammography applications.
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Affiliation(s)
- J S al-Bahri
- Department of Physics, University of Surrey, Guildford, UK
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Ito T, Brill AB. Validity of tissue paste standards for quantitative whole-body autoradiography using short-lived radionuclides. INTERNATIONAL JOURNAL OF RADIATION APPLICATIONS AND INSTRUMENTATION. PART A, APPLIED RADIATION AND ISOTOPES 1990; 41:661-7. [PMID: 2170297 DOI: 10.1016/0883-2889(90)90081-q] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
A method of preparing radioactive standards for quantitative whole-body autoradiography (WBARG) using short-lived radionuclides is described and evaluated. Radioactive standards were prepared from bovine brain paste which was mixed with serial dilutions of the radionuclide being studied. Homogeneous distribution of the radionuclide in the brain paste was verified by direct counting and autoradiographic techniques. In addition, there was good agreement between the amounts of radioactivity obtained from quantitative WBARG and tissue counting in all of the major tissues sampled. Therefore, this method is effective for quantitative analysis of WBARG using short-lived radionuclides, for which permanent reference standards are unavailable.
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Affiliation(s)
- T Ito
- Department of Nuclear Medicine, University of Massachusetts Medical Center, Worcester 01655
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Farrell TJ, Webber CE. The error due to fat inhomogeneity in lumbar spine bone mineral measurements. CLINICAL PHYSICS AND PHYSIOLOGICAL MEASUREMENT : AN OFFICIAL JOURNAL OF THE HOSPITAL PHYSICISTS' ASSOCIATION, DEUTSCHE GESELLSCHAFT FUR MEDIZINISCHE PHYSIK AND THE EUROPEAN FEDERATION OF ORGANISATIONS FOR MEDICAL PHYSICS 1989; 10:57-64. [PMID: 2785442 DOI: 10.1088/0143-0815/10/1/006] [Citation(s) in RCA: 33] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
Bone mineral mass measurements using dual photon absorptiometry rely on the assumption that fat thickness is constant within the region scanned by the photon beam. This assumption has been tested using both single and multiple slices from archived CT scans. In 26 patients, the difference in fat content between the bone and baseline measurement sites, the fat deviation, was found to vary from -2.7 to 18.7%. The median fat deviation was 4.4% which can lead to errors in measured lumbar spine bone mineral of 6 to 11%. Approximately one third of patients will have errors greater than 10%.
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Affiliation(s)
- T J Farrell
- Department of Nuclear Medicine, Chedoke-McMaster Hospitals, Ontario, Canada
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18
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Abstract
Normal and neoplastic breast tissues have been characterised in terms of x-ray attenuation. Samples of normal fat and fibrous tissue were obtained from reduction mammoplasty and autopsy, and infiltrating duct carcinoma specimens from mastectomy and lumpectomy. A high-purity germanium spectroscopy system and a beam of 120 kV constant potential x-rays were used to determine the linear attenuation coefficient from 18 to 110 keV. Densities were determined from buoyancy measurements and were used to obtain mass attenuation coefficients. Infiltrating duct carcinomas and fat are well distinguished by x-ray attenuation. For photon energies used for film-screen mammography, infiltrating duct carcinomas are more attenuating than fibrous tissue. Above 31 keV, the ranges of attenuation of the two tissue types overlap. The attenuation coefficients of tissues have been concisely represented by equivalent thicknesses of lucite and aluminium. Analysis based on the average attenuation properties of tissues indicates that dual-energy mammography, using an ideal imaging system, would require 0.06 cGy to provide images in which 1 cm infiltrating duct carcinomas are displayed with a signal to noise ratio of 5 against a background over which the fat/fibrous contrast has been suppressed. This dose is similar to that currently used in conventional film-screen mammography.
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Webber CE. The effect of fat on bone mineral measurements in normal subjects with recommended values of bone, muscle and fat attenuation coefficients. CLINICAL PHYSICS AND PHYSIOLOGICAL MEASUREMENT : AN OFFICIAL JOURNAL OF THE HOSPITAL PHYSICISTS' ASSOCIATION, DEUTSCHE GESELLSCHAFT FUR MEDIZINISCHE PHYSIK AND THE EUROPEAN FEDERATION OF ORGANISATIONS FOR MEDICAL PHYSICS 1987; 8:143-58. [PMID: 3297473 DOI: 10.1088/0143-0815/8/2/005] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Published data concerning the amount, distribution and composition of bone marrow and soft tissue fat in normal subjects are reviewed. Experimental studies of the effect of fat upon bone mineral measurement have been examined. Values of calculated and measured attenuation coefficients for bone, soft tissue and fat in the energy range of interest for bone mineral measurements have been collected and compared. For most measurement sites and in most normal subjects the thickness of fat within bone marrow is comparable with the thickness of the subcutaneous fat layer, although in obese individuals subcutaneous fat thickness can be twice the marrow fat thicknesses. In specific measurement sites there is also a contribution from deep-seated soft tissue fat which is of a similar magnitude to marrow fat. The presence of bone marrow fat alters measured values to the greatest extent in CT measurements of lumbar spine mineral, partly because the incident photon energy is higher than in single and dual photon absorptiometry but also because the fraction occupied by fat in the volume of tissue examined is larger. For scattering techniques the measured value is reduced by the volume fraction occupied by fat. The normal changes in marrow and soft tissue fat observed with aging have little influence on either scattering or transmission measurement. The values of measured and calculated linear attenuation coefficients given by previous workers show reasonable agreement despite considerable differences between measurement techniques and calculation procedures.
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Dale RG. A Monte Carlo derivation of parameters for use in the tissue dosimetry of medium and low energy nuclides. Br J Radiol 1982; 55:748-57. [PMID: 7127026 DOI: 10.1259/0007-1285-55-658-748] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
A technique for deriving the tissue-absorbed dose resulting from the use of a selection of nuclides commonly employed in brachytherapy is given. The various parameters required have been obtained from a Monte Carlo computer program which derives tissue attenuation data from the equations of White and Fitzgerald (1977a). Some inconsistencies in the data used to obtain the equations are noted and corrected. Useful results are presented and, in particular, possible dosimetric errors associated with the clinical use of 125I seeds are highlighted.
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Shrimpton PC. Electron density values of various human tissues: in vitro Compton scatter measurements and calculated ranges. Phys Med Biol 1981; 26:907-11. [PMID: 7291311 DOI: 10.1088/0031-9155/26/5/010] [Citation(s) in RCA: 36] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Brooks RA, Mitchell LG, O'Connor CM, Di Chiro G. On the relationship between computed tomography numbers and specific gravity. Phys Med Biol 1981; 26:141-7. [PMID: 7243863 DOI: 10.1088/0031-9155/26/1/014] [Citation(s) in RCA: 35] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Nutton DH, Harris SJ. Tissue equivalence in neutron dosimetry. Phys Med Biol 1980; 25:1173-80. [PMID: 7208630 DOI: 10.1088/0031-9155/25/6/015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
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Battista JJ, Rider WD, Van Dyk J. Computed tomography for radiotherapy planning. Int J Radiat Oncol Biol Phys 1980; 6:99-107. [PMID: 6154027 DOI: 10.1016/0360-3016(80)90211-4] [Citation(s) in RCA: 48] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Kouris K, Spyrou NM. Usefulness of photon mass attenuation coefficients in elemental analysis. ACTA ACUST UNITED AC 1978. [DOI: 10.1016/0029-554x(78)90994-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Raikar UR, Ganatra RD. Attenuation of monoenergetic photons from 125I in thyroid nodules. INTERNATIONAL JOURNAL OF NUCLEAR MEDICINE AND BIOLOGY 1978; 5:92-4. [PMID: 752661 DOI: 10.1016/0047-0740(78)90033-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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Powell WJ, Wittenberg J, Dinsmore RE, Miller SW, Maturi RA. Definition of cardiac structures using computerized tomography in isolated arrested and beating canine hearts. Am J Cardiol 1977; 39:690-6. [PMID: 855796 DOI: 10.1016/s0002-9149(77)80130-6] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Computerized axial tomography of the brain is a revolutionary noninvasive technique that has provided remarkable resolution of intracerebral structures. This study was undertaken to determine the potential of computerized tomography for defining the anatomy of 40 arrested and 9 beating (ejecting left heart preparation) canine hearts. Using an EMI cranial unit, scanning was performed in hearts under in vitro conditions with a lactated Ringer's interface. The tomographic scans obtained were later compared with comparable 8 mm thick sections of the heart. At physiologic levels of hematocrit (range 36 to 45%) external structures were well defined, but because of the lack of a differential between cavitary and myocardial densities, it was not possible to distinguish intracardiac structures. With very small amounts of iodinated contrast material (remotely administered in the case of the beating hearts) or with anemia (hematocrit less than 33%), the right and left ventricular cavities became clearly visible in both horizontal and longitudinal tomographic scans. It was possible to distinguish readily the boundaries of the ventricular and atrial cavities, the papillary muscles, the major trabeculae and the aorta. Rhythmic motion of the beating heart, suspended in its pericardium, did not eliminate structural definition. Thus, computerized tomography provides a new approach to the definition of cardiac structure with a relatively high degree of resolution. These observations point to the potential usefulness of this noninvasive technique for the evluation of both cardiac function and ventricular wall abnormalities.
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Powell WJ, wittenberg J, Maturi RA, Dinsmore RE, Miller SW. Detection of edema associated with myocardial ischemia by computerized tomography in isolated, arrested canine hearts. Circulation 1977; 55:99-108. [PMID: 851470 DOI: 10.1161/01.cir.55.1.99] [Citation(s) in RCA: 53] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
This study was undertaken to determine if computerized tomography (CT scanning) with an EMI cranial scanner could detect edema associated with myocardial ischemia in canine hearts. A localized area of decreased density in the posterior papillary muscle and surrounding myocardium was detected on serial 8 mm CT scan slices of each heart after 60 min of circumflex artery occlusion and 45 min of reflow of blood. The wet/dry weight ratios and previous electron microscope studies of the ischemic posterior papillary muscles revealed edema accumulation. After 1 hour of arterial occlusion and 12 hours of reflow (which produces extensive necrosis and a decrease in the wet/dry ratio) lesions were still discernible but were less consistently as severe. Permanent ligation of the left anterior descending coronary artery and major collateral arteries for 6 hours also resulted in a lesion of decreased density in the distribution of the occluded arteries. Thus, CT scanning can detect, and is a potential means for sequential noninvasive quantitation of myocardial edema associated with ischemia.
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Brooks RA, Di Chiro G. Principles of computer assisted tomography (CAT) in radiographic and radioisotopic imaging. Phys Med Biol 1976; 21:689-732. [PMID: 788005 DOI: 10.1088/0031-9155/21/5/001] [Citation(s) in RCA: 578] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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