Computerized Evaluation of Mammographic Lesions:What Diagnostic Role Does the Shape of the Individual Microcalcifications Play Compared with the Geometry of the Cluster?

OBJECTIVE

The objective of this study was to compare the diagnostic role of features reflecting the geometry of clusters with features reflecting the shape of the individual microcalcification in a mammographic computer-aided diagnosis system.

MATERIALS AND METHODS

Three hundred twenty-four cases of clustered microcalcifications with biopsy-proven results were digitized at 42-microm resolution and analyzed on a computerized system. The shape factor and number of neighbors were computed for each microcalcification, and the eccentricity of the cluster was computed as well. The shape factor is related to the individual microcalcification; the average number of neighbors and the cluster eccentricity reflect the cluster geometry. Stepwise discriminant analysis was used to evaluate the contribution of the extracted features in predicting malignancy. The performance of a classifier based on the features selected by stepwise discriminant analysis was evaluated by receiver operating characteristic (ROC) analysis.

RESULTS

To obtain the best discrimination model, we used stepwise discriminant analysis to select the average number of neighbors and the shape of the individual microcalcification, but excluded cluster eccentricity. A classification scheme assigned the average number of neighbors a weighting factor, which was 1.49 times greater than that assigned to the shape factor of the individual microcalcification. A scheme based only on these two features yielded an ROC curve with an area under the curve (A(z)) of 0.87, indicating a positive predictive value of 61% for 98% sensitivity.

CONCLUSION

Computerized analysis permitted calculations reflecting the shape of individual microcalcification and the geometry of clusters of microcalcifications. For the computerized classification scheme studied, the cluster geometry was more effective in differentiating benign from malignant clusters than was the shape of individual microcalcification.

Optimizing parameters for computer-aided diagnosis of microcalcifications at mammography

RATIONALE AND OBJECTIVES

The purpose of this study was to optimize selection of the mammographic features most useful in discriminating benign from malignant clustered microcalcifications.

MATERIALS AND METHODS

The computer-aided diagnosis (CAD) system automatically extracted from digitized mammograms 13 quantitative features characterizing microcalcification clusters. Archival cases (n = 134; patient age range, 31-77 years; mean age, 56.8 years) with known histopathologic results (79 malignant, 55 benign) were selected. Three radiologists at three facilities independently analyzed the microcalcifications by using the CAD system. Stepwise discriminant analysis selected the features best discriminating benign from malignant microcalcifications. A classification scheme was constructed on the basis of these optimized features, and its performance was evaluated by using receiver operating characteristic (ROC) analysis.

RESULTS

Six of the 13 variables extracted by the CAD system were selected by stepwise determinant analysis for generating the classification scheme, which yielded an ROC curve with an area (Az) of 0.98, specificity of 83.64%, positive predictive value of 89.53%, and accuracy of 91.79% for 98% sensitivity. When patient age was an additional variable, the scheme's performance improved, but this was not statistically significant (Az = 0.98). The ROC curve of the classifier (without age as an additional variable) yielded a high Az of 0.96 for patients younger than 50 years and an even higher (P < .02) Az of 0.99 for those 50 years or older.

CONCLUSION

Stepwise discriminant analysis optimized performance of a classification scheme for microcalcifications by selecting six optimized features. Scheme performance was significantly (P < .02) higher for women 50 years or older, but the addition of patient age as a variable did not produce a statistically significant increase in performance.

Quantitative characterization of mass lesions on digitized mammograms for computer-assisted diagnosis

RATIONALE AND OBJECTIVES

To investigate features for discriminating benign from malignant mammographic findings by using computer-aided diagnosis (CAD) and to test the accuracy of CAD interpretations of mass lesions.

METHODS

Fifty-five sequential, mammographically detected mass lesions, referred for biopsy, were digitized for computerized reevaluation with a CAD system. Quantitative features that characterize spiculation were automatically extracted by the CAD system. Data generated by 271 known retrospective cases were used to set reference values indicating the range for malignant and benign lesions. After conventional interpretation of the 55 prospective cases, they were evaluated a second time by the radiologist using the extracted features and the reference ranges. In addition, a pattern-recognition scheme based on the extracted features was used to classify the prospective cases. Accuracy of interpretation with and without the CAD system was evaluated using receiver operating characteristic (ROC) curve analysis.

RESULTS

Sensitivity of the CAD diagnosis for the prospective cases improved from 92% to 100%. Specificity improved significantly from 26.7% to 66.7%. This was accompanied by a significant increase in the accuracy of diagnosis from 56.4% to 81.8% and in the positive predictive value from 51.1% to 71.4%. The Az for the CAD ROC curve significantly increased from 0.73 to 0.90. The performance of the classification scheme was slightly lower than that of the radiologists' interpretation with the CAD system.

CONCLUSIONS

Use of the CAD system significantly improved the accuracy of diagnosis. The findings suggest that the classification scheme may improve the radiologist's ability to differentiate benign from malignant mass lesions in the interpretation of mammograms.

Improved mammographic interpretation of masses using computer-aided diagnosis

The aim of this study was to evaluate the effectiveness of computerized image enhancement, to investigate criteria for discriminating benign from malignant mammographic findings by computer-aided diagnosis (CAD), and to test the role of quantitative analysis in improving the accuracy of interpretation of mass lesions. Forty sequential mammographically detected mass lesions referred for biopsy were digitized at high resolution for computerized evaluation. A prototype CAD system which included image enhancement algorithms was used for a better visualization of the lesions. Quantitative features which characterize the spiculation were automatically extracted by the CAD system for a user-defined region of interest (ROI). Reference ranges for malignant and benign cases were acquired from data generated by 214 known retrospective cases. The extracted parameters together with the reference ranges were presented to the radiologist for the analysis of 40 prospective cases. A pattern recognition scheme based on discriminant analysis was trained on the 214 retrospective cases, and applied to the prospective cases. Accuracy of interpretation with and without the CAD system, as well as the performance of the pattern recognition scheme, were analyzed using receiver operating characteristics (ROC) curves. A significant difference (p < 0.005) was found between features extracted by the CAD system for benign and malignant cases. Specificity of the CAD-assisted diagnosis improved significantly (p < 0.02) from 14 % for the conventional assessment to 50 %, and the positive predictive value increased from 0.47 to 0.62 (p < 0.04). The area under the ROC curve (A(z)) increased significantly (p < 0. 001) from 0.66 for the conventional assessment to 0.81 for the CAD-assisted analysis. The A(z) for the results of the pattern recognition scheme was higher (0.95). The results indicate that there is an improved accuracy of diagnosis with the use of the mammographic CAD system above that of the unassisted radiologist. Our findings suggest that objective quantitative features extracted from digitized mammographic findings may help in differentiating between benign and malignant masses, and can assist the radiologist in the interpretation of mass lesions.

The use of an interactive software program for quantitative characterization of microcalcifications on digitized film-screen mammograms

RATIONALE AND OBJECTIVES

Mammography is relatively nonspecific for the early detection of breast cancer. This study evaluates the accuracy of mammographic interpretation using quantitative features characterizing microcalcifications, which are extracted by a computerized system.

METHODS

A computer-aided diagnosis (CAD) system enabling digitization of film-screen mammograms and automatic feature extraction was developed. A classification scheme (discriminant analysis) based on these features was constructed and trained on 217 cases with known pathology. The diagnostic performance of the classification scheme was tested against the radiologist's conventional interpretation on 45 additional cases of microcalcifications, each analyzed independently by four radiologists.

RESULTS

The sensitivity of the CAD system analysis (95.7%) was significantly better than that of conventional interpretation (84.8%). The positive predictive value of interpretation increased significantly, as did the area under the receiver operating characteristic curve.

CONCLUSIONS

This classification scheme for microcalcifications, based on quantitative features characterizing the lesion, significantly improved the accuracy of mammographic interpretation.

Chronic radiodermatitis following cardiac catheterization

BACKGROUND

Fluoroscopy and cineradiography used during coronary angiography expose patients to some of the highest doses of ionizing radiation in diagnostic radiology. The possibility of radiation-induced damage has been discussed by several authors in the past. However, to the best of our knowledge, chronic radiation dermatitis caused by exposure to x-rays during cardiac catheterization has not been described.

OBSERVATIONS

We describe 4 patients in whom chronic radiodermatitis developed following multiple cardiac catheterizations and coronary angioplasties. The cumulative radiation doses to which these patients were exposed were retrospectively calculated to be a mean of 24.6 Gy per patient, with a range of 11.4 to 34.9 Gy.

CONCLUSIONS

Chronic radiodermatitis is a threat in patients undergoing multiple cardiac catheterizations and angioplasties. In susceptible patients, radiation doses as small as 11.4 Gy, which can sometimes be emitted during 1 or 2 procedures, are potentially harmful. Awareness and protective measures against this long-term side effect of cardiac catheterization should be encouraged.

Tibial implant mineralization in rats is inversely related to serum osteogenic capacity

In this study, the correlation between the mineralization of healing bone defects and the osteogenic capacity of the serum was tested in rats. The purpose of the study was to test the hypothesis that during callus formation, some serum factors are consumed. The bone defects in the tibia contained two different implant types, and all sustained juxta-implant fractures. One implant type was the coral Porites and the other was its recrystallized version (Interpore-200), which exhibit different mineralization rates during fracture healing. Use of these two implant types permitted generation of an expanded mineralization spectrum suitable for regression analysis. Mineralization was assessed by measuring the mineral content change (MCC) using dual-energy X-ray absorptiometry. Osteogenic capacity of sera of the implanted rats was assessed by its ability to increase specific alkaline phosphatase (ALP) activity in stromal cell cultures. The MCC was followed for 5 weeks in the Porites and Interpore-200 implants, and it was found that the MCC in Interpore-200 implants exceeded that of the Porites implants. Thus, the two implant types generated a wide mineralization spectrum. Induction of ALP in stromal cell culture was lower for sera derived from rats implanted with Interpore-200 than for sera derived from rats implanted with Porites. Two weeks after implantation, the change in serum ALP induction correlated inversely with the MCC of bone defects. This indicates that during callus formation, the mineralization rate is reciprocally related to the serum osteogenic capacity. The decreased serum osteogenic capacity may be interpreted by the hypothesis that callus formation consumes certain serum osteogenic factors.

Extended duration of vertical position might impair bone metabolism

Bone-remodelling is markedly influenced by vectors of gravitational forces. Sleep-deprivation, common during military training, involves a change in the normal balance between horizontal and vertical forces enacting on the skeleton. Stress fractures are likewise prevalent among army recruits. In order to investigate the impact of sleep-deprivation on bone-metabolism, three groups of young, healthy volunteers were selected to exercise the following: 63 h of sleeplessness (17 participants, group A); vertical sleep in a seated position for three consecutive nights (9 participants, group B); controls who slept 6 h a night horizontally (14 participants, group C). During periods of wakefulness, all participants were kept in an upright position. Twenty-four hours' urine collection was strictly observed from two days prior to the experiment until two days after it (1 week). Changes in levels of the most characteristic bone-metabolites, calcium and hydroxyproline indicate an increased bone-resorption in the two experimental groups, but not in controls. The calcium excreted in the fasting urine peaked significantly at 72 h after the beginning of the experiment (+ 170% in group A; + 68% in group B, relative to the basal level). Qualitatively, similar results were obtained with hydroxyproline. On an individual basis, approximately 40% of the participants in either group responded by exceeding urinary-calcium elevation. A comparison of pre-test bone-density between responders and non-responders, reveals a significantly lower bone-density (-5%) in calcium and hydroxyproline excretors. These results suggest a pre-disposition to bone-resorption associated with responsiveness to changes in the balance between gravitational forces.

Alfacalcidol (alpha D3) and calcium in osteoporosis

In a prospective, randomized study, 66 osteoporotic postmenopausal women (mean age, 67 years) were scheduled to receive either alfacalcidol 0.25 microgram twice daily together with calcium 500 mg twice daily (treatment group, n = 24) or placebo twice daily with calcium 500 mg twice daily (control group, n = 42) for three years. In the treatment group, bone mineral content at the distal radius may have increased by 2% compared to a significant decrease of 7.8% in the control group. The difference between the two groups was also significant. Since the dose of alfacalcidol and calcium remained unadjusted, frequent hypercalciuria, as well as occasional mild, transient elevations of serum calcium, were observed in the treatment group. No changes in serum creatinine levels or creatinine clearance throughout the study were observed. The two groups did not differ with respect to the frequency of clinical side effects, which were mainly gastrointestinal and probably related to the calcium supplementation. Alfacalcidol and calcium may prevent further bone loss in women suffering from postmenopausal osteoporosis.

Trabecular bone density in a two year controlled trial of peroral magnesium in osteoporosis

Since magnesium regulates calcium transport, and magnesium replacement in magnesium-deficient postmenopausal patients resulted in unexpected improvement in documented osteoporosis, we investigated the effect of magnesium treatment on trabecular bone density in postmenopausal osteoporosis. Thirty-one postmenopausal patients (mean age +/- SD = 57.6 +/- 10.6 years), consecutively admitted to the Back Rehabilitation Unit with musculoskeletal pain of non-malignant origin and bone density values of < or = 1.19 g/cm3 (measured by Compton Bone Densitometer), received two to six tablets daily of 125 mg each of magnesium hydroxide (Magnesium Magma USP/; 'Mazor', Israel) for 6 months and two tablets for another 18 months in a 2 year, open, controlled therapeutic trial. Twenty-three symptom-free postmenopausal women (mean +/- SD = 61.2 +/- 6.2 years) whose bone density was concurrently assessed at the same laboratory and who were found to have osteoporosis but refused treatment, served as controls. No new fractures occurred. Twenty-two patients (71 per cent) responded by a 1-8 per cent rise of bone density. The mean bone density of all treated patients increased significantly after 1 year (P < 0.02) and remained unchanged after 2 years (P > 0.05). The mean bone density of the responders increased significantly both after one year (P < 0.001) and after 2 years (P < 0.02), while in untreated controls, the mean bone density decreased significantly (P < 0.001). The disparity between the initial mean bone density and bone density after one year in all osteoporotic patients and in the responders differed significantly from that of the controls (both P < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Bone density, mineral content, and cortical index in patients with thalassemia major and the correlation to their bone fractures, blood transfusions, and treatment with desferrioxamine

In an attempt to explain the increased frequency of pathological fractures found in thalassemia major patients, we examined noninvasively several properties of bones in 17 patients. We found a significant decrease in the bone mineral content (BMC) and the bone density (BD) of both trabecular (34% and 4% diminution, respectively) and cortical bone (24% and 3% diminution, respectively), as compared with normal controls. We also found that metacarpal cortical indices (CI) were significantly lower in thalassemic patients as compared with normal controls (36% diminution). As expected, upper limb fractures were more frequent in those patients with greater bone diminution. Furthermore, the degree of bone diminution was greater in patients receiving fewer blood transfusions and shorter courses of desferrioxamine. Bone densitometry should probably be included in the comprehensive evaluation of thalassemia patients in order to help guide overall treatment.

Effect of swimming on prednisolone-induced osteoporosis in elderly rats

We investigated the possible ameliorating and preventive effect of swimming on prednisolone-induced osteoporosis in elderly rats. A total of 48 female Sabra strain rats were randomly assigned to the following groups and treatments: (1) control (C), (2) swimming (S), (3) prednisolone-treated (CP), and (4) swimming + prednisolone (SP). An additional 8 rats were sacrificed and examined at the onset of the study. Groups C and S were sham injected; groups CP and SP were injected with prednisolone (Ultracorten), 80 mg/kg three times per week for 10 weeks. Groups S and SP swam 1 h daily, 5 days per week for 10 weeks. SP rats swam simultaneously with prednisolone administration. At the end of the swimming period, in vivo bone mineral content (BMC) measurements were performed on rat vertebrae L4-5 by single-photon absorptiometry. Later, the humerus and femur were removed for the following measurements: morphometric, bone density (BD) by Compton scattering technique, bone ion content by atomic absorption, and hydration fraction by proton magnetic resonance (PMR). We found that the humeral BD of S rats was greater by 14% for group S over C and 3% greater for group SP over CP (P less than 0.05). Vertebral BMC was higher by 15% in group S over C and 11% higher for group SP over CP (P less than 0.05). Femoral calcium (mg/g dry bone) ion content was higher by 5% in group S over C and 8% in group SP over CP group (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Use of dual-energy X-ray absorptiometry (DEXA) to follow mineral content changes in small ceramic implants in rats

Dual energy X-ray absorptiometry (DEXA) imaging was used to quantify bone ingrowth into hydroxyapatite (HA) ceramic implants in rats. HA cylinders implanted in the proximal tibiae were followed for 13 wk. The increase in alkaline phosphatase (ALP) activity within the implants preceded the increase in mineral content as measured non-invasively by the DEXA technique. This was consistent with the timing of ALP activity in respect of mineralization as they occur during fracture healing. The results show that DEXA imaging is useful in measuring bone ingrowth into small ceramic HA implants in vivo, despite the high mineral content background of the implant scaffold.

Evaluation of the calcium phosphate ceramic implant by non-invasive techniques

Current routine radiological procedures do not quantify the degree of calcium phosphate ceramic implant integration with the host bone, nor the rate of remodelling processes in the latter. The successful clinical use of non-invasive techniques in assessing bone mass deserves attention from surgeons and scientists dealing with hard tissue prosthetics and implants. Two suitable techniques for such non-invasive sequential analysis of the ceramic implant and host bone are outlined.

The effect of swimming on bone modeling and composition in young adult rats

The purpose of this study was to investigate the adaptability of long bones of young adult rats to the stress of chronic aquatic exercise. Twenty-eight female Sabra rats (12 weeks old) were randomly assigned to two groups and treatments: exercise (14 rats) and sedentary control (14 rats) matched for age and weight. Exercised animals were trained to swim in a water bath (35 degrees +/- 1 degree C, 1 hour daily 5 times a week) for 12 weeks loaded with lead weights on their tails (2% of their body weight) (BW). At the end of the training period following blood sampling for alkaline phosphatase, all rats were sacrificed and the humeri and tibiae bones were removed for the following measurements: bone morphometry, bone water compartmentalization, bone density (BD), bone mineral content (BMC), and bone ions content (Ca, Pi, Mg, Zn). The results indicate that exercise did not significantly affect the animals' body weight, bone volume, or length and diameters. However, bone hydration properties, BD, bone mass, and mineralization revealed significant differences between swim-trained rats and controls (P less than 0.05). Longitudinal (R1) measurement was higher by 43% for both humerus and tibia, and Transverse (R2) relaxation rates of hydrogen proton were higher by 117 and 76% for humerus and tibia, respectively; fraction of bound water was higher by 36 and 46% for humerus and tibia, respectively. BD, bone weight, and ash were higher by 13%. BMC and bone ions content were higher by 10%, and alkaline phosphatase was higher by 67%.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic emission from trabecular bone during mechanical testing: the effect of osteoporosis and osteoarthritis

This study examines the relation between the nature of acoustic emission signals emitted from cancellous bone under compression and the mechanical properties of the tissue. The examined bone specimens were taken from 12 normal, 31 osteoporotic and six osteoarthritic femoral heads. The mechanical behaviour of the osteoporotic bone specimens was found to be significantly different from that of the normal specimens both in the pre-yield and post-yield ranges. In the osteoarthritic bones only the elastic behaviour was significantly different. The rates of acoustic events before yield and beyond it were found to be significantly higher both in the osteoporotic and osteoarthritic bone specimens. The average peak amplitude of the signals was also significantly higher in the diseased bones. Stepwise regression analysis showed that a combination of the acoustic emission parameters could significantly predict some mechanical properties of the bone. The energy absorbed during compression and the ultimate compressive stress of the specimens could be estimated from the rate of pre-yield acoustic events, the average amplitude of the signals and the rate of post-yield events. However, the explanation power of the acoustic emission parameters was only moderate. The nature of acoustic emission signals was thus demonstrated to be a potential tool for assessing bone quality.

Progressive bone loss during long-term home total parenteral nutrition

Metabolic bone disease occurs in patients receiving prolonged home total parenteral nutrition (HTPN). We studied bone-mass status in 10 patients (seven males, three females, age 19-66 years) who had been receiving HTPN for 0 to 67 months (mean 24 months), mostly for short-bowel syndrome. Four patients had spinal osteoporosis on radiograms. The density of various bone components at the wrist was measured noninvasively using a novel technique based on Compton scattering effect. The density of the cancellous and cortical bone was decreased in nine and six patients, respectively. During a follow-up period of up to 19 months, a further significant decrease in the density of both bone components was found. We conclude that prolonged HTPN is associated with an ongoing bone diminution, affecting mainly the cancellous bone.

Role of the calcaneal inclination in the energy storage capacity of the human foot--a biomechanical model

The energy storage capacity of the human foot as a passive structure depends on both its geometry and elastic properties. The present study examines theoretically the relationship between the energy stored in the longitudinal arch and the inclination of the calcaneus, when a vertical load is applied. A simple two-dimensional model was used, consisting of two inclined rigid elements, hinged at the apex of the arch and connected by a horizontal tension spring at the bottom of the arch. The spring serves as the energy-storing element of the model, representing the foot plantar ligaments. The behaviour of the model was examined using both a linear and an exponential spring. It demonstrated that the stored energy depends strongly on the calcaneal inclination. For a given vertical load, the energy storage capacity is low at both large and small inclinations and rises markedly at an intermediate value. Assuming that the incidence of stress fractures during locomotion is affected by insufficient energy attenuation of the foot, this model provides an explanation for the higher prevalence of tibial and femoral stress fractures in subjects with high or low arches.

Effect of swimming on bone growth and development in young rats

The effect of chronic swimming on bone modelling was studied. Forty female Sabra rats (5 weeks old) were randomly assigned to the following experimental groups: 30 rats were trained to swim (water bath 35 +/- 1 degree C, one h daily, five times a week) for 20 weeks--20 of them loaded with lead weights (1% body weight) while the rest (10 animals) swam load free. Ten sedentary rats matched for age and weight served as controls. At the end of the twenty-week swimming period, all rats were sacrificed, both humeri bones were dissected and prepared for the following examinations: morphometric, bone density (BD), bone mineral content (BMC), compression tests and cross-sectional geometrical parameters, histomorphometry and biochemical analysis of minerals (Ca, Pi, Mg, Zn). All measured parameters were found to be significantly higher (P less than 0.05) in the swimming rats irrespective of load, as compared with the controls. Bone weight was higher by 19%, bone volume by 11%, bone length by 2.8%, cortical area by 16%, BD by 7% and BMC by 15%. The compression breaking force at the distal shaft of the humerus was higher by 24% in the trained group, while the ultimate compressive stress was not significantly different. Maximal and minimal moment of inertia at the distal diaphysis were 33.4 and 40% higher, respectively, for the swimming groups than the controls. Ca, Pi, Mg and Zn levels per total humeral bone were significantly higher in the exercising rats. The histomorphometry and cross-sectional data emphasize longitudinal and transversal growth. These data indicate that swimming exercise exerts a positive effect on bone growth and development in young rats.

Structural and compositional changes in aging bone: osteopenia in lumbar vertebrae of Wistar female rats

Changes in vertebral bone mineral content and density during aging were quantified in female Wistar rats. This study represents a longitudinal follow up utilizing single photon absorptiometry for the measurement of bone mineral content (BMC), quantitative computed tomography (QCT) for the measurement of bone mineral density (BMD), and image analysis histomorphometry for the measurement of trabecular bone volume (TBV) and bone cortical area (BCA). The above measurements were accompanied by biochemical assays of calcium concentrations in the respective bones. All aging animals experienced significant decreases in BMC, BMD, TBV, BCA and in the calcium content of their bones. The above features have been further emphasized through the use of scanning electron micrographs showing the age-related structural changes in a three-dimensional fashion. New, advanced technologies will enable the quantitation of 3-dimensional images that are currently obtained from the scanning electron micrograph; thus will provide new consideration as related to trabecular bone compactness (density). Energy dispersive x-ray spectroscopy indicated that the nature of crystals in aging bones does not differ markedly from that encountered in young specimens. Data are also provided with regard to the health of the animals, and it became apparent that aging rats undergo changes in their kidneys yet do not show any significant change in renal functional parameters as measured in both the serum and the urine. Hence, new noninvasive methodologies are currently available for longitudinal studies related to the skeleton in laboratory animals enabling reliable monitoring of age-related and hormonally induced changes in bones (spine and hip) of well defined experimental models.

Combined effect of foot arch structure and an orthotic device on stress fractures

In a prospective study, quantitative measures of the structure of the longitudinal arch of the foot were established and related to the incidence of stress fractures in the bones of the lower limbs of military recruits. In addition, the role of a semirigid orthotic device (Langer military stress orthotic) in preventing stress fractures was evaluated as a function of the structure of the longitudinal arch. Femoral and tibial stress fractures were found to be more prevalent in the presence of feet with high arches, whereas the incidence of metatarsal fractures was higher in feet with low arches. The use of an orthotic device reduced the incidence of femoral stress fractures only in the presence of feet with high arches and the incidence of metatarsal fractures only among feet with low arches. The findings suggest that the normal foot with a low arch acts as a better shock absorber than the normal foot with a high arch, and that an orthotic device may improve the shock absorbing capacity of the arch.

The effect of swimming activity on bone architecture in growing rats

The effect of non-habitual physical activity on bone architecture in the rat humeral shaft was examined. Two groups of rats were trained to swim for 1 h a day, for 20 weeks, at two training levels. The control group consisted of sedentary rats. Parameters of cross-sectional bone morphology (cross-section areas, principal area moments of inertia and their ratio) were used to evaluate the response of bone architecture to mechanical loading. The strength of bone was assessed by measuring the ultimate compressive force and stress. The cortical cross-section area and principal moments of inertia were found to be significantly higher in the swimming groups than in the controls. Examination of the ratio between the major and minor moments of inertia revealed a pronounced change in the shape of the bone cross-section which became more rounded following swimming training. The ultimate compressive force was significantly higher in the swimming rats while the changes in ultimate stress were not significant. Our results indicate a gain of bone strength due to increased periosteal apposition and modified bone tissue distribution. The marked changes in bone morphology are attributed to the different nature of the forces and moments exerted on the humerus during swimming compared to those prevailing during normal locomotion.

Gain in mass density of bone following strenuous physical activity

A group of 223 military recruits aged 18-21 years underwent strenuous physical training for a period of 14 weeks. The absolute bone density of the distal tibia in both lower limbs was measured before the training period and at its end. The density was determined by the Compton scattering technique, which has been developed in our laboratory; this method provides the bone mass of all bone constituents per unit volume. The distribution curve of the bone density in both tibiae shifted to higher values at the end of the training period. The mean bone density in the right and left tibia increased significantly by 7.5%. This study indicates that following an intensive physical exercise regime, a significant increase in the mass density of bone can be obtained in young adults within a short period.

Ability of different techniques of measuring bone mass to determine vertebral bone loss in aging female rats

Changes in vertebral trabecular bone were quantified in female Wistar rats. This study utilized single photon absorptiometry for the measurement of bone mineral content (BMC), quantitative computed tomography (QCT) for the measurement of bone mineral density (BMD), and image analysis histomorphometry for the measurement of trabecular bone volume (TBV). The above measurements were accompanied by biochemical assays of protein and calcium concentrations in the tissues. Also, the activity of bone alkaline and acid phosphatases was measured. Lumbar vertebrae (L4, L5) in old rats 27 months old, compared with those of young rats 7 months old, showed significant decreases in BMC, BMD, TBV, protein and calcium, and enzyme activity. A high degree of correlation was recorded between the above changes. The various changes were accompanied by a marked reduction in the overall wet weight of the vertebrae. Hence, new noninvasive methods to quantitate bone mass can be applied in vivo to small laboratory animals such as the rat. These methods are much more accurate than standard radiographs in quantitating bone loss and are, therefore, recommended for experimental longitudinal studies related to aging of the skeleton.

Can the weight-bearing capacity of the femoral neck be estimated by physical measurements on the greater trochanter?

Early detection of mechanical weakening of the femoral neck would help to prevent fractures at this site which are the most serious clinical problem in osteoporosis. In the vicinity of the femoral neck, the greater trochanter is a superficial bone structure more easily accessible to in vivo measurements. The purpose of the present study was to evaluate the relation between the strength of the femoral neck and the composition of the trabecular tissue in the greater trochanter. Twenty-nine fresh human intact femora were examined. The relationship between the average shear stress in failure of the femoral neck (ASS) and the Ca concentration (CC), mineral density (BMD), and overall mass density (BD) of the greater trochanter was investigated. Linear stepwise regression analysis showed that the ASS of the femoral neck can be predicted from the BD, CC, and BMD of the trochanteric tissue, and their contribution to the estimation of the ASS was ranked in the above order. The linear function relating the ASS to these variables showed a highly significant multiple correlation ( R = 0.87, p < 0.001). Therefore in vivo measurements of the density and mineral content in the greater trochanter should be considered useful in assessing the risk of fracture of the femoral neck.

The relative significance of trabecular and cortical bone density as a diagnostic index for osteoporosis

The density of the distal radius in the non-dominant forearm was measured non-invasively by Compton spectrometry in 234 post-menopausal women. The density of the trabecular tissue was determined almost independently from that of cortical tissue by horizontal and vertical scanning of the bone. It was found that the lower the density of the trabecular bone, the greater the difference between the density of the cortical and trabecular bone. As osteoporosis progresses, trabecular bone density in the distal radius seems to decrease faster than that of compact bone. Hence the severity of the disease is best determined by measuring the density of trabecular bone.

Dynamic bone loading exercises for postmenopausal women: effect on the density of the distal radius

A set of dynamic bone loading exercises for the distal forearm, designed for high rates of loading, within physiologic range, and diversity of strain regime, was applied to a group of postmenopausal osteoporotic women. The effect of five months of three weekly sessions, 50 minutes each, on the bone status was studied by measuring the bone density at the distal radius by the Compton scattering technique. A group of 14 women who participated in the program and an inactive group of 26 women were examined one year prior to the study, at its beginning and at its end. During the year preceding the exercise program the mean bone density in both groups decreased significantly. During the exercise period the bone density of the exercise group increased by 3.8% while that of the control group continued to decline. This study demonstrates that an appropriate physical activity regime may be effective as a prophylactic treatment for postmenopausal bone loss.

Increased trabecular bone density due to bone-loading exercises in postmenopausal osteoporotic women

A program of diverse and dynamic loading exercises of the distal forearm, a common site of osteoporotic fractures, was applied three times a week for 5 months to 14 postmenopausal osteoporotic women. Two parameters were used to assess the effect of the exercises on bone mass. The mass density of bone (g/cm3) was measured by the Compton scattering technique. The bone mineral content (g/cm2) was measured by single photon absorptiometry. Both measurements were taken at the same location in the distal radius 1 year prior to the exercise period, at its beginning, and at its end, in both the exercised group and a matched control group of 26 osteoporotic women. During the exercise period the mean bone density decreased by 1.9% in the control group whereas it increased by 3.8% in the exercise group. The bone mineral content results did not demonstrate any significant trend over the whole period of the study. It is concluded that the trabecular bone tissue in the distal radius of postmenopausal osteoporotic women responds favorably to dynamic and diverse bone stressing exercises even in the seventh decade of life.

Effect of intense physical activity on the bone-mineral content in the lower limbs of young adults

The effect of intense physical training on the bone-mineral content of young adults who are unaccustomed to physical activity has not yet been established. In this study, 268 male recruits, eighteen to twenty-one years old, were evaluated before and after fourteen weeks of strenuous physical training. The bone-mineral content of both legs at the level of the distal third of the tibia in each individual was measured using single-beam photon absorptiometry. The subjects started their training with equal values for bone-mineral content in both legs. During the training period, the average bone-mineral content of the left leg increased by 11.1 per cent and that of the right leg, by 5.2 per cent. In the group of subjects who did not complete the training course, mainly because they incurred stress fractures, the increase in bone-mineral content was significantly less than the increase in those who completed the program. This study indicated that in young adults a high level of loading of bone results in either a stress fracture or a rapid increase in bone-mineral content.

A correlative assessment of photon interaction and histomorphometric measurements of bone density

Thirty-four femoral necks from human cadavers were measured by techniques assessing bone density and bone mineral density, and by the Singh index. These methods are based on photon interaction with biological components and can be applied noninvasively for clinical evaluation of changes in skeletal status. Trabecular bone volume, mineralized bone volume, and relative osteoid volume were evaluated histomorphometrically using undecalcified histologic sections obtained from the same samples. The trabecular and mineralized bone volumes showed significant correlations with the bone density and mineral density. These results enhance the validity of recently developed photon-interaction techniques for evaluating bone properties.

Trabecular bone mineral density measurement in vivo: use of the ratio of coherent to Compton-scattered photons in the calcaneus

Trabecular bone mineral density (TBMD) was measured in vivo in the calcaneus by a new method that uses the ratio of coherent to Compton-scattered photons arising from irradiation of a small volume of trabecular bone by a gamma ray source with highly collimated geometry. TBMD values for healthy men (22-77 years) were in the range of 180-357 mg/ml, and values for healthy women (18-73 years) were in the range of 160-321 mg/ml. In contrast, values in a small group of paraplegics were in the range of 90-199 mg/ml.

Quantitative assessment of bone mineral by photon scattering: accuracy and precision considerations

A method to determine the bone mineral density of the calcaneum has been reported earlier by our laboratory. In this method, the calcaneum is irradiated by a 60-keV photon beam from 241Am source and both the coherent and Compton scattered photons are detected by a high-purity Ge detector. The bone mineral density is determined by measuring the ratio of coherent-to-Compton scattered photons. The accuracy and the precision (in vitro) of the method are reported in this paper. The accuracy was determined to be 5%. This was obtained by comparing the bone mineral density values of cadaver calcanea measured directly by Archimedes' volume displacement method with the values measured by the scattering method. The precision was determined to be 3% by measuring the bone mineral density of a calibration phantom intermittently over a ten-month period by the scattering method.

Quantitative assessment of bone mineral by photon scattering: calibration considerations

The ratio of the coherent-to-Compton photons scattered from bone can be used to measure its mineral density. Conversion of this ratio (R) to bone mineral density (BMD) requires calibration using bone simulating phantoms. The widely used aqueous solution of K2HPO4 proved unsatisfactory for calibration purposes when using the coherent-to-Compton technique. These solutions differ markedly in their scatter spectra and composition from trabecular bone. In this study a new and more realistic series of phantoms is proposed which simulates well the trabecular bone of the calcaneum. These phantoms are made of bone ash suspended in white petrolatum in varying concentrations. A calibration curve has been established using these phantoms with a range of BMD values of 0 to 347 mg/cm3. The scatter spectra, and range of R values and BMD of these phantoms are in very good agreement with those of real trabecular bone. A measuring device has been built for the determination of the BMD of the calcaneum by using the established calibration curve.

The effect of the momentum transfer on the sensitivity of a photon scattering method for the characterization of tissues

The ratio of coherent to Compton photon scattered by a tissue-like material depends on its effective atomic number. This ratio can, therefore, be used for the in vivo characterization of tissues. The intrinsic sensitivity of this measurement is defined as the change in the coherent-to-Compton ratio for a given change in the atomic number. The effect of the scatter angle on the sensitivity has already been described by us in a paper recently submitted to this journal. In this study, the dependence of the sensitivity on the energy of the incident photons is investigated in two ways. The first approach is quasitheoretical and is based on computations of the cross sections of the coherent and Compton scattering for various energies. The second approach is experimental and it involves the measurement of the scatter ratio from a series of K2HPO4 solutions for three primary photon energies: 60, 81, and 140 keV. The combined effect of both the photon energy and the scatter angle on the sensitivity can be described by a single parameter which is the momentum transfer. It is concluded that for the limited range of the atomic numbers which apply to trabecular bone (8 less than or equal to Z less than or equal to 11) the momentum transfer reflects completely the effect of the scatter angle and photon energy on the sensitivity.

Fracture of the human femoral neck: effect of density of the cancellous core

Thirty three fresh femora from 18 cadavera were loaded to fracture at a deformation rate of 5 mm/min to study the effect of density of the cancellous core in fracture initiation of the femoral neck. The neck of the femur was modelled as a composite beam subjected to bending and the ultimate strength of the bone at the superior aspect of the neck was calculated from the model, which was fed by the mechanical tests and geometry measurements. The area porosity of the cancellous core was introduced into the beam model after measuring the apparent density of dry fat-free bone for each specimen. The results showed a strong dependence between the ultimate strength obtained and the cancellous bone density, the latter previously measured for each specimen by the non-invasive Compton scattering technique. Area porosity of the femoral neck was found to have little effect on the results obtained, permitting the use of an average value for this parameter in calculating the ultimate strength of the neck of the femur.

Characterization of tissue via coherent-to-Compton scattering ratio: sensitivity considerations

It is known that the ratio (R) of the detected coherent and Compton scattered photons from bone can be used in order to determine its mineral density. This technique utilizes the dependence of the coherent scattering on the effective atomic number (Z) of the scattering medium. It is generally accepted that a small scatter angle is preferred in order to ensure adequate counting statistics by favoring the detection of more coherent photons. Moreover, it has been assumed that a change in the scatter angle does not affect the sensitivity of the measurement. Our theoretical calculations for 60-keV photons and for the range of Z that corresponds to trabecular bone, indicate that increasing the scatter angle results in a stronger power dependence of the measured ratio on Z. This implies that by increasing the scatter angle, smaller changes in the mineral density can be detected, thus improving the sensitivity of the measurement. This effect was investigated experimentally by using a collimated beam of 59.54-keV photons from Am-241 (44.4 GBq) and a collimated intrinsic germanium detector. Solutions of K2HPO4 with different concentrations were used in order to simulate trabecular bone. The scatter spectra were recorded for all solutions at six scatter angles between 37 degrees and 98 degrees and the value of R was computed for each spectrum. The sensitivity of the measurement, evaluated from these experiments increased, with the increase of the scatter angle.

A new method of measuring bone density in the lower tibia of normal and postinjury limbs. A quantitative and comparative study

In osteoporosis, a pathologic state of diminution of bone mass, radiography is the most widely used diagnostic method, but it is only descriptive and mainly depicts changes in the compacta. Based on the Compton photon-scattering phenomenon, a noninvasive yet quantitative measuring method for analyzing bone density was developed. The values of repeated measurements taken at identical locations did not vary by more than 2%. Using this technique, bone density of the lower tibia was measured in 39 men and 36 women; 14 had been affected by an injury to a knee or calf and immobilized five to eight years prior to this investigation. The measured values demonstrated an impressive equality between the tibiae of each individual and between the two sexes up to 50 years of age. However, these values correlated poorly with the bone density of the distal radius. In women older than 50 years of age, bone density decreased. Bone density was also low in all postinjury limbs. When compared with radiographic and bone mineral content (BMC) measurements of the same limb at the same location, the bone density measurements were useful and reduced the range of uncertainty of diagnosing osteoporosis by radiography only. Little or no correlation was found between bone density values and BMC measurements. The Compton scattering technique may become a precise and sensitive method for the clinical diagnosis of postinjury osteoporosis and quantitation of the long-term effects of limb injuries.

The relationship between bone density, mineral content, and mechanical strength in the femoral neck

The bone density, mineral content and average shear stress in bending at failure were measured in vitro in 33 femoral necks of women and men of different ages. The correlations between these three parameters as well as their correlation with the Singh index were carefully analyzed and found to show that the Singh index is of no clinical value. The best correlation exists between bone density and shear stress at failure. Practically no correlation is found between the breaking stress and Singh index. The breaking stress decreases with age much faster than the bone density or bone mineral content. The correlation between the work to fracture and the bone density or its mineral content is only moderate. The bone density is best indicator for the compressive bone strength. The changes of bone strength are apparently influenced by factors other than the bone density and mineral content, although the possibility that small changes in bone density or mineral content cause large changes in bone strength cannot be excluded.

The effect of age and sex on bone density, bone mineral content and cortical index

The density of cancellous bone in the nondominant radius of healthy subjects has been observed by the Compton scattering method as a function of age and sex. The average density for males is higher than for females. In males the density does not change up to the age of 80 years, while in females the density decreases beginning at age 50. A significant decrease in the bone mineral content of the distal radius is observed at earlier ages as measured by the Cameron-Sorenson technique. The average value of the cortical index of the third metacarpal shows some difference between the sexes over the age of 50, the index in males being higher than in the females. Between 30 and 50 years the female cortical index is greater than in the males. Little correlation was found among the three parameters studied, suggesting that they measure different phases of the pathophysiological processes involved in aging bone.

The effective attenuation coefficient of soft tissue in the presence of Compton scattering from bone: experiments on models

Calibration methods are investigated for the determination of bone density by the Compton scattering method. The scattered radiation from materials of different densities and dimensions is measured for this purpose. A function for the dependence of the intensity on these parameters is derived and compared with the experimental results. The influence of the surrounding soft tissue is studied by simulation experiments with water. It is found that the 'effective attenuation coefficient' of water for the incident and scattered radiation depends on the thickness of the surrounding water layer itself, as well as on the density of the scattering material. The implications of these findings for the evaluation of bone density measurements are discussed.

The early detection of osteoporosis by Compton gamma ray spectroscopy

The density of the distal end of the radius is one of the parameters used to determine the presence and degree of osteoporosis in patients. In this work the bone density has been determined by measuring the intensity of the Compton scattered photons, since this is proportional to the absolute density of the scatterer, in materials for which Z/A is constant. A collimated beam from a 500 mCi 137Cs source was used and the intensity of the scattered radiation measured at an angle of 90 degrees. The exact point of measurement was determined by a two-dimensional scanning technique. A plastic water phantom was used to calculate the correction needed for absorption and backscatter by the surrounding tissue. Bone density was measured by this method in 50 subjects. A good correlation was found between density of the radius and the degree of morphological change in the vertebrae. In a number of cases a low bone density was discovered without signs of osteoporosis in the spine. These findings were considered indicative of early osteoporotic change, not definable by routine X-ray techniques. This technique may be of value in the follow-up of patients and in controlling the effect of various treatment schedules.