Changes In Radiographic Density Research Articles

Perioperative changes in radiographic density in erector spinae muscle and mortality after lung transplantation

RationaleThe radiographic density of the erector spinae muscle (ESM) is often decreased early after lung transplantation (LTx). The prognostic impact of this change has not been elucidated. ObjectiveTo investigate whether the decrease in the radiographic density of ESMs early after LTx is associated with a poor prognosis. MethodsThis study is a single center retrospective cohort study. Routine follow-up chest computed tomography scan data just before and 12 weeks after LTx were retrospectively retrieved for adult patients who underwent primary LTx at Kyoto University Hospital. The radiographic density of ESM was quantitatively evaluated as the mean attenuation of the ESM (ESMct), and the impact of the decreased ESMct during the 12 weeks after LTx on overall survival (OS) was examined by Cox proportional hazard regression. ResultsA total of 151 recipients (94 cadaveric LTx, 57 living-donor lobar LTx) were included in this study. The median duration of postoperative observation was 4.4 years, during which time 39 recipients (26%) died. Decreased postoperative ESMct was significantly associated with poor OS (HR, 1.64; 95% CI, 1.14–2.35, P = 0.008 per 1 Z score decrease) in the multivariate model adjusted for age, sex, episodes of acute rejection, and preoperative ESMct. Similar results were obtained when the subjects were limited to those with cadaveric LTx. ConclusionA decreased perioperative ESMct was strongly associated with a poor prognosis after LTx in addition to low preoperative ESMct. Maintaining postoperative muscle radiographic density, which reflects muscle quality, may be important for a better prognosis after LTx.

Bone regeneration in critical-size defects of the mandible using biomechanically adapted CAD/CAM hybrid scaffolds: An in vivo study in miniature pigs

The study aimed to analyze bone regeneration in critical-size defects using hybrid scaffolds biomechanically adapted to the specific defect and adding the growth factor rhBMP-2.For this animal study, ten minipigs underwent bilateral defects in the corpus mandibulae and were subsequently treated with novel cylindrical hybrid scaffolds. These scaffolds were designed digitally to suit the biomechanical requirements of the mandibular defect, utilizing finite element analysis. The scaffolds comprised zirconium dioxide-tricalcium phosphate (ZrO2-TCP) support struts and TCP foam ceramics. One scaffold in each animal was loaded with rhBMP-2 (100 μg/cm³), while the other served as an unloaded negative control. Fluorescent dyes were administered every 2 weeks, and computed tomography (CT) scans were conducted every 4 weeks. Euthanasia was performed after 3 months, and samples were collected for examination using micro-CT and histological evaluation of both hard and soft tissue.Intravital CT examinations revealed minor changes in radiographic density from 4 to 12 weeks postoperatively. In the group treated with rhBMP-2, radiographic density shifted from 2513 ± 128 (mean ± SD) to 2606 ± 115 Hounsfield units (HU), while the group without rhBMP-2 showed a change from 2430 ± 131 to 2601 ± 67 HU. Prior to implantation, the radiological density of samples measured 1508 ± 30 mg HA/cm³, whereas post-mortem densities were 1346 ± 71 mg HA/cm³ in the rhBMP-2 group and 1282 ± 91 mg HA/cm³ in the control group (p = 0.045), as indicated by micro-CT measurements. The histological assessment demonstrated successful ossification in all specimens. The newly formed bone area proportion was significantly greater in the rhBMP-2 group (48 ± 10%) compared with the control group without rhBMP-2 (42 ± 9%, p = 0.03). The mean area proportion of remaining TCP foam was 23 ± 8% with rhBMP-2 and 24 ± 10% without rhBMP-2.Successful bone regeneration was accomplished by implanting hybrid scaffolds into critical-size mandibular defects. Loading these scaffolds with rhBMP-2 led to enhanced bone regeneration and a uniform distribution of new bone formation within the hybrid scaffolds. Further studies are required to determine the adaptability of hybrid scaffolds for larger and potentially segmental defects in the maxillofacial region.

Quantitative Evaluation of Normal Lung Density Changes in Non-Small Cell Lung Cancer Patients Treated With Radiotherapy and PD-1 Immune Checkpoint Inhibitors

Radiographic density changes in normal lung parenchyma are a function of radiation dose, are associated with inflammation, and vary among patients. The purpose of this study is to evaluate these radiation-induced changes quantitatively in different patient cohorts treated with PD-1 Immune Checkpoint Inhibitors (ICI) and investigate them as possible RT-related imaging biomarker for outcome.We looked at two groups of non-small cell lung cancer (NSCLC) patients drawn from two institutions: patients with metastatic disease treated with non-curative intent and normal lung in the radiation field, and patients receiving definitive chemo-radiation (CRT) followed by adjuvant PD-L1 blockade (durvalumab), some of which received durvalumab also concurrently. Normal lung parenchyma on the first post-treatment chest computer tomography (CT) scans (median time 3 months post RT) was deformably registered to the treatment plan to analyze lung density changes as function of dose, normalized to 2Gy-equivalent, and quantified as Hounsfield Unit (HU)/Gy. Differences between groups were assessed using Wilcoxon's rank sum test, correlation to progression-free and overall survival using Cox regression.We analyzed a total of 26 patients treated with non-curative intent RT and 60 patients who received CRT. For metastatic patients, RT delivered concurrently with ICI (n = 16) led to significantly larger changes compared to patients receiving RT before initiation of ICI (median 2.21 vs 0.27 HU/Gy, P = 0.02), even though the former received significantly lower doses to the normal lung (median 27.6 vs 55.8 Gy, P = 0.02). Fraction sizes were smaller when RT was delivered concurrently with ICI (median 3.3 vs 5.5 Gy/fraction). Number of patients and events in metastatic patients were too low for survival analysis. During CRT, patients receiving concurrent durvalumab (n = 20) did not show significant lung density changes compared to those that did not (median 1.39 vs 1.28 HU/Gy, P = 0.99). All CRT patients received 1.8-2.2 Gy/fraction. The amount of change in each patient did not correlate with progression-free or overall survival (HR = 0.91, 95% CI [0.71-1.16] and HR = 0.92, [0.72-1.17] respectively).RT delivered concurrently with PD-1 ICI leads to significantly increased normal lung density changes in metastatic patients but not in locally advanced patients treated with CRT, possibly related to the different fraction size. For CRT patients treated with adjuvant durvalumab, normal lung changes after CRT do not correlate with outcome. The correlation of lung density changes to oncologic outcomes in metastatic patients' needs to be studied in larger cohorts.

Correlation of Clinical and Dosimetric Parameters With Radiographic Lung Injury Following Stereotactic Body Radiotherapy

Radiographic changes occur in over half of patients treated with stereotactic body radiotherapy (SBRT) to the lung, correlating histopathologically with injury. We quantified radiographic density changes (ie, fibrosis) at 3, 6, and 12 months and investigated the relationship between these volumes and clinical and dosimetric parameters. The study population consisted of patients treated with SBRT to the lung for stage I primary lung cancers (n = 39) or oligometastatic lesions (n = 17). Fractionation schemes included 3 fractions of 12, 14, or 18 gray (Gy) and 4 fractions of 12 or 12.5 Gy prescribed to cover 95% of the planning target volume (PTV). Planning computed tomography (CT) scans were rigidly registered to follow-up CT scans obtained at intervals of 3, 6, and 12 months. Fibrotic volumes were contoured on the follow-up scans. Associations between the volume of fibrosis and clinical and dosimetric parameters were investigated using univariate linear regression. Scans were available for 65 and 47 lesions at 6 and 12 months, respectively. Age, years since quitting smoking, and GOLD Global Initiative for Chronic Obstructive Lung Disease score were significantly associated with increasing volume of fibrosis (P < .05). Total dose, dose per fraction, PTV, and volumetric parameters (V0-V55) were also significantly associated with increasing volumes of fibrosis (P < .01). For dosimetric parameters, the effect was largest for V55. Age, significant smoking history, and GOLD score were significantly associated with increasing volumes of fibrosis following SBRT. In a multivariate model adjusted for age and smoking history, V10 through V50 and PTV size remained significant predictors of fibrotic volume. Further, there is a strong dose-response relationship between the volume of lung exposed to a certain dose and the fibrotic volume. The predominant kinetic patterns of fibrosis demonstrate peaking fibrotic volumes at 6 and 12 months. These results provide insight for expectations of fibrosis after SBRT.

The assessment of the automatic exposure control system for mammography x-ray machine

In the U.S., performance assessment on the Automatic Exposure Control system (AEC) is managed according to the Mammography Quality Standards Act (MQSA). However, The AEC is not available in the performance assessment conducted in Korea. Also, there is no study made on the performance of the automatic exposure control system for mammography in Korea. For this reason, this study examined the performance of the automatic exposure control system for mammography that was clinically used in the Incheon area. Result showed that the difference of the mean optical density was 0.79 ~ 2.81. This implies that some devices caused unnecessary x-ray exposure to patients. Furthermore, only 61.5% of the entire experimental device was shown to be satisfactory in terms of change in mean optical density. Moreover, in terms of the subject's thickness, change in radiographic density was shown to be severe among lower X-ray tube voltage while there was severe density change in X-ray image depending on X-ray tube voltage among the subjects with more thickness. Therefore, it is suggested to provide performance management on the AEC for mammography.

Bone Structure Changes in Iliac Crest Grafts Combined with Implants

Remodeling of onlay grafts combined with implants to the mandible results in predictable changes in the graft's radiographic density. We studied the relationship between changes in radiographic density and trabecular structure during the first year after onlay grafting with simultaneous implant placement to the mandible. The aim of this study was to evaluate changes in bone structure after onlay grafting. Standardized extraoral radiographs were taken regularly of 16 mandibular sides. Bone structure was measured using the Carl Zeiss Vision KS 400 3.0 imaging system. The parameters studied were trabecular area and perimeter, cavity area and perimeter, end points, branching points, skeleton length, branch angle and direction, and texture. No differences were found between measurements ventrally versus dorsally of the implant, nor close to versus away from the implant. Early cortical changes suggest partial resorption and formation of a more complex structure. In the fourth quarter after surgery, progressive resorption is seen in the graft's upper cortex. In the graft's upper spongiosa, most parameters indicate bone formation during the first postoperative year. Loading-induced structure changes could not yet be found. The technique can be used to study changes in the architecture of bone grafts. Changes found in the graft's architecture are in accordance with changes in bone density.

Platelet Rich Plasma to Facilitate Wound Healing Following Tooth Extraction

Following tooth removal bone formation normally takes 16 weeks and may result in less than adequate volume for the necessary reconstruction. Platelet rich plasma (PRP) has been promoted as an effective method for improving bone formation. Its use is often expensive, time consuming, or not clinically convenient for the patient and/or clinician. This study examines a simple method for obtaining a "Buffy Coat"-PRP (BC-PRP) and its effect on bone healing following the removal of bilateral mandibular 3rd molars. Subtraction digital radiography and CT scan analysis were used to track changes in radiographic density at PRP treated sites in comparison to ipsilateral non-PRP treated sites. PRP treated sites demonstrated early and significant increased radiographic density over baseline measurements following tooth removal. The greatest benefit of PRP is during the initial 2-week postoperative healing time period (P < .001). During weeks 3 though 12, BC-PRP treatment resulted in significant (P < .0001) increases in bone density compared to control, but there was no significant interaction between time and treatment (P > .05). For the entire time period (0-25 weeks) PRP treatment was significant (P < .0001) and time was significant (P < .0001) but there was no significant interaction (P > .05) between the effect of PRP treatment and time. It required 6 weeks for control extraction sites to reach comparable bone density that PRP treated sites achieved at week 1. Postoperative pain, bleeding, and numbness were not significantly affected by BC-PRP application. Results suggest that this simple technique may be of value to clinicians performing oral surgery by facilitating bone regeneration following tooth extraction.

Qualitative and quantitative radiographic assessment of sealed carious dentin: a 10-year prospective study

The objective of this study was to assess radiographic outcomes after partial carious dentin removal performed in deep caries lesions over a 10-year period. Baseline image was compared to 3 follow-up radiographs (at 6-7 months, 3 years, and 10 years). Tertiary dentin deposition and lesion depth were qualitatively assessed. Radiographic density changes in the radiolucent zone (RZ) beneath the restoration were quantitatively compared to the control areas (CA) using digital subtraction radiography (Friedman repeated-measures analysis of variance). A total of 13 teeth were evaluated. In most cases, lesion depth remained unchanged or decreased (12/13) and tertiary dentin formation was observed (10/13) after the 10-year follow-up. Differences between RZ and CA at the 6- to 7-month and 3-year follow-up periods were similar but significantly lower than those at the 10-year assessment. Sealing of carious dentin arrested the caries process, promoted deposition of tertiary dentin, and induced mineral gain in the radiolucent zone.

Deep Caries Lesions after Incomplete Dentine Caries Removal: 40-Month Follow-Up Study

Radiographic changes after indirect pulp capping (32 teeth in 27 patients) were studied for up to 36–45 months. Radiolucent zone (RZ) depth and tertiary dentine formation were assessed qualitatively and changes in radiographic density (by image subtraction) in RZ and control areas (CA) were estimated. During follow-up there were 1 pulp necrosis, 1 pulp exposure, 3 fractures and 3 withdrawals. Twelve cases showed decreased RZ depth and 4 displayed tertiary dentine. No changes with time in density of CA or RZ, or in the difference between them, were observed. It is concluded that indirect pulp capping arrests lesion progression, suggesting that complete dentine caries removal is not essential for caries control.

Accuracy of quantitative digital subtraction radiography for determining changes in calcium mass in mandibular bone: an in vitro study.

The aim of this in vitro study was to determine the accuracy of digital subtraction radiography (DSR) to detect small changes in calcium mass in alveolar bone adjacent to tooth roots. In each of 4 dried porcine mandible segments, one interproximal and one buccal "defect" region was defined adjacent to a premolar root. A series of cortical and cancellous bone slices with a 50 microns--stepwise increasing thickness (0-5000 microns) were attached to the mandible segments covering the respective "defect" region. Standardized radiographs were quantitatively assessed for density changes using DSR. After dissolving each bone slice in hydrochloric acid, its calcium concentration was photometrically determined. For each bone slice, the mean calcium mass covering a single pixel of the subtraction image was calculated. The Wilcoxon signed-rank test and the Mann-Whitney U-test were used for statistical analysis (alpha = 0.05). A strong linear correlation (r2 = 0.86-1.00; p < or = 0.001) was found between the thickness of the bone slices and their calcium mass. Cortical bone showed a 3.5 times higher mean calcium mass/pixel than cancellous bone. Furthermore, a strong linear correlation (r2 = 0.63-1.00; p < or = 0.001) was found between the mean calcium mass per image pixel and the radiographic density changes. Neither the bone type nor the "defect" localization had a significant influence on radiographic density changes caused by changes in calcium mass. A change in mean calcium mass per image pixel of 0.1-0.15 mg was necessary to be detected by DSR. In conclusion, this study revealed a high accuracy of DSR to detect small changes in calcium mass in alveolar cortical and cancellous bone.

Quantitative digital subtraction radiography for the determination of small changes in bone thickness: An in vitro study

Objective. The objective of this study was to determine the ability of quantitative digital subtraction radiography to detect small changes in bone thickness adjacent to tooth roots. Study design. A series of cortical or cancellous bone slices with a 50 μm-stepwise increasing thickness were attached to 4 porcine mandible sections covering buccal and interproximal “defect” regions. Standardized radiographs were quantitatively evaluated for radiographic density changes with the use of digital subtraction radiography. Furthermore, all radiographs were conventionally evaluated by 10 clinicians. The Wilcoxon signed-rank test and the Mann-Whitney U test were used for statistical analysis (α = 0.05). Results. A high linear correlation was found between the actual thickness of bone slices and radiographic density changes (cortical bone: r 2 = 0.89 to 0.99; cancellous bone r 2 = 0.61 to 0.86, p ≤ 0.001). A certain increase in bone thickness caused a 3 times higher increase in radiographic density for cortical bone than for cancellous bone ( p ≤ 0.05). The detection limits of digital subtraction radiography were 200 μm for cortical and 500 μm for cancellous bone, whereas the detection limits of conventional radiography were 600 μm and 2850 μm, respectively. Conclusions. This in vitro study demonstrated a very high correlation between the objective, quantitative assessment of subtle changes in alveolar bone by digital subtraction radiography and the true changes in bone thickness.

Quantitative digital subtraction radiography for assessment of bone density changes following periodontal guided tissue regeneration.

The quantitative assessment of alveolar bone density changes in periodontal defects following guided tissue regeneration (GTR). Twelve patients with 30 intrabony lesions and 16 furcation defects took part. Standardized radiographic and clinical examinations were carried out immediately before and then 5 and 13 months after surgery. Intra-oral radiographs were evaluated by means of digital subtraction radiography (DSR). Within the subtraction images, a window ('experimental region') was defined covering the visible density changes in the defect area. Background noise was measured by using a similarly sized window ('control region') located in an area not affected by GTR. Bone density changes were quantitatively evaluated by calculation of the mean, standard deviation and maximum and minimum values of the grey-level histogram within these windows. DSR revealed significant bone density gain after GTR in intrabony and furcation defects. While a continuous increase was observed over the 13 month period in intrabony defects, changes in furcation defects occurred mostly in the 5-13 month period. Clinically, a distinct vertical and horizontal attachment gain was found. The correlation coefficients between changes in radiographic density and clinical parameters were low, indicating a difference in the information obtained by the two diagnostic methods. Quantitative DSR is a valuable, non-invasive, objective method to obtain information on density changes in intrabony and furcation defects treated by GTR. However, a full assessment of soft and hard tissue changes requires both clinical evaluation and DSR.

The Relationship Between Probing Attachment Loss and Computerized Radiographic Analysis in Monitoring Progression of Periodontitis

This study attempted to evaluate quantitative changes in radiographic density as an indicator of progression of periodontitis. Twenty-one subjects with a history of periodontitis were monitored at baseline, 3, 6, and 9 months using duplicate probing attachment level (PAL) measurements from stents and computer assisted densitometric image analysis (CADIA) of standardized radiographs. Results indicate that the majority of sites exhibited no PAL change during the 9-month period; however, the percentage of sites with loss increased with time. A mean of 6.1% of the sites/patient exhibited probing attachment loss during the study, as compared to a mean of 38.3% of the sites/patient that exhibited a loss of radiographic density. Due to the two dimensional nature of radiographs, density analysis was calculated in terms of radiographic "complexes" of multiple probing sites. There was significantly more density loss at complexes with greater than or equal to 2 mm of attachment loss than at sites with no change in PAL at 9 months; there was no such difference noted at 3 and 6 months. Also, density loss tended to increase as more sites within each complex experienced PAL. Although there was a significant correlation between mean density and PAL changes during the same time interval, there were wide variations at individual sites. This study suggests that there is a complex relationship between density change on radiographs and PAL change. The difficulties inherent in comparing highly sensitive new technologies to relatively imprecise clinical measurements of the attachment level are discussed.(ABSTRACT TRUNCATED AT 250 WORDS)

Detection and Measurement of Simulated Early Rheumatoid Lesions of the Hand Using Digital Subtraction Radiography

The ability of digital subtraction radiography, a new technique to detect and quantify small bone lesions, is demonstrated. Discrete lesions in the metacarpals of cadaver hands simulated erosive bone loss. Radiographs made before and after removal of bone were digitized and subtracted. Density changes on subtraction images were determined, and bone loss was estimated by an automatic procedure that compared changes in radiographic density with a calibration wedge included in the radiographs. Comparison of estimated bone loss with the weight of bone removed showed reproducible detection and measurement of bone lesions as small as 4.6 mg, a size undetectable using current radiographic methods. Subtraction radiographs of bone chips overlaid on the hand of a volunteer indicated detection limits were similar in vivo. This technique enhanced the radiographic visibility of erosive lesions and thus has the potential to improve the detection of subtle bone changes in clinical settings.

Visualization of stannous fluoride treatment of carious lesions by subtraction radiography

To determine whether treatment with SnF 2 results in changes in radiographic density, eight extracted teeth with lesions confined to the enamel and five with lesions extending into the dentin were radiographed before and after treatment with a 10% SnF 2 solution. Although visual comparison of pretreatment and post-treatment radiographs showed increased density in some areas where the pretreatment radiographs had shown demineralization and unchanged conditions in other instances, subtraction images of these radiographs revealed density increase in all the demineralized areas. Even in cases with white spot lesion not visible on radiographs, the subtraction images disclosed an increase in radiographic density.

Quantitative Radiographic Measurement of Dentinal Lesions

The purpose of this investigation was the comparison of the precision and accuracy of two reference ramp techniques for the quantification of radiographic density changes in teeth. Radiographs (65 kVp, 10 ma, 1 s, and intra-oral ultraspeed film) of transverse sections from extracted permanent human molars were made before and after dentinal lesions were created. Each radiograph contained the image of a tooth section and the aluminum reference ramp. Method A used the image of the ramp on both the before- and after-lesion radiographs, and method B used the image of the ramp only on the before-lesion radiograph. Three groups of lesions (0.525-mm diameter, n = 11; 0.675-mm diameter, n = 9; and the 0.525-mm holes enlarged to 0.675 mm) were measured radiographically by each technique and by direct planimetry of the lesions. Radiographic method B produced results in close agreement with the planimetric measurements. Method B differentiated (p less than 0.05) between groups that had a mean planimetric size difference of 0.10 mm (equivalent to a change in density difference of 0.6%). These density change measurements are in absolute units of mm of aluminum that can be compared between lesions and between samples. This technique may prove useful for the quantification of changes in mineral density of caries lesions detectable in longitudinal radiographic records.

Videodensitometry and chest radiography in the evaluation of pulmonary blood flow and pulmonary oedema in a porcine model of early adult respiratory distress syndrome.

The adult respiratory distress syndrome was induced in pigs (n = 11) by a continuous infusion of E. coli endotoxin in order to evaluate the use of radiographic videodensitometry and chest radiography for assessment of pulmonary circulation and pulmonary oedema. A further aim was to determine the effect of an ionic contrast medium, Urografin 60%, on extravascular lung water (EVLW). The infusion resulted in a decline in arterial oxygen tension. Mean pulmonary arterial pressure increased, and cardiac output decreased, resulting in a marked rise in pulmonary vascular resistance. EVLW increased moderately. The corresponding variables in control animals (saline infusion; n = 5) changed very little. Good correlations were found (r = 0.87-1.0) between absolute flows as measured by the thermodilution technique and relative flows as determined by videodensitometry in animals with pulmonary damage. In the endotoxin group there was a significant correlation (r = 0.75) between the change in EVLW from baseline to the final measurement (at 6 hours) and the corresponding change in radiographic density. Radiographic signs of pulmonary damage were sparse. Only 3 of 11 animals displayed increased radiographic density of the lung parenchyma indicative of pulmonary oedema. Pleural effusion developed in 4 animals. Injection of Urografin 60%, 1 ml X kg-1, caused a slight but significant decrease in EVLW. We propose that at this concentration and dosage the contrast medium acts mainly as an osmotic diuretic.

Estimation of changes in bone calcium content by radiographic densitometry.

A point of conflict often arises when investigators of calcium mobility (as determined by metabolic balance studies) meet with investigators of radiographic bone densitometry (1–6). This is the apparent inability to explain the magnitude of change sometimes observed by densitometry with that thought physiologically possible by proponents of metabolic balance technics. The opinion has often been expressed that changes detectable by quantitative x-ray densitometry are unexplainable on the basis of metabolic balance studies in which a daily negative calcium balance on the order of 500 mg is considered to be high while 500 mg of calcium represents only 0.03 per cent of the entire skeleton. How then can reported changes in radiographic density on the order of 5 to 10 per cent within a single bone (7) be explained on the basis of metabolic balance studies? The described investigation was carried out in an attempt to reconcile the apparent discrepancies between the two methods of measuring bone turnover rate. Th...

STUDIES OF BONE METABOLISM

From the foregoing experiments, it is concluded that viability of the bone cells is not essential in the process of inorganic salt uptake by bone, provided the organic matrix is present and normal. The term "uptake", as used in this report, includes several possible processes: ionic exchange, recrystallization, and the formation of new crystals either in the old matrix or in conjunction with the formation of a new matrix. The latter can be demonstrated histologically in living tissue cultures of bone (Fig. 3). However, the amount of matrix formed over a ten-day period is probably insignificant in the over-all process of salt metabolism in tissue cultures, and, of course, need not be considered in the case of the dead bone (Fig. 4). Mobilization of the inorganic salts from bone, on the other hand, is facilitated by the presence of living cells. A corollary of these conclusions is that uptake of radio-active isotopes is probably not an accurate index of bone-cell "viability". This confirms the conclusion previously suggested by the work of Odell and his associates. A second conclusion reached from the present experiment is that the change in radiographic density in aseptic necrosis of bone is probably the result of combined failure of mobilization of inorganic salts and continued uptake by the necrotic bone from the tissue fluids, in addition to the decrease in density of the surrounding viable bone,—that is, the increase in density of the dead bone is actual as well as relative. An interesting sidelight on these observations is that bone-seeking radio-active emitters, such as radium, probably become relatiely fixed in the skeleton when radiation damage is sufficient to cause necrosis of the cells.

Dental roentgenologic manifestations of systemic disease. I. Endocrine disturbances.

The endocrine glands which are known to have an influence upon the skeleton are the pituitary, thyroid, parathyroid) adrenal, and sex glands. Any quantitative change in the hormones secreted by these glands, be it underproduction or overproduction, may lead to disturbances of growth and metabolism of bones. The teeth and jaws reflect endocrine dysfunction just as do other parts of the skeleton, and the dental effects may remain as a permanent record of the disorder. Any influence that endocrine dysfunction may have upon the teeth themselves is almost entirely limited to the period of their development and is manifested by either retardation or acceleration of development and eruption, or by faulty and imperfect structural development. Defects which occurred in the incisor teeth of rats deprived of their parathyroid glands first led Erdheim (1), in 1911, to the realization that secretion from these glands has an influence upon calcium metabolism. In general, the size of the teeth is not altered in endocrine disturbances. Dwarfs do not have dwarfed teeth, nor are the teeth of the giant necessarily larger than those which might well be seen in persons of normal size. Teeth in which calcification has been completed prior to the onset of the disturbance are unaffected. Hard tooth structure undergoes no demineralization or hypercalcification; therefore) there is no change in radiographic density. Thus the teeth can serve as a gauge of density or as a penetrometer to aid in the recognition of cases in which skeletal complications are present. Effects of endocrine disturbances upon the bone of the jaws are in a large measure similar to those on other bones of the skeleton. Disturbances which occur during the period of growth and development may be manifested by retardation and underdevelopment or by acceleration and overdevelopment of the jaws. In instances in which overdevelopment of the skeleton occurs, the mandible, because of the normal persistence of growth cartilage of the condyle, is prone to undergo relatively greater enlargement than the majority of the other bones. Where the structure or quality of the bone is altered, the intraoral dental roentgenogram is of value, for it often reveals minimal distortion of trabecular pattern and mild demineralization in instances in which it may not be demonstrable in other roentgenograms. One of the changes which may take place in case of demineralization is the obliteration or disappearance of the lamina dura, the uniform radiopaque line which represents the alveolar socket. This observation has been made use of in the diagnosis, notably, of hyperparathyroidism. It is not, however, peculiar to hyperparathyroidism, but is seen also in several other conditions in which there are associated demineralization and osteoporosis, among them, Cushing's syndrome, sprue, vitamin D deficiency, and Paget's disease.