Bony Regions Research Articles

Sub-second high dose rate brachytherapy Monte Carlo dose calculations withbGPUMCD

To establish the accuracy and speed of bGPUMCD, a GPU-oriented Monte Carlo code used for high dose rate brachytherapy dose calculations. The first objective is to evaluate the time required for dose calculation when full Monte Carlo generated dose distribution kernels are used for plan optimization. The second objective is to assess the accuracy and speed when recalculating pre-optimized plans, consisting of many dwell positions. bGPUMCD is tested with three clinical treatment plans : one prostate case, one breast case, and one rectum case with a shielded applicator. Reference distributions, generated with GEANT4, are used as a basis of comparison. Calculations of full dose distributions of pre-optimized treatment plans as well as single dwell dosimetry are performed. Single source dosimetry, based on TG-43 parameters reproduction, is also presented for the microSelectron V2 (Nucletron, Veenendaal, The Netherlands). In timing experiments, the computation of single dwell position dose kernels takes between 0.25 and 0.5 s. bGPUMCD can compute full dose distributions of previously optimized plans in ∼2 s. bGPUMCD is capable of computing pre-optimized brachytherapy plans within 1% for the prostate case and 2% for the breast and shielded applicator cases, when comparing the dosimetric parameters D90 and V100 of the reference (GEANT4) and bGPUMCD distributions. For all voxels within the target, an absolute average difference of approximately 1% is found for the prostate case, less than 2% for the breast case and less than 2% for the rectum case with shielded applicator. Larger point differences (>5%) are found within bony regions in the prostate case, where bGPUMCD underdoses compared to GEANT4. Single source dosimetry results are mostly within 2% for the radial function and within 1%-4% for the anisotropic function. bGPUMCD has the potential to allow for fast MC dose calculation in a clinical setting for all phases of HDR treatment planning, from dose kernel calculations for plan optimization to plan recalculation.

Accuracy of CT-based attenuation correction in PET/CT bone imaging

We evaluate the accuracy of scaling CT images for attenuation correction of PET data measured for bone. While the standard tri-linear approach has been well tested for soft tissues, the impact of CT-based attenuation correction on the accuracy of tracer uptake in bone has not been reported in detail. We measured the accuracy of attenuation coefficients of bovine femur segments and patient data using a tri-linear method applied to CT images obtained at different kVp settings. Attenuation values at 511 keV obtained with a 68Ga/68Ge transmission scan were used as a reference standard. The impact of inaccurate attenuation images on PET standardized uptake values (SUVs) was then evaluated using simulated emission images and emission images from five patients with elevated levels of FDG uptake in bone at disease sites. The CT-based linear attenuation images of the bovine femur segments underestimated the true values by 2.9 ± 0.3% for cancellous bone regardless of kVp. For compact bone the underestimation ranged from 1.3% at 140 kVp to 14.1% at 80 kVp. In the patient scans at 140 kVp the underestimation was approximately 2% averaged over all bony regions. The sensitivity analysis indicated that errors in PET SUVs in bone are approximately proportional to errors in the estimated attenuation coefficients for the same regions. The variability in SUV bias also increased approximately linearly with the error in linear attenuation coefficients. These results suggest that bias in bone uptake SUVs of PET tracers ranges from 2.4% to 5.9% when using CT scans at 140 and 120 kVp for attenuation correction. Lower kVp scans have the potential for considerably more error in dense bone. This bias is present in any PET tracer with bone uptake but may be clinically insignificant for many imaging tasks. However, errors from CT-based attenuation correction methods should be carefully evaluated if quantitation of tracer uptake in bone is important.

Feasibility of Whole-body MRI for Detecting Metastatic Myxoid Liposarcoma: A Case Series

No feasible method currently exists to evaluate systemic metastasis in patients with myxoid liposarcoma. The purpose of this study was to determine the feasibility of performing whole-body magnetic resonance imaging (MRI) to detect metastatic myxoid liposarcoma. From June 2008 to May 2010, all patients who were newly diagnosed with myxoid liposarcomas at our institution underwent whole-body MRI along with other conventional imaging methods. We divided the whole body into 38 sections (7 soft tissue sections and 31 bone tissue sections). In total, there were 570 regions (105 soft tissue regions and 465 bony regions) in 15 patients (10 men and 5 women) who underwent whole-body MRI.Of 105 soft tissue regions, there were 4 true positives, 3 false positives, 1 false negative, and 97 true positives. Of 465 bone tissue regions, there were 11 true positives, 5 false positives, 2 false negatives, and 447 true negatives. In soft tissue, whole-body MRI for the detection of metastatic lesion showed a sensitivity of 80%, a specificity of 97.0%, a positive predictive value of 57.1%, and a negative predictive value of 99.0%. In bone tissue, whole-body MRI had a sensitivity of 84.6%, a specificity of 98.9%, a positive predictive value of 68.8%, and a negative predictive value of 99.6%.Whole-body MRI is feasible and effective for detecting bone and soft tissue metastasis in patients with myxoid liposarcoma.

Optical metrology analysis of the lower jaw deformations

New optical stereometric methods based on both contact and noncontact mechanisms for displacement measurement have become common methods in biomechanical behavior research of biomaterials, bone and soft tissue. The aim of this study was to register and measure possible deformations of the lower jaw (mandible) with the intact dental arch using optical metrology method. The system for full field measurement of deformations (strains) comprised of two digital cameras for a synchronized stereoview of the specimen, and the Aramis software. The maximum mandibular bone strains were measured in the regions of the lower first premolar and the lower second molar. In the action force of 500 N simulated in the region of the first lower premolar the intensity of deformation was 86 microm. The value of maximum strain in the bone around the molars was 24 microm for the force of 500 N acting on the second lower molar. When it comes to premolars, 3-5 times stronger deformation was observed in the region of the first lower premolar, compared to the deformation values of the second lower premolar area. Under loading of the applied forces the measured strains were in the elastic deformation area, meanning that the dependence of force and deformity is linear. The highest values of strain measurements obtained by the optical method were found in the jaw bone tissue around the loading teeth, and the bony regions of the triangle and mental region. According to the obtained results from the Aramis processing software it can be concluded that this method is applicable in a variety of biomedical research.

Development of pigmentation and skeleton in ontogenesis of Fedorov eelpout Zoarces fedorovi (Zoarcidae, Perciformes) from the Sea of Okhotsk

The development of pigmentation of the Fedorov eelpout (Zoarces fedorovi) from hatching out of egg integuments to delivery is studied. In Z. fedorovi, the adult coloration develops immediately, without larval coloration, obviously, due to viviparity. Comparative analysis of the sequence of anlage and morphogenesis of elements of the cartilaginous skeleton and the bony skeleton demonstrated that the sequence of anlage of cartilaginous and bony regions of the skeleton of Z. fedorovi principally correspond to the sequence in Z. viviparus and in other perciform fishes. Morphogenesis of the bones of ethmoidal and interorbital regions of the skull, of the axial skeleton, and of the skeleton of the caudal fin is highly similar in eelpouts and other fishes of the suborder Zoarcoidei, differing from that in the generalized perciform fishes. At the same time, the larvae of Z. fedorovi in comparison with Z. vivparus are characterized by a higher rate of development of the skeleton. Advanced structural traits in structure of the skeleton of larvae of Z. viviparus in comparison with Z. fedorovi are pointed out. Differences in size at which anlage of bony elements occurs, as well as in the formation of particular bony elements seem to indicate to a rather prolonged divergence of these species.

Analysis of the Anatomic Changes of the Aging Facial Skeleton Using Computer-Assisted Tomography

The bony skeleton serves as the scaffolding for the soft tissues of the face; however, age-related changes of bony morphology are not well defined. This study sought to compare the anatomic relationships of the facial skeleton and soft tissue structures between young and old men and women. A retrospective review of CT scans of 100 consecutive patients imaged at Duke University Medical Center between 2004 and 2007 was performed using the Vitrea software package. The study population included 25 younger women (aged 18-30 years), 25 younger men, 25 older women (aged 55-65 years), and 25 older men. Using a standardized reference line, the distances from the anterior corneal plane to the superior orbital rim, lateral orbital rim, lower eyelid fat pad, inferior orbital rim, anterior cheek mass, and pyriform aperture were measured. Three-dimensional bony reconstructions were used to record the angular measurements of 4 bony regions: glabellar, orbital, maxillary, and pyriform aperture. The glabellar (p = 0.02), orbital (p = 0.0007), maxillary (p = 0.0001), and pyriform (p = 0.008) angles all decreased with age. The maxillary pyriform (p = 0.003) and infraorbital rim (p = 0.02) regressed with age. Anterior cheek mass became less prominent with age (p = 0.001), but the lower eyelid fat pad migrated anteriorly over time (p = 0.007). The facial skeleton appears to remodel throughout adulthood. Relative to the globe, the facial skeleton appears to rotate such that the frontal bone moves anteriorly and inferiorly while the maxilla moves posteriorly and superiorly. This rotation causes bony angles to become more acute and likely has an effect on the position of overlying soft tissues. These changes appear to be more dramatic in women.

Consequences of modern anthropometric dimensions for radiographic techniques and patient radiation exposures

Radiographic techniques are devised on the basis of anatomic dimensions. Inaccurate dimensions can cause radiographs to be exposed inappropriately and patient radiation exposures to be calculated incorrectly. The source of anatomic dimensions in common usage dates back to 1948. The objective of this study was to compare traditional and modern anthropometric data, use modern dimensions to estimate potential errors in patient exposure, and suggest modified technique guidelines. Anthropometry software was used to derive modern anatomic dimensions. Data from routine annual testing were analyzed to develop an x-ray generator output curve. Published tabulated data were used to determine the relationship between tissue half-value layer and kilovoltage. These relationships were used to estimate entrance skin exposure and create a provisional technique guide. While most anatomic regions were actually larger than previously indicated, some were similar, and a few were smaller. Accordingly, exposure estimates were higher, similar, or lower, depending on the anatomic region. Exposure estimates using modern dimensions for clinically significant regions of the trunk were higher than those calculated with traditional dimensions. Exposures of the postero-anterior chest, lateral chest, antero-posterior (AP) abdomen, male AP pelvis, and female AP pelvis were larger by 48%, 31%, 54%, 52%, and 112%, respectively. The dimensions of bony regions of the anatomy, such as the joints and skull, were unchanged. These findings are consistent with the idea that anatomic areas where fat is deposited are larger in the modern U.S. population than they were in previous years. Exposure techniques for manual radiography and calculations of patient dose for automatic exposure control radiography should be adjusted according to the modern dimensions. Population radiation exposure estimates calculated in national surveys should also be modified appropriately.

Poster - Thurs Eve-39: Full 3D dose calculation for total body irradiation: A comparison study between treatment planning systems in homogeneous and heterogeneous conditions.

To perform full 3D heterogeneous dose calculations for total body irradiation (TBI) cases and compare different treatment planning softwares (TPS). A retrospective study was performed on 7 patients. Dose distributions obtained with Pinnacle3 v.7.9u (Philips Medical Systems) were compared with the ones calculated using our actual TBI planning system Theraplan Plus (TPP) by MDS Nordion/Nucletron. Two different Pinnacle3 models were studied: standard beam commissioning (std_Pinnacle3 ) and TBI commissioning (TBI_Pinnacle3 ). For the later case, commissioning was adapted for the special TBI conditions (extended SSD of 190cm, large field, acrylic beam spoiler, and out of field dose (OFD)). Significant differences are found between the TPP, std_Pinnacle3 and TBI_Pinnacle3 dose distributions. For the relative mid-line doses, differences up to 12% were observed. Systematic overestimations of 5% were found in patients extremities between TPP and TBI_Pinnacle3 . Average dose underestimation of 3% was observed between std_Pinnacle3 and TBI_Pinnacle3 . Differences in patient extremities are attributed to the OFD contribution which is not correctly computed in TPP and std_Pinnacle3 . Dose comparison outside the patient's mid-line showed greater differences (up to 20%) between models. Accurate 3D heterogeneous dose calculations with TBI_Pinnacle3 model show major differences (homogeneous versus heterogeneous) in high and low density regions. Dose overestimation of 5% was observed in bony regions and dose underestimation of 5% to 10% was observed in lung regions. Those results are of major interest since they show a strong dependence of the dose calculation outcome on both TPS and commissioning used, potentially leading to significant dose misevaluation.

SU‐GG‐T‐425: Radiobiologically Quantified Treatment Setup Uncertainties Based On Megavoltage (MV) CT Imaging

Purpose: To evaluate and compare the expected effectiveness of the planned and delivered dose distributions in prostate cancer radiotherapy. The average setup uncertainties were determined by using the on‐board megavoltage computed tomography (MVCT) capabilities of the tomotherapy HiArt unit. Method and Materials: Co‐registrations between daily MVCT and planning CT were used. Before the delivery of each treatment an MVCT image was acquired. The therapists registered the MVCT image with the planning kilovoltage computed tomography (kVCT) images. The registration criteria were based on bony anatomy and contoured regions of interest. For a typical prostate cancer patient the dose distributions of the Helical Tomotherapy plan and that of the average shifted delivery registration were used. The dose distributions were compared based on dosimetric criteria and the biologically effective uniform dose (BEUD) together with the complication‐free tumor control probability (P+). Results: The average shifts that were observed are 10.7 mm for the vertical, 4.0 mm for the longitudinal and 0.5 mm for the lateral directions, respectively. At the optimum dose levels of the planned and delivered dose distributions, the P+ values are 84.7% and 84.0%, respectively. The total control probabilities, PB are 93.0% and 92.9%, whereas the total complication probabilities, PI are 8.3% and 8.9%. More specifically, the response probabilities of the different tissues are 95.6% and 95.5% for the GTV, 97.4% and 97.3% for the seminal vesicles, 0.8% and 0.7% for bladder and 7.6% and 8.3% for rectum. Conclusion: It is shown that the intra‐fraction movement of tumors can be reduced by using the MVCT co‐registration. This appears to be a powerful tool, which can result in improved sparing of critical structures, while delivering high doses to the target. The use of P+ — BEUD diagrams to compare similar treatment plans may show that in radiobiological terms they may be quite different.

Early‐onset degeneration of the intervertebral disc and vertebral end plate in mice deficient in type IX collagen

Type IX collagen is an important component of the intervertebral disc extracellular matrix. Mutations in type IX collagen are associated with premature disc degeneration in mice and a predisposition to disc disorders in humans. The aim of this study was to assess the prevalence and timeline of intervertebral disc degeneration in mice homozygous for an inactivated Col9a1 gene. Intact spine segments were harvested from wild-type (WT) and type IX collagen-knockout (Col9a1(-/-)) mice at 3, 6, and 12 months of age. Sagittal spine sections were evaluated for evidence of histologic changes, by 2 blinded graders, using a semiquantitative grading method. There was evidence of more degeneration of the disc and end plate in the spines of Col9a1(-/-) mice compared with those of WT controls, at most time points. These findings were significant for the disc region at 3 and 6 months (P<0.01) and at 12 months (P<0.10) and for the end plate region only at 6 months (P<0.10). Degenerative changes in the disc consisted of cellular changes and mucous degeneration. Degeneration in the end plates was associated with more cell proliferation, cartilage disorganization, and new bone formation. A deletion mutation for type IX collagen is associated with connective tissue changes characteristic of musculoskeletal degeneration in bony and cartilaginous tissue regions. Some of the observed changes were similar to cartilage changes in osteoarthritis, while others were more similar to disc degenerative changes in humans. The finding of premature onset of intervertebral disc degeneration in this mouse model may be useful in studies of the pathology and treatment of human disc degeneration.

Validation of phalanx bone three-dimensional surface segmentation from computed tomography images using laser scanning

To examine the validity of manually defined bony regions of interest from computed tomography (CT) scans. Segmentation measurements were performed on the coronal reformatted CT images of the three phalanx bones of the index finger from five cadaveric specimens. Two smoothing algorithms (image-based and Laplacian surface-based) were evaluated to determine their ability to represent accurately the anatomic surface. The resulting surfaces were compared with laser surface scans of the corresponding cadaveric specimen. The average relative overlap between two tracers was 0.91 for all bones. The overall mean difference between the manual unsmoothed surface and the laser surface scan was 0.20 mm. Both image-based and Laplacian surface-based smoothing were compared; the overall mean difference for image-based smoothing was 0.21 mm and 0.20 mm for Laplacian smoothing. This study showed that manual segmentation of high-contrast, coronal, reformatted, CT datasets can accurately represent the true surface geometry of bones. Additionally, smoothing techniques did not significantly alter the surface representations. This validation technique should be extended to other bones, image segmentation and spatial filtering techniques.

Clinical significance of musculoskeletal finite element model of the second and the fifth foot ray with metatarsal cavities and calcaneal sinus

The aim of this study was to establish musculoskeletal finite element (FE) model of the second and the fifth foot ray accounting for metatarsal cavities and calcaneal sinus. The model was then used to predict the effects of metatarsal cavities and calcaneal sinus on internal stresses/strains of plantar longitudinal arches. The geometry of foot bones and soft tissues were constructed by CT and MRI images of Virtual Chinese Human "female No. 1". Two types of nonlinear FE models of sagittal foot rays were developed with or without metatarsal cavities and calcaneal sinus using ANSYS software package. The sagittal trabecular architecture of metatarsals and calcaneus were obtained by cutting, defatting and bleaching fresh foot specimen of a cadaver. The model proposed was able to describe the isostatic stress flows in sagittal planes of plantar longitudinal arches. The size of metatarsal cavity or calcaneal sinus could affect stress/strain distributions on metatarsals and calcaneus, but had almost no effects on stress/strain of other foot bones and plantar soft tissues. During balance standing, the maximum von Mises stresses were predicted at the shaft and the basis of metatarsals, while the maximum strains of bony regions were found around metatarsal cavities. Among plantar soft tissues, relative high tensions were burdened by plantar fascia, followed by long plantar ligament. The minimum tensions occurred in plantar intrinsic muscles. The study shows that the tension/compression stress flows are geometrically similar with the tension/compression trabecular architectures in sagittal sections of metatarsal and calcaneus. The FE predictions of stress/strain concentration on metatarsals and fascia are useful in enhancing biomechanical knowledge on metatarsal stress fractures and plantar fasciitis.

Important macroscopic and microscopic differences in the bony and cartilaginous regions adjacent to the lumbar intervertebral disc between animal and man: a caveat to overinterpretation of animal experiments

Important macroscopic and microscopic differences in the bony and cartilaginous regions adjacent to the lumbar intervertebral disc between animal and man: a caveat to overinterpretation of animal experiments

Correlation study of scanning acoustic microscope reflection coefficients and image brightness intensities of micrographed osteons.

Scanning acoustic microscopy (SAM) of Haversian bone at high frequency clearly shows differences in the brightness (gray) levels of individual osteons, which were observed to correspond to the differences in reflection coefficients measured with the SAM technique: the darker the bony regions on the SAM micrographs, the lower the SAM reflection coefficient values, and vice versa. We studied the correlation between differences in brightness and the related reflection coefficients of osteons on undecalcified transverse sections of goat tibial diaphysis using a 400-MHz burst mode lens on the Olympus UH3 SAM. Results showed that there was a strong linear correlation between brightness intensities and the corresponding reflection coefficients, with a correlation coefficient r = 0.99 ( P << 0.001) using gray level 210 as cutoff. This result suggested that the image brightness intensity of osteonic bone could be measured retrospectively to provide information on the stiffness of the corresponding bone matrix.

Osteocyte-based Image Analysis for Quantitation of Histologically Apparent Femoral Head Osteonecrosis: Application to an Emu Model

Femoral head osteonecrosis is often characterized histologically by the presence of empty lacunae in the affected bony regions. The shape, size and location of a necrotic lesion influences prognosis, and can, in principle, be quantified by mapping the distribution of empty lacunae within a femoral head. An algorithm is here described that automatically identifies the locations of osteocyte-filled vs. empty lacunae. The algorithm is applied to necrotic lesions surgically induced in the emu, a large bipedal animal model in which osteonecrosis progresses to collapse, as occurs in humans. The animals' femoral heads were harvested at sacrifice, and hematoxylin and eosin-stained histological preparations of the coronal midsections were digitized and image-analyzed. The algorithm's performance in detecting empty lacunae was validated by comparing its results to corresponding assessments by six trained histologists. The percentage of osteocyte-filled lacunae identified by the algorithm vs. by the human readers was statistically indistinguishable.

Biosynthesis of proteoglycan in bone and cartilage of parathyroid hormone-related protein knockout mice

Proteoglycans are suggested to regulate cell adhesion, differentiation and mineralization of hard tissues. In vitro studies have shown that many humoral and local factors regulate proteoglycan synthesis. Among them, parathyroid hormone (PTH) and parathyroid hormone-related protein (PTHrP) have potent stimulating effects on proteoglycan synthesis. However, the exact role of PTHrP on the biosynthesis and metabolism of proteoglycans during skeletal development is not clear. To clarify this point, we examined bony and cartilaginous explants of newborn mice with disrupted PTHrP alleles. Ribs of homozygous PTHrP-knockout mice and wildtype littermates were dissected into bony and cartilaginous regions and metabolically labeled with [35S]sulfate in culture. Radiolabeled proteoglycans were analyzed by column chromatography. The elution profiles of [35S]-labeled proteoglycan from cartilaginous explants did not differ between homozygous PTHrP-knockout mice and wild-type littermates. However, the amount of labeled proteoglycan in homozygous PTHrP-knockout mice was only 4%-5% that of wild-type littermates. In contrast with cartilaginous explants, the amount of labeled proteoglycans in bony explants did not differ between the two genotypes. Interestingly, besides the common major peak (Kd = 0.10-0.16) observed in the bony explants of both genotypes, a minor peak (Kd = 0.42) was specifically present in homozygous PTHrP-knockout mice. This minor peak was earlier than that of free glycosaminoglycan (GAG) chains, suggesting that the core protein, but not GAG chain, was cleaved in the bony explants of homozygous PTHrP. These findings demonstrate a crucial nonredundant role of PTHrP in the regulation of proteoglycan synthesis and metabolism during skeletal development.

A comparison of clinical target volumes determined by CT and MRI for the radiotherapy planning of base of skull meningiomas

Purpose: To assess the utility of image registration and to compare the localization of clinical target volumes (CTV) using CT and MRI for patients with base of skull meningiomas undergoing radiotherapy. Methods and Materials: Seven patients were imaged using CT and a T1-weighted MR volumetric sequence. Following image registration using a chamfer-matching algorithm, transaxial MR slices were reconstructed to match the planning CT slices. The accuracy of the image fusion was assessed in a preliminary study with matching accuracy better than 1.5 mm. The CTV in each patient was separately segmented by two independent observers for both CT and reconstructed MR image sets. Scalar and vector assessments were made of the difference in radial extent between the two outlines on each transaxial plane for all patients. A positive vector value corresponded to a greater extension of the tumor on MR compared to CT and vice versa. Scalar measurements compared the modulus of the differences between MR and CT, regardless of which volume was more extensive. Qualitative comparisons were also performed. Results: Interobserver difference was small with a mean (± 1SD) volume difference of 1.5 ± 1.5 cm 3 for CT and 0.5 ± 1.0 cm 3 for MRI. The mean CT- and MR- CTVs were 17.6 ±10.8 and 19.6 ±14.2 cm 3 respectively. The mean overlap and composite volumes were 13.8 ±10.1 and 23.3 ±14.8 cm 3 respectively. Average scalar differences in the left, right, anterior, and posterior directions were 6.0 ± 7.0, 3.3 ± 2.5, 4.9 ± 3.9, and 4.5 ± 5.0 mm respectively. The average vector differences were 3.3 ± 8.5, −0.3 ± 3.8, 1.1 ± 5.8, 1.5 ± 6.4 mm (for left, right, anterior, and posterior directions respectively). Qualitatively, MR appeared to discern more tumor involvement in soft tissue regions adjacent to the skull base whereas CT appeared to provide larger target volumes within bony regions. Conclusions: MRI appeared to define CTVs that were larger but not inclusive of CT-defined CTVs. Although the average vector differences were small, the differences on individual borders could be large. In some instances, the CT or MR volumes were vastly different, each providing separate information. Therefore, the use of MRI and CT is complementary. Until accurate histological confirmation of disease extent is available, it is prudent to consider composite CT/MR volumes for the radiotherapy planning of base of skull meningiomas.

Fractal dimension in radiographic analysis of alveolar process bone

This in vitro study examined radiographic fractal dimension changes in alveolar process bone during simulated osteoporosis. Ten specimens of human maxillary alveolar process bone were progressively decalcified, and the percentage of calcium lost at each decalcification stage was quantified. Four radiographs of each specimen, together with an aluminum step-wedge, were exposed at 70 kVp at each stage. The test set of 560 radiographs was digitized, identical bony regions of interest were selected from the density-corrected images of each specimen, the regions were digitally filtered to reduce film-grain noise, and fractal dimension was computed on a line-to-line basis. Correlation analysis quantified the relationship between calcium loss and fractal dimension change. Analysis of variance and Duncan's multiple range test determined whether a difference existed in fractal dimension computed from images at x-ray beam angulations of -5, 0, and +5 degrees. A strong correlation (average r = -0.94, p < or = 0.0037) was found between generalized demineralization and decreasing fractal dimension. In every bone sample fractal dimension changed significantly (p < or = 0.0189) with angular change. Radiographic fractal dimension holds promise for detecting simulated osteoporosis in the maxilla under ideal conditions, but the sensitivity of fractal dimension to small x-ray beam angular change renders its clinical application questionable.

Fractal analysis of trabecular patterns in projection radiographs. An assessment.

Fractal analysis of digitized images has been investigated in recent years as a potential measure of structural bone strength. Several technical issues associated with such measurements are assessed. In a series of experiments using a hand phantom, the effects of system noise and modulation transfer function on fractal dimension were explored. The authors evaluated a method for correcting the estimated power spectrum using a step-wedge image exposed and digitized under identical conditions as a reference. System noise and modulation transfer function significantly affect estimated fractal dimension in bony regions computed from conventional radiographs. Before conventional radiographs are used for fractal analysis in the clinical environment, many of the technical problems associated with this methodology must be addressed.

Biocytin: a neuronal tracer compatible with rapid decalcification procedures

The compatibility of neuronal tract-tracing and decalcification procedures was examined in salamander nasal chemosensory systems. Biocytin, but not horseradish peroxidase, retained its labeling capacity following rapid decalcification of the cranial bone. The combination of biocytin tract-tracing and decalcification procedures allows the visualization of labeled neurons and/or their projections within bony regions of intact specimens.