Accuracy of microCT in the quantitative determination of the degree and distribution of mineralization in developing bone

Purpose: To evaluate the accuracy and applicability of a commercially available microCT system for comparative measurements of the degree and distribution of mineralization of developing bone. Material and Methods: Homogeneous K₂HPO₄ solutions with different concentrations (range 0-800 mg/cm³) were used to assess the accuracy of a microCT system equipped with a polychromatic X-ray source. Both high (45 kV) and low (70 kV) tube peak voltages were explored. The resulting attenuation was compared with calculated theoretical attenuation values to estimate the accuracy. As an example of its applicability, the method was used to assess changes in the degree of mineralization of various regions of the mandible from two pigs of different developmental age. Results: On average, the estimated error of the measured linear attenuation was 10% or less. Accuracy was dependent on the average mineral concentration, the size of the sample, and the energy of the X-ray beam. The accuracy of the microCT system appeared sufficient to distinguish regional differences in the degree of mineralization within and between specimens of developing mandibular bone. Furthermore, the resolution of the system allowed identification of different degrees of mineralization within trabeculae. Conclusion: Accuracy of microCT with polychromatic radiation can be considered adequate for assessment of the degree of mineralization of developing bone. Therefore, this method provides a three-dimensional means by which to simultaneously investigate the bone structure as well as the degree of mineralization during development in a non-destructive manner and with high resolution.     

The reproducibility of single photon absorptiometry in a clinical setting

The reproducibility of single photon absorptiometry (SPA) results for detection of changes in bone mineral content (BMC) was evaluated in a clinical setting. During a period of 18 months with 4 different sources, the calibration scans of an aluminium standard had a variation of less than 1% unless the activity of the ¹²⁵I source was low. The calibration procedure was performed weekly and this was sufficient to correct for drift of the system. The short term reproducibility in patients was assessed with 119 duplicate measurements made in direct succession. The best reproducibility (CV=1.35%) was found for fat corrected BMC results expressed in g/cm, obtained at the site proximal to the 8 mm space between the radius and ulna. Analysis of all SPA scans made during 1 year (487 scans) showed a failure of the automatic procedure to detect the space of 8 mm between the forearm bones in 19 scans (3.9%). A space adjacent to the ulnar styloid was taken as the site for the first scan in these examinations. This problem may be recognized and corrected relatively easy. A significant correlation was found between BMC of the lower arm and BMC of the lumbar spine assessed with dual photon absorptiometry. However, the error of estimation of proximal BMC (SEE=20.0%) and distal BMC (SEE=19.4%) made these measurements of little value to predict BMC at the lumbar spine in individuals. The short term reproducibility in patients combined with the long term stability of the equipment in our clinical setting showed that SPA is a reliable technique to assess changes in bone mass at the lower arm of 4% between 2 measurements with a confidence level of 95%.     

Coralline hydroxyapatite bone graft substitutes in a canine diaphyseal defect model: radiographic features of failed and successful union

Radiographic and densitometric evaluation of a new type of bone graft substitute derived from reef-building sea coral via a hydrothermal chemical exchange process was undertaken in a canine diaphyseal defect model. Comparably sized blocks of this material and autogenous iliac cortical-cancellous graft were implanted into the respective radial diaphyses of seven dogs. Qualitative and quantitative radiographic assessment was performed during the immediate postoperative period and at 3 months following surgery. Significant complications were observed radiographically in over half of the coralline implanted limbs, including failed union, graft fracture, and loosening of internal fixation hardware. No significant difference was noted in degree of native osseous ingrowth between the implants and the autografts, and the latter exhibited a higher success rate. Radiographic film densitometry was found not to be reliably predictive of coralline implant behavior in the individual case. It is concluded that coralline hydroxyapatite bone graft substitutes appear to offer no particular advantage over autogenous grafts in the management of diaphyseal defects, although further investigation is warranted since other factors may be responsible for the unfavorable findings in this study.This work has been presented at the 34th Annual Meeting of The Association of University Radiologists. Hartford, Connecticut, May 4–9, 1986     

MR Imaging of Medullary Streaks in Osteosclerosis: A Case Report

We present a case of medullary sclerosis of the appendicular skeleton in a patient with chronic renal insufficiency for whom MR imaging findings were characteristic. T1- and T2-weighted MR images showed multiple vertical lines (medullary streaks) of low signal intensity in the metaphyses and diaphyses of the distal femur and proximal tibia.     

Bone metastases as the presenting manifestation of rhabdomyosarcoma in childhood

Rarely, rhabdomyosarcoma can present with bone pain and bone lesions on radiographs without evidence of a primary tumor. Of 428 children with biopsyproven rhabdomyosarcoma, four presented with radiographic evidence of bone metastases, but no primary tumor was found on subsequent evaluation. On radiographs, these metastases, located most commonly in the metaphyses of the extremities and in the spine, displayed a destructive or diffusely permeative pattern without sclerotic margins and mimicked the more common neuroblastoma. One patient also had diaphyseal cortical lytic metastases of the tibia. Radiographs defined metastases of the extremities better than the correlative bone scans. In the spine, on T2-weighted magnetic resonance (MR) images, metastases displayed high signal intensity which contrasted with the low-signal-intensity marrow in these pediatric patients. On histopathologic examination, metastatic rhabdomyosarcoma was composed of small cells of variable size, shape, and growth pattern similar to other round cell tumors. A positive desmin immunohistochemical test helped to establish the diagnosis. The radiologist, pathologist, and clinician should be aware of this unusual presentation of rhabdomyosarcoma so that suitable immunohistochemical tests are performed and appropriate chemotherapy given.     

骨血管源性恶性肿瘤的临床分析

目的 回顾性分析临床上少见的血管源性恶性骨肿瘤的诊断、治疗和临床疗效.方法 从1998年10月至2008年11月我科诊治7例骨血管源性恶性肿瘤患者,包括5例血管内皮瘤和2例血管肉瘤.男4例,女3例;年龄19～76岁,平均42.6岁.1例为多中心病变,6例为单中心.1例病变位于椎体,其余6例位于四肢骨.所有患者均以局部疼痛就诊,病变影像学表现均为溶骨性破坏.其中2例血管肉瘤伴有软组织包块.1例脊柱病变接受边缘切除和术后放疗,5例接受广泛切除重建或截肢术,未行放化疗,另外1例放弃治疗.所有患者均经病理学诊断确诊,平均随访40个月(1～89个月).结果 股骨上段血管肉瘤患者半盆截肢后于术后17个月死于肺和内脏多发转移.脊柱血管内皮瘤患者术后3年死于其他原因.胫骨上端血管内皮瘤患者术后6年出现局部软组织复发,予以再次完整切除.保守治疗的患者带瘤生存,其他3例患者均无瘤生存.结论 骨的血管源性恶性肿瘤临床少见,主要根据病理学检查确诊,同一解剖部位的多中心病灶对诊断有一定特异性.手术广泛切除为治疗四肢病变的主要手段,椎体病变瘤内刮除后可辅以术后放疗.血管肉瘤恶性程度高、预后差.     

X线灰度与骨质厚度相关关系测试

目的：在仅采用X线平片条件下实现对骨的局部区域进行三维测量。方法：采用低速骨锯制作多层薄骨片，叠摞成螺旋阶梯，作为与临床实际拍摄对象最接近的标定块，测试了其厚度与X线灰度的相关关系。结果：得到厚度与X线灰度的相关关系可用三次曲线拟合，并且在骨质厚度小于3．8mm时，可以简化为线性拟合。结论：借助本文骨性螺旋阶梯标定块，能实现通过X线平片灰度较精确地计算X线穿过的骨质厚度。     

不同灭菌法对深冻及冻干人骨拉力螺钉生物力学性能的影响

目的 测试不同灭菌法对深冻及冻干人骨拉力螺钉（ｌａｇ－ｓｃｒｅｗ ｍａｄｅ ｗｉｔｈ ｈｕｍａｎ ｂｏｎｅ,ＬＨＢ）的剪切和扭转生物力学性能的影响。方法 取青壮年新鲜尸体标本的股骨干,经深冻后制成４８枚直径为５ｍｍ的ＬＨＢ,随机等分成６组（Ｆ￣Ｆ）。分别作如下处理：Ａ组：单纯深冻;Ｂ组：深冻＋环氧乙烷（ｅｔｈｙｌｅｎｅ ｏｘｉｄｅ,ＥＯ）熏蒸;Ｃ组：深冻＋＾６０Ｃｏ照射,Ｄ组：深冻＋冻干;Ｅ组：深     

Anatomy and pathology of the sesamoid bones

Summary The sesamoid bones were studied in 100 hands and feet in 50 cadavers and in 1000 radiographs of the hands of South Sinai Bedouin children. The sesamoids of the metacarpophalangeal joint of the thumb and metatarsophalangeal joints of the hallux were always present in the dissections and radiographs. Other sesamoids were observed in the radiographs of the metacarpophalangeal joints of the index finger in 50% of the cases, the middle finger in 3%, the ring finger in 1% and the little finger in 70%. Sesamoids were also seen in 62% of the interphalangeal joints of the thumb. There are differences between the hand and the foot in relation to the occurrence of degenerative changes in the joints. In the thumb, the metacarpophalangeal joint is involved macroscopically in 75% of the cases, and only in 13% of the radiographs, with the pathological changes located in one or the other part of the joint. In the hallux, 40% of the cases are involved both macroscopically and in radiographs, but all the parts of the joint are affected.

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Résumé Pour étudier les os sésamoïdes (OS), 100 mains et 50 pieds ont été disséqués sur le cadavre et les radiographies des mains de 1000 enfants bédouins du sud Sinaï ont été examinées.Les os des articulations métacarpo-phalangienne du pouce et métatarso-phalangienne du gros orteil, ont toujours été retrouvés, aussi bien dans les dissections que sur les radiographies. Les autres OS observés dans l'articulation MP se répartissent ainsi: index: 50% des cas; médius: 3%; annulaire: 1%; petit doigt: 70%. Ils ont été mis en évidence dans 62% des cas au niveau de l'articulations interphalangienne du pouce.Il y a des différences entre la main et le pied dans la fréquence des changements dégénératifs de ces articulations. Au niveau du pouce l'articulation n'a été trouvée affectée que dans 75% des cas à l'examen macroscopique et dans 13% seulement à l'examen radiographique. Les modifications pathologiques atteignaient l'une des deux extrémités articulaires. Pour le gros orteil, 40% des cas pathologiques ont été décelés tant à l'examen macroscopique que radiologique, mais dans cette localisation tous les composants de l'articulation étaient affectés.

     

Determination of Background Gradients with Diffusion MR Imaging

A new magnetic resonance (MR) imaging technique, opposite-polarity pulsed-field-gradient technique, with which the effects of background magnetic field gradients can be separated from the effects of diffusion, is described. It is based on the processing of two sets of diffusion-weighted images, the acquisition parameters of which differ only in the polarity of the applied diffusion pulses. The two effects can be separated because the cross term (b_c) of the gradient factor function is antisymmetric with respect to reversal of the sign of the applied diffusion pulses. The technique permits simultaneous measurement of the spatial distribution of both the diffusion constants and background magnetic field gradients, with the same spatial resolution as the parent images from which they were derived. The technique has been validated with a phantom in which the spatial distribution of susceptibility-induced background gradients is known, the results showing excellent agreement with theory. The technique was applied to two systems in which the spatial distribution of the background gradient is unknown. Sources of error in the measurement of background gradients and (unrestricted) diffusion constants are analyzed, including the effects of voxel size, partial volumes, and interactions between background and imaging gradients.