Optimizing data acquisition and analysis of morphometric X-ray absorptiometry

Vertebral fracture assessment: Current research status and application in patients with kyphoplasty

Imaging of the spine is of paramount importance for the recognition of osteoporotic vertebral fractures (VFs), and standard radiography (SR) of the spine is the suggested diagnostic method but is not routinely used because of the cost and radiation exposure considerations. VF assessment (VFA) is an efficient, low radiation method for identifying VFs at the time of bone mineral density (BMD) measurement. Prediction models used to indicate the need for VFA may have little predictive power in subspecialty referral populations such as rheumatologic patients or patients who underwent kyphoplasty. Rheumatologic patients are frequently at increased risk for VFs, and VFA should be performed on an individual basis, also taking in account the guidelines for the general population. Kyphoplasty is a new minimal invasive procedure for the treatment of VFs and is being performed with increasing frequency. Following kyphoplasty, there may be a risk of new VFs in adjacent vertebrae. The assessment and follow-up of patients who underwent kyphoplasty requires repetitive X-ray imaging with the known limitations of SR. Thus, VFA may facilitate the evaluation of VFs in these patients because most of the kyphoplasty patients would fulfill the criteria. In a pilot study, we measured the BMD and performed VFA in 28 patients treated with kyphoplasty. Ratios of anterior to posterior (A/P) and middle to posterior (M/P) height were measured, and Genant’s method was used to classify vertebrae accordingly. Intraobserver and interobserver reliability for A/P, M/P and the Genant’s method were determined. Only 1 patient did not meet the criteria for VFA. Of the 364 available vertebrae, 295 could be analyzed. Most missing data (concerning 69 vertebrae) occurred in the upper thoracic region. Three of the 69 non-eligible vertebrae were lumbar vertebrae with cement leakage from the kyphoplasty procedure. In our hands, VFA was highly reproducible, demonstrating very good agreement in terms of intraobserver and interobserver reliability. Agreement was very good on the vertebral level, “vertebrae with kyphoplasty” level and “2 above and 1 below the kyphoplasty vertebrae” level. The application of Genant’s method to these patients also resulted in perfect agreement. We believe that the potential value of VFA in patients treated with kyphoplasty requires further evaluation, particularly comparing VFA with SR and performing a longitudinal follow-up. More research will help to adopt care processes that determine which patients require VFA and how often VFA should be performed, while also considering the impact of this technique on the cost of healthcare organizations.

Vertebral fracture assessment scans enhance targeting of investigations and treatment within a fracture risk assessment pathway

Vertebral fracture assessment (VFA) scanning is a useful tool to aid vertebral fracture identification. In this evaluation, we show that introduction of a comprehensive fracture risk assessment pathway incorporating VFA has enhanced diagnosis of vertebral fractures and improved targeting of investigations and treatment.

INTRODUCTION

Vertebral fractures are a common manifestation of osteoporosis and are associated with an increased risk of future vertebral and non-vertebral fractures. VFA is a method of imaging the thoraco-lumbar spine and a useful tool to aid vertebral fracture identification. In August 2008, a new one-stop pathway was introduced incorporating VFA and laboratory investigations at the time of bone mineral density assessment. The aims of this evaluation were to evaluate the clinical utility of VFA in identifying vertebral fractures which had not presented clinically and to evaluate the impact of this on management.

METHODS

We performed a retrospective 6-month review of the new pathway focussing on those patients undergoing VFA who were suspected to have a vertebral fracture. The outcomes of VFA, spinal X-rays and investigations were evaluated.

RESULTS

Three thousand five hundred twenty-six individuals underwent fracture risk assessment over a 6-month period, of which 1,833 underwent VFA. Previously undiagnosed vertebral fractures were found in 202 individuals (36 were in retrospect apparent on prior imaging, and 29 were new vertebral fractures in patients with pre-existing vertebral fractures). Diagnosis of a vertebral fracture led to further investigation in all individuals and altered management in 59 (29 %) individuals. A potentially modifiable underlying cause was found in 42 (21 %).

CONCLUSIONS

Introduction of a fracture risk assessment service incorporating VFA and a one-stop pathway has enhanced vertebral fracture identification and targeting of treatment and management.

Vertebral morphometry by dual-energy X-ray absorptiometry (DXA) for osteoporotic vertebral fractures assessment (VFA)

PURPOSE

This study was done to evaluate the diagnostic accuracy of dual-energy X-ray absorptiometry (DXA) compared with conventional radiography for identifying vertebral fractures.

MATERIALS AND METHODS

A total of 930 postmenopausal women underwent conventional radiography and DXA imaging of the spine. The images were evaluated by two expert skeletal radiologists using the semiquantitative (SQ) method for conventional radiography and the morphometric vertebral fracture assessment (VFA) for DXA.

RESULTS

The SQ method for radiography (SQ-Rx) analysed 99.1% of vertebrae, identifying 442 vertebral fractures; VFA analysed 97.5% vertebrae, detecting 420 vertebral fractures. Agreement between SQ-Rx and VFA reached 98.76%, and the κ-score was 0.96 [95% confidence interval (CI), 0.95-0.98]. Assessing the grading of vertebral fractures, agreement reached 97.5% and the κ-score was 0.841 (95% CI, 0.821-0.891). Considering SQ-Rx method as "gold standard", VFA had a sensitivity of 97.85 % and a specificity of 99.81%. The negative (NPV) and positive (PPV) predictive value for VFA were 99.83 % and 98.15%, respectively. Fractures were identified in 251 (27 %) and 242 (26 %) of patients on SQ-Rx and VFA, respectively. On a per-patient basis, the agreement between the two methods was 97% and the κ-score was 0.95 (95% CI, 0.920-0.968). The diagnostic parameters for VFA were 97.23% sensitivity, 98.86% specificity, 97.60% PPV and 98.84% NPV.

CONCLUSIONS

This study demonstrated that VFA with DXA may reach a high level of accuracy for diagnosing vertebral fractures, suggesting that VFA should be introduced in the screening of individuals with a risk of osteoporosis and in the follow-up of osteoporotic patients receiving treatment.

Osteoporosis and vertebral fractures in men aged 60-74 years

BACKGROUND

limited information on the prevalence of osteoporosis and VFxs in men in high-risk populations is available. The choice of reference values for dual X-ray absorptiometry (DXA) is debated. We evaluated the prevalence of osteoporosis and vertebral deformities in a population-based sample of men.

METHODS

bone mineral density (BMD) was measured and vertebral deformities assessed using DXA and VFx assessment (VFA), respectively, in a random sample of 600 Danish men aged 60-74 years. Osteoporosis was defined as a T-score of -2.5 or less.

RESULTS

the study population was comparable with the background population with regard to age, body mass index and co-morbidity. Osteoporosis was diagnosed in less than 1% of the participants at inclusion. Using Danish and NHANES III reference data, 10.2 and 11.5% of the study population had osteoporosis, respectively. In all, 6.3% participants had at least one VFx. BMD was significantly lower in participants with vertebral deformities, but only 24% of these cases had osteoporosis.

CONCLUSIONS

osteoporosis and VFxs are prevalent in men aged 60-74 years. Although the majority of deformities were present in individuals without osteoporosis, BMD was lower in patients with VFxs at all sites investigated. Male osteoporosis was markedly underdiagnosed.

The Prevalence of Undetected Vertebral Fracture in Patients with Back Pain by Dual-Energy X-ray Absorptiometry (DXA) of the Lateral Thoracic and Lumbar Spine

STUDY DESIGN

This is a prospective study.

PURPOSE

This study is conducted to determine the prevalence of unrecognized vertebral fracture (VF) in patients who present with back pain.

OVERVIEW OF LITERATURE

VF is often unrecognized, and significantly increases the risk of further fractures. Unfortunately, the patients at a high risk for VF usually do not receive adequate therapy to reduce the fracture risk.

METHODS

This is a prospective study of 344 patients who presented with back pain from April 2008 to May 2009. The patients underwent dual-energy X-ray absorptiometry (DXA) evaluation and vertebral fracture assessment from T4 to L4 using a hologic densitometer.

RESULTS

Three hundred forty four of 386 patients who presented with back pain were included. Forty two patients were excluded because of a prior history of VF or the lack of written consent. Most of the patients were female (95.3%). The mean age of the patients was 58.21 ± 11.74 years. According to the World Health Organization definition (based on the T-score), 13.4% of the patients had normal lumbar spine bone mineral density (BMD). 27.9% of them were osteopenic and 58.7% were osteoporotic. The overall prevalence of VF, as established by lateral vertebral assessment, was 39% (n = 134). Moreover, 62.6% (n = 84) of the patients with VF had more than one fracture and 64.1% (n = 86) of them had Grade 2 or 3 fracture.

CONCLUSIONS

We recommend performing not only DXA scanning for BMD evaluation, but also VFA by DXA in old patients with back pain.

Detection of vertebral fractures in DXA VFA images using statistical models of appearance and a semi-automatic segmentation

SUMMARY

Morphometric methods of vertebral fracture diagnosis lack specificity. We used detailed shape and image texture model parameters to improve the specificity of quantitative fracture identification. Two radiologists visually classified all vertebrae for system training and evaluation. The vertebral endplates were located by a semi-automatic segmentation method to obtain classifier inputs.

INTRODUCTION

Vertebral fractures are common osteoporotic fractures, but current quantitative detection methods (morphometry) lack specificity. We used detailed shape and texture information to develop more specific quantitative classifiers of vertebral fracture to improve the objectivity of vertebral fracture diagnosis. These classifiers require a detailed segmentation of the vertebral endplate, and so we investigated the use of semi-automated segmentation methods as part of the diagnosis.

METHODS

The vertebrae in a training set of 360 dual energy X-ray absorptiometry images were manually segmented. The shape and image texture of vertebrae were statistically modelled using Appearance Models. The vertebrae were given a gold standard classification by two radiologists. Linear discriminant classifiers to detect fractures were trained on the vertebral appearance model parameters. Classifier performance was evaluated by cross-validation for manual and semi-automatic segmentations, the latter derived using Active Appearance Models (AAM). Results were compared with a morphometric algorithm using the signs test.

RESULTS

With manual segmentation, the false positive rates (FPR) at 95% sensitivity were: 5% (appearance) and 18% (morphometry). With semi-automatic segmentations the sensitivities at 5% FPR were: 88% (appearance) and 79% (morphometry).

CONCLUSION

Specificity and sensitivity are improved by using an appearance-based classifier compared to standard height ratio morphometry. An overall sensitivity loss of 7% occurs (at 95% specificity) when using a semi-automatic (AAM) segmentation compared to expert annotation, due to segmentation error. However, the classifier sensitivity is still adequate for a computer-assisted diagnosis system for vertebral fracture, especially if used in a triage approach.

Evaluation of vertebral fracture assessment by dual X-ray absorptiometry in a multicenter setting

SUMMARY

The utility of vertebral fracture assessment (VFA) by DXA to detect prevalent vertebral fracture in a multicenter setting was investigated by comparison to conventional radiography. While limited by lower image quality, overall performance of VFA was good but had a tendency to miss mild prevalent fractures.

INTRODUCTION

In osteoporosis clinical trials standardized spine radiographs are used to detect vertebral fractures as a study endpoint. Lateral spine imaging with dual X-ray absorptiometry (DXA) scanners, known as vertebral fracture assessment (VFA) by DXA, presents a potential alternative to conventional radiography with lower radiation dose and greater patient convenience.

METHODS

We investigated in a multicenter setting the ability of VFA to detect fractures in comparison with conventional radiography. The study examined 203 postmenopausal women who had imaging of the spine by DXA and radiography. Three radiologists experienced in vertebral fracture assessment independently read the VFA scans and radiographs using the Genant semiquantitative method on two occasions.

CONCLUSIONS

Analyzing the data from all readable vertebrae, the kappa statistic, sensitivity, and specificity ranged from 0.64-0.77, 0.65-0.84, and 0.97-0.98, respectively. Considering only moderate and severe fractures improved the kappa statistic (0.80-0.91) and sensitivity (0.70-0.86). While image quality of VFA is inferior to radiography, the detection of vertebral fractures using visual scoring is feasible. However, VFA underperformed due to unreadable vertebrae and reduced sensitivity for mild fractures. Nevertheless, VFA correctly identified most moderate and severe vertebral fractures. Despite this limitation, VFA by DXA provides an important tool for clinical research.

Data acquisition analysis for femoral morphometric X-ray absorptiometry

Bone mineral density (BMD) is a contributing factor of hip fracture risk. Other factors, such as lifestyle, the propensity for falls, and femoral geometry may influence the risk of hip fracture. The DMS Lexxos densitometer, a dual-energy X-ray densitometer can produce either a single-energy X-ray or a BMD image. The purpose of this study was to evaluate which of these 2 images enables the best detection to make femoral morphometry measurements. Spatial resolution, contrast, and noise were evaluated separately. A contrast-detail phantom was also used for the purpose of overall visual analysis. The spatial resolution was the same in the 2 images. The contrast was better with the BMD image, but the noise was higher. Using the contrast-detail phantom, the single-energy X-ray image allowed globally a better detection of the objects, but results were in the same range with high contrast values. Hip volunteers' morphometric measurements and the Singh Index were evaluated 3 times for each image by 3 observers, and the intra-, inter-, and global reproducibility was computed. The reproducibility of the measurements seems to be better with the single-energy X-ray image but results were not statistically significantly different. These results suggest that even if the image-quality indices were different, the single-energy X-ray image and BMD image are closely useful for clinical morphometric femoral evaluation.

Vertebral fracture assessment (VFA) with a densitometer predicts future fractures in elderly women unselected for osteoporosis

Low radiation dose imaging of the lateral spine acquired with a bone densitometer for vertebral fracture assessment (VFA) has great potential for clinical use. We have undertaken an evaluation of VFA in a prospective population cohort of elderly women to examine the prevalence of vertebral fractures, their ability to predict incident fractures, and their use in targeting therapy. Women (n = 5157) >or=75 yr of age living in the general community in the United Kingdom underwent posteroanterior and lateral imaging of the spine (T(4)-L(4)) with a densitometer (Hologic QDR4500A) at entry to a randomized, double-blind, controlled trial of 800 mg oral clodronate (Bonefos) or matching placebo daily over 3 yr. The women were identified from general practice registers and recruited by letter of invitation regardless of skeletal status. The proportion of vertebrae interpretable varied from 98.2% at T(12) to 57.1% at T(4), with >92% interpretable at levels between T(8) and L(3). As judged by BMD at the total hip, 19.6% of the women had osteoporosis, and the prevalence of vertebral fracture was 14.5%. Women with one or more vertebral fractures had a relative risk (RR) for incident osteoporotic fractures of 2.01 (95% CI, 1.64-2.47). The RR for hip fractures was 2.29 (95% CI, 1.63-3.21). After adjustment for age, femoral neck BMD, weight, and treatment, the RR was 1.50 (95% CI, 1.21-1.86) for osteoporotic fractures, with similar results for hip fractures (RR, 1.41; 95% CI, 0.99-2.02). For women with two or more vertebral fractures, the adjusted RRs were 1.97 (95% CI, 1.24-2.72) and 1.86 (95% CI, 1.14-3.03) for osteoporotic and hip fractures, respectively. We conclude that VFA can frequently detect vertebral fractures in a population cohort of elderly women. These fractures, like radiographic fractures, predict future clinical fractures independent of age, weight, and BMD. Having multiple vertebral fractures was associated with greater risk of incident osteoporotic fractures and hip fractures.

Vertebral Fracture Assessment: the 2007 ISCD Official Positions

Vertebral fracture assessment (VFA) is an established, low radiation method for detection of prevalent vertebral fractures. Vertebral fractures are usually not recognized clinically at the time of their occurrence, but their presence indicates a substantial risk for subsequent fractures independent of bone mineral density. Significant evidence supporting VFA use for many post-menopausal women and older men has accumulated since the last ISCD Official Position Statement on VFA was published. The International Society for Clinical Densitometry considered the following issues at the 2007 Position Development Conference: (1) What are appropriate indications for Vertebral Fracture Assessment; (2) What is the most appropriate method of vertebral fracture detection with VFA; (3) What is the sensitivity and specificity for detection of vertebral fractures with this method; (4) When should additional spine imaging be performed following a VFA; and (5) What are the reporting obligations for those interpreting VFA images?

Bone densitometry in the diagnosis of vertebral fractures in children: accuracy of vertebral fracture assessment

BACKGROUND

DXA scanner derived images of the spine are used for vertebral fracture detection in adults. It is unknown whether the method could be used in pediatrics. This study evaluated the diagnostic accuracy of DXA images in vertebral fracture assessment (VFA) in children.

METHODS

The study included 65 children (37 males; median age 12.1 years) with primary or secondary osteoporosis. Data on clinical history were collected from hospital records. Patients were assessed for spinal compression fractures by standard spinal radiographs and by bone densitometry (Hologic Discovery A) derived VFA images. The visibility and morphology of each vertebra in VFA images was assessed by two readers and by a semi-computerized software developed for the DXA scanner. The findings were compared with those in spinal radiographs and correlated with clinical parameters.

RESULTS

The visibility of vertebrae in VFA images was good in T8-L4 but compromised in the upper thoracic region (T4-T7) and was constantly inferior to that in standard radiographs. A total of 25 vertebral fractures were diagnosed in radiographs, but only 9 (36%) of these also in VFA images. The semi-computerized software could not accurately detect vertebrae in most of the children; accuracy increased with increasing age, height and BMD but was not sufficient to detect vertebral fractures.

CONCLUSIONS

The utility of DXA scanner derived images of the spine in vertebral fracture detection in children is limited by compromised visibility and poor diagnostic accuracy. The semi-computerized software is not suitable for pediatric use. These limitations should be kept in mind when assessing pediatric patients for osteoporosis.

Clinical review: Clinical applications of vertebral fracture assessment by dual-energy x-ray absorptiometry

CONTEXT

Vertebral fracture (VF) is the most common type of fragility fracture, yet most VFs are not clinically apparent. VFs are associated with a significant increase in morbidity, mortality, and risk of future fracture. Many patients with VFs do not have T-scores classified as osteoporosis. Knowledge of VFs may change diagnostic classification, estimation of future fracture risk, and clinical management. VF assessment (VFA) by dual-energy x-ray absorptiometry is a method for imaging the spine to diagnose VFs.

EVIDENCE ACQUISITION

Background information and medical evidence on the technology and clinical applications of VFA was acquired by electronic searching of PubMed for appropriate terms that included vertebral fracture, imaging, diagnosis, dual-energy x-ray absorptiometry, and cost effectiveness. Matches with the highest levels of medical evidence were selected for review, recognizing that the new and evolving nature of the field required inclusion of some material that relied partly on expert opinion.

EVIDENCE SYNTHESIS

The sensitivity and specificity of VFA compare favorably with spine radiographs in the ability to diagnose grade 2 and 3 VFs. VFA involves less radiation, lower cost, and often greater patient convenience than spine radiography. Cost effectiveness modeling suggests that imaging of the spine in selected patients provides essential diagnostic and therapeutic information at a nominal cost. Patients with T-scores that are classified as low bone mass (osteopenia) who are selected for pharmacological therapy based on the presence of a VF benefit by reduction in fracture risk. Guidelines for the clinical application of VFA have been developed by the International Society for Clinical Densitometry.

CONCLUSIONS

VFA is a technology for diagnosing VFs that may alter diagnostic classification, improve fracture risk stratification, and identify patients likely to benefit from pharmacological therapy who otherwise might not be treated.

Diagnosis of vertebral fractures by vertebral fracture assessment

Vertebral fractures are independent risk factors for both vertebral and peripheral fractures and only one-third of these fractures come to clinical attention. Vertebral fracture assessment (VFA) is a radiographic method using dual X-ray absorptiometry (DXA) to assess vertebral deformities during bone density measurement. We performed VFA of the spine from T4 to L5 on a Delphi W device (Hologic, Bedford, MA) in 136 postmenopausal patients (69+/-10 yr). These patients also had X-rays of the thoracic and lumbar spine. VFA was independently compared with X-rays by two rheumatologists, for the diagnosis of vertebral fractures at both the patient and vertebral levels. Using X-rays, 61 patients (45%) had at least one vertebral fracture. The percentage of unreadable vertebrae was 1% and 12.4% on X-rays and VFA, respectively (p<0.0001). At the patient level, VFA allowed to diagnose if the patient had no fracture or had at least one fracture in 74% of patients. In 11.2% of cases, VFA misclassified the patients. At the vertebral level, diagnostic efficacy of VFA as compared with X-rays was 97%. Concordance between both observers was good (kappa-score=0.69). We designed an algorithm for decision of performing X-rays in postmenopausal women: Using results of VFA would avoid X-rays in 32% of our patients. VFA is a reliable technique with low radiation, and is easily and rapidly applicable during bone density measurement by DXA, which could improve management of osteoporotic patients.

Vertebral fracture assessment: the 2005 ISCD Official Positions

Vertebral Fracture Assessment (VFA) is a low radiation method for imaging the thoraco-lumbar spine using bone densitometers. VFA can easily be performed at the time of bone mineral density (BMD) measurement, allowing integration of BMD and vertebral fracture information into clinical patient care. As VFA is a relatively new procedure, it has received limited study and heretofore has not had widespread clinical application. Consequently, the International Society for Clinical Densitometry (ISCD) considered the following VFA issues at the 2005 Position Development Conference: (1) indications for VFA; (2) methodology for the diagnosis of vertebral fractures using VFA; and (3) indications for additional imaging after VFA. The ISCD Official Positions with respect to the above issues, as well as the rationale and evidence used to derive these positions, are presented here.

Morphometric X-ray absorptiometry in the assessment of vertebral fractures in renal transplant patients

BACKGROUND

Bone mineral density (BMD) is widely employed to evaluate the risk of fractures, but more than mineral content is bone quality that accounts for bone strength. In fact, occasionally, subjects with normal or only mildly reduced BMD also experience pathologic fractures. In metabolic bone disease, like renal transplantation, the agreement between fractures and BMD is less predictable. We assessed the prevalence of vertebral fractures by means of a new, DEXA-based method (morphometric absorptiometry, MXA) and compared its concordance with the two mostly employed radiological techniques (Visual semi-quantitative, SQ, and morphometric radiography, MRX) in an asymptomatic population of transplanted patients. Moreover, the association of bone fractures with low BMD values was examined.

METHODS

Fifty-three renal transplant patients underwent spinal radiographs and BMD measurements by DEXA. In order to obtain a morphometric assessment, a lateral DEXA scan was performed.

RESULTS

Patients with vertebral fracture were 17/53 (32%) with both SQ and MRX, and 12/53 (23%) with MXA (chi(2) = n.s.). A single fracture was detected in 9/53 patients (17%) with SQ and MRX, and in 4/53 (7.5%) with MXA; multiple fractures were 8/53 (15%) with any technique. With SQ as the standard reference, predictive indexes were excellent with MRX (invariably 100%) and quite good with MXA (sensitivity 70.6%; specificity 100%). Of the total of 689 vertebrae, 49 were fractured with SQ, 54 with MRX and 41 with MXA. Mild deformities were present in 21 (SQ), 26 (MRX) and 13 (MXA) vertebral bodies, respectively, while moderate-severe deformities were 28 with any technique. Again, with SQ as standard reference, predictive indexes were good (MRX: sensitivity 100%, specificity 99.2%; MXA: sensitivity 83.7%, specificity 100%). When we classified patients according to BMD T-score values, SQ and MRX recognized fractures in 4/18 normal (22%), 10/22 osteopenic (45%) and 3/13 osteoporotic (23%). With MXA 3/18 (17%) normal, 6/22 (27%) osteopenic and 3/13 (23%) osteoporotic were fractured. The lower performance of MXA was very likely due to the poor quality of images from the upper thoracic spine of obese subjects.

CONCLUSIONS

Prevalence of vertebral fractures in renal transplant patients is quite high and randomly associated with reduced BMD. A surveillance of the spine by Rx, implemented with vertebral morphometry, is therefore warranted to recognize the disease. (MXA is a reliable alternative technique, especially in more severely affected individuals.) MXA, although less sensitive than the conventional techniques because of possible technical biases, is very specific, and can be proposed for follow-up purposes in this population of patients.

Radiologic assessment of osteoporotic vertebral fractures: diagnostic and prognostic implications

As populations age osteoporosis becomes an increasingly important public health issue. Among osteoporotic fractures vertebral fractures are of particular relevance: they are the most common fractures, frequently are asymptomatic but have an important influence on prognosis and morbidity in the osteoporotic patient. Previous studies have suggested that these fractures are frequently not diagnosed and that radiologists miss a high percentage of osteoporotic, vertebral fractures present on lateral chest radiographs. The aims of this review are (1) to emphasize the important role that radiologists play in the accurate and clear reporting of vertebral fractures, (2) to provide guidance in assessing these fractures in radiographs, MRI and computed tomography imaging of the vertebral spine and (3) to sensitize the radiologist in diagnosing fractures in chest radiographs.

Assessment of vertebral fracture using densitometric morphometry

Diagnosis of vertebral fracture is critical for management of osteoporosis, as existence of such deformities substantially increases the risk of subsequent fracture. Thus, accurate and precise techniques allowing detection of such deformities are essential to clinicians. So far, this detection has been performed by spinal lateral X-rays. More advanced techniques have recently been developed, based on dual energy X-ray absorptiometry (DXA). This review describes these different techniques and discusses the effectiveness of the DXA technique to assess vertebral deformities compared to X-ray. The use of DXA detection of vertebral fracture for clinical practice and clinical trials is discussed. Specifically, vertebral morphometry using DXA provides an excellent specificity, with moderate sensitivity. The major limitation of the DXA vertebral assessment is the poor quality of images of thoracic vertebrae. The clinical utility of vertebral morphometry using densitometry may help screening patients with vertebral fracture, but technological improvements are necessary to improve image quality.

Comparison of dual-energy X-ray absorptiometry and conventional radiography for the detection of vertebral fractures

Prevalent vertebral fractures confer a high risk of subsequent fractures; therefore, fracture identification is a key issue in osteoporosis management. Dual-energy X-ray absorptiometry has become the most widespread technique for the assessment of bone density, and can also provide images for assessment of vertebral morphometry (MXA) that are undistorted by parallax. The radiation dose is very low compared with conventional radiography. Whether the resolution of MXA is adequate for vertebral morphometry is uncertain. The present study compares MXA with conventional radiography in detecting vertebral deformities. MXA scans and lateral radiographs were performed in 61 women with osteoporosis. Adequate images were obtained in 99.1% of the 793 vertebrae by radiography and 95.6% by MXA. Poor image quality was mostly at T4-6 by MXA. Precision of repeat analyses was comparable between the techniques. Heights measured by MXA were 24 to 35% less than the radiographic values, the methods produced equivalent results for the ratio of anterior to posterior heights, but the MXA values for middle to posterior ratios were about 10% lower than for the radiographs (p < 0.0001). The extent of agreement between the techniques in identifying vertebral fractures was dependent on the strictness of the fracture definition used. With a 3 standard deviation (SD) criterion, the techniques found similar numbers of patients to have vertebral deformities, and the concordance in classification of individual vertebrae was 94%. At a 2 SD, cut-off concordance was 79%, and at 4 SD, it was 96%. Receiver-operating characteristic curves using cut-offs of > or = 3 SDs also showed excellent diagnostic accuracy. We conclude that MXA shows acceptable performance for clinical use in diagnosing vertebral deformities, as long as cut-offs of > or = 3 SDs are used, although a few percent of vertebrae in the upper thoracic region cannot be imaged adequately using this technique.

Incidence of vertebral deformities in 255 female rheumatoid arthritis patients measured by morphometric X-ray absorptiometry

To date, no studies have been published on incident deformities in patients with rheumatoid arthritis (RA). Morphometric X-ray absorptiometry (MXA) is an alternative to conventional X-rays for identifying vertebral deformities. The aim of the present study was to describe the incidence of vertebral deformities in 255 female RA patients measured by MXA, and the relationship between incident deformities and clinical and demographic variables. MXA is still under evaluation for its ability to identify deformities, so we explored four different cut-off thresholds including fixed percentage reduction and the principle of least significant change (LSC). MXA (T4-L4) and BMD (L2-L4 and total hip; Lunar Expert) were performed on 255 patients (mean age 54.3, range 29.2-70.8 years) at baseline and after a mean period of 2.3 years. MXA scans were analyzed pairwise by the same trained technician, and incident deformities calculated applying LSC with a 99.9% and 99.99% confidence limit, and a fixed reduction of 20% and 25% for anterior, middle or posterior heights. Long term precision (%CV) of height measurements for all vertebrae combined (T4-L4) were 4.8, 4.8 and 4.4, respectively. Frequency and distribution of incident deformities varied from 39 deformities in 33 patients (fixed 20% reduction) to 17 deformities in 15 patients (fixed 25% reduction), and quality control analyses revealed a high number of presumed false deformities. Incidence per 100 patient years varied from 2.9 to 6.7 deformities according to method, and was comparable to those obtained from intervention studies in corticosteroid-induced osteoporosis. Patients with incident deformities were significantly older, had lower BMD, higher disability and more often a previous non-vertebral fractures than those without incident deformities Incident deformities by MXA need further evaluation in secondary osteoporosis. It seems, however, that older patients with previous limb fractures and low BMD are especially prone to this complication.

Recognizing and reporting osteoporotic vertebral fractures

Vertebral fractures are the hallmark of osteoporosis, and occur with a higher incidence earlier in life than any other type of osteoporotic fractures. It has been shown that both symptomatic and asymptomatic vertebral fractures are associated with increased morbidity and mortality. Morbidity associated with these fractures includes decreased physical function and social isolation, which have a significant impact on the patient's overall quality of life. Since the majority of vertebral fractures do not come to clinical attention, radiographic diagnosis is considered to be the best way to identify and confirm the presence of osteoporotic vertebral fractures in clinical practice. Traditionally, conventional lateral radiographs of the thoracolumbar spine have been visually evaluated by radiologists or clinicians to identify vertebral fractures. The two most widely used methods to determine the severity of such fractures in clinical research are the semiquantitative assessment of vertebral deformities, which is based on visual evaluation, and the quantitative approach, which is based on different morphometric criteria. In our practice for osteoporosis evaluation we use the Genant semiquantitative approach: an accurate and reproducible method tested and applied in many clinical studies. The newest generation of fan-beam DXA systems delivering "high-resolution" lateral spine images offers a potential practical alternative to radiographs for clinical vertebral fracture analysis. The advantages of using DXA over conventional radiographic devices are its minimal radiation exposure and high-speed image acquisition. It also allows combined evaluation of vertebral fracture status and bone mass density, which could become a standard for patient evaluation in osteoporosis. The disadvantage of DXA use is that upper thoracic vertebrae cannot be evaluated in a substantial number of patients due to poor imaging quality. We truly believe that the that there is a major role for radiologists and clinicians alike to carefully assess and diagnose vertebral fractures using standardized grading schemes such as the one outlined in this review. Quantitative morphometry is useful in the context of epidemiological studies and clinical drug trials; however, the studies would be flawed if quantitative morphometry were to be performed in isolation without additional adjudication by a trained and highly experienced radiologist or clinician.

Development of a phantom for morphometric X-ray absorptiometry

Morphometric X-ray absorptiometry (MXA) has recently been developed to assess vertebral deformity status using dual energy X-ray absorptiometry (DXA) machines. In contrast to bone densitometry, a vertebral morphometry phantom is not supplied by any machine manufacturer. The aim of this study was to develop a suitable phantom to quantify the accuracy and precision of the vertebral measurement software on three DXA scanners in vitro and to perform a weekly quality control (QC) scan over a 30-month period to evaluate any drift or changes in measurement accuracy over time. The phantom was constructed from Perspex and aluminium to simulate soft tissue and bone, respectively. 13 aluminium rectangles (each 30 mm wide, 25 mm high and 3 mm thick, with edges ("endplates") 6 mm thick) were set into one side of a solid Perspex block to represent the vertebral bodies from the fourth thoracic (T4) to the fourth lumbar (L4). The phantom was scanned on both the Hologic QDR2000plus and the QDR-4500A as well as the Lunar Expert-XL. Three consecutive lateral MXA scans were acquired on the Hologic machines using each of the scan modes available. On the QDR-2000plus, the lateral scan modes available are fast, array and high definition, which are all dual energy modes. These three scan modes are also available on the QDR-4500A, with the addition of a single energy scan mode. Four lateral scans were acquired on the Expert-XL machine using the single scan mode available. Each MXA scan was analysed twice by a trained operator using the standard software supplied by each manufacturer. A QC scan was performed approximately weekly over a 30-month period on only the QDR-4500A machine, and total phantom height was measured from the inferior edge of L4 to the superior edge of T4. Accuracy of "vertebral" height measurement varied between the three DXA machines and between the scan modes available. All underestimated "true" vertebral height by between 0.4% and 8.6%, with the scan modes using finer collimation producing the most accurate results. Repeat analysis precision of vertebral height measurement was best on the QDR-4500A, followed by the Expert-XL, and was poorest on the QDR-2000plus. The QC scans acquired on the QDR-4500A suggested that it was a highly stable machine, little affected by even major repairs. It must be remembered that these in vitro phantom results may not be representative of the true in vivo situation. The MXA phantom appears to be a useful tool for documenting the stability of the mechanical instruments and for checking the long-term consistency of operator precision.

Instant vertebral assessment: a noninvasive dual X-ray absorptiometry technique to avoid misclassification and clinical mismanagement of osteoporosis

The presence of a vertebral fracture significantly increases the risk of future fracture, classifies a patient with "clinical" osteoporosis, and usually results in treatment for osteoporosis. However, the majority of vertebral fractures are silent, and lateral X-rays (the standard method for identification) are not routinely obtained. Instant vertebral assessment (IVA), a technology that utilizes dual X-ray absorptiometry (DXA), provides rapid assessment of vertebral fractures and is highly correlated with vertebral fractures, as assessed on standard lateral spine X-rays. To assess the role of IVA in patient management, we examined standard bone mineral density (BMD) of the spine, total hip, and femoral neck and spine IVA by DXA in 482 participants screened for an osteoporosis study, who had no previous knowledge of vertebral fractures. Using World Health Organization (WHO) guidelines, subjects were classified using BMD at the spine, total hip, femoral neck, or any combination of these central sites. In addition, we considered subjects as osteoporotic if they had vertebral fractures independent of low bone density. We found that vertebral fractures assessed by IVA were present in 18.3% of asymptomatic postmenopausal women recruited for this study. The sensitivity of BMD alone to diagnose osteoporosis based on either a vertebral fracture or low BMD using WHO criteria ranged from 40 to 74%. This means that between 26 and 60% of osteoporotic individuals could have potentially been missed. Furthermore, 11.0-18.7% of clinically osteoporotic individuals would have been classified as normal by BMD criteria alone. We conclude that IVA is a useful adjunct in the clinical identification of osteoporosis and may prevent mismanagement of osteoporotic patients.

Morphometric X-ray absorptiometry and morphometric radiography of the spine: a comparison of prevalent vertebral deformity identification

Prevalent vertebral deformities are associated with a substantially increased risk of subsequent vertebral and nonvertebral fractures. Knowledge of vertebral fracture status is an important component in the prediction of further fractures in patients with osteoporosis. This study reports a comparison of the quantitative identification of vertebral deformities on morphometric X-ray absorptiometry (MXA) scans and conventional radiographs (MRX) in 161 postmenopausal women (mean age +/- SD, 64 +/- 7.1 years) recruited from patients referred by their family doctor for bone density measurement (n = 119) and osteoporotic subjects with known vertebral deformities attending an osteoporosis clinic (n = 42). Each subject had MXA scans and MRXs of the thoracolumbar spine, to image the vertebrae from T4-L4, at a single visit. The scans and radiographs were analyzed by two trained observers using six points to quantify the shape of each vertebral body. From these points, three vertebral heights were measured: anterior, middle, and posterior. Vertebral deformities were identified using the algorithms proposed by Eastell and by McCloskey. Generally good to excellent agreement (per vertebra, kappa = 0.87-0.93; per subject, kappa = 0.81-0.91) was observed between the two algorithms used for quantitative vertebral deformity identification using MXA or MRX. More moderate agreement (per vertebra, kappa = 0.70-0.79; per subject, kappa = 0.67-0.75) was seen when comparing the same algorithm between MXA and MRX. Agreement between MXA and MRX for the McCloskey algorithm was better than for the Eastell algorithm, largely because of the lower number of false positives produced by the McCloskey methodology. Deformity identification by MXA was limited because of poor image quality, primarily in the upper thoracic spine. One in six MRX deformities were missed by MXA as they occurred in vertebrae not visualized sufficiently for analysis on the MXA scans. Deformity identification was poorer in the upper thoracic spine in analyzable vertebrae with a sensitivity of 50.0% for MXA in terms of MRX using the Eastell algorithm for the vertebral levels T4-T7, compared with 80.6% for L1-L4A. MXA proved to be more effective at identifying moderate to severe MRX deformities producing a sensitivity of 22.0% for MXA in terms of identifying MRX grade 1 deformities using the Eastell algorithm, compared with 81.6% for grade 2 deformities. Although MXA image quality is inferior to that of conventional radiographs, MXA has distinct advantages such as a substantially reduced effective dose to the patient and acquisition of a single image of the spine. MXA is a potentially useful, relatively fast, low-radiation technique to identify prevalent vertebral deformities, particularly moderate to severe deformities in the middle/lower thoracic and lumbar spine, in conjunction with morphometric radiography in some patients.

Identification of vertebral deformities in women: comparison of radiological assessment and quantitative morphometry using morphometric radiography and morphometric X-ray absorptiometry

Our aim was to compare normal vertebral reference values for morphometric radiography (MRX) and morphometric X-ray absorptiometry (MXA) and to compare these methods for the identification of vertebral deformities. We calculated MXA reference values (Hologic QDR 4500 A) for 327 women (ages 22-88 years) randomly selected from local General Practice lists in Sheffield, U.K. MRX reference values were calculated from spinal radiographs for 123 of these subjects (ages 56-88 years). We used these reference values to identify deformities in the MRX and MXA reference populations and in 83 women with osteoporosis (ages 49-87 years). We observed differences in mean deformity of vertebral height ratios measured by MRX and MXA, especially for the mid-to-posterior ratio. We compared agreement between quantitative methods (MRX and MXA) and qualitative radiological assessment. Severity of deformity was defined by semiquantitative (SQ) assessment. Agreement was moderate for MRX (k = 0.59; 95% CI = 0.43-0.77) and for MXA (k = 0.47; 95% CI = 0.29-0.66) in the reference population. Agreement was good for MRX (k = 0.86; 95% CI = 0.82-0.89) and MXA (k = 0.71; 95% CI = 0.66-0.75) in the osteoporotic population. MRX and MXA correctly identified a greater proportion of moderate or severe deformities compared with mild deformities. Sensitivity, specificity, predictive values, and accuracy were slightly better for MRX than for MXA. Although MXA agrees well with qualitative radiological assessment, the large proportion of vertebrae excluded from analysis because of poor image quality limits the diagnostic value of the technique. Reference intervals should be technique specific.

Vertebral fractures in osteoporosis: a new method for clinical assessment

Vertebral fractures are the most common consequence of osteoporosis, and are an important risk factor for subsequent fractures. Patients with reduced bone mineral density (BMD) and vertebral fractures have significantly increased risk for future fractures, indicating great potential for the combined use of fracture assessment and BMD in risk evaluation. Despite the established importance of fractures, however, vertebral assessment is not typically performed in the clinical evaluation of patients at risk for osteoporosis. Radiographs are the accepted standard for assessment of fractures, but are rarely obtained in osteoporosis assessment for a variety of practical reasons, including cost, radiation dose, and the lack of office-based radiological facilities. Clinical assessment of fractures is difficult because most are asymptomatic. Consequently, this strong risk factor for osteoporotic fractures is often overlooked. High-resolution lateral spine images, obtained on advanced fan-beam dual X-ray absorptiometry (DXA) systems, provide a practical, low-radiation dose, point-of-care methodology for assessment of vertebral fractures, and have the potential to address this important clinical need. In this article, we review the importance of vertebral fractures and the methods of assessing them. We also review clinical data supporting the feasibility of visual evaluation of lateral spine images obtained using a fan-beam DXA system, and discuss the potential positive impact of this new methodology on clinical patient evaluation.