The effect of common artifacts lateral to the spine on bone mineral density in the lumbar spine

The choice of region of interest after spinal procedures alters bone mineral density measurements

PURPOSE

Vertebrae affected by artifacts, such as metallic implants or bone cement, should be excluded when measuring the spine bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA). Exclusion may be performed using two methods: first, the affected vertebrae are included in the region of interest (ROI) and subsequently excluded from the analysis; second, the affected vertebrae are completely excluded from the ROI. This study aimed to investigate the influence of metallic implants and bone cement on BMD with and without the inclusion of artifact-affected vertebrae in the ROI.

METHODS

DXA images of 285 patients, including 144 with spinal metallic implants and 141 who had undergone spinal vertebroplasty from 2018 to 2021, were retrospectively reviewed. Spine BMD measurements were performed when the images were evaluated using two different ROIs for each patient during the same examination. In the first measurement, the affected vertebrae were included in the ROI; however, the affected vertebrae were excluded from the BMD analysis. In the second measurement, the affected vertebrae were excluded from the ROI. Differences between the two measurements were evaluated using a paired t-test.

RESULTS

Among 285 patients (average age, 73 years; 218 women), spinal metallic implants led to an overestimation of bone mass in 40 of 144 patients, whereas bone cement resulted in an underestimation of bone mass in 30 of 141 patients when the first measurement was compared with the second measurement. The opposite effect occurred in 5 and 7 patients, respectively. Differences in results between the inclusion and exclusion of the affected vertebrae in the ROI were statistically significant (p<0.001). Spinal implants or cemented vertebrae included in the ROI might significantly alter BMD measurements. Additionally, different materials were associated with varying modifications in BMD.

CONCLUSION

The inclusion of affected vertebrae in the ROI may notably alter BMD measurements, even when they are excluded from the analysis. This study suggests that the vertebrae affected by spinal metallic implants or bone cement should be excluded from the ROI.

A Rare Pitfall in Bone Mineral Densitometry: Gaucher Disease

ABSTRACT

We report a rare case of type 3 Gaucher disease presenting with calcified mesenteric lymph nodes that interfere with bone mineral densitometric measurements.

Operator-Related Errors and Pitfalls in Dual Energy X-Ray Absorptiometry: How to Recognize and Avoid Them

Dual-energy X-ray absorptiometry (DXA) is the most common modality for quantitative measurements of bone mineral density. Nevertheless, errors related to this exam are still very common, and may significantly impact on the final diagnosis and therapy. Operator-related errors may occur during each DXA step and can be related to wrong patient positioning, error in the acquisition process or in the scan analysis. The aim of this review is to provide a practical guide on how to recognize such errors in spine and hip DXA scan and how to avoid them, also presenting some of the most common artifacts encountered in clinical practice.

"Effect of very dense artifacts on Hologic and general electric bone densitometry results"

Very dense artifacts confound bone density measurement. Hologic and GE densitometers exclude artifact density and GE also excludes associated area. Consequently, BMD is decreased with Hologic software. Despite different manufacturers' approaches, when dense artifacts overlay the spine, the affected vertebral body should be excluded from the reported BMD.

PURPOSE

Very dense objects, such as lead bullets are described as "black hole" artifacts on Hologic densitometers. Whether similar results occur on GE scanners is not reported. We hypothesized that dense artifacts confound both brands of densitometers.

METHODS

Three lead bullets of varying size were placed overlying or adjacent to L3 on anthropomorphic and encapsulated aluminum spine phantoms. Three scans were acquired with and without projectiles on a Hologic Discovery W, GE iDXA, and Prodigy densitometer.

RESULTS

Lead bullets are measured as having high bone mineral content (BMC); they appear black in dual-energy mode on Hologic scanners and are colored blue on GE scanners. On Hologic scanners, BMC of a dense artifact over bone is excluded, but the bone area is not altered. Consequently, bone mineral density (BMD) of the affected vertebra, and of L1-4, is decreased. For example, a .45 caliber bullet over L3 decreased BMD (p < 0.05) by 48.3% and L1-4 by 9.1%. GE scanners excluded associated BMC and area covered by the artifact, thereby minimizing impact on BMD. Dense artifacts over soft tissue on a phantom do not substantially affect BMD on either manufacturer's densitometer when scanned.

CONCLUSION

Densitometer manufacturers handle very dense artifacts differently. GE software removes artifact BMC and area with resultant minimal impact on BMD, Hologic removes only BMC, not area, thereby decreasing BMD. Regardless of this difference, when dense artifacts overlay the spine, it is best to exclude the affected vertebral body. Finally, the BMD stability observed with artifacts over soft tissue may not be replicated in humans.

Bone Mineral Densitometry Reporting: Pearls and Pitfalls

Dual-energy X-ray absorptiometry (DXA) is the method of choice for assessing bone mineral density (BMD). Unfortunately, the performance and interpretation of DXA can be challenging and errors are common. In fact, it has been reported that up to 90% of BMD reports contain at least 1 error. Errors can be the result of technique or interpretative in nature or both and can result in inappropriate diagnosis and management. In this article, we review the various types of pitfalls frequently encountered by physicians interpreting DXA studies. Being aware of these pitfalls will help readers recognize and avoid them when encountered in clinical practice.

ARTIFACTS AFFECTING DUAL-ENERGY X-RAY ABSORPTIOMETRY MEASUREMENTS

OBJECTIVE

To present 3 cases in which the presence of artifacts altered the dual-energy X-ray absorptiometry (DXA) measurements of bone mineral density (BMD) in the lumbar field.

METHODS

Clinical presentation and literature review.

RESULTS

The first patient was a 49-year-old premenopausal woman with a spinal cord stimulator implanted in her lumbar spine. The implant increased the measured BMD in the lumbar region from osteopenia to normal range. The second patient was a 56-year-old man who had a DXA scan after he was administered oral and intravenous iodine-based contrast earlier the same day. The oral contrast in the patient's colon created a dense artifact, which overlapped the lumbar spine and adjacent soft tissue. The effect almost changed his DXA diagnosis from osteoporosis to osteopenia. The third patient was a 64-year-old woman who had undergone laparoscopic adjustable gastric banding (LAGB). A part of the LAGB system adjacent to lumbar vertebra 3 was mistakenly included as part of the vertebrae by the DXA scanner, causing an increase in the measured BMD.

CONCLUSION

There are numerous artifacts that can alter DXA BMD measurement. It is important for providers who interpret DXA scans to be familiar with the potential effects of artifacts and how to adjust for their presence, since erroneous measurements can lead to incorrect decisions regarding treatment and follow-up.

Do Textiles Impact DXA Bone Density or Body Composition Results?

External artifacts can confound dual-energy X-ray absorptiometry (DXA) measurements. It is often accepted that garments free of metal do not affect DXA results; however, little data exist in this regard. It is plausible that some textiles absorb radiation and thereby alter DXA results. We hypothesized that some dense or synthetic textiles, for example, reflective materials, might alter DXA-measured bone and soft tissue mass. Hologic and GE Lunar spine phantoms and a Bioclinica prototype total body phantom were imaged on a GE Lunar iDXA and Prodigy densitometer. Each phantom was scanned 10 times to establish mean values. Subsequently, 2 layers of various fabrics were placed over the entire top surface of the phantom, and 10 scans were performed without repositioning. Samples of natural, synthetic, or embellished fabric (including those with reflective material) and of varying thickness were used. Wilcoxon signed rank tests were used to compare the means between bare phantom and textile-covered phantom. Significant differences were demonstrated often, depending on the scanner, phantom, and textile used. A polyester fabric with reflective strip consistently altered measurements. For example, this fabric increased measured mean lumbar spine bone mineral density and total body bone mineral content by 0.008 g/cm² and 3.6 g, respectively (p < 0.01). Similarly, mean total body fat decreased (-173 g) and lean mass increased (+213 g; p < 0.01). Fat and lean mass were also affected by metallic thread, wool, blend denim, and shiny polyester (p < 0.05), and lean mass was affected by cotton denim and sweatshirt material (p < 0.0003). In conclusion, textiles can affect DXA-measured bone mineral density and body composition results. Even small amounts of reflective material could alter mass measurements by ~25% of the least significant change. Clothing made of dense textiles (e.g., wool and denim) or those with reflective material and metallic thread should be avoided during DXA scanning.

Best Practices for Dual-Energy X-ray Absorptiometry Measurement and Reporting: International Society for Clinical Densitometry Guidance

Dual-energy X-ray absorptiometry (DXA) is a technology that is widely used to diagnose osteoporosis, assess fracture risk, and monitor changes in bone mineral density (BMD). The clinical utility of DXA is highly dependent on the quality of the scan acquisition, analysis, and interpretation. Clinicians are best equipped to manage patients when BMD measurements are correct and interpretation follows well-established standards. Poor-quality acquisition, analysis, or interpretation of DXA data may mislead referring clinicians, resulting in unnecessary diagnostic evaluations, failure to evaluate when needed, inappropriate treatment, or failure to provide medical treatment, with potentially ineffective, harmful, or costly consequences. Misallocation of limited healthcare resources and poor treatment decisions can be minimized, and patient care optimized, through meticulous attention to DXA instrument calibration, data acquisition and analysis, interpretation, and reporting. This document from the International Society for Clinical Densitometry describes quality standards for BMD testing at DXA facilities worldwide to provide guidance for DXA supervisors, technologists, interpreters, and clinicians. High-quality DXA testing is necessary for correct diagnostic classification and optimal fracture risk assessment, and is essential for BMD monitoring.

Lumbar spine and total-body dual-energy X-ray absorptiometry in children with severe neurological impairment and intellectual disability: a pilot study of artefacts and disrupting factors

BACKGROUND

Children with severe neurological impairment and intellectual disability (ID) are susceptible for developing low bone mineral density (BMD) and fractures. BMD is generally measured with dual-energy X-ray absorptiometry (DXA).

OBJECTIVE

To describe the occurrence of factors that may influence the feasibility of DXA and the accuracy of DXA outcome in children with severe neurological impairment and ID.

MATERIALS AND METHODS

Based on literature and expert opinion, a list of disrupting factors was developed. Occurrence of these factors was assessed in 27 children who underwent DXA measurement.

RESULTS

Disrupting factors that occurred most frequently were movement during measurement (82%), aberrant body composition (67%), small length for age (56%) and scoliosis (37%). The number of disrupting factors per child was mean 5.3 (range 1-8). No correlation was found between DXA outcomes and the number of disrupting factors.

CONCLUSION

Factors that may negatively influence the accuracy of DXA outcome are frequently present in children with severe neurological impairment and ID. No systematic deviation of DXA outcome in coherence with the amount of disrupting factors was found, but physicians should be aware of the possible influence of disrupting factors on the accuracy of DXA.

Navel jewelry artifacts and intravertebral variation in spine bone densitometry in adolescents and young women

Non-removable navel jewelry can increase the measured bone density of the underlying vertebra. We measured lumbar spine bone mineral density (BMD) by dual-energy X-ray absorptiometry (DXA) in an observational study of 727 adolescents and young women aged 14-30 yr. We evaluated several methods of correcting BMD: manually erasing a small area, eliminating 1 or 2 vertebrae, estimating the BMD from 1 or 2 vertebrae using data from remaining vertebrae, and estimating the BMD using T-scores of the remaining vertebrae. Ten percent (n=71) of the subjects were wearing navel jewelry. The areal BMD by DXA of L1 and L2 was similar in those with jewels as in controls without jewels, but L3-L4 showed higher bone density in those with jewelry, and the spine BMD of L1-L4 was significantly higher in the bejeweled women (1.043+/-0.011 vs 1.006+/-0.004 g/cm2, p=0.01). The estimated errors in accuracy (g/cm2) were 0.034 due to the jewels; 0.005 from erasing a small area; 0.019 from eliminating L4; 0.044 from eliminating both L3 and L4; 0.016 from predicting BMD using L1-L3; and 0.028 using L1-L2. The T-scores using the Hologic database were progressively lower in the caudal vertebrae, even in 96 local women aged 30-35 yr, whose average T-score was 0.35 at L1 but -0.26 at L4. Thus, we found significant errors due to intravertebral variability. We suggest the optimal method of correcting for small artifacts is to erase the area under the artifact.

The effect of peritoneal dialysate on DXA bone densitometry results in patients with end-stage renal disease

The bone mineral density of patients undergoing peritoneal dialysis (PD) is low compared to a healthy population. No studies have been conducted to investigate whether the presence of peritoneal dialysate affects dual-energy X-ray absorptiometry (DXA) results. We hypothesized that the presence of peritoneal dialysate would not affect the measurement of bone mineral density (BMD) or bone mineral content (BMC) in the spine. Thirty patients on PD had DXA scans of the lumbar spine and hip completed before and after the drainage of peritoneal dialysate. A paired t-test was used to compare the difference in area, BMC, and BMD before and after drainage of dialysate. A significant difference was found in the BMC of the spine before and after the drainage of dialyzate. We recommend that peritoneal dialyzate be removed prior to scanning patients on PD and that densitometry technologists should be observant about the presence of peritoneal dialysate.