Development of a model of soft tissue simulation using ballistic gelatin for CBCT acquisitions related to dentomaxillofacial radiology research

OBJECTIVES

To present the ballistic gelatin as a new material capable of simulating the soft tissues in cone-beam CT (CBCT) images.

METHODS

CBCT images of three piglet heads were acquired with their soft tissues intact (standard group). Subsequently, the piglet heads were fixed in a container using metallic pins and moulded with acrylic resin; the soft tissues were then removed and replaced by ballistic gelatin, with the same thickness of the original soft tissues. The images were evaluated by two oral radiologists, to check the adaptation on bone surfaces, thickness and density, penetration into large bone cavities and cancellous bone, and the presence of air bubbles using a 5-score scale. Additionally, an objective analysis was carried out by one oral radiologist. For each CBCT scan, three axial reconstructions were selected to represent the mandibular, occlusal, and maxillary levels. The mean and standard deviation (SD) of the grey values were calculated in four regions of interest determined on soft tissue areas and compared by two-way ANOVA.

RESULTS

The ballistic gelatin showed subjective scores ranging from good to excellent for all parameters evaluated. There was no significant difference in the mean and SD values of the grey values between ballistic gelatin and the gold standard groups for all levels (p > 0.05). Higher SD values were observed in the occlusal level for both groups (p < 0.05).

CONCLUSIONS

Ballistic gelatin has visual and objective similarity with the gold standard. Thus, the ballistic gelatin is a promising material capable of simulating soft tissues in CBCT images.

Improved prediction of incident vertebral fractures using opportunistic QCT compared to DXA

Objectives

To compare opportunistic quantitative CT (QCT) with dual energy X-ray absorptiometry (DXA) in their ability to predict incident vertebral fractures.

Methods

We included 84 patients aged 50 years and older, who had routine CT including the lumbar spine and DXA within a 12-month period (baseline) as well as follow-up imaging after at least 12 months or who sustained an incident vertebral fracture documented earlier. Patients with bone disorders aside from osteoporosis were excluded. Fracture status and trabecular bone mineral density (BMD) were retrospectively evaluated in baseline CT and fracture status was reassessed at follow-up. BMD_QCT was assessed by opportunistic QCT with asynchronous calibration of multiple MDCT scanners.

Results

Sixteen patients had incident vertebral fractures showing lower mean BMD_QCT than patients without fracture (p = 0.001). For the risk of incident vertebral fractures, the hazard ratio increased per SD in BMD_QCT (4.07; 95% CI, 1.98–8.38), as well as after adjusting for age, sex, and prevalent fractures (2.54; 95% CI, 1.09–5.90). For DXA, a statistically significant increase in relative hazard per SD decrease in T-score was only observed after age and sex adjustment (1.57; 95% CI, 1.04–2.38). The predictability of incident vertebral fractures was good by BMD_QCT (AUC = 0.76; 95% CI, 0.64–0.89) and non-significant by T-scores. Asynchronously calibrated CT scanners showed good long-term stability (linear drift ranging from − 0.55 to − 2.29 HU per year).

Conclusions

Opportunistic screening of mainly neurosurgical and oncologic patients in CT performed for indications other than densitometry allows for better risk assessment of imminent vertebral fractures than dedicated DXA.

Key Points

• Opportunistic QCT predicts osteoporotic vertebral fractures better than DXA reference standard in mainly neurosurgical and oncologic patients.

• More than every second patient (56%) with an incident vertebral fracture was misdiagnosed not having osteoporosis according to DXA.

• Standard ACR QCT-cutoff values for osteoporosis (< 80 mg/cm³) and osteopenia (≤ 120 mg/cm³) can also be applied scanner independently in calibrated opportunistic QCT.

Does Simultaneous Computed Tomography and Quantitative Computed Tomography Show Better Prescription Rate than Dual-energy X-ray Absorptiometry for Osteoporotic Hip Fracture?

Purpose

This study aimed to evaluate the efficacy of simultaneous computed tomography (CT) and quantitative CT (QCT) in patients with osteoporotic hip fracture (OHF) by analyzing the osteoporosis detection rate and physician prescription rate in comparison with those of conventional dual-energy X-ray absorptiometry (DXA).

Materials and Methods

This study included consecutive patients older than 65 years who underwent internal fixation or hip arthroplasty for OHF between February and May 2015. The patients were assigned to either the QCT (47 patients) or DXA group (51 patients). The patients in the QCT group underwent QCT with hip CT, whereas those in the DXA group underwent DXA after surgery, before discharge, or in the outpatient clinic. In both groups, the patients received osteoporosis medication according to their QCT or DXA results. The osteoporosis evaluation rate and prescription rate were determined at discharge, postoperative (PO) day 2, PO day 6, and PO week 12 during an outpatient clinic visit.

Results

The osteoporosis evaluation rate at PO week 12 was 70.6% (36 of 51 patients) in the DXA group and 100% in the QCT group (P<0.01). The prescription rates of osteoporosis medication at discharge were 70.2% and 29.4% (P<0.001) and the cumulative prescription rates at PO week 12 were 87.2% and 60.8% (P=0.003) in the QCT and DXA groups, respectively.

Conclusion

Simultaneous CT and QCT significantly increased the evaluation and prescription rates in patients with OHF and may enable appropriate and consistent prescription of osteoporosis medication, which may eventually lead to patients' medication compliance.

A simple equation to estimate body fat percentage in children with overweightness or obesity: a retrospective study

Background

Dual-energy X-ray absorptiometry (DXA) provides separate measurements of fat mass, fat-free mass and bone mass, and is a quick, accurate, and safe technique, yet one that is not readily available in routine clinical practice. Consequently, we aimed to develop statistical formulas to predict fat mass (%) and fat mass index (FMI) with simple parameters (age, sex, weight and height).

Methods

We conducted a retrospective observational cross-sectional study in 416 overweight or obese patients aged 4–18 years that involved assessing adiposity by DXA (fat mass percentage and FMI), body mass index (BMI), sex and age. We randomly divided the sample into two parts (construction and validation). In the construction sample, we developed formulas to predict fat mass and FMI using linear multiple regression models. The formulas were validated in the other sample, calculating the intraclass correlation coefficient via bootstrapping.

Results

The fat mass percentage formula had a coefficient of determination of 0.65. This value was 0.86 for FMI. In the validation, the constructed formulas had an intraclass correlation coefficient of 0.77 for fat mass percentage and 0.92 for FMI.

Conclusions

Our predictive formulas accurately predicted fat mass and FMI with simple parameters (BMI, sex and age) in children with overweight and obesity. The proposed methodology could be applied in other fields. Further studies are needed to externally validate these formulas.

Osteoporotic fracture risk evaluation. Options when central densitometry is not available

BACKGROUND

Osteoporosis-related fractures represent a major health problem. Although spine and hip bone densitometry is the gold standard to assess bone density, this test is not always accesible. The purpose of this study was to describe two options to assess the risk of fracture due to osteoporosis in post-menopausal women assigned to a primary care unit where bone densitometry is not available.

METHODS

A cross-sectional study was conducted in 332 post-menopausal women without diagnosis or treatment for osteoporosis, attending regularly to a primary care unit. A heel bone peripheral densitometry, physical exam and medical history were performed. The assessment of fracture risk was carried out using the FRAX™ method.

RESULTS

Mean age was 60 ± 8.7 years and body mass index was 28.68 ± 4.24. According to the heel bone peripheral densitometry, 19 (5.7 %) women had osteoporosis (T-score less than or equal to -2.5), 171 (51.8 %) had osteopenia (T-score between -2.5 and less than or equal to -1) and 141 (42.5 %) had normal bone mineral density. According to the FRAX method, 13 (3.9 %) had an increased risk of osteoporotic fracture in a 10-year period and 40 (12 %) of hip fracture.

CONCLUSIONS

There was low concordance in the 10-year risk for major osteoporotic fracture and hip fracture assessed with both the FRAX™ and the peripheral bone densitometry methods.