Opportunistic osteoporosis screening via the measurement of frontal skull Hounsfield units derived from brain computed tomography images

Experimental study of the biological properties of nmHA-SiO2 fiber materials prepared by electrospinning technology

To study the biocompatibility of nanohydroxyapatite (nmHA)-SiO2 fiber material and its efficacy in guided bone regeneration. ① The cytotoxicity of the nmHA-SiO2 fiber material to MC3T3-E1 cells was determined by CCK-8 assay. The adhesion of cells on the surface of the material was observed. ② Bone defects were prepared in the skull of three groups of New Zealand white rabbits. The following treatments were administered: implantation of nmHA-SiO2, implantation of Bio-Oss, and no treatment. The defects were then covered with nmHA-SiO2 membrane or Hai'ao oral repair membrane. Animal samples were analyzed by gross observation, micro-computed tomography, hematoxylin-eosin staining and Masson staining. The data were statistically analyzed by multivariate analysis of variance to evaluate the repair of bone defects. ① The nmHA-SiO2 fiber material has suitable biocompatibility. ② The nmHA-SiO2 fiber material performed more effectively as a barrier membrane than other bone substitute materials in GBR model rabbits.

Opportunistic screening for osteoporosis using routine clinical care computed tomography brain studies

OBJECTIVE

Osteoporosis and falls are both prevalent in the elderly, and CT brain (CTB) is frequently performed post head-strike. We aim to validate the relationship between frontal bone density (Hounsfield unit) from routine CTB and bone mineral density from dual-energy X-ray absorptiometry (DEXA) scan for opportunistic osteoporosis screening.

MATERIALS AND METHODS

Patients who had a non-contrast CTB followed by a DEXA scan in the subsequent year were included in this multi-center retrospective study. The relationship between frontal bone density on CT and femoral neck T-score on DEXA was examined using ANOVA, Pearson's correlation, and receiver operating curve (ROC) analysis. Sensitivity, specificity, negative and positive predictive values, and area under the curve (AUC) were calculated.

RESULTS

Three hundred twenty-six patients (205 females and 121 males) were analyzed. ANOVA analysis showed that frontal bone density was lower in patients with DEXA-defined osteoporosis (p < 0.001), while Pearson's correlation analysis demonstrated a fair correlation with femoral neck T-score (r = 0.3, p < 0.001). On subgroup analysis, these were true in females but not in males. On ROC analysis, frontal bone density weakly predicted osteoporosis (AUC 0.6, 95% CI 0.5-0.7) with no optimal threshold identified. HU < 610 was highly specific (87.5%) but poorly sensitive (18.9%). HU > 1200 in females had a strong negative predictive value for osteoporosis (92.6%, 95% CI 87.1-98.1%).

CONCLUSION

Frontal bone density from routine CTB is significantly different between females with and without osteoporosis, but not between males. However, frontal bone density was a weak predictor for DEXA-defined osteoporosis. Further research is required to determine the role of CTB in opportunistic osteoporosis screening.

Stroke recurrence and osteoporotic conditions in postmenopausal patients with atherosclerotic ischemic stroke

Recurrence after stroke is common, and associated with a high mortality rate. Degradation of the elastic tissue in the arterial wall has been shown to aggravate atherosclerosis in blood vessels. Considering that type 1 collagen is present in both bone and vascular smooth muscle cells, we explored whether osteoporotic conditions affect the likelihood of stroke recurrence in postmenopausal women following atherosclerotic ischemic stroke. To determine actual bone mineral density (BMD), the Hounsfield unit values in the frontal skull were evaluated using brain computed tomography (CT) scans taken at admission. A multivariate Cox regression analysis was also performed to examine if osteoporosis could independently predict stroke recurrence in postmenopausal patients with large artery atherosclerosis (LAA) or small vessel occlusion (SVO) stroke. This study included 2130 consecutive patients (both males and females aged 50 and older) with acute LAA or SVO strokes. After adjusting for all covariates, hypothetical osteoporosis was identified as an independent predictor of stroke recurrence in female patients ≥50 years with acute LAA or SVO stroke (hazard ratio, 1.84; 95 % confidence interval, 1.05 to 3.24; p = 0.034). Our findings showed that osteoporosis could potentially affect the recurrence of ischemic stroke in postmenopausal patients with LAA or SVO stroke.

Risk Factor Analysis of Cryopreserved Autologous Bone Flap Resorption in Adult Patients Undergoing Cranioplasty with Volumetry Measurement Using Conventional Statistics and Machine-Learning Technique

OBJECTIVE

Decompressive craniectomy (DC) with duroplasty is one of the common surgical treatments for life-threatening increased intracranial pressure (ICP). Once ICP is controlled, cranioplasty (CP) with reinsertion of the cryopreserved autologous bone flap or a synthetic implant is considered for protection and esthetics. Although with the risk of autologous bone flap resorption (BFR), cryopreserved autologous bone flap for CP is one of the important material due to its cost effectiveness. In this article, we performed conventional statistical analysis and the machine learning technique understand the risk factors for BFR.

METHODS

Patients aged >18 years who underwent autologous bone CP between January 2015 and December 2021 were reviewed. Demographic data, medical records, and volumetric measurements of the autologous bone flap volume from 94 patients were collected. BFR was defined with absolute quantitative method (BFR-A) and relative quantitative method (BFR%). Conventional statistical analysis and random forest with hyper-ensemble approach (RF with HEA) was performed. And overlapped partial dependence plots (PDP) were generated.

RESULTS

Conventional statistical analysis showed that only the initial autologous bone flap volume was statistically significant on BFR-A. RF with HEA showed that the initial autologous bone flap volume, interval between DC and CP, and bone quality were the factors with most contribution to BFR-A, while, trauma, bone quality, and initial autologous bone flap volume were the factors with most contribution to BFR%. Overlapped PDPs of the initial autologous bone flap volume on the BRF-A crossed at approximately 60 mL, and a relatively clear separation was found between the non-BFR and BFR groups. Therefore, the initial autologous bone flap of over 60 mL could be a possible risk factor for BFR.

CONCLUSION

From the present study, BFR in patients who underwent CP with autologous bone flap might be inevitable. However, the degree of BFR may differ from one to another. Therefore, considering artificial bone flaps as implants for patients with large DC could be reasonable. Still, the risk factors for BFR are not clearly understood. Therefore, chronological analysis and pathophysiologic studies are needed.

Opportunistic measures of bone mineral density at multiple skeletal sites during whole-body CT in polytrauma patients

Whole-body CT in polytrauma patients revealed bone mineral density variations throughout the skeleton. Bone density was the highest in cranial bones and the lowest in proximal extremities and pelvis. Skeletal age-related changes were generally more pronounced than sex-related changes. Cranial bones did not follow the same aging pattern compared to other bones.

INTRODUCTION

Whole-body CT (WBCT) in polytrauma patients enables the detection of numerous incidental findings, such as estimates of bone mineral density (BMD) at multiple skeletal sites. This could help in better understanding of age- and sex-related changes in BMD through skeleton.

METHODS

Data were retrospectively retrieved from the WBCTs requested during a 2-year period. BMD, expressed in CT Hounsfield units (HU), was measured at frontal and occipital bone, four vertebrae (C4, Th7, L4, and S2), iliac bone, and proximal humerus and femur. Measurements were done on native and postcontrast scans. The population sample was age-, sex-, and visceral fat volume adjusted for analysis.

RESULTS

A total of 296 patients were included, with a median age of 51 years. BMD varied from the highest HU in cranial bones (629 HU) to the lowest HU in the pelvic bones (114 HU), P < 0.001. Sex differences were independent predictors of BMD in cranial bones and proximal humerus. The age-related decline in BMD was significant in all other bones, but the association with age differed among the measurement's sites. Visceral fat showed the strongest correlation with the lumbar spine and iliac wing, although multivariate analysis revealed it was not an independent predictor of bone density, such as age and sex.

CONCLUSIONS

BMD varies through skeleton, being the highest in the proximal axial skeleton. Age-related changes in BMD are significant and more pronounced than sex-related changes in almost all bones. Cranial bones do not follow the same pattern compared to other bones.

Routine chest CT combined with the osteoporosis self-assessment tool for Asians (OSTA): a screening tool for patients with osteoporosis

INTRODUCTION

The osteoporosis self-assessment tool for Asians (OSTA) is a common screening tool for osteoporosis. The seventh thoracic CT (CT-T7) Hounsfield unit (HU) measured by chest CT correlates with osteoporosis. This study aimed to investigate the diagnostic value of OSTA alone, CT-T7 alone, or the combination of OSTA and CT-T7 in osteoporosis.

MATERIALS AND METHODS

In this study, 1268 participants were grouped into 586 men and 682 women. We established multiple linear regression models by combining CT-T7 and OSTA. Receiver operating characteristic (ROC) curves were used to evaluate the ability to diagnose osteoporosis.

RESULTS

In the male group, the mean age was 59.02 years, and 108 patients (18.4%) had osteoporosis. In the female group, the mean age was 63.23 years, and 308 patients (45.2%) had osteoporosis. By ROC curve comparison, the CT-T7 (male, AUC = 0.789, 95% CI 0.745-0.832; female, AUC = 0.835, 95% CI 0.805-0.864) in the diagnosis of osteoporosis was greater than the OSTA (male, AUC = 0.673, 95% CI 0.620-0.726; female, AUC = 0.775, 95% CI 0.741-0.810) in both the male and female groups (p < 0.001). When OSTA was combined with CT, the equation of multiple linear regression (MLR) was obtained as follows: female = 3.020-0.028*OSTA-0.004*CT-T7. In the female group, it was found that the AUC of MLR (AUC = 0.853, 95% CI 0.825-0.880) in the diagnosis of osteoporosis was larger than that of CT-T7 (p < 0.01). When the MLR was 2.65, the sensitivity and specificity were 53.9% and 90%, respectively.

CONCLUSION

For a patient who has completed chest CT, CT-T7 (HU) combined with OSTA is recommended to identify the high-risk population of osteoporosis, and it has a higher diagnostic value than OSTA alone or CT-T7 alone, especially among females. For a female with MLR greater than 2.65, further DXA examination is needed.

Low skull bone density is associated with poor motor prognosis in women with Parkinson’s disease

Parkinson’s disease (PD) and osteoporosis are degenerative diseases that have shared pathomechanisms. To investigate the associations of skull bone density with nigrostriatal dopaminergic degeneration and longitudinal motor prognosis in female patients with PD. We analyzed the data of 260 drug-naïve female PD patients aged ≥50 years old who were followed-up for ≥3 years after their first visit to the clinic with baseline dopamine transporter (DAT) imaging. We measured skull bone density as a surrogate marker for systemic bone loss by calculating the Hounsfield unit (HU) in computed tomography scans. A Cox proportional hazard model was built to compare the rates of levodopa-induced dyskinesia (LID) or wearing-off according to skull HU. Longitudinal changes in levodopa-equivalent dose (LED) during a 3-year follow-up were assessed using a linear mixed model. A lower skull HU was associated with lower baseline DAT availability in striatal subregions; however, this relationship was not significant after adjusting for age, disease duration, body mass index, and white matter hyperintensities. After adjusting for confounding factors, a lower skull HU was significantly associated with an increased risk of LID development (hazard ratio = 1.660 per 1 standard deviation decrease, p = 0.007) and wearing-off (hazard ratio = 1.613, p = 0.016) in younger (&lt;67 years) but not in older patients. Furthermore, a lower skull HU was associated with a steeper increase in LED during follow-up in younger patients only (β = –21.99, p &lt; 0.001). This study suggests that baseline skull bone density would be closely linked to motor prognosis in drug naïve women with PD.

Assessment of Lumbar Vertebrae Morphology by Computed Tomography in Older Adults with Osteoporosis

BACKGROUND

Hounsfield units (HU) values derived from computerized tomography (CT) have been used in diagnosis for osteoporosis in the lumbar spine.

OBJECTIVE

This study aimed to identify anatomical dimensions of lumbar vertebrae on CT images, which were different between older normal, osteopenic and osteoporotic subjects.

METHODS

This prospective pilot study enrolled 79 older adults. Based on CT measurements of lumbar vertebrae in HU, participants were classified into three groups: normal (HU > 109), osteopenia (HU: 94-108), and osteoporosis (HU < 93). Altogether, 42 anatomical variables of lumbar vertebrae, L2, L3, L4, and L5, were measured in each participant by CT, including 24 parameters measurable by MRI or plain X-ray, and 18 parameters measurable by MRI only.

RESULTS

Among the morphological measurements also measurable by MRI and plain X-ray, the length upper curve, 50% and 75% of L5, length upper with cortex of L4, length center of cortex of L3, as well as width upper curve 75% of L2, were significantly different between the three groups (p= 0.008, 0.007, 0.035, 0.036, and 0.003 respectively). Among the morphological measurements also measurable by MRI, only width upper cortex 75% of L5 and width lower cortex 25% of L3 were significantly different between the three groups (p= 0.031 and 0.020, respectively).

CONCLUSION

Seven CT morphological measurements may be used as "reference standard" CT measurements for preliminarily diagnosing osteoporosis and osteopenia in older adults.

Correlation between Hounsfield unit derived from head, thorax, abdomen, spine and pelvis CT and t-scores from DXA

OBJECTIVES

CT examination can potentially be utilised for early detection of bone density changes with no additional procedure and radiation dose. We hypothesise that the Hounsfield unit (HU) measured from CT images is correlated to the t-scores derived from dual energy X-ray absorptiometry (DXA) in multiple anatomic regions.

MATERIALS & METHODS

Data were obtained retrospectively from all patients who underwent both CT examinations - brain (frontal bone), thorax (T7), abdomen (L3), spine (T7 & L3) or pelvis (left hip) - and DXA between 2014 and 2018 in our centre. To ensure comparability, the period between CT and DXA studies must not exceed one year. Correlations between HU values and t-scores were calculated using Pearson's correlation. Receiver operating characteristic (ROC) curves were generated, and the area under the curve (AUC) was used to determine threshold HU values for predicting osteoporosis.

RESULTS

The inclusion criteria were met by 1043 CT examinations (136 head, 537 thorax, 159 lumbar and 151 left hip). The left hip consistently provided the most robust correlations (r = 0.664-0.708, p < 0.001) and the best AUC (0.875-0.893). Meanwhile, thorax T7 and lumbar L3 showed average correlations (range of r values is 0.497-0.679, p < 0.001, AUC range = 0.680-0.783, 95% CI 0.561-0.922, all p < 0.02) and moderate AUC (0.680-0.783). Frontal bone shows low correlation and weak AUC with r < 0.5, AUC = 0.538-0.655, all p > 0.05.

CONCLUSION

HU values derived from the hip, T7 and L3 provided a good to moderate correlation to t-scores with a good prediction for osteoporosis. The suggested optimal thresholds may be used in clinical settings after external validations are performed.

Treatment planning system and beam data validation for the ZAP-X: A novel self-shielded stereotactic radiosurgery system

PURPOSE

To evaluate the treatment planning system (TPS) performance of the ZAP-X stereotactic radiosurgery (SRS) system through nondosimetric, dosimetric, and end-to-end (E2E) tests.

METHODS

A comprehensive set of TPS commissioning and validation tests was developed using published guidelines. Nondosimetric validation tests included information transfer, computed tomography-magnetic resonance (CT-MR) image registration, structure/contouring, geometry, dose tools, and CT density. Dosimetric validation included comparisons between TPS and water tank/Solid Water measurements for various geometries and beam arrangements and end-to-end (E2E) tests. Patient-specific quality assurance was performed with an ion chamber in the Lucy phantom and with Gafchromic EBT3 film in the CyberKnife head phantom. RadCalc was used for independent verification of monitor units. Additional E2E tests were performed using the RPC Gamma Knife thermoluminescent dosimeter (TLD) phantom, MD Anderson SRS head phantom, and PseudoPatient gel phantom for independent absolute dose verification.

RESULTS

CT-MR image registrations with known translational and rotational offsets were within tolerance (<0.5 × maximum voxel dimension). Slice thickness and distance accuracy were within 0.1 mm, and volume accuracy was within 0 to 0.11 cm³ . Treatment planning system volume measurement uncertainty was within 0.1 to 0.4 cm³ . Ion chamber point-dose measurements for a single beam in a water phantom agreed to TPS-calculated values within ±4% for collimator diameters 10 to 25 mm, and ±6% for 7.5 mm, for all measured depths (7, 50, 100, 150, and 200 mm). In homogeneous Solid Water, point-dose measurements agreed to within ±4% for cones sizes 7.5 to 25 mm. With 1-cm high/low density inserts, measurements were within ±4.2% for cone sizes 10 to 25 mm. Film-based E2E using 4/5-mm cones resulted in a gamma passing rate (%GP) of 99.8% (2%/1.5 mm). Point-dose measurements in a Lucy phantom with an ion chamber using 36 beams distributed along three noncoplanar arcs agreed to within ±4% for cone sizes 10 to 25 mm. The RPC Gamma Knife TLD phantom yielded passing results with a measured-to-expected TLD dose ratio of 1.02. The MD Anderson SRS head phantom yielded passing results, with 4% TLD agreement and %GP of 95%/93% (5%/3 mm) for coronal/sagittal film planes. The RTsafe gel phantom gave %GP of >95% (5%/2 mm) for all four targets. For our first 58 patients, film-based patient-specific quality assurance has resulted in an average %GP of 98.7% (range, 94-100%) at 2%/2 mm.

CONCLUSIONS

Core ZAP-X features were found to be functional. On the basis of our results, point-dose and planar measurements were in agreement with TPS calculations using multiple phantoms and setup geometries, validating the ZAP-X TPS beam model for clinical use.

Effect of Osteoporotic Condition on Ventriculomegaly and Shunt-Dependent Hydrocephalus After Subarachnoid Hemorrhage

BACKGROUND AND PURPOSE

Hydrocephalus is a common complication in aneurysmal rupture subarachnoid hemorrhage (SAH). As both the bone and arachnoid trabeculae are composed of type 1 collagen, we identified the possible relationship between bone mineral density and ventriculomegaly and shunt-dependent hydrocephalus (SDHC) development after aneurysmal rupture SAH in younger patients.

METHODS

We measured frontal skull Hounsfield unit (HU) values on brain computed tomography upon admission, and mean frontal skull HU values were used instead of T-score value. Hazard ratios were calculated using Cox regression analysis to identify whether osteoporotic condition is an independent predictor for ventriculomegaly and SDHC after surgical clipping for SAH in younger patients.

RESULTS

Altogether, 412 patients (≤65 years) who underwent surgical clipping for primary spontaneous SAH from a ruptured aneurysm were enrolled in this 11-year analysis in 2 hospitals. We observed that the first tertile group of skull HU was an independent predictor of SDHC after SAH compared with the third tertile of skull HU values (hazard ratio, 2.55 [95% CI, 1.25-5.20]; P=0.010). There were no significant interactions between age and skull HU with respect to ventriculomegaly and SDHC in younger patients.

CONCLUSIONS

Our study suggests a relationship between possible osteoporotic conditions and ventriculomegaly and SDHC development after SAH in younger patients. Our findings may be useful in predicting hydrocephalus in young SAH patients using a convenient method of measuring skull HU value on brain computed tomography upon admission.

Effects of Possible Osteoporotic Conditions on the Recurrence of Chronic Subdural Hematoma

The recurrence rate of chronic subdural hematoma (CSDH) has been reported to range from 2.3 to 33%. As bridging veins are composed of abundant collagen bundles and bone matrix, we aimed to investigate the possible associations between skull Hounsfield unit (HU) values and the recurrence of CSDH. We retrospectively enrolled patients with CSDH who underwent burr hole surgery. The HU values of the frontal skull were measured on brain CT scans. The cumulative hazard for recurrence was estimated according to predictive factors. To identify the independent predictors associated with the recurrence of CSDH, hazard ratios (HRs) were estimated using multivariate Cox regression analysis. A total of 208 consecutive patients who underwent burr hole trephination for CSDH over a 7-years period at a single institution were enrolled in this study. We found that age, greater midline shift (≥10.5 mm), lower skull HU (<769.5), and diabetes were independent predictors for the recurrence of CSDH (HR 1.06, 95% confidence interval [CI] 1.00–1.12, p = 0.042; HR 5.37, 95% CI 1.48–19.46, p = 0.010; HR 6.71, 95% CI 1.84–24.45, p = 0.004; and HR 3.30, 95% CI 1.05–10.43, p = 0.042, respectively). A relationship between possible low bone mineral density (BMD) and CSDH recurrence was observed. In addition, age, greater preoperative midline shift, and diabetes were also identified as predictive factors for recurrence. We expect that our findings may facilitate our understanding of the possible association between CSDH and BMD.

Does the skull Hounsfield unit predict shunt dependent hydrocephalus after decompressive craniectomy for traumatic acute subdural hematoma?

Background and purpose

Posttraumatic hydrocephalus affects 11.9%–36% of patients undergoing decompressive craniectomy (DC) after traumatic brain injury and necessitates a ventriculo-peritoneal shunt placement. As bone and arachnoid trabeculae share the same collagen type, we investigated possible connections between the skull Hounsfield unit (HU) values and shunt-dependent hydrocephalus (SDHC) in patients that received cranioplasty after DC for traumatic acute subdural hematoma (SDH).

Methods

We measured HU values in the frontal bone and internal occipital protuberance from admission brain CT. Receiver operating characteristic curve analysis was performed to identify the optimal cut-off skull HU values for predicting SDHC in patients receiving cranioplasty after DC due to traumatic acute SDH. We investigated independent predictive factors for SDHC occurrence using multivariable logistic regression analysis.

Results

A total of 162 patients (>15 years of age) were enrolled in the study over an 11-year period from two university hospitals. Multivariable logistic analysis revealed that the group with simultaneous frontal skull HU ≤797.4 and internal occipital protuberance HU ≤586.5 (odds ratio, 8.57; 95% CI, 3.05 to 24.10; P<0.001) was the only independent predictive factor for SDHC in patients who received cranioplasty after DC for traumatic acute SDH.

Conclusions

Our study reveals a potential relationship between possible low bone mineral density and development of SDHC in traumatic acute SDH patients who had undergone DC. Our findings provide deeper insight into the association between low bone mineral density and hydrocephalus after DC for traumatic acute SDH.

Significance of skull osteoporosis to the development of peritumoral brain edema after LINAC-based radiation treatment in patients with intracranial meningioma

Background and purpose

Disruption of the tumor-brain barrier in meningioma plays a critical role in the development of peritumoral brain edema (PTBE). We hypothesized that osteoporotic conditions may be associated with PTBE occurrence after radiation in patients with intracranial meningioma.

Methods

We measured Hounsfield units (HU) of the frontal skull on simulation brain CT in patients who underwent linear accelerator (LINAC)-based radiation treatment for intracranial meningioma. Receiver operating characteristic curve analysis was performed to determine the optimal cut-off values for several predictive factors. The cumulative hazard for PTBE was estimated and classified according to these factors. Hazard ratios were then estimated to identify independent predictive factors associated with the development of PTBE after radiation in intracranial meningioma patients.

Results

A total of 83 intracranial meningiomas in 76 patients who received LINAC-based radiation treatment in our hospital over an approximate 5-year period were included for the study. We found mean frontal skull HU ≤630.625 and gross tumor volume >7.194 cc to be independent predictors of PTBE after radiation treatment in patients with meningioma (hazard ratio, 8.41; P = 0.019; hazard ratio, 5.92; P = 0.032, respectively). In addition, patients who were ≥65 years showed a marginally significant association with PTBE.

Conclusions

Our study suggests that possible osteoporotic conditions, large tumor volume, and older age may be associated with PTBE occurrence after LINAC-based radiation treatment for intracranial meningioma. In the future we anticipate that these findings may enhance the understanding of the underlying mechanisms of PTBE after radiation in meningioma patients.