Hounsfield Unit Thresholds Research Articles

Computed Tomography-Based Coronary Artery Calcium Score Calculation at a Reduced Tube Voltage Utilizing Iterative Reconstruction and Threshold Modification Techniques: A Feasibility Study.

The coronary artery calcium score (CACS) indicates cardiovascular health. A concern in this regard is the ionizing radiation from computed tomography (CT). Recent studies have tried to introduce low-dose CT techniques to assess CACS. We aimed to investigate the accuracy of iterative reconstruction (IR) and threshold modification while applying low tube voltage in coronary artery calcium imaging. The study population consisted of 107 patients. Each subject underwent an electrocardiogram-gated CT twice, once with a standard voltage of 120 kVp and then a reduced voltage of 80 kVp. The standard filtered back projection (FBP) reconstruction was applied in both voltages. Considering Hounsfield unit (HU) thresholds other than 130 (150, 170, and 190), CACS was calculated using the FBP-reconstructed 80 kVp images. Moreover, the 80 kVp images were reconstructed utilizing IR at different strength levels. CACS was measured in each set of images. The intraclass correlation coefficient (ICC) was used to compare the CACSs. A 64% reduction in the effective dose was observed in the 80 kVp protocol compared to the 120 kVp protocol. Excellent agreement existed between CACS at high-level (strength level = 5) IR in low-kVp images and the standard CACS protocol in scores ≥ 11 (ICC > 0.9 and p < 0.05). Increasing the threshold density to 190 HU in FBP-reconstructed low-kVp images yielded excellent agreement with the standard protocol in scores ≥ 11 (ICC > 0.9 and p < 0.05) and good agreement in score zero (ICC = 0.84 and p = 0.02). The modification of the density threshold and IR provides an accurate calculation of CACS in low-voltage CT with the potential to decrease patient radiation exposure.

Comparison of Hounsfield units and vertebral bone quality score for the prediction of time to pathologic fracture in mobile spine metastases treated with radiotherapy.

Spine metastases are commonly treated with radiotherapy for local tumor control; pathologic fracture is a potential complication of spinal radiotherapy. Both Hounsfield units (HUs) on CT and vertebral bone quality (VBQ) on MRI have been argued to predict stability as measured by odds of pathologic fracture, although it is unclear if there is a difference in the predictive power between the two methodologies. The objective of the present study was to examine whether one methodology is a better predictor of pathologic fracture following radiotherapy for mobile spine metastases. Patients who underwent radiotherapy (conventional external-beam radiation therapy, stereotactic body radiation therapy, or intensity-modulated radiation therapy) for mobile spine (C1-L5) metastases at a tertiary care center were retrospectively identified. Details regarding underlying pathology, patient demographics, and tumor morphology were collected. Vertebral involvement was assessed using the Weinstein-Boriani-Biagini (WBB) system. Bone quality of the non-tumor-involved bone was assessed on both pretreatment CT and MRI. Univariable analyses were conducted to identify independent predictors of fracture, and Kaplan-Meier analyses were used to identify significant predictors of time to pathologic fracture. Stepwise Cox regression analysis was used to determine independent predictors of time to fracture. One hundred patients were included (mean age 62.7 ± 11.9 years; 61% male), of whom 35 experienced postradiotherapy pathologic fractures. The most common histologies were lung (22%), prostate (21%), breast (14%), and renal cell (13%). On univariable analysis, the mean HUs of the vertebrae adjacent to the fractured vertebra were significantly lower among those experiencing fracture; VBQ was not significantly associated with fracture odds. Survival analysis showed that average HUs ≤ 132, nonprostate pathology, involvement of ≥ 3 vertebral body segments on the WBB system, Spine Instability Neoplastic Score (SINS) ≥ 7, and the presence of axial pain all predicted increased odds of fracture (all p < 0.001). Cox regression found that HUs ≤ 132 (OR 2.533, 95% CI 1.257-5.103; p = 0.009), ≥ 3 WBB vertebral body segments involved (OR 2.376, 95% CI 1.132-4.987; p = 0.022), and axial pain (OR 2.036, 95% CI 0.916-4.526; p = 0.081) predicted increased fracture odds, while prostate pathology predicted decreased odds (OR 0.076, 95% CI 0.009-0.613; p = 0.016). Sensitivity analysis suggested that an HU threshold of ≤ 132 and a SINS of ≥ 7 identified patients at increased risk of fracture. The present results suggest that bone density surrogates as measured on CT, but not MRI, can be used to predict the risk of pathologic fracture following radiotherapy for mobile spine metastases. More extensive vertebral body involvement and the presence of mechanical axial pain additionally predict increased fracture odds.

Semiautomatic Weight Bearing Computed Tomography Area Analysis of the Distal Tibiofibular Syndesmotic Incisura in Subtle Chronic Syndesmotic Instability

Category: Ankle; Sports Introduction/Purpose: Syndesmotic injuries and residual chronic subtle distal tibiofibular syndesmotic instability (DTFSI) are relatively common injuries, especially in athletes prone to suffering high ankle sprains. The diagnosis of subtle DTFSI remains challenging, with a high prevalence of false-negative results using conventional non-invasive clinical-radiographical diagnostic tools. The current gold standard for diagnosis, arthroscopy, is a surgical operation, which is invasive and, therefore, not ideal. Weightbearing Computed-Tomography (WBCT) has emerged as a possible dynamic non-invasive alternative diagnostic option, with proven high diagnostic accuracy for syndesmotic incisura area measurements in major DTFSI. Our study aimed to assess the capability of semiautomatic weight-bearing computed tomography (WBCT) syndesmotic incisura area in diagnosing subtle chronic syndesmotic instability. Methods: In this diagnostic case-control study, patients with suspected unilateral chronic subtle DTFSI underwent bilateral standing weight-bearing CT (WBCT) before surgical treatment. All patients had gold-standard arthroscopic assessment for DTFSI, introducing a 3mm diameter arthroscopic sphere into the syndesmotic incisura for diagnosis. Bilateral syndesmotic incisura areas were measured 10mm proximally to the apex of the distal tibia articular dome using a semiautomatic measurement algorithm. Two tangent lines marked the anterior and posterior borders of the syndesmotic incisura to the anterior and posterior edges of the distal tibia and fibula. Once borders were marked, the incisura area was automatically calculated by the software based on a Hounsfield units (HU) contrast algorithm. A HU threshold of 200HU was utilized. Measurements were done independently by two fellowship-trained readers. Comparisons between injured and control ankles were made using Student T-test or Wilcoxon, according to normality. Measurements' reliability was assessed with the Intraclass Correlation Coefficient (ICC). Results: From an initial sample of 32 patients, 20 patients (12 female) with arthroscopically confirmed DTFSI (11 right sides) with a mean age of 31.7 years (range 18 to 55 years) and a mean BMI of 30.35kg/m² (SD +/-8.29 kg/m²) were included in the study. All patients had a history of an old ankle sprain 6 to 182 months before the assessment, and athletic lesions were reported in 53% of the population. ICCs were above 0.98 for both intra and interobserver reliability. The average syndesmotic area was 96.91mm2 (SD +/-27.9mm2) in injured ankles compared to 84.61mm2 (SD +/-26.9 mm2) in uninjured ankles. The difference between injured and non-injured tibiofibular areas was 12.31mm2 (95%CI: 9.04-15.58mm2), which was shown statistically significant (p &lt; 0.001; effect size: 1.43). Conclusion: In this case-control study, we assessed the accuracy of semiautomatic WBCT syndesmotic incisura area measurements in diagnosing subtle chronic DTFSI. We found an increased syndesmotic area in injured ankles that reached statistical significance. Due to the minimal differences between injured and uninjured contralateral ankles, larger cohorts would likely solidify this study's findings further. The use of external rotation stress, volumetric assessment, distance, and coverage maps could increase the diagnostic accuracy in DTFSI. However, automatic area measurements have a higher overall reproducibility and applicability in the clinical setting, which could help providers make therapeutic decisions.

Relationship of Sarcopenia to Tolerance of Chemotherapy During Definitive Treatment of Primary Anal Squamous Cell Carcinoma

Primary therapy for anal squamous cell carcinoma consists of definitive radiation with concurrent chemotherapy, most commonly 5-fluorouracil and mitomycin-C. This regimen is associated with significant cutaneous, hematologic, and gastrointestinal toxicity. Sarcopenia, or low skeletal muscle mass, has been described as an adverse prognostic factor and predictor of poor tolerance to therapy across a range of malignancies, including breast, gynecologic and head and neck cancers. Here, we sought to determine if the presence of sarcopenia at the initiation of therapy is associated with increased rates of toxicity and poorer tolerance of definitive treatment for primary anal squamous cell carcinoma. This was a review of patients treated with curative intent for anal squamous cell carcinoma at a single academic medical center between 2007 and 2017, median follow up was 38 months. Analysis was limited to patients receiving definitive radiation with concurrent chemotherapy. Sarcopenia was objectively defined, using previously validated methods, as a skeletal muscle index (SMI) <41 cm2/m2 for female patients regardless of body mass index (BMI); for male patients sarcopenia was defined as SMI<43cm2/m2 for BMI<25 and <53 cm2/m2 for BMI >25. SMI calculations were performed using the average skeletal muscle cross sectional areas of two sequential axial CT slices at the L3 vertebral level obtained from radiation planning computed tomography scans. The image analysis was performed by a single trained observer using Sliceomatic software with a Hounsfield unit threshold of -29 to 150 to define skeletal muscle. Sarcopenia as a predictor for treatment toxicity was analyzed using Chi-Square testing. Overall survival and progression free survival were compared with 2-sample t tests. Sixty-one patients were included in the analysis with 49% meeting criteria for sarcopenia. Stage did not differ although sarcopenic patients were significantly more elderly than those without sarcopenia (mean 72 vs 58 years, p<0.001). Patients with sarcopenia were significantly more likely to have chemotherapy breaks, chemotherapy dose reductions, and incomplete chemotherapy courses compared to non-sarcopenic patients (33.3% vs 9.7%; p = 0.02). Sarcopenia was not predictive of more radiation treatment breaks, hematologic toxicity, progression free survival or overall survival. Sarcopenia is predictive of reduced tolerance to chemotherapy among patients receiving definitive combined modality therapy for primary anal carcinoma. We found no association between sarcopenia and tolerance of radiation therapy or survival outcomes.

Quantifying the Dosimetric Impact of Tissue Hounsfield Unit Assignment in Deep Learning-based Synthetic CT Images For MRI-Only Radiation Therapy of The Head and Neck

MRI-only simulation for head and neck (HN) radiotherapy (RT) could allow for single-image modality planning with excellent soft tissue contrast. In the MRI-only simulation workflow, synthetic CTs (sCTs) are generated from MRI to provide electron density information for dose calculation. Bone/air regions produce little MRI signal which could lead to electron density misclassification in sCTs. Establishing the dosimetric impact of this error could inform quality assurance (QA) procedures using MRI-only RT planning. In this study we quantify differences in Hounsfield Unit (HU) values between paired CT/ sCTs of HN cancer patients and investigate the dosimetric impact on clinical treatment plans. Fourteen patients with head and neck cancer undergoing same-day CT and 3T MRI simulation were retrospectively identified. MRIs were deformed to the CT using multimodal deformable image registration. SCTs were generated from T1w DIXON MRI using a commercially available deep learning-based generator (MRIplanner, Spectronics). Tissue voxel assignment was quantified by creating a CT-derived HU threshold contour. CT/sCT HU differences for anatomical/target contours and tissue classification regions including air (<-250HU), adipose tissue (-250HU to -51HU), soft tissue (-50HU to 199HU), spongy (200HU to 499HU) and cortical bone (> 500HU) were quantified. T-test was used to determine if sCT/CT HU differences were significant. The frequency of structures that had a HU difference >70HU (the CT window-width setting for intra-cranial structures) was computed to establish structure classification accuracy. Clinical IMRT treatment plans created on CTs were retrospectively recalculated on sCT images using compared using the gamma metric. The mean ratio of sCT HUs relative to CT for air, adipose tissue, soft tissue, spongy and cortical bone were 1.7±0.3, 1.1±0.1, 1.0±0.1, 0.9±0.1 and 0.8±0.1 (value of 1 indicates perfect agreement). T-tests (significance set at t = 0.05) identified differences in HU values for air, spongy and cortical bone in sCT images compared to CT. The structures with sCT/CT HU differences > 70HU were the L/R cochlea and mandible, occurring in >78% of the tested cohort. These structures contain dense bone/air interfaces. Plans recalculated on sCTs yielded global/local gamma pass rates of 98.7%±1.2% (3mm,3%) and 95.5%±2.5% (1mm,1%). Mean differences in D95, D50, D10 and D2 dose volume histogram (DVH) metrics for organ-at-risk (OAR) and planning tumor volumes (PTV) were 0.8%±1.5% and 2.1% ± 1.2% respectively. In this cohort, HU differences in sCTs were observed but did not translate into a reduction in gamma pass rates and OAR/PTV DVH metrics. The acquisition of additional training data such as ultrashort echo time MRI could improve bone/air contrast and reduce bone/air sCT misclassifications. Further studies will establish the variation in sCT dosimetric accuracy using a larger retrospective cohort to inform QA limits on clinical sCT usage.

Analysis of tissue lipidomics and computed tomography pulmonary fat attenuation volume (CTPFAV ) in idiopathic pulmonary fibrosis.

There is increasing interest in the role of lipids in processes that modulate lung fibrosis with evidence of lipid deposition in idiopathic pulmonary fibrosis (IPF) histological specimens. The aim of this study was to identify measurable markers of pulmonary lipid that may have utility as IPF biomarkers. IPF and control lung biopsy specimens were analysed using a unbiased lipidomic approach. Pulmonary fat attenuation volume (PFAV) was assessed on chest CT images (CTPFAV ) with 3D semi-automated lung density software. Aerated lung was semi-automatically segmented and CTPFAV calculated using a Hounsfield-unit (-40 to -200HU) threshold range expressed as a percentage of total lung volume. CTPFAV was compared to pulmonary function, serum lipids and qualitative CT fibrosis scores. There was a significant increase in total lipid content on histological analysis of IPF lung tissue (23.16 nmol/mg) compared to controls (18.66 mol/mg, p = 0.0317). The median CTPFAV in IPF was higher than controls (1.34% vs. 0.72%, p < 0.001) and CTPFAV correlated significantly with DLCO% predicted (R2 = 0.356, p < 0.0001) and FVC% predicted (R2 = 0.407, p < 0.0001) in patients with IPF. CTPFAV correlated with CT features of fibrosis; higher CTPFAV was associated with >10% reticulation (1.6% vs. 0.94%, p = 0.0017) and >10% honeycombing (1.87% vs. 1.12%, p = 0.0003). CTPFAV showed no correlation with serum lipids. CTPFAV is an easily quantifiable non-invasive measure of pulmonary lipids. In this pilot study, CTPFAV correlates with pulmonary function and radiological features of IPF and could function as a potential biomarker for IPF disease severity assessment.

Artificial intelligence tool detection of intravenous contrast enhancement using spleen attenuation.

To assess the ability of an automated AI tool to detect intravenous contrast material (IVCM) in abdominal CT examinations using spleen attenuation. A previously validated automated AI tool measuring the attenuation of the spleen was deployed on a sample of 32,994 adult (age ≥ 18) patients (mean age, 61.9 ± 14.7 years; 13,869 men, 19,125 women) undergoing 65,449 supine position CT examinations (41,020 with and 24,429 without IVCM by DICOM header) from January 1, 2000 to December 31, 2021. After exclusions, receiver operating characteristic (ROC) curve analysis was performed to determine the optimal threshold for binary classification of IVCM status (non-contrast vs IVCM enhanced), which was then applied to the sample. Discordant examinations (i.e., IVCM status determined by AI tool did not match DICOM header) were manually reviewed to establish ground truth. Repeat ROC curve and contingency table analysis were performed to assess AI tool performance. ROC analysis of the initial study sample of 61,783 CT examinations yielded AUC of 0.970 with Youden index suggesting an optimal spleen attenuation threshold of 65 Hounsfield units (HU). Manual review of 2094 discordant CT examinations revealed discordance due to DICOM header error in 1278 (61.0%) and AI tool misclassification in 410 (19.6%), with 406 (9.4%) meeting exclusion criteria. Analysis of 61,377 CT examinations in the final study sample yielded AUC of 0.999 with accuracy of 99.3% at the 65 HU threshold. Error rate for DICOM header information was 2.1% (1278/61,377) versus 0.7% (410/61,377) for the AI tool. The automated spleen attenuation AI tool was highly accurate for detection of IVCM at a threshold of 65 HU.

Trunk muscle quality and quantity are associated with renal volume in nondiabetic people.

Renal disease is a major problem in terms of community health and the economy. Skeletal muscle is involved in crosstalk with the kidney. We therefore investigated the relationship between muscle quality and quantity, and renal parenchymal volume (RPV). The association between the parameters of skeletal muscle and RPV/body surface area (BSA) was analyzed by computed tomography in 728 middle-aged participants without kidney disease or diabetes mellitus in a cross-sectional study. A retrospective cohort study of 68 participants was undertaken to analyze the association between changes in RPV/BSA and muscle parameters. Parameter change was calculated as follows: parameter at the follow-up examination/parameter at the baseline examination. The normal attenuation muscle (NAM) and low attenuation muscle (LAM) were identified by Hounsfield Unit thresholds of +30 to +150, and -29 to +29, respectively. Positive correlations were found between estimated glomerular filtration rate and RPV/BSA (r=0.451, P<.0001). Multiple regression analyses revealed that the NAM index was positively related to RPV/BSA (β=0.458, P<.0001), whereas the LAM index was negatively related to RPV/BSA (β=-0.237, P<.0001). In this cohort study, a change in the LAM index was independently associated with a change in RPV/BSA (β=-0.349, P=.0032). Both trunk muscle quantity and quality were associated with renal volume related to renal function in nondiabetic people. An increase in low quality muscle volume might be related to a decrease in renal volume.

197. Level-specific Hounsfield unit thresholds as a predictor of subsidence following transformational and posterior lumbar interbody fusion

197. Level-specific Hounsfield unit thresholds as a predictor of subsidence following transformational and posterior lumbar interbody fusion

Impact of Dual-Energy Computed Tomography (DECT) Postprocessing Protocols on Detection of Monosodium Urate (MSU) Deposits in Foot Tendons of Cadavers.

To evaluate two different dual-energy computed tomography (DECT) post-processing protocols for the detection of MSU deposits in foot tendons of cadavers with verification by polarizing light microscopy as the gold standard. A total of 40 embalmed cadavers (15 male; 25 female; median age, 82 years; mean, 80 years; range, 52-99; SD ± 10.9) underwent DECT to assess MSU deposits in foot tendons. Two postprocessing DECT protocols with different Hounsfield unit (HU) thresholds, 150/500 (=established) versus 120/500 (=modified). HU were applied to dual source acquisition with 80 kV for tube A and 140 kV for tube B. Six fresh cadavers (4 male; 2 female; median age, 78; mean, 78.5; range 61-95) were examined by DECT. Tendon dissection of 2/6 fresh cadavers with positive DECT 120 and negative DECT 150 studies were used to verify MSU deposits by polarizing light microscopy. The tibialis anterior tendon was found positive in 57.5%/100% (DECT 150/120), the peroneus tendon in 35%/100%, the achilles tendon in 25%/90%, the flexor halluces longus tendon in 10%/100%, and the tibialis posterior tendon in 12.5%/97.5%. DECT 120 resulted in increased tendon MSU deposit detection, when DECT 150 was negative, with an overall agreement between DECT 150 and DECT 120 of 80% (p = 0.013). Polarizing light microscope confirmed MSU deposits detected only by DECT 120 in the tibialis anterior, the achilles, the flexor halluces longus, and the peroneal tendons. The DECT 120 protocol showed a higher sensitivity when compared to DECT 150.

Initial end-to-end testing of the ExacTrac dynamic deep inspiration breath hold workflow using a breath hold breast phantom

ExacTrac Dynamic (ETD) provides a Deep Inspiration Breath Hold (DIBH) workflow for breast patients. Stereoscopic x-ray imaging combined with optical and thermal mapping allows localisation against simulation imaging, alongside surface guided breath hold monitoring. This work aimed to determine appropriate imaging parameters, the optimal Hounsfield Unit (HU) threshold for patient contour generation and workflow evaluation via end-to-end (E2E) positioning using a custom breast DIBH phantom. After localisation via existing Image Guidance (IG), stereoscopic imaging was performed with a range of parameters to determine best agreement. Similarly, residual errors in prepositioning were minimised using a range of HU threshold contours. E2E positioning was completed for clinical workflows allowing residual isocentre position error measurement and existing IG comparison. Parameters of 60 kV and 25mAs were determined appropriate for patient imaging and HU thresholds between −600 HU and −200 HU enabled adequate prepositioning. The average and standard deviation in residual isocentre position error was 1.0 ± 0.9 mm, 0.4 ± 1.0 mm and 0.1 ± 0.5 mm in the lateral, longitudinal and vertical directions, respectively. Errors measured using existing IG were −0.6 ± 1.1 mm, 0.5 ± 0.7 mm and 0.2 ± 0.4 mm in the lateral, longitudinal and vertical directions, and 0.0 ± 1.0o, 0.5 ± 1.7o and −0.8 ± 1.8o for pitch roll and yaw. The use of bone weighted matching increased residual error, while simulated reduction of DIBH volume maintained isocentre positioning accuracy despite anatomical changes. This initial testing indicated suitability for clinical implementation during DIBH breast treatments.

Validation of a Length-Adjusted Abdominal Arterial Calcium Score Method for Contrast-Enhanced CT Scans.

The Agatston score on noncontrast computed tomography (CT) scans is the gold standard for calcium load determination. However, contrast-enhanced CT is commonly used for patients with atherosclerotic cardiovascular diseases (ASCVDs), such as peripheral arterial occlusive disease (PAOD) and abdominal aortic aneurysm (AAA). Currently, there is no validated method to determine calcium load in the aorta and peripheral arteries with a contrast-enhanced CT. This study validated a length-adjusted calcium score (LACS) method for contrast-enhanced CT scans. The LACS (calcium volume in mm3/arterial length in cm) in the abdominal aorta was calculated using four-phase liver CT scans of 30 patients treated between 2017 and 2021 at the University Medical Center Groningen (UMCG) with no aortic disease. Noncontrast CT scans were segmented with a 130 Hounsfield units (HU) threshold, and a patient-specific threshold was used for contrast-enhanced CTs. The LACS was calculated and compared from both segmentations. Secondly, the interobserver variability and the influence of slice thickness (0.75 mm vs. 2.0 mm) was determined. There was a high correlation between the LACS from contrast-enhanced CT scans and the LACS of noncontrast CTs (R2 = 0.98). A correction factor of 1.9 was established to convert the LACS derived from contrast-enhanced CT to noncontrast CT scans. LACS interobserver agreement on contrast-enhanced CT was excellent (1.0, 95% confidence interval = 1.0-1.0). The 0.75 mm CT threshold was 541 (459-625) HU compared with 500 (419-568) HU on 2 mm CTs (p = 0.15). LACS calculated with both thresholds was not significantly different (p = 0.63). The LACS seems to be a robust method for scoring calcium load on contrast-enhanced CT scans in arterial segments with various lengths.

The importance of Hounsfield units in adult spinal deformity surgery: finding an optimal threshold to minimize the risk of mechanical complications.

Low bone mineral density (BMD) is a well-established risk factor for mechanical complications following adult spinal deformity (ASD) surgery. Hounsfield units (HU) measured on computed tomography (CT) scans are a proxy of BMD. In ASD surgery, we sought to: (I) evaluate the association of HU with mechanical complications and reoperation, and (II) identify optimal HU threshold to predict the occurrence of mechanical complications. A single-institution retrospective cohort study was undertaken for patients undergoing ASD surgery from 2013-2017. Inclusion criteria were: ≥5-level fusion, sagittal/coronal deformity, and 2-year follow-up. HU were measured on 3 axial slices of one vertebra, either at the upper instrumented vertebra (UIV) itself or UIV ±4 from CT scans. Multivariable regression controlled for age, body mass index (BMI), postoperative sagittal vertical axis (SVA), and postoperative pelvic-incidence lumbar-lordosis mismatch. Of 145 patients undergoing ASD surgery, 121 (83.4%) had a preoperative CT from which HU were measured. Mean age was 64.4±10.7 years, mean total instrumented levels was 9.8±2.6, and mean HU was 153.5±52.8. Mean preoperative SVA and T1PA were 95.5±71.1 mm and 28.8°±12.8°, respectively. Postoperative SVA and T1PA significantly improved to 61.2±61.6 mm (P<0.001) and 23.0°±11.0° (P<0.001). Mechanical complications occurred in 74 (61.2%) patients, including 42 (34.7%) proximal junctional kyphosis (PJK), 3 (2.5%) distal junctional kyphosis (DJK), 9 (7.4%) implant failure, 48 (39.7%) rod fracture/pseudarthrosis, and 61 (52.2%) reoperations within 2 years. Univariate logistic regression showed a significant association between low HU and PJK [odds ratio (OR) =0.99; 95% confidence interval (CI): 0.98-0.99; P=0.023], but not on multivariable analysis. No association was found regarding other mechanical complications, overall reoperations, and reoperations due to PJK. HU below 163 were associated with increased PJK on receiver operating characteristic (ROC) curve analysis [area under the curve (AUC) =0.63; 95% CI: 0.53-0.73; P<0.001]. Though several factors contribute to PJK, it appears that 163 HU may serve as a preliminary threshold when planning ASD surgery to mitigate the risk of PJK.

Prediction of low DEXA T-scores by routine computed tomography body scans at different kilovoltage peaks.

Previous studies have demonstrated positive correlations between computed tomography (CT) attenuation of lumbar spine vertebrae and their bone mineral density (BMD) measured by dual-energy X-ray absorptiometry (DEXA). However, these studies were performed using a standard 120 kilovoltage peak (kVp) setting. As radiation attenuation in mineralised tissues varies by the tube voltage applied, we determined the diagnostic accuracy of CT attenuation at identifying individuals with low BMD at different kVp settings. Single centre retrospective study of adults who had CT and DEXA scans within 6 months of each other. CT scans were performed at either 100 kVp, 120 kVp or dual energy (80 kVp/140 kVp). Attenuation was measured in axial cross-sections of L1-4 vertebrae and correlated with the results of DEXA. Receiver operated characteristic (ROC) curves were generated to determine diagnostic cut-off thresholds. Analysis included 268 subjects (169 females; mean age: 70, range: 20-94 years). CT attenuation values at L1 or mean L1-4 correlated positively with DEXA-derived T-scores. At L1, the optimal Hounsfield units (HU) thresholds for predicting DEXA T-scores of -2.5 or less at 100 kVp, 120 kVp and dual-energy scans were <170, <128 and <164, with corresponding AUCs of 0.925, 0.814 and 0.743 respectively. For mean L1-4, the HU thresholds were <173, <134 and <151, with corresponding AUCs of 0.933, 0.824 and 0.707 respectively. CT attenuation thresholds differ depending on the tube voltage used. We provide voltage-specific, probability-optimised thresholds for the identification of persons likely to have low BMD on DEXA scanning.

CT texture analysis reliability in pulmonary lesions: the influence of 3D vs. 2D lesion segmentation and volume definition by a Hounsfield-unit threshold

ObjectiveReproducibility problems are a known limitation of radiomics. The segmentation of the target lesion plays a critical role in texture analysis variability. This study’s aim was to compare the interobserver reliability of manual 2D vs. 3D lung lesion segmentation with and without pre-definition of the volume using a threshold of − 50 HU.MethodsSeventy-five patients with histopathologically proven lung lesions (15 patients each with adenocarcinoma, squamous cell carcinoma, small cell lung cancer, carcinoid, and organizing pneumonia) who underwent an unenhanced CT scan of the chest were included. Three radiologists independently segmented each lesion manually in 3D and 2D with and without pre-segmentation volume definition by a HU threshold, and shape parameters and original, Laplacian of Gaussian–filtered, and wavelet-based texture features were derived. To assess interobserver reliability and identify the most robust texture features, intraclass correlation coefficients (ICCs) for different segmentation settings were calculated.ResultsShape parameters had high reliability (64–79% had excellent and good ICCs). Texture features had weak reliability levels, with the highest ICCs (38% excellent or good) found for original features in 3D segmentation without the use of a HU threshold. A small proportion (4.3–11.5%) of texture features had excellent or good ICC values at all segmentation settings.ConclusionInterobserver reliability of texture features from CT scans of a heterogeneous collection of manually segmented lung lesions was low with a small proportion of features demonstrating high reliability independent of the segmentation settings. These results indicate a limited applicability of texture analysis and the need to define robust texture features in patients with lung lesions.Key Points• Our study showed a low reproducibility of texture features when 3 radiologists independently segmented lung lesions in CT images, which highlights a serious limitation of texture analysis.• Interobserver reliability of texture features was low regardless of whether the lesion was segmented in 2D and 3D with or without a HU threshold.• In contrast to texture features, shape parameters showed a high interobserver reliability when lesions were segmented in 2D vs. 3D with and without a HU threshold of − 50.

Discrepancy between DXA and CT-based assessment of spine bone mineral density.

Adequate bone mineral density (BMD) is necessary for success in spine surgery. Dual-energy X-ray absorptiometry (DXA) is the gold standard in determining BMD but may give spuriously high values. Hounsfield units (HU) from computed tomography (CT) may provide a more accurate depiction of the focal BMD encountered during spine surgery. Our objective is to determine the discrepancy rate between DXA and CT BMD determinations and how often DXA overestimates BMD compared to CT. We retrospectively reviewed 93 patients with both DXA and CT within 6months. DXA lumbar spine and overall T scores were classified as osteoporotic (T Score ≤ - 2.5) or non-osteoporotic (T Score > -2.5). L1 vertebral body HU were classified as osteoporotic or non-osteoporotic using cutoff thresholds of either ≤ 135 HU or ≤ 110 HU. Corresponding DXA and HU classifications were compared to determine disagreement and overestimation rates. Using lumbar T scores, the CT vs DXA disagreement rate was 40-54% depending on the HU threshold. DXA overestimated BMD 97-100% of the time compared to CT. Using overall DXA T scores, the disagreement rate was 33-47% with DXA greater than CT 74-87% of the time. In the sub-cohort of 10 patients with very low HU (HU < 80), DXA overestimated BMD compared to CT in every instance. There is alarge discrepancy between DXA and CT BMD determinations. DXA frequently overestimates regional BMD encountered during spine surgery compared with CT. While DXA remains the gold standard in determining BMD, CT may play an important role in defining the focal BMD pertinent to spine surgery.

Correlation between Forearm Bone Mineral Density Measured by Dual Energy X-ray Absorptiometry and Hounsfield Units Value Measured by CT in Lumbar Spine.

Our aim was to determine if the dual-energy X-ray absorptiometry (DXA)-measured forearm bone mineral density (BMD) correlates with the Hounsfield unit (HU) values obtained from computed tomography (CT). A retrospective analysis of 164 patients with degenerative diseases of the lumbar spine was performed. DXA was used to measure the BMD and T-scores of each patient's forearm. Lumbar CT was used to measure the CT HU values in three axial images of the L1-L4 vertebral bodies, and the average was calculated. According to the preoperative DXA T-score, they were divided into a normal group, an osteopenia group, and an osteoporosis group. Pearson's correlation coefficient was used to analyze the correlations of CT HU values in L1-L4 with BMD and T-scores in the corresponding vertebral body. The receiver operating characteristic curve (ROC) was used to determine the CT HU thresholds between osteoporosis and non-osteoporosis groups. Forearm BMD was moderately correlated with L1-L4 CT HU values (0.4<R2<0.6), and the correlation coefficients (R2) were 0.552, 0.578, 0.582, and 0.577, respectively (all p<0.001). Forearm T-scores were moderately correlated with L1-L4 CT HU values (0.4<R2<0.6), and the correlation coefficients (R2) were 0.595, 0.609, 0.605, and 0.605, respectively (all p<0.001). The thresholds of L1-L4 between the osteoporosis group (t ≤ -2.5) and the non-osteoporosis group (t>-2.5) were 110.0HU (sensitivity 74% and specificity 76%), 112.5HU (sensitivity 67% and 83% specificity), 92.4HU (81% sensitivity and 70% specificity), and 98.7HU (74% sensitivity and 78% specificity), respectively. Based on the moderate positive correlation between forearm DXA-measured BMD and HU values, forearm DXA provides a theoretical basis for evaluating lumbar vertebral bone mass. Preoperative forearm DXA may be useful in the formulation of surgical plans and the prevention of postoperative complications in patients with lumbar degenerative diseases.

535 CT SCAN AORTIC VALVE CALCIFICATION PATTERNS AND HEMODYNAMIC PERFORMANCE OF SELF-EXPANDING INTRA-ANNULAR TRANSCATHETER PROSTHESES

Abstract Introduction Aortic valve calcification (AVC) represents a negative prognostic factor in patients undergoing transcatheter aortic valve implantation (TAVI). Recent randomized clinical trials comparing commercially available self-expanding (SE) supra-annular and balloon-expandable (BE) devices with second-generation SE intra-annular devices demonstrated the clinical non-inferiority of the latter in terms of procedural success. However, no current data are available in vivo regarding the potential impact of AVC on SE intra-annular device performance and clinical outcomes. Purpose to evaluate the potential impact of different AVC patterns on SE intra-annular device performance in a consecutive cohort of patients undergoing TAVI. Methods this is an observational, non-randomized, prospective, single-center study preliminarily enrolling 53 consecutive patients who underwent TAVI with a SE intra-annular device (Portico - Abbott Structural Heart, St Paul, MN, USA) between 2019 and 2022 at our department. All patients underwent transthoracic echocardiography, contrast-enhanced multidetector row computed tomography (MDCT) with volumetric calcium score and coronary angiography before TAVI. Patients with bicuspid aortic valve and previous surgical aortic valve replacement eligible for valve-in-valve TAVI were excluded. AVC and left ventricle outflow tract (LVOT) calcification (up to 15 mm below the basal annular plane) were quantified in the contrast images by using a Hounsfield unit threshold of 850. Results Patients undergoing post-TAVI pacemaker implantation (19% of the overall study population) had higher AVC levels compared with those that did not show this complication (all three cusps AVA calcium score 270.6±409.6 vs 158.1±137.1, p=0.146; p=0.048, p=0.181 and p=0.346 for left cusp- LCC, right cusp – RCC- and non-coronary cusp-NCC, respectively). Severe LVOT calcification was also associated with a higher incidence of AV conduction abnormalities (37.9±44.5 vs 13.4±39.0 of patients without AV defects, p=0.045). Moreover, post-procedural moderate/severe aortic regurgitation occurred more frequently in patients with LCC calcification (183.7±87.0 vs 64.2±99.6, p=0.018) and RCC calcification (188.7±149.5 vs 58.7±120.8, p=0.019) rather than those with NCC or LVOT calcification. Conclusion(s) preliminary results of our observational registry highlight the potential impact of AVC patterns on the occurrence of aortic regurgitation and pacemaker implantation after a SE intra-annular device. A larger sample size is needed to better understand the impact of calcium patterns on each single outcome in order to identify patients at higher risk and to early manage these complications, improving long-term outcomes.

Comparison of epicardial adipose tissue volume quantification between ECG-gated cardiac and non-ECG-gated chest computed tomography scans

BackgroundThis study investigated accuracy and consistency of epicardial adipose tissue (EAT) quantification in non-ECG-gated chest computed tomography (CT) scans.MethodsEAT volume was semi-automatically quantified using a standard Hounsfield unit threshold (− 190, − 30) in three independent cohorts: (1) Cohort 1 (N = 49): paired 120 kVp ECG-gated cardiac non-contrast CT (NCCT) and 120 kVp non-ECG-gated chest NCCT; (2) Cohort 2 (N = 34): paired 120 kVp cardiac NCCT and 100 kVp non-ECG-gated chest NCCT; (3) Cohort 3 (N = 32): paired non-ECG-gated chest NCCT and chest contrast-enhanced CT (CECT) datasets (including arterial phase and venous phase). Images were reconstructed with the slice thicknesses of 1.25 mm and 5 mm in the chest CT datasets, and 3 mm in the cardiac NCCT datasets.ResultsIn Cohort 1, the chest NCCT-1.25 mm EAT volume was similar to the cardiac NCCT EAT volume, while chest NCCT-5 mm underestimated the EAT volume by 7.5%. In Cohort 2, 100 kVp chest NCCT-1.25 mm were 13.2% larger than 120 kVp cardiac NCCT EAT volumes. In Cohort 3, the chest arterial CECT and venous CECT dataset underestimated EAT volumes by ~ 28% and ~ 18%, relative to chest NCCT datasets. All chest CT-derived EAT volumes were similarly associated with significant coronary atherosclerosis with cardiac CT counterparts.ConclusionThe 120 kVp non-ECG-gated chest NCCT-1.25 mm images produced EAT volumes comparable to cardiac NCCT. Chest CT EAT volumes derived from consistent imaging settings are excellent alternatives to the cardiac NCCT to investigate their association with coronary artery disease.

Comprehensive abdominal composition evaluation of rectal cancer patients with anastomotic leakage compared with body mass index-matched controls.

Anastomotic leakage (AL) is a fatal complication in patients with rectal cancer after undergoing anterior resection. However, the role of abdominal composition in the development of AL has not been studied. To investigate the relationship between abdominal composition and AL in rectal cancer patients after undergoing anterior resection. A retrospective case-matched cohort study was conducted. Complete data for 78 patients with AL were acquired and this cohort was defined as the AL group. The controls were matched for the same sex and body mass index (± 1 kg/m2). Parameters related to abdominal composition including visceral fat area (VFA), subcutaneous fat area (SFA), subcutaneous fat thickness (SFT), skeletal muscle area (SMA), skeletal muscle index (SMI), abdominal circumference (AC), anterior to posterior diameter of abdominal cavity (APD), and transverse diameter of abdominal cavity (TD) were evaluated based on computed tomography (CT) images using the following Hounsfield Unit (HU) thresholds: SFA: -190 to -30, SMA: -29 to 150, and VFA: -150 to -20. The significance of abdominal composition-related parameters was quantified using feature importance analysis; an artificial intelligence method was used to evaluate the contribution of each included variable. Two thousand two hundred and thirty-eight rectal cancer patients who underwent anterior resection from 2010 to 2020 in a large academic hospital were investigated. Finally, 156 cases were enrolled in the study. Patients in the AL group showed longer operative time (225.03 ± 55.29 vs 207.17 ± 40.80, P = 0.023), lower levels of preoperative hemoglobin (123.32 ± 21.17 vs 132.60 ±1 6.31, P = 0.003) and albumin (38.34 ± 4.01 vs 40.52 ± 3.97, P = 0.001), larger tumor size (4.07 ± 1.36 vs 2.76 ± 1.28, P < 0.001), and later cancer stage (P < 0.001) compared to the controls. Patients who developed AL exhibited a larger VFA (125.68 ± 73.59 vs 97.03 ± 57.66, P = 0.008) and a smaller APD (77.30 ± 23.23 vs 92.09 ± 26.40, P < 0.001) and TD (22.90 ± 2.23 vs 24.21 ± 2.90, P = 0.002) compared to their matched controls. Feature importance analysis revealed that TD, APD, and VFA were the three most important abdominal composition-related features. AL patients have a higher visceral fat content and a narrower abdominal structure compared to matched controls.