Hounsfield Units Research Articles

AI-based algorithm for assessing coronary artery calcium score on contrast-enhanced cardiac computed tomography scans

Abstract Introduction In cardiac computed tomography (CT) examinations, non-contrast scans are often performed in addition to contrast-enhanced scans to quantify the coronary artery calcification (CAC) score. These calcium score scans are associated with additional exposure to ionizing radiation. Purpose We sought to develop a fully automated artificial intelligence (AI)-based algorithm capable of determining CAC score based solely on contrast-enhanced CT scans, eliminating the need for additional non-contrast scans. Methods An automated CAC scoring algorithm on contrast-enhanced CT scans was developed and trained using a dataset of 297 cardiac CT studies. Coronary artery calcifications were manually segmented in contrast-enhanced scans using a threshold of 2 standard deviations above the mean attenuation value of the ascending aorta. On non-contrast scans, CAC was manually assessed using a standard threshold of ≥130 Hounsfield Units. A correction factor for calcium score results assessed on contrast-enhanced scans was determined using linear regression. The algorithm was tested on an independent set of 90 contrast-enhanced CT scans (four manufacturers, eight scanner models). We compared automated CAC scores to manual expert reader reference assessments on non-contrast CT scans. CAC scores were categorized into four risk categories following the Society of Cardiovascular Computed Tomography recommendations: 0, 1-100, 101-300, and >300 Agatston Units. Results In the assessment of 90 CT studies (mean age 61.0±11.4 years, 46.7% males), the AI-model detected CAC in 69 contrast-enhanced scans (76.7%), comparable to the human reader's detection rate of CAC in 71 non-contrast scans (78.9%) (p = 0.63). The CAC score was initially calculated using AI-based segmentation of coronary calcification on contrast-enhanced scans and then the result was multiplied by established linear correction factor of 1.97. There was an excellent correlation between AI-model and manual reference total CAC scores (Pearson’s r = 0.96, 95% CI 0.94–0.97, p < 0.001). The model correctly classified 77 patients (85.6%) into the same CAC risk category as the human reader (Figure 1). Among 19 patients (21.1%) with a CAC score of zero, only 1 patient (5.3%) was reclassified with a non-zero CAC score by the AI-model. Cohen’s kappa value for CAC score risk categorization was 0.80 (p < 0.001), indicating very good agreement (Figure 2). Bland–Altman analysis revealed minimal bias of -9.7 Agatston Unit with 95% limits of agreement ranging from -184.8 to 165.5 Agatston Unit. Conclusions CAC score can be accurately quantified on contrast-enhanced cardiac CT scans using an automated AI-based algorithm. This approach has the potential to eliminate the necessity for an additional non-contrast CT scan, thereby reducing the patient's exposure to ionizing radiation.

Three-dimensional source position verification in image-guided high-dose-rate brachytherapy using an XCT-based gel dosimeter.

Comprehensive quality assurance (QA) for a seamless workflow of high-dose-rate brachytherapy, from imaging to planning and irradiation, is uncommon, and QA of the source dwell position is performed in one- or two-dimensions. Gel dosimetry using magnetic resonance imaging (MRI) is effective in verifying the three-dimensional distribution of doses for image-guided brachytherapy (IGBT). However, MRI scanners are not readily accessible, and MRI scanning is time-consuming. Nevertheless, X-ray computed tomography (XCT) is available for IGBT planning. In this study, we designed and developed an efficient method for QA for a seamless workflow of IGBT with a new commercially available XCT-based polymer gel dosimeter. To enable direct insertion of brachytherapy applicators, the gelatinizing agent of the dosimeter was modified. A cylindrical polyvinyl chloride jar was filled with the modified gel dosimeter, which was subsequently used to determine the reproducibility of source dwell positions, detectability of source positional errors from intentionally introduced catheter length offsets, effect of looped source transfer tubes on the average displacement, extent of inter-observer variation, and gel robustness following multiple needle-insertions. Three ProGuide sharp needles were inserted into the jar. The dwell time at each point was determined to identify the irradiated volume with a diameter of approximately 10mm on XCT images. All the times were the same. The plan was delivered using an afterloader with an Ir-192 radioactive source, and the irradiated gel dosimeter was scanned using an XCT scanner. The subtracted images were generated from pre- and post-irradiated images. Volumes with incremented Hounsfield units were manually identified and contoured. The centroid of the volume was defined as the measured source dwell position. Subsequently, planned source dwell positions were extracted from the DICOM file of the plan. Finally, the source dwell positions in plan and irradiated gel were compared in three axes. The hardness of the dosimeter was 1250% greater than that of the previously reported gel dosimeter. Source dwell positions were visually identified in the XCT image. Testing of CT acquisition, planning, irradiation, and analysis was completed in approximately 1h. In the reproducibility test of source dwell positions, created by inserting three needles (each with three source dwell positions), the average displacements of the source positions from the first source dwell position were within 0.5mm in all three directions. In the detectability test, displacements were less than 1mm in the x-y plane but greater than 1mm in the z-axis, which was the source path direction. When errors of 1-3mm were intentionally introduced, the measured displacement was within 0.7mm of the median (range: 0.21-1.65mm) of intentional errors. When the transfer tube was looped, the source dwell position displaced by approximately 1mm. After 20 needle-insertions, the source dwell position displacement was within 1mm. The maximum inter-observer variation of contouring was 0.57mm. The XCT-based gel dosimeter enabled verification of three-dimensional source dwell positions for a seamless workflow of IGBT with high precision and efficiency.

Hounsfield Unit on Preoperative Computed Tomography as an Indicator of Prognosis in Patients with Liposarcoma.

Liposarcoma (LPS) is classified into 4 subtypes. As some subtypes have a high recurrence rate, knowing the risk of recurrence before surgery is important. Here, we aimed to investigate the relationship between Hounsfield units (HU) derived from preoperative computed tomography (CT) and the prognosis of patients undergoing surgery. We included 32 patients who underwent surgery for LPS between 2014 and 2022. Preoperative plain CT images were collected, and the HU value of each LPS was measured. The association between 2 HU categories (HU < cut-off vs. ≥ cut-off) and clinical variables was assessed. The optimal cut-off value was determined using statistical methods. We used the Kaplan-Meier method to determine the differences between the 2 HU categories at 2 endpoints: recurrence-free survival (RFS) and overall survival (OS). The dedifferentiated subtype showed significantly higher HU values than the other subtypes (P < .001). The optimal cut-off value for HU was 20. HU < 20 was associated with young age, low-performance status, low Charlson Comorbidity Index, and well-differentiated pathology. The Kaplan-Meier curves demonstrated that RFS and OS were significantly shorter in patients with HU ≥ 20 than in those with HU < 20 (P = .007 and .04, respectively). However, when stratified based on subtype, no significant differences were observed between dedifferentiated and other subtypes. HU ≥ 20 on preoperative CT was associated with poor prognosis in LPS patients. Our findings suggest that preoperative CT-derived HU values may serve as useful predictors of prognosis.

Quantitative ROI differences for assessment of occult intertrochanteric extension of greater trochanteric fractures on pelvis CT.

To determine if difference in Hounsfield Units (HU) of the medullary bone between the injured and non-injured femurs in patients with greater trochanteric fractures is associated with occult intertrochanteric (IT) extension. Retrospective review was performed of 81 patients (age range 54-102, 54 females and 27 males) who underwent CT and subsequent MRI after identification of a greater trochanteric fracture without evidence of IT extension on radiography and/or CT. Hounsfield units of the injured and non-injured femurs on CT were recorded at the level of the base of the greater trochanter centrally (ROI1) and the level of the upper border of the lesser trochanter posteromedially (ROI2). The difference between the injured and non-injured femur for each ROI1 and ROI2 were calculated. Absence or presence, and if present, extent of IT extension was assessed on MRI. Analysis was performed to determine if there is correlation of difference in density with presence, and extent of occult IT fractures. 81 cases met inclusion criteria, 14 (17%) had no IT extension, 11 (14%) had less than 50% IT extension and 56 (69%) had 50% or greater IT extension. There was statistical significance between presence and absence of IT extension between the injured and non-injured femur for ROI1 (HU) no IT extension median (IQR): 18.8(4-40), ROI1 (HU) present IT extension median (IQR): 65.5(46-90) p < .0001, and for ROI2 no IT extension median (IQR): 3(-8-25.5) and ROI2 present IT extension 51(40.5-76), p < .0001. There was statistical significance of the extent of IT extension: ROI1 less than 50% IT extension median (IQR): 37.5(27.5-57), ROI1 50% or greater IT extension median (IQR): 72.3(53.5-91.3), p < .0001, and for ROI2 less than 50% IT extension median (IQR): 17.5(8-49), and ROI2 50% or greater IT extension median (IQR): 55.8(45.3-81.5), p < .0001. A threshold ROI2 difference of 50 HU resulted in specificity of 92% and sensitivity 60.7% of for IT extension 50% or greater. Patients presenting with greater trochanteric fractures, an asymmetric increased density measured by ROI differences within the medullary space of the IT region between the injured and non-injured femur is associated with occult IT extension.

First test beam of the DMAPS-based proton tracker at the pMBRT facility at the Curie Institute

Objective.Proton radiotherapy's efficacy relies on an accurate relative stopping power (RSP) map of the patient to optimise the treatment plan and minimize uncertainties. Currently, a conversion of a Hounsfield Units map obtained by a common x-ray computed tomography (CT) is used to compute the RSP. This conversion is one of the main limiting factors for proton radiotherapy. To bypass this conversion a direct RSP map could be obtained by performing a proton CT (pCT). The focal point of this article is to present a proof of concept of the potential of fast pixel technologies for proton tracking at clinical facilities.Approach.A two-layer tracker based on the TJ-Monopix1, a depleted monolithic active pixel sensor (DMAPS) chip initially designed for the ATLAS, was tested at the proton minibeam radiotherapy beamline at the Curie Institute. The chips were subjected to 100 MeV protons passing through the single slit collimator (0.4×20mm2) with fluxes up to1.3×107p s-1 cm-2. The performance of the proton tracker was evaluated with GEANT4 simulations.Main results.The beam profile and dispersion in air were characterized by an opening of 0.031 mm cm-1, and aσx=0.172mm at the position of the slit. The results of the proton tracking show how the TJ-Monopix1 chip can effectively track protons in a clinical environment, achieving a tracking purity close to 70%, and a position resolution below 0.5 mm; confirming the chip's ability to handle high proton fluxes with a competitive performance.Significance.This work suggests that DMAPS technologies can be a cost-effective alternative for proton imaging. Additionally, the study identifies areas where further optimization of chip design is required to fully leverage these technologies for clinical ion imaging applications.

Development of a novel automated algorithm for patient dosimetry in computed tomography: a step towards the facilitation of size-specific dose estimates and organs dosimetry estimations in a busy clinical workflow

Abstract Accurate dosimetry in computed tomography (CT) is essential for patient safety and effective radiation management. This study presents the development of an automated algorithm designed to enhance patient dosimetry by facilitating size-specific dose estimates (SSDE) and organ dose estimations. Utilizing a Python-based script, the proposed method integrates advanced image preprocessing, contour detection, and mathematical calculations to quantify key metrics from CT images. This automated approach addresses the limitations of manual measurement techniques. A retrospective analysis was conducted on CT axial images from examinations acquired with an 80-detector scanner. The algorithm processes DICOM images, converts pixel values to Hounsfield Units, applies Gaussian smoothing, windowing, and thresholding, followed by morphological operations to refine segmentation. It measures the water equivalent diameter (Dw) and estimates both region SSDE and organ doses, incorporating tissue attenuation. Validation was performed using an adult anthropomorphic ATOM phantom, with organ doses measured by optically stimulated luminescence dosimeters. The results demonstrated the algorithm's potential in estimating SSDE and organ doses. Validation of the automated method revealed strong correlations for Dw and SSDE between the proposed method and manual measurements of five expert reviewers ranging from 0.86 to 0.99 for determination coefficient. Comparative analysis of organ doses showed close agreement between results from experimental setup against the proposed algorithm. The automated algorithm estimated brain dose with a mean of 21.8 mGy, while measurements from the ATOM phantom and CT Expo indicated 19.74 mGy and 23.05 mGy, respectively. For lung doses, the automated algorithm estimated 12.5 mGy compared to 11.0 mGy from the ATOM phantom and 13.1 mGy from CT Expo. Liver doses were measured at 12.7 mGy by the automated method, versus 12.1 mGy from the ATOM phantom and 11.1 mGy from CT Expo. This study shows the potential of automated image analysis techniques in enhancing dosimetry accuracy in CT examinations.

Does Bone Density Affect Outcomes in Lateral Lumbar Interbody Fusion? A Propensity Score-Matched Analysis of Preoperative Hounsfield Units.

Background: This study aimed to assess whether preoperative Hounsfield unit (HU) values differ in short-term clinical outcomes after lateral lumbar interbody fusion (LLIF) surgery. Methods: In a retrospective analysis, 109 patients undergoing LLIF for lumbar degenerative diseases (LDD) were reviewed. Preoperative Computed Tomography (CT) scans measured HU values at the L1-L4 vertebrae, dividing patients into low and high HU groups. After conducting a cluster analysis of preoperative Hounsfield unit (HU) values, patients were categorized into low and high HU groups using propensity score matching (PSM). The outcomes measured one-year post-surgery included pain intensity (Numeric Rating Scales for Low Back Pain (NRSLBP), Leg Pain (NRSLP), and Leg Numbness (NRSLN)) and quality of life (Japanese Orthopedic Association Back Pain Evaluation Questionnaire: JOABPEQ). Results: After PSM, there were 26 patients in each group. Significant improvements were noted in both low and high HU groups post-surgery, with the low HU group showing a decrease in NRSLBP from 6.2 to 3.7, NRSLP from 7.4 to 2.5, and NRSLN from 6.4 to 3.0. The high HU group exhibited similar improvements (NRSLBP: 6.5 to 3.6, NRSLP: 6.3 to 2.5, NRSLN: 6.2 to 2.4). JOABPEQ scores improved significantly in both groups across all domains, with no significant differences observed. Preoperative HU values have little correlation with the short-term outcomes of pain and quality of life in LLIF surgery. Conclusions: This study suggests reconsidering the role of HU values following indirect decompression via LLIF, particularly in evaluating pain and patient-reported outcome measures in patients with LDD.

Lymphadenopathy Secondary to Metastatic Squamous Cell Carcinoma Mistaken for Malignant Lymphoma.

It is difficult to identify disease entities underlying lymphadenopathy in the head and neck region based solely on imaging. This often results in metastatic squamous cell carcinoma (Sqcc)-induced lymphadenopathy being mistaken for lymphoma. This study aimed to analyze clinical characteristics and computed tomographic features that aid in distinguishing between metastatic Sqcc and lymphoma when lymphadenopathy resembles a large solitary lymphoma. The authors retrospectively enrolled 5 patients, managed between 2010 and 2024, with metastatic Sqcc mistaken for lymphoma and 9 patients with lymphadenopathy of 2cm or larger due to lymphoma. Among the 5 patients, 3 exhibited a homogeneous lymphadenopathy phenotype, whereas the remaining 2 displayed heterogeneous enhancement with multiple small necrotic areas within the affected masses. Measurement of the Hounsfield units (HU) for lymphadenopathy, the sternocleidomastoid muscle, and the submandibular gland (SMG) was conducted for each patient. The ratio of lymphadenopathy HU to the average HU of the sternocleidomastoid muscle and the SMG was significantly higher in patients diagnosed with metastatic Sqcc compared with those with lymphoma (P = 0.01). In computed tomography scans, heterogeneous lymphadenopathy or enhancement levels that approach or exceed those of the SMG may indicate the likelihood of Sqcc rather than lymphoma.

Risk Factors for Adjacent Vertebral Fractures Following Cement Vertebroplasty: The Clinical Significance of Multiple Preexisting Vertebral Compression Fractures.

A retrospective cohort study. The study retrospectively analyzed the factors associated with the development of adjacent vertebral fractures. Adjacent vertebral fractures (AVF) may occur following cement vertebroplasty, and several risk factors have been reported with controversies. A total of 123 patients, with a mean age of 79.2 years, who underwent single-level vertebroplasty were included in the investigation. We systematically collected data encompassing baseline demographics, osteoporosis parameters, surgical details, radiologic measurements, and Hounsfield unit (HU) values in the lumbar spine. Subsequently, univariable, followed by multivariable logistic regression analyses, were employed to identify the risk factors of AVFs. Thirty of 123 patients had AVFs within 6 months following vertebroplasty. The AVF group exhibited a higher percentage of multiple preexisting vertebral compression fractures (P=0.006), a greater volume of injected cement (P=0.032), and a more pronounced reduction in local kyphosis (P=0.007). Multivariable logistic regression analysis revealed multiple preexisting vertebral compression fractures and a reduction in local kyphosis exceeding 8 degrees were independent risk factors for AVFs (P=0.008 and 0.003, respectively), with odds ratios of 3.78 (95% confidence interval: 1.41-10.12) and 4.16 (95% CI: 1.65-10.50), respectively. Subgroup analysis showed that patients with multiple preexisting vertebral compression fractures (VCFs) had significantly lower bone mineral density Z-score, T-score, and HU values compared with those without preexisting VCFs (P<0.05). Conversely, there were no significant differences in T-score or HU values between patients with no VCFs and those with a single VCF. This study demonstrated that both bone strength and local alignment are key factors associated with adjacent vertebral fractures. Specifically, having multiple preexisting vertebral compression fractures and a reduction in local kyphosis exceeding 8 degrees are independent risk factors. The presence of more than one previous vertebral compression fracture serves as a significant clinical indicator of advanced bone density reduction in patients with osteoporosis, offering a quick and straightforward method for identifying high-risk patients. Patients exhibiting these risk factors should be monitored more closely for favorable clinical outcomes. Level III-retrospective nonexperimental study.

Size-specific dose estimates calculated using patient size measurements from scanned projection radiograph in high-resolution chest computed tomography.

Size-specific dose estimates (SSDE) are used to assess patient-specific radiation exposure in Computed Tomography (CT), complementing the volume CT dose index (CTDIvol). This study compared SSDE calculated using patient's lateral size from scan projection radiograph (SPR) with SSDE calculated using water equivalent diameter (Dw) from tomographic images in adult chest high-resolution CT (HRCT). In a single-centre study, the CTDIvol and dose-length product (DLP) were recorded from HRCT dose reports of adult patients. Lateral width (SLat), at the centre of the scan range, from the SPR was measured and the SSDE (SSDER) was calculated using conversion factors related to SLat. Average CT number, area of the slice, and lateral size of the patient (AxLat) were measured on the middle slice. The Dw and SSDE from Dw (SSDEW) were calculated. SSDER and SSDEW were compared using Wilcoxon signed rank test. Correlation between patient size and dosimetry parameters were investigated using Spearman Correlation test with statistical significance at P < 0.05. Bland-Altman plot was also used to test agreement between the two SSDE values. Median CTDIvol, DLP, SSDER and SSDEW were 11.0 mGy, 372 mGy.cm, 11.6 mGy and 12.9 mGy, respectively. Small but statistically significant differences (P < 0.03) were found between SLat and AxLat as well as between SSDER and SSDEW. Bland-Altman analysis resulted in borderline agreement between SSDE values. Moderate correlations were observed between dosimetry quantities and patient size measurements (ρ > 0.640; P < 0.001). SSDEw showed statistically significant correlation (ρ = 0.587 and P < 0.001) with SSDER. SSDER may be used to assess patients' absorbed radiation dose, before the scan, in adult chest HRCT. The median value of SSDER was about 10% lower than the median value SSDEW. However, the SSDEW should be used after the scan to establish effective dose and radiation risk to the patient.

Ruptured solitary fibrous tumor of the pleura with hemothorax: a case report

BackgroundThe majority of the patients with a solitary fibrous tumor (SFT) of the pleura are asymptomatic, and rupture of an SFT with hemothorax is rare.Case presentationA 48-year-old man was taken by ambulance to our hospital because of sudden onset of left chest pain. Two months before the referral, a tumor was detected in the left upper lobe of the lung by screening computed tomography at another hospital, and further observation was recommended, because the tumor was suspected to be benign. Our contrast-enhanced computed tomography analysis of the chest revealed a solid tumor (5 cm in diameter) with an irregular enhancement effect close to the pericardium and pleural effusion in the left thoracic cavity. Pleural effusion was not detected in the previous imaging analysis. CT number of the pleural effusion was 40 HU, and the pleural effusion was suspected to be hematogenous. Therefore, rupture of the tumor with bleeding was suspected as the cause of the effusion because of the sudden onset. Preoperative diagnosis was a mediastinal tumor, such as a teratoma, because the tumor was close to the pericardium. Thoracoscopic surgery was performed with the patient in the right lateral decubitus position; bloody pleural effusion was observed and drained. The tumor originated from the visceral pleura of the left upper lobe of the lung and was resected with a surgical stapler. Macroscopic analyses of the resected tumor indicated that bleeding were caused by the rupture of the tumor at the defect of the capsule wall. The operation took 63 min. The postoperative pathological diagnosis was a benign SFT. Hemorrhage was observed just under the capsule wall of the tumor. The postoperative course of the patient was uneventful, and he was discharged 2 days after surgery.ConclusionsEven when an SFT is neither huge nor malignant, rupture can occur, and resection should be considered regardless of the size or malignant characteristics. After an SFT rupture, careful follow-up is needed to monitor for the intrathoracic recurrence or dissemination of the tumor.

Hounsfield units and vertebral bone quality score for predicting mechanical complications after adult spinal deformity surgery: a systematic review and meta-analysis.

The purpose of this systematic review and meta-analysis is to assess existing literature and determine the association between the Hounsfield unit (HU) value and the vertebral body quality (VBQ) score with mechanical complications (MCs) after adult spinal deformity (ASD) surgery. Although bone quality is considered an increasingly important factor for MCs after ASD surgery, the utility of the HU value assessed by computed tomography and the VBQ score assessed by magnetic resonance imaging remains unknown. A systematic review of PubMed, Embase, and Cochrane Library databases was performed to find studies evaluating the association between the HU value and the VBQ score with MCs after ASD surgery. In the subsequent meta-analysis, MC outcomes were combined using a random-effects model, and the standardized mean difference and 95% confidence interval were calculated. The final analysis included a total of 20 studies. Nineteen studies reported HU values, and two studies reported VBQ scores. Proximal junctional kyphosis/failure (PJK/PJF) was reported as the MC in 16 studies, whereas other MCs were included in 6 studies. Six studies with a pool of 506 patients with ASD revealed that preoperative HU values at the upper instrumented vertebra (UIV) and UIV+1 were significantly lower in patients with PJK/PJF (standardized mean difference, -0.74; 95% confidence interval, -1.09 to -0.40). Three studies suggested an cutoff HU value of approximately ≤120, yielding a pooled sensitivity of 0.77, specificity of 0.67, and diagnostic odds ratio of 7.01. However, two studies reported conflicting results on the relationship between the VBQ score and PJK/PJF. Low HU values predicted the risk of certain MCs, particularly PJK/PJF, after ASD surgery. An HU value of <120 should alert surgeons to be cautious about the postoperative occurrence of PJK/PJF. Future studies are needed to validate the cutoff HU value and evaluate the utility of the VBQ score.

Presentation and management of patients with adrenal masses: a large tertiary centre experience.

Adrenal masses are found in up to 5-7% of adults. The 2016 European guidelines on the management of adrenal incidentalomas have standardised the workup of these patients, but evidence of their impact on clinical practice is lacking. Retrospective review of clinical presentation, radiological characteristics, and final diagnosis of a large cohort of patients with adrenal masses referred to a tertiary care centre 1998 to 2022. Sub-analysis compares outcomes before and after implementing the 2016 guidelines. 1397 patients (55.7% women; median age 60 years [interquartile range, IQR, 49-70]) were included. Incidental discovery was the most frequent mode of presentation (63.7%) and 30.6% of patients had masses ≥4 cm (median 2.9 cm [IQR, 1.9-4.7]). Unenhanced computed tomography (CT) Hounsfield Units (HU) were available for 763 patients; of these, 32.9% had heterogeneous masses or >20 HU. The most common diagnoses were adrenocortical adenoma (ACA, 56.0%), phaeochromocytoma (12.7%), adrenocortical carcinoma (10.6%), and metastases (5.7%). At multivariable analysis, significant predictors of malignancy included HU >20 or heterogeneous density (Odds Ratio, OR 28.40), androgen excess (OR 27.67), detection during cancer surveillance (OR 11.34), size ≥4 cm (OR 6.11) and male sex (OR 3.06). After implementing the 2016 guidelines, the number of adrenalectomies decreased (6.1% pre-2016 vs. 4.5% post-2016) and the number of patients discharged increased (4.4% pre-2016 vs. 25.3% post-2016) for benign non-functioning adrenal masses. Implementing the 2016 guidelines positively impacted clinical practice, reducing unnecessary surgeries and increasing the discharge rate for benign adrenal masses, thereby preserving healthcare resources and patient burden.

Predicting Proximal Humerus Fracture Mechanical Complications: Are Computed Tomography Hounsfield Units the Answer?

The purpose was to determine whether computed tomography (CT) Hounsfield units (HU) as a proxy for bone quality can predict postoperative complications following surgical treatment of proximal humerus fractures. Sixty-six patients with 2-, 3-, or 4-part proximal humerus fractures who underwent surgical fixation at single institution and had complete radiographic data available were included. Radiographic measurements included the deltoid tuberosity index (DTI) on preoperative anterior-posterior shoulder radiographs, and the HU value from the surgical proximal humerus was determined by measuring the humeral head at the midaxial/coronal/sagittal CT image using a circle-type region of interest (≥35 mm2). Postoperative complications recorded were implant failure, development of osteonecrosis, nonunion, and acute periprosthetic fracture. Patients with and without complications were statistically compared, and binary logistic regression was performed to determine whether preoperative proximal humerus CT HU were predictive of complications. Eight patients (12.1%) developed 11 overall complications, with three patients experiencing multiple complications each. Complications included osteonecrosis (4), implant failure (5), nonunion (1), and acute periprosthetic fracture (1). No difference was observed in demographics or Neer or AO/OTA classification between those with and without complications. Patients with complications had markedly lower DTI and overall HU as well as HU in the coronal and sagittal planes. Regression analysis for average DTI demonstrated a higher DTI and had a 10 times decreased risk of complication (P = 0.040, odds ratio = -10.5, 95% confidence interval, 0.000 to 0.616). Regression analysis for average total HU also found a higher HU associated with a decreased risk of complications (P = 0.034, odds ratio = -0.020, 95% confidence interval, 0.980 to 0.962). Logistic regression analysis, including age, age-adjusted Charlson Comorbidity Index, mean DTI, and mean total HU, only found mean total HU to be notable within the model. CT HU may identify patients with poorer bone quality and thus help predict postoperative complications. Diagnostic Level III.

Assessing suitability and stability of materials for a head and neck anthropomorphic multimodality (MRI/CT) phantoms for radiotherapy.

&#xD;This study aims to identify and evaluate suitable and stable materials for developing a head and neck anthropomorphic multimodality phantom for radiotherapy purposes. These materials must mimic human head and neck tissues in both computed tomography (CT) and magnetic resonance imaging (MRI) and maintain stable imaging properties over time and after radiation exposure, including the high levels associated with linear accelerator (linac) use.&#xD;Approach:&#xD;Various materials were assessed by measuring their CT numbers and T1 and T2 relaxation times. These measurements were compared to literature values to determine how closely the properties of the candidate materials resemble those of human tissues in the head and neck region. The stability of these properties was evaluated monthly over a year and after radiation exposure to doses up to 1000 Gy. Statistical analyses were conducted to identify any significant changes over time and after radiation exposure.&#xD;Main Results:&#xD;10% and 12.6% Polyvinyl alcohol cryogel (PVA-c) both exhibited T1 and T2 relaxation times and CT numbers within the range appropriate for brain grey matter. 14.3% PVA-c and some plastic-based materials matched the MRI properties of brain white matter, with CT numbers close to the clinical range. Additionally, some plastic-based materials showed T1 and T2 relaxation times consistent with MRI properties of fat, although their CT numbers were not suitable. Over time and after irradiation, 10% PVA-c maintained consistent properties for brain grey matter. 12.6% PVA-c's T1 relaxation time decreased beyond the range after the first month.&#xD;Significance:&#xD;This study identified 10% PVA-c as a substitute for brain grey matter, demonstrating stable imaging properties over a year and after radiation exposure up to 1000 Gy. However, the results highlight a need for further research to find additional materials to accurately simulate a wider range of human tissues.&#xD.

Trabecular Attenuation of L1 in Adult Patients with Multiple Myeloma: An Observational Study on Low-Dose CT Images.

The aim of this study was to evaluate the impact of trabecular attenuation of the L1 vertebral body in low-dose CT in adult patients with multiple myeloma (MM), smoldering multiple myeloma (SMM), and monoclonal gammopathy of undetermined significance (MGUS). The study population consisted of 22 patients with MGUS and 51 consecutive patients with newly diagnosed MM (SMM, n = 21; symptomatic MM, n = 36). CT scans were conducted using a 128-slice CT scanner (Somatom go.Top, Siemens, Munich, Germany). Low-dose whole-body CT scans were performed at a single time point for each patient. Trabecular bone density values were obtained by defining regions of interest on non-contrast images at the level of L1 vertebra. A threshold of p = 0.05 was applied to determine statistical significance. The median Hounsfield unit (HU) value in patients with MGUS, SMM, and MM was 148 HU (range 81-190), 130 HU (range 93-193), and 92 HU (range 26-190), respectively, with a statistically significant difference between the groups (p = 0.0015). Patients with HU values ≤ 92 had lower progression-free survival with statistically significant differences compared to the group with HU values > 92 (p < 0.0499). This is the earliest evidence of the importance of evaluating L1 attenuation values in low-dose CT images in patients with MGUS, SMM, and MM. Further prospective studies could contribute to reinforcing these results and exploring the clinical applicability and generalization of L1 attenuation values in low-dose whole-body CT scans in routine clinical practice.

Visceral Obesity and Its Association with Severe Coronary Artery Calcification in Patients with Metabolic Dysfunction-Associated Steatotic Liver Disease.

Background/Objectives: The role of body composition parameters in patients with metabolic dysfunction-associated steatotic liver disease (MASLD) with presence and severity of coronary artery calcification (CAC) is still not fully elucidated. We aimed to evaluate the impact of computed tomography (CT)-based body composition parameters in patients with MASLD with CAC severity. Methods: In this multicenter study, 1870 individuals underwent cardiac CT for the detection of CAC as well as ultrasonography for the diagnosis of hepatic steatosis. The presence of CAC was defined by a CAC score threshold of >0, while severe CAC was defined by a threshold of >300. Using the abdominal cross-sectional CT images at the L3 vertebra level, we analyzed the skeletal muscle index, visceral to subcutaneous adipose tissue ratio, and muscle density using the Hounsfield unit. Results: Of 648 patients with MASLD, the proportions of presence of CAC and severe CAC were 45.2% and 9.9%, respectively. Visceral obesity was not associated with the presence of CAC after adjustment for age, sex, smoking, statin therapy, type 2 diabetes, and advanced fibrosis (adjusted odds ratio (aOR), 1.38; 95% confidence interval (CI), 0.86-2.23; p = 0.180). However, visceral obesity was independently associated with severe CAC after adjustment for several metabolic risk factors (aOR, 3.54; 95% CI, 1.25-14.90; p = 0.039), and adjustment for atherosclerotic cardiovascular disease risk scores (aOR, 3.74; 95% CI, 1.31-15.79; p = 0.032). Conclusions: Visceral obesity may serve as a novel prognostic CT-based radiological biomarker for patients with MASLD with severe CAC.

Computed tomography employing sensing of high energy particle current

Objective. We demonstrate High Energy Current Computed Tomography (HEC-CT) employing megavoltage linac x-rays.Approach. Using deterministic radiation transport we simulate two-parameter HEC-CT projections and using inverse Fourier transform we reconstruct two distinct material parameters for water phantoms with ICRP tissue inserts and materials of different atomic number Z. The HEC-CT projections are obtained by beam scanning and rotating the object.Main Results. The first HEC-CT material parameter is alike the standard attenuation coefficient with dependence on atomic number and material density similar to the Hounsfield Units. The second material parameter has opposite trends and does not find any analogy in the standard CT framework.Significance. New CT method has been invented for medical imaging or non-destructive testing. The key feature of the technique is a two-value CT reconstruction based on particle current instead of transmitted dose.

Bolus tracking from pulsed x-ray projections: A feasibility study using a five-dimensional cardiac CT contrast dynamics model.

Cardiac computed tomography (CT) exams are some of the most complex CT exams due to the need to carefully time the scan when the heart chambers are near the peak contrast concentration. With current "bolus tracking" and "timing bolus" techniques, after contrast medium is injected, a target vessel or chamber is scanned periodically, and images are reconstructed to monitor the opacification. Both techniques have opportunities for improvement, such as reducing the contrast medium volume, the exam time, the number of manual steps, and improving the robustness of correctly timing the peak opacification. The objective of our study is to (1) develop a novel autonomous cardiac CT clinical workflow to track contrast bolus dynamics directly from pulsed x-ray projections, (2) develop a new five-dimensional virtual cardiac CT data generation tool with programmable cardiac profiles and bolus dynamics, and (3) demonstrate the feasibility of projection-domain prospective bolus tracking using a neural network trained and tested with the virtual data to find the contrast peak. In our proposed workflow, pulsed mode projections (PMPs) are acquired with a wide-open collimator under sparse view conditions (monitoring phase). Each time a new PMP is acquired, the neural network is used to estimate the contrast enhancement inside the target chambers. To train such a network, we introduce a new approach to generate clinically realistic virtual scan data based on a five-dimensional cardiac model, by synthesizing user-defined contrast bolus dynamics and patient electrocardiogram profiles. In this study, we investigated a scenario with one single PMP per rotation. To find the optimal PMP view angle, 20 angles were explored. For each angle, 300 virtual exams were generated from 115 human subject datasets and divided into training, validation, and testing groups. Twenty neural networks were trained and evaluated in total to find the optimal network. Finally, a simple bolus peak time estimation algorithm was developed and evaluated by comparing to the ground truth bolus peak time. To evaluate the accuracy of a bolus time-intensity curve estimated by the network, the cosine similarity between the estimation and the ground truth was computed. The cosine similarity was larger than 0.97 for all projection angles. A view angle corresponding to the x-ray tube at 30 degrees from vertical (left-anterior of subject) showed the lowest errors. The amplitude of the estimated bolus curves (in Hounsfield Units) was not always correctly predicted, but the shape was accurately predicted. This resulted in an RMSE of 1.23s for the left chambers and 0.78s for the right chambers in the contrast peak time estimation. In this study, we proposed an innovative real-time way to predict the contrast bolus peak in cardiac CT as well as an innovative approach to train a neural network using virtual but clinically realistic data. Our trained network successfully estimated the shape of the time-intensity curve for the target chambers, which led to accurate bolus peak time estimation. This technique could be used for autonomous diagnostic cardiac CT to trigger a diagnostic scan for optimal contrast enhancement.

Correlation of CT measurements of total body gas volume and hounsfield units with post-mortem interval

Accurate estimation of the post-mortem interval (PMI) may be a matter of crucial importance in forensic investigations.A preliminary investigation to assess whether longitudinal changes in organ Hounsfield units (HU) and total body gas volume (TBGV), as measured from serial PMCT scans, correlate with postmortem interval (PMI).: Eight euthanised lambs each had five whole body CT scans performed over seven days and measurements were taken from the brain, heart, lungs, liver, kidneys and spleen. HU tissue density was measured directly from the PMCT images, while TBGV was calculated using ImageJ software. A random effect model was fitted with the subject fitted as a random intercept. Ethical and Animal Welfare approval was obtained. : The average increase in TBGV was 422 ml/Kg with a change of 77 ml/Kg per day. For each additional post-mortem day, the HU of the brain, heart, lung, liver and spleen decreased by per day since death, while HU for the kidneys increased by day since death. Expect for the kidney where it increased, there was clear and progressive decrease in tissue densities and for all organs there was an increase in TBGV over time. However, the overlap in values between cases indicates that more work is required before either HU or TBGV can be developed as non-invasive methods to reliably determine time of death in humans.