Mean Hounsfield Unit Research Articles

Single-Center Experience with Swiss LithoClast® Trilogy for Kidney Stones.

PCNL remains the gold standard for larger kidney stones. Reducing the operating time of PCNL and its complication rate seems to be the next logical step in optimizing this classical technique. To achieve these objectives, some new methods of lithotripsy emerge. We present the data of a single, high-volume, academic center with combined ultrasonic and ballistic lithotripsy in PCNL using the Swiss LithoClast® Trilogy device. We designed a prospective, randomized study including patients who underwent PCNL or miniPerc with lithotripsy using the new EMS Lithoclast Trilogy or EMS Lithoclast Master. The procedure was carried out with all patients in prone position, by the same surgeon. The working channel size was 24 Fr-15.9 Fr. We evaluated the stones' features, operative time, fragmentation time, complications, stone clearance rate and stone-free rate. Our study included 59 patients, 38 females and 31 males, of an average age of 54.5 years old. The Trilogy group included 28 patients and the comparator included 31 patients. Urine culture was positive in seven cases which required seven days of antibiotics. The mean stone diameter was 35.6 mm with a mean Hounsfield unit (HU) of 710.1. The average number of stones was 2.08 (6 complete staghorn stones and 12 partial staghorn stones). A total of 13 patients presented a JJ stent (46.4%). We found a very significant difference in all the parameters favoring the Trilogy device. The most important result in our opinion is the probe active time, which was almost six times shorter in the Trilogy group. The stone clearance rate was about double in the Trilogy group, leading to shorter overall and intra-renal operating times. The overall complication rate was 17.9% in the Trilogy group and 23% in the Lithoclast Master group. The mean hemoglobin drop was 2.1 g/dL with a mean creatinine rise of 0.26 mg/dL. Swiss LithoClast® Trilogy, a device combining ultrasonic and ballistic energy, is a safe and efficient method of lithotripsy for PCNL, proving statistically significant benefits over its predecesor. It can achieve the goal of reducing complication rates and operative times for PCNL.

Assessment of Radiodensity at Mandibular Periapical Bone Sites using Three-Dimensional Cone-Beam Computed Tomography.

The aims of this retrospective study were to objectively assess bone density values obtained by cone-beam computed tomography and to map the periapical and inter-radicular regions of the mandibular bone. In total, periapical bone regions of 6898 roots scanned by cone-beam computed tomography were evaluated retrospectively, and the results were recorded using Hounsfield units (HU). The correlation between periapical HU values of adjacent mandibular teeth were strongly positive (P ˂ 0.01). The anterior region of the mandible yielded highest mean HU value (633.55). The mean periapical HU value of the premolar region (470.58) was higher than that was measured for molar region (374.58). The difference between furcation HU values of the first and second molars was unnoticeable. The results of this study have tried to evaluate the periapical regions of all mandibular teeth, which could ease to predict the bone radiodensity before implant surgery. Even though the Hounsfield units provide the average radio-bone density, a site-specific bone tissue evaluation of each case is essential for appropriate cone-beam computed tomography preoperative planning.

The Utility of 18F-NaF-PET/CT in Measuring the Metabolic Activity of Aging Spine: Implications for Osteoporosis.

Cross-sectional; observational. To determine whether NaF-PET/CT can be used to monitor decreased bone turnover with aging in the spine. Osteoporosis is characterized by structural changes in the bone such as decreased bone mineral density leading to increased risk for fractures. An imaging modality capable of identifying molecular changes that precede these structural changes could be critical for the early diagnosis and monitoring of osteoporosis and other metabolic bone disorders. The potential of 18F-sodium fluoride (NaF)-PET/CT in detecting changes in bone turnover associated with aging was examined in the lumbar spine of 88 healthy volunteers (43 females, 45 males; mean age 44.6y). Regions of interest equal to the trabecular body of the L1-L4 vertebrae were used to calculate the mean standardized uptake value (SUVmean) and average Hounsfield unit (HU) values. Receiver-operating characteristic (ROC) curve analysis with area under the curve (AUC) using the Wilson/Brown method were generated to assess the value of NaF uptake (SUVmean) in predicting osteoporosis as defined by HU-threshold values. To determine the correlation among global SUVmean, mean HU values, and age, Spearman correlation test was performed on images acquired at 90-minutes post injection. There was a significant negative correlation between NaF SUVmean and age in females (P < 0.0001, r=-0.59), and a weaker, but also significant correlation in males (P=0.03, r=-0.32). In females only, there was a significant correlation between NaF uptake and age at all acquisition time points. Measured NaF uptake increased by 10-15% with acquisition time in both sexes, from 45 to 90 min and from 90 to 180 min. NaF-PET/CT detects decreased vertebral bone turnover with aging particularly in females. Measured NaF uptake increased with PET acquisition time after tracer injection, which must be considered in follow-up studies monitoring disease development and treatment effects.

Normative Bone Mineral Density Measured on Computed Tomography Scans in Children and Adolescents.

Retrospective chart review. To provide reference values for Hounsfield unit (HU) measured on computed tomography (CT) scans of children and adolescents. Spine surgeons increasingly use HU on spine CT as a measure of bone mineral density (BMD). This has not been described in children and adolescents. Pediatric patients who had a spine CT between 2012 and 2022 were identified. Patients who had more than 1 comorbidity or were syndromic were excluded. Using the bone window, 3 axial images (cephalad, middle, and caudal) of each vertebra were selected. In each axial view, the HU was measured using a "region of interest" (ROI) that included the total cancellous bone area and an ROI excluding the radiolucency present in the posterior vertebral body ("total" vs . "limited"). HU values were compared between total and limited areas and between the axial images at the cephalad, middle, and caudal levels. Each age category data were estimated and stratified. A total of 144 patients (79 females and 65 males) from 2 to 17 years old were included. Mean limited HU was consistently lower than total HU across all images and lumbar levels except for L1. Limited HU taken mid-vertebral body was also consistently lower than those taken cephalad or caudad. Mean limited HU across all ages including all levels was 227 ± 50 (range: 109-357). Stratifying by age showed a gradual decrease in BMD from age 2 to 10 followed by an increase. This is the first study to measure HU on lumbar CTs in children and adolescents. The technique of measuring BMD in adults should be modified in children by using an ROI that excludes the rarefaction present in the posterior vertebral body. Further studies are needed to evaluate the age-dependent changes in BMD seen in this study.

Differentiating and predicting HU values of 12 aluminum alloys via X-ray computed tomography

X-ray computed tomography (XCT) scanning as a quantitative analysis method is hindered by the lack of literature-reported values for countless metals and their alloys. Given the large number of scanning parameters and the ever-increasing number of material alloys, this gap cannot be remedied simply by running an infinitely large number of scans. This study aims to develop a novel method of predicting the mean Hounsfield Unit (HU) value of a metal alloy from the knowledge of its elemental composition. The weighted average mixture model is utilized to predict the mean HU value for aluminum (atomic number 13, amu 26.98) based alloys. The model can generate predictions for the mean HU value and its standard deviation given the elemental composition and the HU values of each constitutive element. The model is validated using XCT scans of 12 aluminum alloys (one 1XXX, two 2XXX, two 5XXX, five 6XXX, and two 7XXX series) conducted at three thickness levels (1.5, 3, and 6 mm).The findings show that increasing sample thickness results in an increased ability to differentiate between alloy pairs with 12 pairs being differentiable at 1.5 mm, 39 at 3 mm, and 45 pairs at 6 mm thickness. The predictions of the model (average error of 5.01%) are tested for individually enclosed aluminum samples. The model is then applied to generate predictions (average error was 5.65%) of stacked aluminum samples to simulate cases where scanned objects are often composed of multiple materials. Even when HU values for some constituent elements were unavailable (as the case for AA6020 where 4 out of 11 elements could not be found), the model achieved a predictive accuracy of 76%.

Fatty liver and acute pancreatitis severity: A prospective analysis utilizing computerized tomographic scan

Introduction: Fatty liver (FL) is often recognized in patients with acute pancreatitis (AP) and is frequently found in clinical practice because of substantial variables that put one at risk of complications. Aim: To evaluate the severity of acute pancreatitis in patients with and without fatty liver using CT severity index. Methodology: In this prospective study was carried out from June 2020 till December 2022. Liver and spleen mean attenuation values were examined using plain CT scans abdomen of patients with AP. Fatty liver was defined as a mean Hounsfield Unit (HU) liver/spleen) ratio &lt; 1. Contrast-enhanced computed tomography (CECT) scan and CT Severity Index (CTSI) to grade the severity of AP. Analyzed information in SPSS. Degree of significance was determined using the chi-square test. Results: This study comprised of 100 Patients with AP (88 (88.0%) males and 32 (32.0%) female, mean age 34.68 12.762 years), 46 (46.0%) had FL and 54 (54.0%), without FL. Patients with FL experienced much worse pancreatitis than patients without FL. Acute edematous pancreatitis (39.4% vs. 60.6%) and acute necrotic collections (58.8% vs. 41.2%) were observed in patients with FL and without FL respectively. Conclusion: The severity of acute pancreatitis is significantly influe

The Impact of Cage and End plate-Related Factors on Cage Subsidence in Oblique Lateral Interbody Fusion

To identify cage and end plate factors of cage subsidence (CS) in patients who underwent oblique lateral interbody fusion (OLIF) and their association with patient-reported outcomes. Sixty-one patients (43 women and 18 men), with a total of 69 segments (138 end plates) which underwent OLIF at a single academic institution between November 2018 and November 2020, were included. All the end plates were separated into CS and nonsubsidence groups. Cage-related parameters (cage height, cage width, cage insertion level, and cage position) and end plate-related parameters (position of end plate, Hounsfield unit value of the vertebra, end plate concave angle [ECA], end plate injury, and angular mismatch measured with cage/end plate angle [C/EA]) were compared and analyzed using logistic regression to predict CS. Receiver operating characteristic curve analysis was used to determine the cutoff points of the parameters. Postoperative CS was identified in 50 of the 138 end plates (36.2%). The CS group had significantly lower mean Hounsfield unit values of the vertebra, higher rate of end plate injury, lower ECA, and higher C/EA than the nonsubsidence group. ECA and C/EA were identified as independent risk factors for developing CS. The optimal cutoff points for ECA and C/EA were 176.9° and 5.4°, respectively. An ECA greater than 176.9° and a cage/end plate angular mismatch greater than 5.4° were found to be independent risk factors of postoperative CS after the OLIF procedure. These findings aid in preoperative decision-making and intraoperative technical guidance.

Dual-Energy Computed Tomography in Stroke Imaging

ObjectiveTo assess if a new dual-energy computed tomography (DECT) technique enables an improved visualization of ischemic brain tissue after mechanical thrombectomy in acute stroke patients.Material and MethodsThe DECT head scans with a new sequential technique (TwinSpiral DECT) were performed in 41 patients with ischemic stroke after endovascular thrombectomy and were retrospectively included. Standard mixed and virtual non-contrast (VNC) images were reconstructed. Infarct visibility and image noise were assessed qualitatively by two readers using a 4-point Likert scale. Quantitative Hounsfield units (HU) were used to assess density differences of ischemic brain tissue versus healthy tissue on the non-affected contralateral hemisphere.ResultsInfarct visibility was significantly better in VNC compared to mixed images for both readers R1 (VNC: median 1 (range 1–3), mixed: median 2 (range 1–4), p < 0.05) and R2 (VNC: median 2 (range 1–3), mixed: 2 (range 1–4), p < 0.05). Qualitative image noise was significantly higher in VNC compared to mixed images for both readers R1 (VNC: median 3, mixed: 2) and R2 (VNC: median 2, mixed: 1, p < 0.05, each). Mean HU were significantly different between the infarcted tissue and the reference healthy brain tissue on the contralateral hemisphere in VNC (infarct 24 ± 3) and mixed images (infarct 33 ± 5, p < 0.05, each). The mean HU difference between ischemia and reference in VNC images (mean 8 ± 3) was significantly higher (p < 0.05) compared to the mean HU difference in mixed images (mean 5 ± 4).ConclusionTwinSpiral DECT allows an improved qualitative and quantitative visualization of ischemic brain tissue in ischemic stroke patients after endovascular treatment.

Differential Cortical Volumetric Bone Mineral Density within the Human Rib

Introduction: The human rib provides a vital role in the protection of thoracic contents. Rib fractures are linked to injuries and health complications that can be fatal. Current clinical methods to assess fracture risk and bone quality are insufficient to quantify intra-element differences in bone mineral density (BMD) or to identify at-risk populations. Utilizing quantitative computed tomography (QCT) provides accurate measures of volumetric BMD (vBMD) along the length of the rib which can help delineate factors influencing differential fracture risk. Methodology: One mid-level rib was obtained from 54 post-mortem human subjects (PMHS) and scanned using QCT. Volumes of interest (VOIs) were created for sites at 30%, 50%, and 75% of rib total curve length. Mean Hounsfield units (HU) from each VOI were converted to vBMD using a scan-specific cortical phantom calibration curve. Additionally, rib and lumbar areal BMD (aBMD) were obtained from a sub-sample of 33 PMHS. Results: Significant differences in vBMD were found between all sites within the rib (p<0.01). When analyzed by sex, vBMD between the 30% and 50% site were no longer different in either males or females (p>0.05). Separating the sample into discrete age groups demonstrated the relative differences in vBMD between sites diminished with age. Further, age as a continuous variable significantly predicted rib vBMD at all sites (p<0.05), but with little practical or clinical utility (R2, 14.7- 22.8%). Similarly, only small amounts of variation in rib vBMD were explained from DXA lumbar and rib aBMD (R2 , 1.1-21.8%). Conclusions: vBMD significantly decreased from the posterior (30%) site to the anterior (75%) site within the rib which may represent adaptation to localized mechanical loading. These differences could result in differential fracture risk across the rib. As thoracic injury can be fatal, using comprehensive assessments of bone quality that accounts for variation within the rib may provide more accurate identification of at-risk populations.

The predictive value of Hounsfield units for titanium mesh cage subsidence after anterior cervical corpectomy and fusion.

To investigate whether bone mineral density (BMD) measured in Hounsfield units (HUs) correlates with titanium mesh cage (TMC) subsidence after anterior cervical corpectomy and fusion (ACCF). A total of 64 patients who underwent one or two levels of ACCF with TMC with a mean follow-up of 19.34 ± 7.86 months were analysed. HU values were measured three times in 3 different planes in the upper and lower vertebrae according to published methods. Subsidence was defined as segmental height loss of more than 3 mm. Pearson correlation analysis was performed. Receiver operating characteristic (ROC) curve analysis was used to obtain optimal thresholds. A multivariate logistic regression analysis was also conducted. Twenty-two patients (34.38%) had evidence of TMC subsidence on follow-up x-ray. The mean HU values in the subsidence group (317.34 ± 32.32, n = 22) were significantly lower than those in the nonsubsidence group (363.07 ± 25.23 n = 42, p < 0.001, t test). At last follow-up, mean disc height loss was 4.80 ± 1.16 mm in the subsidence group and 1.85 ± 1.14 mm in the nonsubsidence group (p < 0.001). There was a negative correlation between HU values and disc height loss (Pearson's coefficient -0.494, p < 0.001). HU values decreased gradually from the C3 vertebra to the C7 vertebra, and the HU values of the C5, C6, and C7 vertebrae in the nonsubsidence group were significantly higher than those in the subsidence group (p < 0.05). Furthermore, there were significant differences between the groups in the segmental angle at the last follow-up and the mean changes in segmental angle (p < 0.05). The area under the ROC curve was 0.859, and the most appropriate threshold of the HU value was 330.5 (sensitivity 100%, specificity 72.7%). The multivariate logistic regression analysis showed that older age (p = 0.033, OR = 0.879), lower LIV HU value (p < 0.001, OR = 1.053) and a greater segmental angle change (p = 0.002, OR 6.442) were significantly associated with a higher incidence of TMC subsidence after ACCF. There are strong correlations between a lower HU value and TMC subsidence after ACCF. More accurate assessment of bone quality may be obtained if HU measurement can be used as a routine preoperative screening method together with DXA. For patients with HU values <330.5, a more comprehensive and cautious preoperative plan should be implemented to reduce TMC subsidence.

Difference of mean Hounsfield units (dHU) between follow-up and initial noncontrast CT scan predicts 90-day poor outcome in spontaneous supratentorial acute intracerebral hemorrhage with deep convolutional neural networks

ObjectivesThis study aimed to investigate the usefulness of a new non-contrast CT scan (NCCT) sign called the dHU, which represented the difference in mean Hounsfield unit values between follow-up and the initial NCCT for predicting 90-day poor functional outcomes in acute supratentorial spontaneous intracerebral hemorrhage(sICH) using deep convolutional neural networks. MethodsA total of 377 consecutive patients with sICH from center 1 and 91 patients from center 2 (external validation set) were included. A receiver operating characteristic (ROC) analysis was performed to determine the critical value of dHU for predicting poor outcome at 90 days. Modified Rankin score (mRS) >3 or >2 was defined as the primary and secondary poor outcome, respectively. Two multivariate models were developed to test whether dHU was an independent predictor of the two unfavorable functional outcomes. ResultsThe ROC analysis showed that a dHU >2.5 was a critical value to predict the poor outcomes (mRS >3) in sICH. The sensitivity, specificity, and accuracy of dHU >2.5 for poor outcome prediction were 37.5%, 86.0%, and 70.6%, respectively. In multivariate models developed after adjusting for all elements of the ICH score and hematoma expansion, dHU >2.5 was an independent predictor of both primary and secondary poor outcomes (OR = 2.61, 95% CI [1.32,5.13], P = 0.006; OR = 2.63, 95% CI [1.36,5.10], P = 0.004, respectively). After adjustment for all possible significant predictors (p < 0.05) by univariate analysis, dHU >2.5 had a positive association with primary and secondary poor outcomes (OR = 3.25, 95% CI [1.52,6.98], P = 0.002; OR = 3.42, 95% CI [1.64,7.15], P = 0.001). ConclusionsThe dHU of hematoma based on serial CT scans is independently associated with poor outcomes after acute sICH, which may help predict clinical evolution and guide therapy for sICH patients.

Evaluation of beam hardening artifacts around dental implants: CT study on bovine ribs

Background/Aim: The aim of this study was to evaluate beam hardening artifacts generated by Grade 4 and Grade 5 dental implants on computed tomography (CT) images at low and high kilovoltage peaks (kVp). Material and Methods: A total of 16 implants, 8 of which were Grade 4 and 8 were Grade 5, were inserted into bovine ribs. CT images of bovine ribs were acquired using two different exposure protocol: low kVp and high kVp. Beam hardening artifacts generated by Grade 4 and Grade 5 dental implants were calculated by the mean Hounsfield unit (HU) within a standardized region-of-interest (ROI). Results: Artifact in Grade 4 implants were greater than that in Grade 5 implants. Also, artifacts at the high kVp were lower than that at the low kVp. Conclusions: CT scans providing HU values can be used to evaluate the beam hardening artifact. Beam hardening artifacts decreased in the CT images with high kVp. Grade 5 dental implants have an advantage by producing less severe beam hardening artifacts.

Accuracy and Feasibility of Synthetic CT for Lung Adaptive Radiotherapy: A Phantom Study.

The respiratory variations will lead to inconsistency between the actual delivery dose and the planning dose. How the minor interfractional amplitude changes affect the geometry and dose delivery accuracy remains to be investigated in the context of lung adaptive radiotherapy. Planning 4-dimensional-computed tomography and kV-cone beam computed tomography were scanned based on the Computerized Imaging Reference Systems phantom, which was employed to simulate the minor interfractional amplitude variations. The corresponding synthetic computed tomography for a particular motion pattern can be generated from Velocity program. Then a clinically meaningful synthetic computed tomography was analyzed through the geometrical and dosimetric assessment. The image quality of synthetic computed tomography was improved obviously compared with cone beam computed tomography. Mean absolute error was minimized when no significant interfractional motion occurs and Velocity can be qualified for dealing with the regular breathing motion patterns. The mean percent hounsfield unit difference of the synthetic hounsfield unit values per organ relative to the planning 4-dimensional-computed tomography image was 22.3%. Under the same conditions, the mean percent hounsfield unit difference of the cone beam computed tomography hounsfield unit values per organ, relative to the planning 4-dimensional-computed tomography image was 83.9%. Overall, the accuracy of hounsfield unit in synthetic computed tomography was improved obviously and the variability of the synthetic image correlates with the planning 4-dimensional-computed tomography image variability. Meanwhile, the dose-volume histograms between planning 4-dimensional-computed tomography and synthetic computed tomography almost coincided each other, which indicates that Velocity program can qualify lung adaptive radiotherapy well when there were no interfractional respiratory variations. However, for cases with obvious interfractional amplitude change, the volume covered at least by 100% of the prescription dose was only 59.6% for that synthetic image. The synthetic computed tomography images generated from Velocity were close to the real images in anatomy and dosimetry, which can make clinical lung adaptive radiotherapy possible based on the actual patient anatomy during treatment.

Supine Percutaneous Nephrolithotomy in A High-Volume Center: First 60 Cases

Aim: To present the first 60 supine percutaneous nephrolithotomy (PCNL) surgeries performed in our clinic with regard to the results and reliability of this surgery. Material and Methods: A retrospective study carried out on 40 patients who had undergone PCNL in supine position due to the kidney stone between September 2021 and May 2022. The following parameters were studied: Demographic characteristics, stone size and HU index, operation time and postoperative complications. Results: Patient’s mean age was 46,95, the oldest one was 90 years old, and 13 of them were female. Two of the patients had solitary kidney and 15 of them had previous surgery for kidney stone. 10 patients had this surgery under spinal anesthesia. Mean stone surface area and Hounsfield Unit were 595,4 mm2 and 916.6, respectively. In 3 cases, endoscopic combined intrarenal surgery was performed. Mean operation time was 63,75 minutes and scopy time was 16.5 seconds. 27 patient had totally tubeless procedure and 30 patient had tubeless surgery. None of the patient was required to blood transfusion or any other approach related to bleeding. Only two patient had fever and needed IV antibiotics. Stone free rate was 95 % in one session. Discussion: Supine PCNL surgery is a feasible surgery with low complication rate and high stone-free rate. It is easier to switch to the supine position in clinics where this surgery is performed intensively in the prone position. It should become more widespread especially in terms of the advantages it offers compared to prone PCNL.

Could twinkling artifact be a parameter in predicting the success of shock wave lithotripsy? A prospective study.

It is important to predict success before the treatment of urolithiasis. We aimed to predict the success of shock wave lithotripsy (SWL) by comparing twinkling artifact (TA) revealed through colour Doppler ultrasonography (CDUS) with stone density in non-contrast computed tomography (NCCT). Eighty patients who underwent SWL between January 2021 and January 2022 were included in the study. Patients with stones of 5-20 mm in the renal pelvis and proximal ureter at NCCT were included. Patients' demographics, Hounsfield units (HU) in NCCT, and TA grades in CDUS were recorded. The stone-free rate after SWL, additional treatments, overall success rates, and the association between TA and success rates were evaluated. The mean age was 47.41 ±15.08 years. The mean BMI was 24.49 ±3.67 kg/m2. Twenty-three (28.8%) patients were TA grade 0, 33 (41.2%) patients were grade 1, and 24 (30%) were grade 2. The mean HU of TA grades 0, 1, and 2 of stones were 628 ±107, 864 ±123, and 1166 ±292, respectively. The HU increased along with the increase in the TA grade of the stone (p <0.01). The mean number of SWL sessions was 2.26 ±0.75 in patients with TA grade 0, and 2.92 ±0.40 in patients with TA grade 2. The mean number of SWL sessions increased along with the increase in TA grade (p <0.01). The stone-free rate decreased as the TA grade increased. Stone diameter and TA were the only predictors of SWL success. We think that TA may be useful in predicting SWL success.

Ureteral wall thickness and distal ureteral density in patients with residual fragments after Ho:YAG laser semi-rigid ureterolithotripsy.

Recent data suggest that greater ureteral density distal to ureteral stones or increased ureteral wall thickness (UWT) can predict impacted stones. The aim of our study was to evaluate if patients with residual fragments present with greater ureteral density and larger UWT when compared to stone-free patients. From January onward, a consecutive series of patients undergoing semi rigid Ho:YAG laser ureterolithotripsy (ULT) for ureteral stones were enrolled. A non-contrast enhanced computed tomography (CT) scan was performed before the procedure to evaluate distal ureteral density (DUD) and wall ureteral thickness (UWT) at the site of ureteral stones. Patients with residual fragments were compared to stone-free patients using a matched-pair analysis (1:1 scenario). Cases were matched sequentially using the following criteria: age, gender, body mass index (BMI), stone length, hydronephrosis, location of stones, and mean Hounsfield unit (HU) of the stone. Overall, 160 patients were enrolled, mean age was 57.9 ± 14years, mean BMI was 25.8 ± 4kg/m2, mean length of the stone was 10.6 ± 4.9mm, and mean UWT was 1.4 ± 1.6mm. A total of 150/160 (94%) patients presented hydronephrosis; mean HU stone was 868 ± 327; mean DUD was 54 ± 17.8 HU. Ureteral distal density (51.7 vs 56.6; p = 0.535) and ureteral distal thickness (1.39 vs 1.54; p = 0.078) were similar in both groups of patients. In our study, the evaluation of distal ureteral density does not predict stone-free rate. Further studies should evaluate the role for preoperative computer tomography in predicting surgery outcome.

983. Pathogen-specific PET/CT imaging for Gram negative implant-associated spinal infections

983. Pathogen-specific PET/CT imaging for Gram negative implant-associated spinal infections

Forearm T-score as a predictor of cage subsidence in patients with degenerative lumbar spine disease following posterior single-segment lumbar interbody fusion

BackgroundPosterior lumbar interbody fusion (PLIF) has become a classic treatment modality for lumbar degenerative diseases, with cage subsidence as a potentially fatal complication due to low bone mineral density (BMD), which can be measured by forearm T-score. Hounsfield units (HU) derived from computed tomography have been a reliable method for assessing BMD.ObjectiveTo determine the accuracy of forearm T-score in predicting cage subsidence after PLIF compared with lumbar spine HU values.MethodsWe retrospectively analyzed the clinical data of 71 patients who underwent PLIF and divided them into cage subsidence group and nonsubsidence group. The differences in preoperative HU value and forearm T-score were compared between groups, and the correlation between cage subsidence and clinical efficacy was analyzed.ResultsThe subsidence rate for all 71 patients (31 men and 40 women) was 23.9%. There was no significant difference in age, sex ratio, body mass index, smoking status, follow-up time, spine BMD, and spine T-score between groups, except in the forearm T-score and lumbar spine HU values (P < 0.05). The forearm T-score (AUC, 0.840; 95% CI, 0.672–1.000) predicted cage subsidence more accurately than the mean global HU value (AUC, 0.744; 95% CI, 0.544–0.943). In logistic regression analysis, both forearm T-score and mean global HU value were found to be independent risk factors for cage subsidence (P < 0.05).ConclusionsLower forearm T-scores and lower lumbar spine HU values were significantly associated with the occurrence of cage subsidence. Lower forearm T-scores indicated a higher risk of cage subsidence than lumbar spine HU values. Forearm T-score is more effective in predicting cage subsidence than spine T-score. Therefore, forearm dual-energy X-ray absorptiometry may be a fast, simple, and reliable method for predicting cage subsidence following PLIF. However, our results suggest that the degree of cage subsidence is not associated with clinical efficacy.

Longitudinal analyses and predictive factors of radiation-induced lung toxicity-related parameters after stereotactic radiotherapy for lung cancer.

The purpose of this prospective study was to investigate changes in longitudinal parameters after stereotactic radiotherapy for lung cancer and to identify possible pretreatment factors related to radiation-induced lung toxicity and the decline in pulmonary function after radiotherapy. Protocol-specified examinations, including 4-D CT, laboratory tests, pulmonary function tests (PFTs) and body composition measurements, were performed before SRT and at 1 month, 4 months and 12 months after stereotactic radiotherapy. Longitudinal differences were tested by using repeated-measures analysis of variance. Correlations were examined by using the Pearson product-moment correlation coefficient (r). Sixteen patients were analyzed in this study. During a median follow-up period of 26.6 months, grade 1 and 2 lung toxicity occurred in 11 patients and 1 patient, respectively. The mean Hounsfield units (HU) and standard deviation (SD) of the whole lung, as well as sialylated carbohydrate antigen KL-6 (KL-6) and surfactant protein-D (SP-D), peaked at 4 months after radiotherapy (p = 0.11, p<0.01, p = 0.04 and p<0.01, respectively). At 4 months, lung V20 Gy (%) and V40 Gy (%) were correlated with changes in SP-D, whereas changes in the mean HU of the lung were related to body mass index and lean body mass index (r = 0.54, p = 0.02; r = 0.57, p = 0.01; r = 0.69, p<0.01; and r = 0.69, p<0.01, respectively). The parameters of PFTs gradually declined over time. When regarding the change in PFTs from pretreatment to 12 months, lung V5 Gy (cc) showed significant correlations with diffusion capacity for carbon monoxide (DLCO), DLCO/alveolar volume and the relative change in DLCO (r = -0.72, p<0.01; r = -0.73, p<0.01; and r = -0.63, p = 0.01, respectively). The results indicated that some parameters peaked at 4 months, but PFTs were the lowest at 12 months. Significant correlations between lung V5 Gy (cc) and changes in DLCO and DLCO/alveolar volume were observed.

A Machine Learning Approach Using PET/CT-based Radiomics for Prediction of PD-L1 Expression in Non-small Cell Lung Cancer.

We explored the prediction of programmed cell death ligand 1 (PD-L1) expression level in non-small cell lung cancer using a machine learning approach with positron emission tomography/computed tomography (PET/CT)-based radiomics. A total of 312 patients (189 adenocarcinomas, 123 squamous cell carcinomas) who underwent F-18 fluorodeoxyglucose PET/CT were retrospectively analysed. Imaging biomarkers with 46 CT and 48 PET radiomic features were extracted from segmented tumours on PET and CT images using the LIFEx package. Radiomic features were ranked, and the top five best feature subsets were selected using the Gini index based on associations with PD-L1 expression in at least 50% of tumour cells. The areas under the receiver operating characteristic curves (AUCs) of binary classifications afforded by several machine learning algorithms (random forest, neural network, Naïve Bayes, logistic regression, adaptive boosting, stochastic gradient descent, support vector machine) were compared. The model performances were tested by 10-fold cross validation. We developed and validated a PET/CT-based radiomic model predicting PD-L1 expression levels in lung cancer. Long run high grey-level emphasis, homogeneity, mean Hounsfield unit, long run emphasis from CT, and maximum standardised uptake value from PET were the five best feature subsets for positive PD-L1 expression. The Naïve Bayes model (AUC=0.712), with a sensitivity of 75.3% and specificity of 58.2%, outperformed all other classifiers. It was followed by the neural network model (AUC=0.711), random forest (AUC=0.700), logistic regression (AUC=0.673) and adaptive boosting (AUC=0.604). PET/CT-based radiomic features may help clinicians identify tumours with positive PD-L1 expression in a non-invasive manner using machine learning algorithms.