Higher Hounsfield Unit Research Articles

Impact of osteosclerosis on cervical pedicle screw insertion using preoperative CT-based navigation.

Preoperative computed tomography (CT)-based navigation is used for cervical pedicle screw (CPS) insertion to mitigate the risk of spinal cord and vertebral artery injury. In vertebrae with osteosclerosis due to degeneration or other factors, however, probing may not proceed easily, with difficulty creating the CPS insertion hole. This study investigated the impact of osteosclerosis on the accuracy of CPS insertion. A total of 138 patients with CPS inserted at the C3-C7 level using preoperative CT navigation were retrospectively analyzed. Pre- and postoperative CT was employed to investigate screw position and Hounsfield unit (HU) values at the lateral mass to evaluate the degree of osteosclerosis in the CPS insertion pathway. Among 561 CPS insertions, the Grade 3 perforation rate was 1.8%, and the Grade 2 or higher perforation rate was 8.0%. When comparing insertions with and without CPS perforation, HU values were significantly higher in the perforation group (578 ± 191 vs. 318 ± 191, p < 0.01). The frequency of CPS insertion into the mid-cervical spine was also significantly greater in the perforation group (68.9% vs. 62.5%, p < 0.01). Logistic regression analysis revealed that a high HU value at the lateral mass (odds ratio 1.09, 95% confidence interval: 1.07-1.11, p < 0.01) was a significant independent factor associated with CPS deviation. The screw perforation rate of Grade 2 or higher in CPS insertion using preoperative CT-based navigation was 8.0%. Since osteosclerosis was an independent factor related to CPS deviation, additional care may be required during insertion into affected vertebrae.

Prevalence of acute kidney injury following percutaneous nephrolithotomy.

The objective is to evaluate the prevalence of acute kidney injury (AKI) as an early complication of the percutaneous nephrolithotomy (PCNL) procedure. From May 2022 to October 2022, we conducted a retrospective study on patients undergoing PCNL procedures in two of the tertiary medical centers affiliated with Isfahan University of Medical Sciences. Patients' baseline characteristics, laboratory values, perioperative data, and stone features were documented. AKI was defined either as a ≥0.3 mg/dL increase in the serum creatinine level within 2 days, or a ≥1.5-fold increase in baseline serum creatinine level within 7 days after the operation. Laboratory values were measured 1 day before PCNL and daily thereafter until discharge. Patients were followed 1 week later to detect all of the possible cases of AKI. The final analysis was performed on 347 individuals. AKI developed in 16 (4.61%) cases. The two groups were comparable regarding age (P = 0.887), gender (P = 0.566), and underlying comorbidities including diabetes mellitus (P = 0.577) and hypertension (P = 0.383). The mean body mass index (BMI) (P < 0.001) and both frequency and severity of hydronephrosis (P < 0.001) were significantly different. A higher mean PCNL duration (P < 0.001), period of hospitalization (P < 0.001), and blood loss volume (P < 0.001) were observed in those who developed AKI. Overall, 56.3% (9) of patients in the AKI group and 2.7% (9) in the non-AKI group required the establishment of more than one access tract, during the procedure (P < 0.001). A lower preoperative hemoglobin level was observed in the AKI group (P < 0.001). Those with AKI had significantly larger stones (3.08 ± 0.46 vs. 2.41 ± 0.23 cm, P < 0.001) and higher Hounsfield units (P < 0.001). In addition, in the AKI group, most of the calculi (81.3%, 13) were of staghorn type, whereas in the non-AKI group, calculi were most frequently located in the middle calyx (30.2%, 100), (P < 0.001). The prevalence of post-PCNL AKI is approximately 4.61%. The mean BMI, preoperative hemoglobin level, PCNL duration, intraoperative blood loss volume, and hospitalization period were significantly higher among patients who developed AKI. Those with AKI had significantly larger stones with higher Hounsfield units and more frequently of staghorn type. The two groups were not statistically different regarding age, gender, and presence of comorbidities (hypertension and diabetes mellitus).

Impact of cone-beam computed tomography artifacts on dose calculation accuracy for lung cancer.

To implement image-guided adaptive radiotherapy (IGART), many studies investigated dose calculations on cone-beam computed tomography (CBCT). A high HU accuracy is crucial for a high dose calculation accuracy and many imaging sites showed satisfactory results. It has been shown that the dose calculation accuracy for lung cancer lags behind. To examine why the dose calculation accuracy for lung is insufficient, the relative effects of the field-of-view (FOV), breathing motion, and scatter on dose calculation accuracy were studied. A framework was built to simulate CBCT scans for lung cancer patients by forward projecting repeat CT (rCT) scans for two scan geometries: small (SFOV) and medium FOV (MFOV). Breathing motion was modeled by applying a 4D deformation vector field to the mid-position rCT. Scatter was modeled by Monte-Carlo simulations with/without an anti-scatter grid (ASG). Simulated projections were reconstructed using filtered back-projection with/without scatter correction. In case of the SFOV, the CBCT images were patched with the planning CT scan in axial direction. The treatment plan was recalculated on the rCT and simulated CBCT. The mean Hounsfield unit (HU) difference (ΔHUmean), the structural similarity index measure (SSIM), and γ metrics were calculated for the CBCT datasets of various imaging settings. The differences in HU, SSIM and dose calculation accuracy for CBCTs with and without breathing motion were negligible (mean ΔHUmean=6.4vs. 13.7, mean SSIM=0.941vs. 0.957, mean γ (ref=MFOV)=0.75). The SFOV resulted in a lower HU (mean ΔHUmean=-9.2vs. 13.7) and SSIM (mean SSIM=0.912vs. 0.957), and therefore in dose differences compared to the MFOV (mean γ=1.22). Scatter led to considerable discrepancies in all metrics. Adding only the ASG improved the results more than only applying a scatter correction algorithm. Combining ASG and scatter correction algorithm resulted in an even higher dose calculation accuracy. Scatter and FOV are the main contributors to dose inaccuracies and motion has only a minor effect on dose calculation accuracy. Therefore, utilizing an appropriate scatter correction and FOV is important to achieve sufficient dose calculation accuracy to facilitate IGART for lung.

Relationship between pain and intra-articular pathology in patients with chronic lateral ankle instability.

Repeated ankle sprains can lead to chronic lateral ankle instability (CLAI). It is unclear whether CLAI causes pain unless complicated by intra-articular lesions. This study aimed to analyze the characteristics of pain and the relationship between pain and intra-articular pathology in patients with CLAI. Fifty-three ankles in 46 patients with CLAI who had undergone surgery were retrospectively reviewed. The self-administered foot evaluation questionnaire (SAFE-Q) was given to patients the day before surgery. Intra-articular lesions were assessed using arthroscopy and magnetic resonance imaging (MRI). In addition, the Hounsfield Unit (HU) on computed tomography (CT) of the medial gutter was measured. The relationship between pain and intra-articular findings was also analyzed. The pain and pain-related scores in the SAFE-Q were significantly correlated with synovitis in 96.3% (rs = - 0.532). HU ratios in the tibia and talus were also significantly correlated with pain (rs = - 0.603, - 0.534, respectively). The arthroscopic synovitis score and HU ratios in patients with high pain scores were significantly higher than those in patients with low pain scores. Forty ankles (75.5%) had synovitis and articular cartilage injuries were observed in 22 ankles (41.5%). Patients with fluid collection or bone marrow lesions (BML) scored significantly lower in pain than those without, but there was no significant difference between patients with and without cartilage injury. Multiple regression analysis revealed that a high synovitis score and HU ratio of the talus were significantly associated with high pain. Intra-articular lesions such as synovitis and BML were associated with pain in patients with CLAI. Osteosclerotic changes in the medial gutter also induced ankle pain, indicating that osteoarthritic changes had already begun. Therefore, lateral ankle ligament injuries after ankle sprain should be appropriately treated to avoid secondary degenerative changes.

Lower preoperative Hounsfield unit values as a risk factor for poor 5-year clinical outcomes after lumbar spine surgery.

Hounsfield Unit (HU) value has been associated with future osteoporotic fractures and postoperative complications. However, no studies on the impact of low HU values on mid-term clinical outcomes following lumbar spine surgery have been reported. We aimed to evaluate the usefulness of preoperative HU values for 5-year clinical outcomes following lumbar spine surgery. We enrolled 200 patients who underwent lumbar surgery (≤ 3-disc levels) for lumbar spinal stenosis. HU values were assessed using preoperative lumbar computed tomography as part of routine preoperative planning for lumbar surgery. Patients were divided into two groups based on the cutoff value of the HU values obtained from the receiver operating characteristic curve for the incidence of vertebral fractures within five years postoperatively. Clinical scores preoperatively and 1, 2, and 5years postoperatively, including Japanese Orthopedic Association Back Pain Evaluation Questionnaire (JOABPEQ) and Short Form-36 (SF-36), were compared using a mixed-effects model. Comparative analysis indicated that all domains of JOABPEQ, except for lumbar function, and the physical component summary of the SF-36 were significantly worse in the low HU group than in the high HU group. Using multiple regression analysis, low HU values were significantly correlated with worse 5-year postoperative scores in all domains of JOABPEQ and SF-36. Low preoperative HU values are a risk factor for poor 5-year clinical outcomes after lumbar spine surgery. HU values are not only a valuable tool for analyzing bone mineral density but also may be a valuable poor prognostic factor of postoperative clinical outcomes.

Risk Factors of Screw Malposition in Robot-Assisted Cortical Bone Trajectory: Analysis of 1344 Consecutive Screws in 256 Patients.

Retrospective single-center study using prospectively collected data. To describe the incidence of and identify risk factors for intraoperative screw malposition secondary to skive or shift during robot-assisted cortical bone trajectory (RA-CBT) insertion. RA-CBT screw malposition occurs through 2 distinct modes, skive or shift. Skive occurs when a downward force applied to the cannula, drill, tap, or screw, causes the instrument to deflect relative to its bony landmark. Shift is a change in the position of the RA system relative to the patient after registration. A consecutive series of patients older than 18 years who underwent RA-CBT screw placement between January 2019 and July 2022 were enrolled. Baseline demographic and surgical data, Hounsfield Units (HUs) at L1, and vertebral shape related to screw planning were collected. Skive or shift was recorded in the operating room on a data collection form. Of 1344 CBT screws in 256 patients, malposition was recognized intraoperatively in 33 screws (2.4%) in 27 patients (10.5%); 19 through skive in 17 and 14 through shift in 10 patients. These patients had higher body mass index than patients without malposition (33.0 vs. 30.5 kg/m 2 , P = 0.037). Patients with skive had higher HU (178.2 vs . 145.2, P = 0.035), compared with patients with shift (139.2 vs . 145.2, P = 0.935) and patients without screw malposition. More than half of the screw malposition was observed at the upper instrumented vertebra. At the upper instrumented vertebra, if the screw's overlap to the bone surface at the insertion point was decreased, skive was more likely (57% vs . 87%, P < 0.001). No patients were returned to the operating room for screw revision. Intraoperative screw malposition occurred in 2.4% of RA-CBT. High body mass index was associated with screw malposition, regardless of etiology. Skive was associated with high HU and decreased screw overlap to the bone surface at the insertion point.

High Endplate Hounsfield Units Value Indicate Intervertebral Disc Degeneration Following Transforaminal Lumbar Interbody Fusion Surgery.

Lumbar disc degeneration (LDD) is a common cause of low back pain and disability, and its prevalence increases with age. The aim of this study is to investigate whether endplate Hounsfield unit (HU) values have an effect on lumbar disc degeneration (LDD) after transforaminal lumbar interbody fusion (TLIF) surgery in patients with degenerative lumbar stenosis. This study was a retrospective analysis of patients who underwent TLIF surgery in January 2016 to October 2019. One hundred and fifty-seven patients who underwent TLIF surgery for degenerative lumbar stenosis were enrolled in this study. Demographic data was recorded. VAS and ODI values were compared to assess the surgical outcomes in patients with or without process of LDD after TLIF surgery. Correlation analysis was performed to investigate associations between LDD and endplate HU value. Binary logistic regression analysis was carried out to study relationships between the DDD and the multiple risk factors. There was a statistically significant correlation between LDD, body mass index (BMI), age, paraspinal muscle atrophy, and total endplate scores (TEPS). Also, a strong and independent association between endplate HU value and LDD was found at every lumbar disc level (p < 0.01). After conditioning on matching factors, multivariate logistic regression analysis showed that higher endplate HU (odds ratio [OR]: 1.003, p = 0.003), higher TEPS (OR: 1.264, p = 0.002), higher BMI (odds ratio [OR]: 1.202, p = 0.002), a smaller cross-sectional area (CSA) of the paraspinal muscle preoperatively (OR: 0.096, p < 0.001) were significant predictors of LDD development after TLIF surgery. There is a significant association between LDD and endplate HU value after TLIF surgery in patients with degenerative lumbar stenosis. Beyond that, results from this study provide a mechanism by which high endplate HU value predisposes to LDD after TLIF surgery.

Development and validation of a predictive model for major complications after extracorporeal shockwave lithotripsy in patients with ureteral stones: based on a large prospective cohort.

The risk factors of complications after SWL are not well characterized. Therefore, based on a large prospective cohort, we aimed to develop and validate a nomogram for predicting major complications afterextracorporeal shockwave lithotripsy (SWL) in patients with ureteral stones. The development cohort included 1522 patients with ureteral stones who underwent SWL between June 2020 and August 2021 in our hospital. Five hundred and fifty-three patients with ureteral stones participated in the validation cohort from September 2020 to April 2022. The data were prospectively recorded. Backward stepwise selection was applied using the likelihood ratio test with Akaike's information criterion as the stopping rule. The efficacy of this predictive model was assessed concerning its clinical usefulness, calibration, and discrimination. Finally, 7.2% (110/1522) of patients in the development cohort and 8.7% (48/553) of those in the validation cohort suffered from major complications. We identified five predictive factors for major complications: age, gender, stone size, Hounsfield unit of stone, and hydronephrosis. This model showed good discrimination with an area under the receiver operating characteristic curves of 0.885 (0.872-0.940) and good calibration (P = 0.139). The decision curve analysis showed that the model was clinically valuable. In this large prospective cohort, we found that older age, female gender, higher Hounsfield unit, size, and grade of hydronephrosis were risk predictors of major complications after SWL. This nomogram will be helpful in preoperative risk stratification to provide individualized treatment recommendations for each patient. Furthermore, early identification and appropriate management of high-risk patients may decrease postoperative morbidity.

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

Whole-body CT (WBCT) in polytrauma patients enables the detection of numerous incidental findings, such as estimates of bone mineral density (BMD) at multiple skeletal sites. This could help in better understanding of age- and sex-related changes in BMD through skeleton. Data were retrospectively retrieved from the WBCTs requested during a 2-year period. BMD, expressed in CT Hounsfield units (HU), was measured at frontal and occipital bone, four vertebrae (C4, Th7, L4, and S2), iliac bone, and proximal humerus and femur. Measurements were done on native and postcontrast scans. The population sample was age-, sex-, and visceral fat volume adjusted for analysis. A total of 296 patients were included, with a median age of 51years. BMD varied from the highest HU in cranial bones (629 HU) to the lowest HU in the pelvic bones (114 HU), P < 0.001. Sex differences were independent predictors of BMD in cranial bones and proximal humerus. The age-related decline in BMD was significant in all other bones, but the association with age differed among the measurement's sites. Visceral fat showed the strongest correlation with the lumbar spine and iliac wing, although multivariate analysis revealed it was not an independent predictor of bone density, such as age and sex. BMD varies through skeleton, being the highest in the proximal axial skeleton. Age-related changes in BMD are significant and more pronounced than sex-related changes in almost all bones. Cranial bones do not follow the same pattern compared to other bones.

GOLD AND SILVER NANOPARTICLES AS COMPUTED TOMOGRAPHY (CT) CONTRAST AGENTS PRODUCED BY A PULSED LASER ABLATION TECHNIQUE: STUDY In-vitro AND In-vivo

High-purity metal nanoparticles such as gold and silver nanoparticles become an interesting subject for application in the medical field. Using the laser ablation approach, these nanoparticles were successfully synthesized in this present work. Experimentally, a pulse neodymium yttrium aluminum garnet laser (1064 nm, 30 mJ, 10 Hz) was used to irradiate high-purity metals immersed in an iodine liquid medium. Purple, yellow, and dark purple colloidal nanoparticles of Au, Ag, and Au-Ag were successfully synthesized. The results certified that all nanoparticles have a spherical shape; Au nanoparticles had an average diameter of 26 nm and a standard deviation of 4 nm, while Ag nanoparticles had an average diameter of 24 nm and a standard deviation of 5 nm. The diameter distribution of AuAg nanoparticles is extraordinarily vast, ranging from 18 to 80 nm. Colloids of mixed Au-Ag nanoparticles had the highest Hounsfield Units (HU) value in an in vivo test, with a value of 302. This was supported by the results of an in vitro contrast enhancement evaluation, which determined that a mixture of Au-Ag nanoparticles provided the best contrast enhancement compared to other colloids. These results confirmed that the Au-Ag nanoparticles are very suitable as contrast agents in CT.

The use of the gold compound (AuCl4) solution as an alternative contrast medium for iodine in computed tomography (CT-Scan) imaging

In computerized tomography (CT-Scan), iodine solution was used as a contrast medium to improve imaging. But the iodine solution has different side effects for patients. In the present work, one of the gold compounds AuCl4 was used as an alternative contrast agent. The study used rabbits in an in vivo method to examine both the organs of the heart and the kidneys. Hounsfield unit (HU) values from computed tomography of rabbit and kidney angiography findings were found and compared with HU values for iodine contrast medium. Iodine solution is the only contrast medium currently used in the present study, gold tetrachloride (AuCl4) solution has been chosen as an alternative contrast medium in computed tomography scanning (CT-scan). It was found that using AuCl4 solution as an alternative contrast medium in rabbits enhanced the CT-scan imaging in the resolution and increasing the of heart and kidney organs in comparison with the iodine compound without any side effects. Rabbit’s heart and kidney were selected to study the effect of using 1.4 M iodine solution and 0.1 M AuCl4 as an alternative contrast medium in CT-scan. The HU value for the heart has 53 HU when used high concentration of Iodine complex, while the HU value at low concentration of alternative contrast medium of 0.1 M of gold compound has 50.5. The same results were found in the kidney organ. From these results, the resolution of the CT image is good and cleared when an alternative contrast medium (AuCl4) used. We can conclude that the alternate contrast medium for AuCl4 solution has high HU values for both heart and kidney compared to iodine solution.

Changes in CT Attenuation Values of Pericardium Months after Radiotherapy as Surrogates for Later Major Cardiotoxicity

<h3>Purpose/Objective(s)</h3> Radiation-induced pericardial disease (RIPD) can manifest as pericardial swelling, thickening, effusion, fluid or calcification. While mostly asymptomatic or underdetected due to self-limiting nature, RIPD could be a surrogate marker for radiation-induced cardiotoxicity. Pericardial screening is not part of standard of care (SOC) for thoracic cancer patients' radiotherapy (RT). Here, we analyze SOC images in patients treated with thoracic RT for radiographically identifiable pericardial changes. We hypothesize that these changes have potential signatures for predicting late major cardiac events. <h3>Materials/Methods</h3> In this retrospective study, pericardium was manually contoured following standard contouring atlases in 30 locally advanced non-small cell lung cancer patients (15 females, 15 males) treated with chemoradiation. A 4mm inner wall was generated as the region of interest. Using pre-RT and (average 10-month) post-RT CT scans, we investigated whether changes in pericardium Hounsfield unit (HU) could predict major late cardiac events reported in patients' clinical records. Taking the effect of contrast-enhancement in some scans into account, HU value ranges representing effusion/fluid, normal tissue and calcification were considered as [-10,30], [31,132] and [133,500], respectively. Support vector machine analysis was performed using data from 24 patients with ≤12 months follow-up for training, and data from the remaining 6 patients for testing. Other parameters of interest for late cardiotoxicity were pericardial doses (mean and max), patient age at the time of RT, sex, history of cardiovascular diagnoses, smoking status, diabetes and hypertension. The CT scans were also revisited by a radiologist for verification of the existence of effusion, fluid, calcification or implants. <h3>Results</h3> In the training group, 11 patients, and in the testing group, 1 patient had a reported major cardiotoxicity several years post-RT. In the cohort of 30 patients, median changes, from pre-RT to post-RT, in the volumes of low, mid, and high HU regions were 17, 24 and 27cc, respectively. In the training set, the volumes of [31,132] HU region showed significant reduction (Mann-Whitney non-parametric test) from pre-RT to post-RT in CT scans of the patients with late cardiotoxicity (p=0.049) compared to those without. Also, patient age at the time of RT was a significant predictor of late cardiotoxicity (p=0.008), while mean dose to pericardium showed borderline significance (p = 0.09). Due to the confounding effect of both contrast-enhancement and implants on the higher HU value analysis, the accuracy of the classification model was limited in training group to 92% and in the test group to 67% (total 4 errors in patients with pre-existing calcifications). <h3>Conclusion</h3> Our preliminary study suggests that radiation-induced cardiotoxicity may be modelled based on patient demographic, dosimetric parameters, and detectable changes in pericardium sac HU volumes.

Hounsfield Units (HU) as a Predictor of Stone Clearance after Percutaneous Nephrolithotomy (PCNL)

Objective: To compare the outcomes of percutaneous nephrolithotomy (PCNL) in patients with renal stones with high (≥700) versus low (&lt;700) HU. Patients and Methods: A total of 200 patients having age 18 to 60 years, with diagnosis of unilateral renal stone disease, having stone size 2 to 4 cm in diameter on non-contrast computed tomography (NCCT) of Urology Unit of Ibn e Sina Hospital and Research Institute Multan were included. The study duration was May-2021 to July-2021. NCCT was done pre-operatively in every patient to measure Hounsfield units (HU). Post-procedural X-ray KUB was done 2 weeks after the surgical procedure to determine the stone clearance in every patient. Results: Mean age was 45.79±11.17 Years. Mean duration of disease of patients included in this study was 8.78±8.59 months. Mean stone size in patients included in this study was 3.11±0.61 cm. On comparison of stone clearance rate between the patients having high-HU versus low-HU, stone clearance was found in 61 (72.6%) patients having low HU value and in 105 (90.5%) patients having high HU value (p-value 0.001). Conclusion: HU-value ≥700 is a significant predictor of success rate of percutaneous nephrolithotomy (PCNL) in patients having renal stone disease. Keywords: Renal Stone Disease, Percutaneous nephrolithotomy, Hounsfield units (HU).

The Effect of Sarcopenia and Metabolic PET-CT Parameters on Survival in Locally Advanced Non-Small Cell Lung Carcinoma

The treatment of stage III non-small cell lung cancer (NSCLC) is complex. Here, we aimed to examine the prognostic utility of sarcopenia and metabolic muscle volumes and evaluate their relationship with oncological treatments in patients with locally advanced NSCLC. Patients with unresectable stage III NSCLC were evaluated retrospectively. Muscle fields were measured, and metabolic parameters of the psoas were obtained. The skeletal muscle index (SMI), sarcopenia, sarcopenic obesity, and body mass index (BMI)-associated sarcopenia were evaluated. Fifty-three (94.6%) patients were men, and three (5.4%) were women. Sarcopenia was identified in 36 (64.3%) patients. Pretreatment sarcopenia and BMI-associated sarcopenia negatively affected overall survival (p = 0.040 and 0.023, respectively). A high psoas SUVmean (Standardized Uptake Value mean) and low mean psoas HU (Hounsfield unit) were poor prognostic factors (p = 0.009 and 0.014, respectively). SMI and muscle mass decreased after oncological treatment. Advanced age, inability to complete treatment, administration of chemoradiotherapy after chemotherapy, presence of sarcopenia, and a low mean psoas HU decreased survival. In conclusion, sarcopenia and BMI-associated sarcopenia are poor prognostic factors in patients with lung cancer. Oncological treatments can adversely affect muscle mass. The metabolic parameters of the psoas muscle can predict patient prognosis.

Analysis of CBCT Bone Density Using the Hounsfield Scale

Assessing bone density in prospective dental implant sites is crucial both for choosing the implant type and for planning a drilling procedure that will ensure the implant’s primary stability and osseointegration. This study aimed to investigate possible differences between the bone densities of various edentulous sites in the maxilla and mandible. The study was conducted on a group of forty partly edentulous patients who underwent radiological examination by scanning the areas of interest using cone beam computed tomography (CBCT). Hounsfield units (HU) were analyzed using dedicated software. Higher HU were observed at the site of mandibular central incisors compared to the site of maxillary central incisors. The HU values in the mandibular first molars region were higher than those of the maxillary first molars. Buccal vs. lingual or palatal cortical HU values did not differ significantly. Within the limitations of this study, it can be stated that an objective assessment of site-specific bone density before the installation of dental implants may provide valuable clinical information for the selection of implant size and the planning of a patient-specific drilling protocol.

Unsupervised segmentation and quantification of COVID-19 lesions on computed Tomography scans using CycleGAN.

Lesion segmentation is a critical step in medical image analysis, and methods to identify pathology without time-intensive manual labeling of data are of utmost importance during a pandemic and in resource-constrained healthcare settings. Here, we describe a method for fully automated segmentation and quantification of pathological COVID-19 lung tissue on chest Computed Tomography (CT) scans without the need for manually segmented training data. We trained a cycle-consistent generative adversarial network (CycleGAN) to convert images of COVID-19 scans into their generated healthy equivalents. Subtraction of the generated healthy images from their corresponding original CT scans yielded maps of pathological tissue, without background lung parenchyma, fissures, airways, or vessels. We then used these maps to construct three-dimensional lesion segmentations. Using a validation dataset, Dice scores were computed for our lesion segmentations and other published segmentation networks using ground truth segmentations reviewed by radiologists. The COVID-to-Healthy generator eliminated high Hounsfield unit (HU) voxels within pulmonary lesions and replaced them with lower HU voxels. The generator did not distort normal anatomy such as vessels, airways, or fissures. The generated healthy images had higher gas content (2.45±0.93 vs 3.01±0.84L, P<0.001) and lower tissue density (1.27±0.40 vs 0.73±0.29 Kg, P<0.001) than their corresponding original COVID-19 images, and they were not significantly different from those of the healthy images (P<0.001). Using the validation dataset, lesion segmentations scored an average Dice score of 55.9, comparable to other weakly supervised networks that do require manual segmentations. Our CycleGAN model successfully segmented pulmonary lesions in mild and severe COVID-19 cases. Our model's performance was comparable to other published models; however, our model is unique in its ability to segment lesions without the need for manual segmentations.

Distributional patterns of subchondral bone density and histopathological features of the first tarsometatarsal joint in hallux valgus feet

BackgroundHypermobility of the first tarsometatarsal (TMT) joint is frequently identified in patients with hallux valgus (HV); however, its association with the development of osteoarthritis in the first TMT joint in such patients remains unknown. The purpose of this study was to clarify the distribution of subchondral bone density of the first TMT joint via computed tomography (CT) using Hounsfield units (HU).MethodsPatients were divided into three groups: the osteotomy (20 feet; 20 women, mean age: 61.8 years), arthrodesis (23 feet; two men, 21 women, 71.2 years), and control group (patients without HV deformity who had undergone CT scans of the foot; 13 feet; seven men, six women, 29.7 years). The HU ratios were calculated, which were defined as the HU value of each subdivision of the subarticular spongiosa of the first TMT joint [dorsomedial (DM), dorsolateral (DL), plantomedial (PM), and plantolateral (PL)] divided by the HU values of the entire joint surface. The ratios for the osteotomy, arthrodesis, and control groups were compared. The degradation of the articular cartilage in the first TMT joint was histologically graded in the arthrodesis group. Tukey–Kramer multiple comparison analysis was conducted to compare the HU ratios among the three groups, and the histological grade in each subdivision.ResultsThe arthrodesis group demonstrated high HU ratios in the DM area of the medial cuneiform, and significantly lower HU ratios in the PL area of the first metatarsal. Lower HU ratios in the DL area were observed in both the osteotomy and the arthrodesis group when compared to that in the medial cuneiform of the control group. The histological evaluation indicated nearly normal articular cartilage for all subdivided areas in both the medial cuneiform and the first metatarsal in patients with severe HV.ConclusionsAlthough high subchondral bone density was identified in the DM area of the medial cuneiform in severe HV, only mild degradation was histologically observed in the articular cartilage of the first TMT joint. Our findings suggest that the indications for arthrodesis of the first TMT should be reconsidered based on the severity of the degenerative changes in the first TMT joint.

Intracranial computed tomography histogram analysis detects changes in the setting of elevated intracranial pressure and normal imaging.

Patients with idiopathic intracranial hypertension (IIH) have elevated intracranial pressure (ICP) of unclear etiology. This study evaluated the ability of quantitative intracranial Hounsfield unit (HU) histogram analysis to detect pathophysiological changes from elevated ICP in the setting of a normal head CT. Retrospective analysis of non-contrast-enhanced head CT images of IIH patients and matched controls. Following skull stripping, total intracranial CT voxels within the range of 0-70 HU were divided into seven 10 HU bins. A measurement of total intracranial HU was also calculated for each patient. Imaging studies for IIH patients were reviewed for features of IIH including transverse sinus stenosis (TSS). Histogram measures were compared between IIH and control groups and correlated with imaging and clinical data. Fourteen IIH patients with CSF opening pressure ≥25cm water, and 31 age-, sex-, and ethnicity-matched controls were included. Compared to controls, IIH patients had a significantly greater proportion of voxels in the 40-50, 50-60, and 60-70 HU bins (p = 0.003, 0.001, and 0.003, respectively) but similar proportion in the 0-10 HU range. Severity of TSS significantly correlated with total intracranial HU measures. 50-60 HU and 60-70 HU bins demonstrated high AUCs of 0.81 and 0.80, respectively, in differentiating IIH from normal status. Idiopathic intracranial hypertension patients have a greater proportion of high intracranial HU voxels representing blood volume, which may be explained by TSS causing venous congestion. The pattern provides further insights into the pathophysiology of IIH and may be useful for detecting elevated ICP in the setting of normal head CT imaging.

Distribution of hounsfield unit values in the pelvic bones: a comparison between young men and women with traumatic fractures and older men and women with fragility fractures: a retrospective cohort study

BackgroundThe fixation strength of bone screws depends on bone mineral density (BMD), so it is important to evaluate bone strength at fracture sites. Few studies have investigated BMD in the pelvis. The aims of this study were to measure the regional Hounsfield unit (HU) values in the cancellous bone of the acetabulum and pelvic ring and to compare these values between young and older patients.MethodsThis study enrolled young patients with high-energy trauma (aged 20–44 years; young group) and older patients with low-energy trauma (aged 65–89 years; older group). Patients without pelvic computed tomography (CT) scans, those with pelvic bone implants, and those who died were excluded. The HU values on the contralateral (non-fractured) side of the pelvis were measured on CT scans. The CT data were divided into 7 areas: the pubic bone, the anterior and posterior walls and roof of the acetabulum, the ischial tuberosity, the body of the ilium, and the third lumbar vertebra. The HU values in each area were compared between the young and older groups.ResultsSixty-one young patients and 154 older patients were included in the study. The highest HU value was in the roof of the acetabulum regardless of age and sex. HU values were significantly higher in the ischial tuberosity and body of the ilium and lower in the pubic bone and anterior wall. The HU values in all pelvic areas were significantly lower in the older group than in the young group, especially in the anterior area.ConclusionsHU values in the 6 pelvic areas were not uniform and were strongly related to load distribution. The HU distribution and age-related differences could explain the characteristic causes and patterns of acetabular fractures in the older and may help in surgical treatment.

Stones hounsfield unit value and predictors of urinary leakage after PCNL

BackgroundTo evaluate the predictive factors of urinary leakage (UL) following percutaneous nephrolithotomy (PNL) and to investigate the relationship between Hounsfield unit (HU) of stone and UL.MethodsWe retrospectively reviewed the data of 728 patients who underwent PNL between January 2012 and January 2017. In total, 396 patients were eligible for the study. Patient demographics, renal factors, stone properties and operative details were collected. The association between UL and these variables were assessed by univariate and multivariate analysis.ResultsThere was no statistically significant correlation considering age, body mass index and the presence of hypertension. The presence of diabetes mellitus (DM) was significantly correlated with UL (p < 0.001). Kidney related factors such as parenchymal thickness, hydronephrosis grade (HN), previous stone treatment, and stone related factors, such as stone surface area, stone burden, stone localization and HU value of stone, were found to affect UL status significantly (p < 0.001). Operation time, fluoroscopy time, treatment outcome, j stent use, percutenous nephrostomy (PCN) catheter stay time and the hospitalization time also had significant effect on UL (p < 0.001). Multivariable logistic analysis showed that presence of DM, parenchymal thickness, HU values, HN, operation time, j stent use, and PCN catheter stay time are independently related with UL following PCNL. Moreover, we determined a HU cut-off value of 933 with ROC analysis, which demostrated 84.9% sensitivity and 67.1% specificity for predicting UL.ConclusionThis study has shown that we are more likely to encounter postoperative UL in stones with higher HU values. Therefore, we suggest clinicians to inform patients with this type of kidney stones about the probable complication of UL.