Hounsfield Unit Density Research Articles

Özefagustan rektuma gastrointestinal lipomların çok kesitli bilgisayarlı tomografi (MDBT) bulguları

Background and Aims: To evaluate the multidedector computed tomography findings of gastrointestinal lipomas in various locations. Materials and Methods: This study included 45 patients who were referred from the gastroenterology or surgery department over the period of 2007 to 2016. The patients were referred for detailed abdominal examination for various reasons and symptoms. Among the included patients, 21 were males and 24 were females. The mean age of the patients was 62.64±11.82 (median 69.5, range 37-81). The main complaints of the patients were abdominal pain, abdominal distension, tiredness, and constipation. All patients were examined through enhanced or nonenhanced multidedector computed tomography. Images were acquired with 64-slice multidedector computed tomography. The densities of the masses were measured in Hounsfield units, and the detailed multidedector computed tomography findings of the masses were summarized. Results: Lipomas were found in 47 patients. Lipomas of the esophagus, stomach, duedonum, jejenum, ileum, and caecum were found in 1 (2.1%), 4 (8.5%), 2 (4.2%), 5 (1.0%), 3 (6.3%), and 9 (19.1%) patients, respectively. Lipomas of the ascending colon, transverse colon, descending colon, sigmoid colon, and rectum were found in 9 (19.1%), 4 (8.5%), 5 (1.0%), 4 (8.5%), and 1 (2.1%) patients, respectively. The lipomas had a mean Hounsfield unit density of −93±10.5 (median 85, range −70-−100). The maximum mean diameter of the lipomas was 23 mm ± 18. 5 (median 20, range 12-50 mm). All lesions were submucosal in location. Conclusion: Lipomas may be located anywhere along the gastrointestinal tract and may be found from the esophagus to the rectum. Multidedector computed tomography is a useful tool for the diagnosis, location, and definition of lesions and does not require or requires minimal assistance from endoscopic biopsy.

Material matters: Analysis of density uncertainty in 3D printing and its consequences for radiation oncology.

Using 3D printing to fabricate patient-specific devices such as tissue compensators, boluses, and phantoms is inexpensive and relatively simple. However, most 3D printing materials have not been well characterized, including their radiologic tissue equivalence. The purposes of this study were to (a) determine the variance in Hounsfield Units (HU) for printed objects, (b) determine if HU varies over time, and (c) calculate the clinical dose uncertainty caused by these material variations. For a sample of 10 printed blocks each of PLA, NinjaFlex, ABS, and Cheetah, the average HU and physical density were tracked at initial printing and over the course of 5 weeks, a typical timeframe for a standard course of radiotherapy. After initial printing, half the blocks were stored in open boxes, the other half in sealed bags with desiccant. Variances in HU and density over time were evaluated for the four materials. Various clinical photon and electron beams were used to evaluate potential errors in clinical depth dose as a function of assumptions made during treatment planning. The clinical depth error was defined as the distance between the correctly calculated 90% isodose line and the 90% isodose line calculated using clinically reasonable, but simplified, assumptions. The average HU measurements of individual blocks of PLA, ABS, NinjaFlex, and Cheetah varied by as much as 121, 30, 178, and 30 HU, respectively. The HU variation over 5 weeks was much smaller for all materials. The magnitude of clinical depth errors depended strongly on the material, energy, and assumptions, but some were as large as 9.0 mm. If proper quality assurance steps are taken, 3D printed objects can be used accurately and effectively in radiation therapy. It is critically important, however, that the properties of any material being used in patient care be well understood and accounted for.

Abstract TP54: Machine-Learned Characterization of Acute Ischemic Stroke Clots Reveals a Correlation Between Clot Composition and Density on CT

Introduction: The composition of acute ischemic stroke (AIS) blood clots can impact their successful removal via endovascular therapy. Identification of the clot composition prior to endovascular treatment may influence the optimal treatment strategy. In this study, we aimed to investigate the relationship between the Hounsfield Unit intensity on CT and machine-learned characterization of clot composition. Methods: Prior to endovascular treatment, each patient had a non-contrast CT performed. Histopathological analysis of the clots was performed and clot composition was quantified via standard thresholding techniques using Adobe Photoshop. In addition, following representative cell labeling by an expert pathologist, image segmentation algorithms (Orbital Image Analysis, Actelion Ltd.) were trained on each case to quantify composition by cell type. The clots were categorized into 3 groups: red blood cell (RBC) dominant (>50%), RBC proportion equal to fibrin and fibrin dominant (>50%). Correlations between clot composition and Hounsfield Units (HU) density on CT were assessed. A positive Hyperdense Artery Sign was defined as ≥50 HU. Results: Twenty patients were included in the study. There was a significant correlation between clots quantified using Adobe Photoshop Image-Pro and Orbit image analysis ( ρ = 0.837, p < 0.001). A significant relationship was found between clot composition and the presence of a HAS sign, ( X 2 (2) = 6.496, p = 0.039). There is a significant positive correlation between percentage of RBC in the clot and the presence of a HAS sign ( ρ = 0.632, p = 0.002**). There is also a significant positive correlation between the presence of fibrin-rich and the absence of a HAS sign ( ρ = 0.600, p = 0.004**). Conclusion: Machine learning software can accurately quantify AIS clot composition. The Hounsfield unit density of an AIS clot on a non-contrast CT correlates with the composition of the clot. Measuring the HU of the clot on CT prior to endovascular intervention may inform the clinician of the clot type and help to determine the most appropriate treatment strategy for that clot.

Pharmacological targeting of BET proteins attenuates radiation-induced lung fibrosis

Radiation-induced lung injury has restricted radiotherapy for thoracic cancer. The purpose of this study was to investigate the radioprotective effects of bromodomain and extra terminal (BET) inhibitor JQ1 in a murine model of pulmonary damage. Chest computed tomography (CT) was performed in a rat model after 20 Gy radiation of the right thorax. And histological evaluation and protein expressions of irradiated tissue were analyzed to confirm the potential anti-fibrosis effect of JQ1 and its underlying mechanisms. Moreover, colony formation assays were used to explore the effects of JQ1 on esophageal cancer Eca109 and breast cancer MCF7. JQ1 attenuated radiologic and histologic presentations of radiation-induced fibrosis, inflammatory reaction and pulmonary structural changes and the increase of Hounsfield units (HU) density and hydroxyproline content after radiation. Additionally, JQ1 suppressed BRD4, c-MYC, Collagen I, TGF-β, p-NF-κB p65, p-Smad2 and p-Smad3 expressions after irradiation, repressed proliferation and transdifferentiation of lung fibroblasts, and impaired clonogenic survival of thoracic cancer cells. Collectively, our study demonstrated for the first time that BET Bromodomain inhibitor JQ1 protected normal lung tissue after radiation, and exerted a radiosensitizing effect in thoracic cancer cells.

Mastoid Air Cell System: Hounsfield Density by Multislice Computed Tomography

Mastoid Air Cell System: Hounsfield Density by Multislice Computed Tomography

Quantitative assessment of nonsolid pulmonary nodule volume with computed tomography in a phantom study

To assess the volumetric measurement of small (≤1 cm) nonsolid nodules with computed tomography (CT), focusing on the interaction of state of the art iterative reconstruction (IR) methods and dose with nodule densities, sizes, and shapes. Twelve synthetic nodules [5 and 10 mm in diameter, densities of -800, -630 and -10 Hounsfield units (HU), spherical and spiculated shapes] were scanned within an anthropomorphic phantom. Dose [computed tomography scan dose index (CTDIvol)] ranged from standard (4.1 mGy) to below screening levels (0.3 mGy). Data was reconstructed using filtered back-projection and two state-of-the-art IR methods (adaptive and model-based). Measurements were extracted with a previously validated matched filter-based estimator. Analysis of accuracy and precision was based on evaluation of percent bias (PB) and the repeatability coefficient (RC) respectively. Density had the most important effect on measurement error followed by the interaction of density with nodule size. The nonsolid -630 HU nodules had high accuracy and precision at levels comparable to solid (-10 HU) nonsolid, regardless of reconstruction method and with CTDIvol as low as 0.6 mGy. PB was <5% and <11% for the 10- and 5-mm in nominal diameter -630 HU nodules respectively, and RC was <5% and <12% for the same nodules. For nonsolid -800 HU nodules, PB increased to <11% and <30% for the 10- and 5-mm nodules respectively, whereas RC increased slightly overall but varied widely across dose and reconstruction algorithms for the 5-mm nodules. Model-based IR improved measurement accuracy for the 5-mm, low-density (-800, -630 HU) nodules. For other nodules the effect of reconstruction method was small. Dose did not affect volumetric accuracy and only affected slightly the precision of 5-mm nonsolid nodules. Reasonable values of both accuracy and precision were achieved for volumetric measurements of all 10-mm nonsolid nodules, and for the 5-mm nodules with -630 HU or higher density, when derived from scans acquired with below screening dose levels as low as 0.6 mGy and regardless of reconstruction algorithm.

Assessing the effects of lumbar posterior stabilization and fusion to vertebral bone density in stabilized and adjacent segments by using Hounsfield unit.

Computed tomography (CT) with Hounsfield unit (HU) is being used with increasing frequency for determining bone density. Established correlations between HU and bone density have been shown in the literature. The aim of this retrospective study was to determine the bone density changes of the stabilized and adjacent segment vertebral bodies by comparing HU values before and after lumbar posterior stabilization. Sixteen patients who had similar diagnosis of lumbar spondylosis and stenosis were evaluated in this study. Same surgical procedures were performed to all of the patients with L2-3-4-5 transpedicular screw fixation, fusion and L3-4 total laminectomy. Bone mineral density measurements were obtained with clinical CT. Measurements were obtained from stabilized and adjacent segment vertebral bodies. Densities of vertebral bodies were evaluated with HU before the surgeries and approximately one year after the surgeries. The preoperative HU value of each vertebra was compared with postoperative HU value of the same vertebrae by using statistical analysis. The HU values of vertebra in the stabilized and adjacent segments consistently decreased after the operations. There were significant differences between the preoperative HU values and the postoperative HU values of the all evaluated vertebral bodies in the stabilized and adjacent segments. Additionally first sacral vertebra HU values were found to be significantly higher than lumbar vertebra HU values in the preoperative group and postoperative group. Decrease in the bone density of the adjacent segment vertebral bodies may be one of the major predisposing factors for adjacent segment disease (ASD).

Clinical utility of computed tomography Hounsfield characterization for percutaneous nephrolithotomy: a cross-sectional study

BackgroundComputed Tomography (CT) is considered the gold-standard for the pre-operative evaluation of urolithiasis. However, no Hounsfield (HU) variable capable of differentiating stone types has been clearly identified. The aim of this study is to assess the predictive value of HU parameters on CT for determining stone composition and outcomes in percutaneous nephrolithotomy (PCNL).MethodsSeventy seven consecutive cases of PCNL between 2011 and 2016 were divided into 4 groups: 40 (52%) calcium, 26 (34%) uric acid, 5 (6%) struvite and 6 (8%) cystine stones. All images were reviewed by a single urologist using abdomen/bone windows to evaluate: stone volume, core (HUC), periphery HU and their absolute difference. HU density (HUD) was defined as the ratio between mean HU and the stone’s largest diameter. ROC curves assessed the predictive power of HU for determining stone composition/stone-free rate (SFR).ResultsNo differences were found based on the viewing window (abdomen vs bone). Struvite stones had values halfway between hyperdense (calcium) and low-density (cystine/uric acid) calculi for all parameters except HUD, which was the lowest. All HU variables for medium-high density stones were greater than low-density stones (p < 0.001). HUC differentiated the two groups (cut-off 825 HU; specificity 90.6%, sensitivity 88.9%). HUD distinguished calcium from struvite (mean ± SD 51 ± 16 and 28 ± 12 respectively; p = 0.02) with high sensitivity (82.5%) and specificity (80%) at a cut-off of 35 HU/mm. Multivariate analysis revealed HUD ≥ 38.5 HU/mm to be an independent predictor of SFR (OR = 3.1, p = 0.03). No relationship was found between HU values and complication rate.ConclusionsHU parameters help predict stone composition to select patients for oral chemolysis. HUD is an independent predictor of residual fragments after PCNL and may be fundamental to categorize it, driving the imaging choice at follow-up.

In vitro Evaluation of the Relationship between Gray Scales in Digital Intraoral Radiographs and Hounsfield Units in CT Scans.

Jaw bone quality plays an essential role in treatment planning and prognosis of dental implants. Regarding several available methods for bone density measurements, they are not routinely used before implant surgery due to hard accessibility. An in vitro investigation of correlation between average gray scale in direct digital radiographs and Hounsfield units in CT-Scan provides a feasible method for evaluating alveolar bone quality prior to implant surgery. 26 sheep's mandibles in which a square shape ROI marked by gutta percha, were prepared. Three direct digital radiographs (CCD sensor) from every specimen were taken using 80, 100 and 200 milli-seconds. Then, the average gray levels for ROIs were calculated using a costume-made software. Next, the specimens were scanned using a 16-slice spiral CT and the Hounsfield Unit of each ROI was calculated. Pearson analysis measured the correlation between Hounsfield units and average gray levels. There was a positive correlation between Hounsfield unit and average gray level in the radiographs and the correlation was better in higher exposure times. It is possible to estimate Hounsfield unit and bone density in the jaw bones using average gray scale in a digital radiograph. This approach is easy, simple and available and also results in lower patient exposure comparing other bone densitometric analysis methods.

CT Texture Analysis of Ex Vivo Renal Stones Predicts Ease of Fragmentation with Shockwave Lithotripsy.

Understanding the factors affecting success of extracorporeal shockwave lithotripsy (SWL) would improve informed decision-making on the most appropriate treatment modality for an individual patient. Although stone size and skin-to-stone distance do correlate with fragmentation efficacy, it has been shown that stone composition and architecture, as reflected by structural heterogeneity on CT, are also important factors. This study aims to determine if CT texture analysis (CTTA), a novel, nondestructive, and objective tool that generates statistical metrics reflecting stone heterogeneity, could have utility in predicting likelihood of SWL success. Seven spontaneously passed, intact renal tract stones, were scanned ex vivo using standard CT KUB and micro-CT. The stones were then fragmented in vitro using a clinical lithotripter, after which, chemical composition analysis was performed. CTTA was used to generate a number of metrics that were correlated to the number of shocks needed to fragment the stone. CTTA metrics reflected stone characteristics and composition, and predicted ease of SWL fragmentation. The strongest correlation with number of shocks required to fragment the stone was mean Hounsfield unit (HU) density (r = 0.806, p = 0.028) and a CTTA metric measuring the entropy of the pixel distribution of the stone image (r = 0.804, p = 0.039). Using multiple linear regression analysis, the best model showed that CTTA metrics of entropy and kurtosis could predict 92% of the outcome of number of shocks needed to fragment the stone. This was superior to using stone volume or density. CTTA metrics entropy and kurtosis have been shown in this experimental ex vivo setting to strongly predict fragmentation by SWL. This warrants further investigation in a larger clinical study for the contribution of CT textural metrics as a measure of stone heterogeneity, along with other known clinical factors, to predict likelihood of SWL success.

Non-Contrast Computed Tomography Scan Based Parameters of Ureteric Stones Affecting the Outcome of Extracorporeal Shock Wave Lithotripsy.

Objective To compare the non-contrast computed tomography (NCCT) scan-based parameters of ureteric stones affecting the outcome of extracorporeal shock wave lithotripsy (ESWL).Materials and methodsWe retrospectively evaluated the pre-procedure NCCT of 74 patients who had ESWL for solitary ureteric calculi of 5-20 mm in diameter. We assessed the age, sex, basal metabolic index (BMI), laterality, location, presence of double 'J' (DJ) stent, skin to stone distance (SSD), stone maximum diameter, Hounsfield unit (HU), Hounsfield density (HD), area, and volume. All those who had no stone on follow-up imaging within 30 days were declared successful while those who had residual stone were declared failures.ResultsThe overall success rate was 78% (58/74). Sixty (81.1%) patients were male. The success of ESWL was correlated with lower SSD, Hounsfield units (HU) and Hounsfield density (HD). However, in multivariate analysis, SSD, Hounsfield unit, and stone area showed correlation with success of procedure but Hounsfield density failed to show correlation. The success rate in patients with stone HU <500, 500-1000 and >1000 were 93.9%, 69%, and 58.3%, respectively. Patients with lower BMI (<30 kg/m2) and HD (<76 HU/mm) were more prone towards success of the procedure than those with higher BMI (>30 kg/m2) and higher HD (>76 HU/mm).ConclusionBMI, SSD, stone Hounsfield units and Hounsfield unit density were strong predictors of outcome of ESWL for ureteric stone.

Predicting the stone composition of children preoperatively by Hounsfield unit detection on non-contrast computed tomography

Many studies have been performed on adult patients to reveal the relationship between Hounsfield unit (HU) value and composition of stone, but none have focused on childhood. We aimed to predict stone composition by HU properties in pre-intervention non-contrast computed tomography (NCCT) in children. This could help to orient patients towards more successful interventions. Data of 94 children, whose pre-intervention NCCT and post-interventional stone analysis were available were included. Stones were grouped into three groups: calcium oxalate (CaOx), cystine, and struvite. Besides spot urine PH value, core HU, periphery HU, and Hounsfield density (HUD) values were measured and groups were compared statistically. The mean age of patients was 7±4 (2-17) years and the female/male ratio was 51/43. The mean stone size was 11.7±5 (4-24) mm. There were 50, 38, and 6 patients in the CaOx, cystine, and struvite groups, respectively. The median values for core HU, periphery HU, and mean HU in the CaOx group were significantly higher than the corresponding median values in the cystine and struvite groups. Significant median HUD difference was seen only between the CaOx and cystine groups. No difference was seen between the cystine and struvite groups in terms of HU parameters. To distinguish these groups, mean spot urine PH values were compared and were found to be higher in the struvite group than the cystine group (Table). The retrospective nature and small number of patients in some groups are limitations of this study, which also does not include all stone compositions. Our cystine stone rate was higher than childhood stone composition distribution in the literature. This is because our center is a reference center in a region with high recurrence rates of cystine stones. In fact, high numbers of cystine stones helped us to compare them with calcium stones more accurately and became an advantage for this study. NCCT at diagnosis can provide some information for determination of stone composition. While CaOx stones can be discriminated from cystine and struvite stones using HU parameters, a simple spot urine pH assessment must be added to distinguish cystine stones from struvite stones.

Diagnostic accuracy of virtual non-contrast enhanced dual-energy CT for diagnosis of adrenal adenoma: A systematic review and meta-analysis.

To compare the diagnostic accuracy of dual-energy (DE) virtual non-contrast computed tomography (vNCT) to non-contrast CT (NCT) for the diagnosis of adrenal adenomas. Search of multiple databases and grey literature was performed. Two reviewers independently applied inclusion criteria and extracted data. Risk of bias was assessed using QUADAS-2. Summary estimates of diagnostic accuracy were generated and sources of heterogeneity were assessed. Five studies (170 patients; 192 adrenal masses) were included for diagnostic accuracy assessment; all used dual-source dual-energy CT. Pooled sensitivity for adrenal adenoma on vNCT was 54% (95% CI: 47-62%). Pooled sensitivity for NCT was 57% (95% CI: 45-69%). Pooling of specificity was not performed since no false positives were reported. There was a trend for overestimation of HU density on vNCT as compared to NCT which appeared related to contrast timing. Potential sources of bias were seen regarding the index test and reference standard for the included studies. Potential sources of heterogeneity between studies were seen in adenoma prevalence and intravenous contrast timing. vNCT images generated from dual-energy CT demonstrated comparable sensitivity to NCT for the diagnosis of adenomas; however the included studies are heterogeneous and at high risk for some types of bias. • Similar sensitivity of vNCT to NCT for diagnosis of adenoma • Heterogeneity could be related to vNCT from early (<=60sec) CECT studies • Could not pool specificity as there were no false positives • Small number of heterogeneous studies at high risk of bias.

A novel method to estimate blood flow velocity in the left atrial appendage using enhanced computed tomography: role of Hounsfield unit density ratio at two distinct points within the left atrial appendage

Low blood flow velocity in the left atrial appendage (LAA) indicates a high risk of thromboembolism. Although transesophageal echocardiography (TEE) has been the standard method with which to evaluate the LAA blood flow velocity, a clinically noninvasive method is desired. We hypothesized that the ratio of the Hounsfield unit (HU) density at two distinct points within the LAA represents the blood flow velocity in the LAA. We retrospectively investigated 60 consecutive patients with atrial fibrillation (paroxysmal type, n=29) who underwent enhanced computed tomography (CT) and TEE. The peak emptying flow velocity in the LAA (LAAPV) was evaluated using TEE. HU density was measured at proximal and distal sites of the LAA (LAAp and LAAd) on CT images. The LAAd/LAAp ratio was correlated with the LAAPV (P<0.01, r=0.69). Among several indices, the HU ratio was the most significant parameter associated with the LAAPV (β=0.469, CI 28.602-68.286, P<0.001). Receiver-operating characteristic analysis (area under the curve, 0.91) demonstrated that an HU density ratio cutoff of 0.32 discriminated a low LAAPV (<25cm/s) with sensitivity of 90% and specificity of 84%. Flow velocity of the LAA can be estimated by the HU density ratio at distal and proximal sites within the LAA. Our method might be a feasible substitution for TEE to discriminate patients with a reduced LAAPV.

Micro Computed Tomography Detects Changes in Liver Density in Control and in Prediabetes Rats

Fatty liver disease is an early event in the development of insulin resistance that predicts the presence and progression of the metabolic syndrome. In humans, fatty liver diagnosis is usually performed by imaging techniques based on ultrasound, computed tomography and magnetic resonance. Rodent models are often used in metabolic research allowing access to tissue biopsies however, studies describing ex vivo computed tomography of biological samples are scarce. X-ray Micro Computed Tomography (Micro-CT) is an imaging technique that reveals the internal structure of materials in great detail, also allowing a quantitative analysis of properties such as density measured as arbitrary Hounsfield Units (HU). Herein, we tested the hypothesis that Micro-CT detects changes in liver tomographic density induced by metabolic diseases and its reversal upon therapeutic surgical intervention. Two groups of male Wistar rats were used: a group submitted to a hypercaloric diet for 14 weeks to induce prediabetes and the control group submitted to a standard diet). The animals were randomly submitted to a surgical treatment and maintained on their respective diets after the procedure for 11 more weeks. Liver and adipose tissues samples were excised and samples were scanned using a compact X-ray micro-CT scanner. The projection images obtained were analyzed and reconstructed and values of HU density were calculated after calibration for all samples. Results showed that liver density was lower in prediabetes rats (74.8±5.87 HU) than in control animals (97.2±6.3 HU), p<0.05. Liver density was not affected by surgical treatment in control animals however, in prediabetes animals, the surgical therapy restored liver density to control values. Visceral fat density was significantly lower than hepatic density, as expected and was affected, neither by the disease condition nor by the surgical treatment. We concluded that micro-CT detects metabolic disease-induced changes in liver density, but not in visceral adipose tissue density in biopsy samples ex vivo. Changes in hepatic density, assessed by micro-CT, correlate with disease state and with therapeutic interventions.

Diagnostic performance of 18-F-FDG-PET-CT in adrenal lesions using histopathology as reference standard.

To determine the diagnostic performance of PET-CT in differentiating benign and malignant adrenal lesions when evaluating PET parameters individually as well as in combination with CT parameters, using histopathology as the reference standard. 18F-FDG-PET-CT scans of patients undertaken within 6 months prior to pathologic evaluation of their adrenal lesion(s) were evaluated. PET assessments consisted individually of maximum standardized uptake value of the adrenal lesion (A-SUVmax) and its ("normalized") ratio to the liver (R-SUVmax). The diagnostic performances of these two PET parameters were also assessed when combined with the Hounsfield density from the non-contrast CT component of the PET-CT (A-HU). Diagnostic performance was assessed by area under the curve (AUC) of the receiver operating characteristics. Multiple logistic regression analysis was used to evaluate the individual and combined parameters. The study cohort consisted of 61 adrenal lesions (59 patients). Malignant lesions (n=52) had significantly higher median PET and CT parameters than benign lesions: A-SUVmax (11.4 vs. 6.1), R-SUVmax (3.3 vs. 1.7), and A-HU (37 vs. 24) [all p<0.023]. AUC for the PET parameters individually was almost identical: 0.75 for A-SUVmax and 0.74 for R-SUVmax. On univariate analysis, thresholds of A-SUVmax >3.47 and R-SUVmax >0.83 yielded maximum accuracy (both 87%). The combination of these PET parameters individually with A-HU improved both AUC and accuracy (0.81% and 93%, respectively). The individual PET parameters A-SUVmax and R-SUVmax have similar diagnostic performance for differentiating malignant and benign adrenal lesions; their performance and accuracy improve when combined with the CT component (A-HU).

SU‐E‐T‐470: Importance of HU‐Mass Density Calibration Technique in Proton Pencil Beam Dose Calculation

Purpose:Stoichiometric calibration of Hounsfield Units (HUs) for conversion to proton relative stopping powers (RStPs) is vital for accurate dose calculation in proton therapy. However proton dose distributions are not only dependent on RStP, but also on relative scattering power (RScP) of patient tissues. RScP is approximated from material density but a stoichiometric calibration of HU‐density tables is commonly neglected. The purpose of this work was to quantify the difference in calculated dose of a commercial TPS when using HU‐density tables based on tissue substitute materials and stoichiometric calibrated ICRU tissues.Methods:Two HU‐density calibration tables were generated based on scans of the CIRS electron density phantom. The first table was based directly on measured HU and manufacturer quoted density of tissue substitute materials. The second was based on the same CT scan of the CIRS phantom followed by a stoichiometric calibration of ICRU44 tissue materials. The research version of Pinnacle3 proton therapy was used to compute dose in a patient CT data set utilizing both HU‐density tables.Results:The two HU‐density tables showed significant differences for bone tissues; the difference increasing with increasing HU. Differences in density calibration table translated to a difference in calculated RScP of −2.5% for ICRU skeletal muscle and 9.2% for ICRU femur. Dose‐volume histogram analysis of a parallel opposed proton therapy prostate plan showed that the difference in calculated dose was negligible when using the two different HU‐density calibration tables.Conclusion:The impact of HU‐density calibration technique on proton therapy dose calculation was assessed. While differences were found in the calculated RScP of bony tissues, the difference in dose distribution for realistic treatment scenarios was found to be insignificant.

Submilisievert ultralow-dose CT colonography using iterative reconstruction technique: a feasibility study.

Computed tomography (CT) colonography is a well established modality for the examination of symptomatic patients as well as in screening. Recent technical advances in improving image quality by iterative reconstruction contribute to the reduction of the radiation dose which is a major concern in CT imaging. To evaluate image quality of ultralow-dose submilisievert CT colonography using hybrid iterative reconstruction technique. Sixteen patients underwent contrast-enhanced CT colonography with standard protocol in supine position and ultralow-dose protocol in prone position. Ultralow-dose datasets were reconstructed with filtered back projection and an advanced hybrid iterative reconstruction technique. Two radiologists independently evaluated 96 colonic segments for image quality in the endoluminal view and axial thin sections. Colonic distension, smoothness of colonic wall and distortion of folds in the endoluminal view, sharpness of colonic wall delineation, perceived image noise, and presence of photon starvation artifact were rated on a five-point scale. Intraluminal noise expressed as standard deviation of Hounsfield density was measured in all segments. The mean radiation dose was 0.42 mSv and 5.48 mSv in prone and supine scans, respectively. All distended segments were rated evaluable in standard dose and ultralow-dose series reconstructed with the iterative reconstruction technique, whereas in 61% segments image quality was rated poor or unacceptable in ultralow-dose series where filtered back projection was used with worst ratings in the rectum and the sigmoid colon. This pilot study shows that iterative reconstruction technique is a feasible method to decrease the radiation dose from CT colonography for both positions below 1mSv. Further investigations of larger scale need to be done to clarify, whether such a low radiation dose would influence the detection of polyps.

Noncontrast computed tomography factors that predict the renal stone outcome after shock wave lithotripsy

ObjectivesExtracorporeal shock wave lithotripsy (ESWL) is a popular treatment for nephrolithiasis. We took advantage of noncontrast abdominal computed tomography (NCCT) to search the possible prognostic factors including abdominal fat distribution influencing stone-free rate. MethodsFrom August 2008 to August 2010, 145 patients who had renal calculus and had undergone ESWL were retrospectively reviewed. All of them received NCCT assessment before ESWL and were followed up after 1 month for stone clearance. These patients were divided into two groups: one was the stone-free group and the other was the residual-stone group. Affecting parameters included stone size, location, stone surface area, Hounsfield unit density (HU density), skin-to-stone distance (SSD), and abdominal fat area as analyzed between these two groups. ResultsOf 145 patients, 70 were stone-free and 75 had residual stone after ESWL treatment and 1-month follow-up. From univariate analysis, stone size, HU density, SSD, and stone surface area were significant predicting factors for ESWL success. On multivariate analysis, the important factors influencing ESWL outcomes were HU density and stone surface area (odds ratio 1.002 vs. 77.18, respectively; P<.05). Abdominal fat accumulation and distribution had no significant difference between these two groups. ConclusionThis study revealed that stone size, HU density, SSD, and stone surface area were associated with stone-free rate after ESWL treatment. Therefore, these factors could be used to assess the feasibility of ESWL before deciding the treatment strategy. Abdominal fat distribution had no significant impact on ESWL outcome for renal stones.

Acoustic property reconstruction of a neonate Yangtze finless porpoise's (Neophocaena asiaeorientalis) head based on CT imaging.

The reconstruction of the acoustic properties of a neonate finless porpoise’s head was performed using X-ray computed tomography (CT). The head of the deceased neonate porpoise was also segmented across the body axis and cut into slices. The averaged sound velocity and density were measured, and the Hounsfield units (HU) of the corresponding slices were obtained from computed tomography scanning. A regression analysis was employed to show the linear relationships between the Hounsfield unit and both sound velocity and density of samples. Furthermore, the CT imaging data were used to compare the HU value, sound velocity, density and acoustic characteristic impedance of the main tissues in the porpoise’s head. The results showed that the linear relationships between HU and both sound velocity and density were qualitatively consistent with previous studies on Indo-pacific humpback dolphins and Cuvier’s beaked whales. However, there was no significant increase of the sound velocity and acoustic impedance from the inner core to the outer layer in this neonate finless porpoise’s melon.