Underwent Computed Tomography Examination Research Articles

Oral Midazolam-Ketamine versus Midazolam alone for Procedural Sedation of Children Undergoing Computed Tomography; a Randomized Clinical Trial.

Motion artifacts are a common problem in pediatric radiographic studies and are a common indication for pediatric procedural sedation. This study aimed to compare the combination of oral midazolam and ketamine (OMK) with oral midazolam alone (OM) as procedural sedatives among children undergoing computed tomography (CT) imaging. The study population was comprised of six-month to six-year old patients with medium-risk minor head trauma, who were scheduled to undergo brain CT imaging. Patients were randomly allocated to two groups: one group received 0.5 mg/kg midazolam (OM group; n = 33) orally and the other one received 0.2 mg/kg midazolam and 5 mg/kg ketamine orally (OMK group; n=33). The vital signs were monitored and recorded at regular intervals. The primary outcome measure was the success rate of each drug in achieving adequate sedation. Secondary outcome measures were the time to achieve adequate sedation, time to discharge from radiology department, and the incidence of adverse events. Adequate sedation was achieved in five patients (15.2%) in OM group and 15 patients (45.5%) in OMK group, which showed a statistically significant difference between the groups (p = 0.015). No significant difference was noted between OM and OMK groups with respect to the time of achieving adequate sedation (33.80 ± 7.56 and 32.87 ± 10.18 minutes, respectively; p = 0.854) and the time of discharging from radiology department (89.60 ± 30.22 and 105.27 ± 21.98 minutes, respectively; p=0.223). The complications were minor and similar among patients of both groups. This study demonstrated that in comparison with OM, OMK was more effective in producing a satisfactory level of sedation in children undergoing CT examinations without additional complications; however, none of these two regimens fulfilled clinical needs for procedural sedation.

Lumbar spine superior-level facet joint violations: percutaneous versus open pedicle screw insertion using intraoperative 3-dimensional computer-assisted navigation

Background Percutaneous pedicle screw use has a high rate of cranial facet joint violations (FVs) because of the facet joint being indirectly visualized. Computer-assisted navigation shows the anatomic structures clearly, and may help to lower the rate of FVs during pedicle screw insertion. This study used computed tomography (CT) to evaluate and compare the incidence of FVs between percutaneous and open surgeries employing computer-assisted navigation for the implantation of pedicle screw instrumentation during lumbar fusions. Methods A prospective study, including 142 patients having lumbar and lumbosacral fusion, was conducted between January 2013 and April 2014. All patients had bilateral posterior pedicle screw-rod instrumentation (top-loading screws) implanted by the same group of surgeons; intraoperative 3-dimensional computer navigation was used during the procedures. All patients underwent CT examinations within 6 months postoperation. The CT scans were independently reviewed by three reviewers blinded to the technique used. Results The cohort comprised 68 percutaneous and 74 open cases (136 and 148 superior-level pedicle screw placements, respectively). Overall, superior-level FVs occurred in 20 patients (20/142, 14.1%), involving 27 top screws (27/284, 9.5%). The percutaneous technique (7.4% of patients, 3.7% of top screws) had a significantly lower violation rate than the open procedure (20.3% of patients, 14.9% of top screws). The open group also had significantly more serious violations than did the percutaneous group. Both groups had a higher violation rate when the cranial fixation involved the L5. A 1-level open procedure had a higher violation rate than did the 2- and 3-level surgeries. Conclusions With computer-assisted navigation, the placement of top-loading percutaneous screws carries a lower risk of adjacent-FVs than does the open technique; when FVs occur, they tend to be less serious. Performing a single-level open lumbar fusion, or the fusion of the L5-S1 segment, requires caution to avoid cranial adjacent FVs.

Computed Tomography Scans as an Objective Measure of Disease Severity in Chronic Rhinosinusitis

A truly objective method of measuring disease severity in chronic rhinosinusitis (CRS) has only recently existed. We evaluated computed tomography (CT) scans of CRS patients using this novel objective 3D computerized system and compared results with a novel 2D computerized analysis of a single coronal slice through the osteomeatal complex (OMC) and subjective methods including Lund-Mackay and Zinreich's modified Lund-Mackay. Prospective multicenter study. Two academic tertiary referral centers. Forty-six adults with a diagnosis of CRS underwent CT examination and received an intramuscular triamcinolone injection, dosage weight dependent, followed by CT scan 4 to 5 weeks later. Recruitment lasted 21 months. Scans were evaluated with all 4 scoring methods over 5 months. The Lin's concordance class correlation (CCC) of the OMC method revealed the best correlation to the 3D volumetric computerized values (0.915), followed by the Zinreich (0.904) and Lund-Mackay methods (0.824). Posttreatment results demonstrated that both the OMC (0.824) and Zinreich's (0.778) methods had strong agreement with the 3D volumetric methods and were very sensitive to change, whereas the Lund-Mackay (0.545) had only moderate agreement. Computerized CT analysis provides the most comprehensive, objective, and reproducible method of measuring disease severity and is very sensitive to change induced by treatment intervention. A 2D coronal image through the OMC provides a valid, user-friendly method of assessing CRS and is representative of CRS severity in all sinuses. Zinreich's subjective method correlated well overall, but the Lund-Mackay method lagged behind in disease representation and sensitivity to change.

Computed Tomography Scans as an Objective Measure of Disease Severity in Chronic Rhinosinusitis

Objectives: A truly objective method of measuring disease severity in CRS does not exist. We evaluated computed tomography (CT) scans of chronic rhinosinusitis (CRS) patients using a novel 3-D computerized method and compared them to a 2-D objective computerized analysis of a single coronal slice through the osteomeatal complex (OMC), and subjective methods including Lund-Mackay and Zinreich’s modification of Lund-Mackay. Methods: Forty-six adults with symptoms and endoscopy confirmation of CRS underwent CT examination and received a triamcinolone injection, followed by CT scan 4-5 weeks later. Analyze software determined the 3-D total volume of inflammatory mucosal thickening in all sinuses. The triamcinolone injection served as a tool to determine each method’s sensitivity to a treatment intervention. Results: The Lin’s concordance class correlation (CCC) of the OMC method revealed the best correlation to the 3-D volumetric computerized values (0.915), followed by the Zinreich (0.904) and Lund-Mackay methods (0.824). Post-treatment results demonstrated that both the OMC (0.824) and Zinreich’s (0.778) methods had strong agreement with the 3-D volumetric methods and were very sensitive to change, whereas the Lund-Mackay (0.545) only had moderate agreement. Conclusions: Computerized CT analysis provides the most comprehensive, objective, and reproducible method of measuring disease severity and is very sensitive to change induced by treatment intervention. A 2-D coronal image through the OMC provides a valid, user-friendly method of assessing CRS and is representative of CRS severity in all sinuses. Zinreich’s subjective method correlated well overall, but Lund-Mackay lagged behind in disease representation and sensitivity to change.

Quantitative Iodine-Based Material Decomposition Images with Spectral CT Imaging for Differentiating Prostatic Carcinoma from Benign Prostatic Hyperplasia

To investigate the value of iodine-based material decomposition images produced via spectral computed tomography (CT) in differentiating prostate cancer (PCa) from benign prostate hyperplasia (BPH). Fifty-six male patients underwent CT examination with spectral imaging during arterial phase (AP), venous phase (VP), and parenchymal phase (PP) of enhancement. Iodine concentrations of lesions were measured and normalized to that of the obturator internus muscle. Lesion CT values at 75keV (corresponding to the energy of polychromatic images at 120 kVp) were measured and also normalized; their differences between AP and VP, VP and PP, and PP and AP were also obtained. The two-sample t-test was performed for comparisons. A receiver operating characteristic curve was generated to establish the threshold for normalized iodine concentration (NIC). Fifty-two peripheral lesions were found, which were confirmed by biopsy as 28 cases of PCa and 24 BPHs. The NICs of prostate cancers significantly differed from those of the BPHs: 2.38±1.72 compared with 1.21±0.72 in AP, respectively, and 2.67±0.61 compared with 2.27±0.77 in VP. Receiver operating characteristic analysis indicated that an NIC of 1.24 in the AP provided a sensitivity of 88% and a specificity of 71% for differentiating PCa from BPH. Spectral CT imaging enabled quantitative depiction of contrast medium uptake in prostatic lesions and improved sensitivity and specificity for differentiating PCa from BPH.

Ankle fractures have features of an osteoporotic fracture

We report the bone attenuation of ankle joint measured on computed tomography (CT) and the cause of injury in patients with ankle fractures. The results showed age- and gender-dependent low bone attenuation and low-energy trauma in elderly females, which suggest the osteoporotic features of ankle fractures. This study was performed to investigate the osteoporotic features of ankle fracture in terms of bone attenuation and cause of injury. One hundred ninety-four patients (mean age 51.0 years, standard deviation 15.8 years; 98 males and 96 females) with ankle fracture were included. All patients underwent CT examination, and causes of injury (high/low-energy trauma) were recorded. Mean bone attenuations of the talus, medial malleolus, lateral malleolus, and distal tibial metaphysis were measured on CT images. Patients were divided into younger age (<50 years) and older age (≥50 years) groups, and mean bone attenuation and causes of injury were compared between the two groups in each gender. Proportion of low-energy trauma was higher in the older age group than in the younger age group, but the difference was only significant in female gender (p = 0.011). The older age group showed significantly lower bone attenuation in the talus, medial malleolus, lateral malleolus, and distal tibial metaphysis than the younger age group in both genders. The older age group showed more complex pattern of fractures than the younger age group. With increasing age, bone attenuations tended to decrease and the difference of bone attenuation between the genders tended to increase in the talus, medial malleolus, lateral malleolus, and distal tibial metaphysis. Ankle fracture had features of osteoporotic fracture that is characterized by age- and gender-dependent low bone attenuation. Ankle fracture should not be excluded from the clinical and research interest as well as from the benefit of osteoporosis management.

Template-Driven Computed Tomography Radiation Dose Reporting: Implementation of a Radiology Housestaff Quality Improvement Project

Radiation exposure from medical imaging has received increasing attention in recent years. Ongoing calls to report radiation doses received during radiology studies as a means of recording cumulative exposure and identifying rare over-exposures have culminated in the State of California passing a mandatory reporting requirement effective July 1, 2012. Herein we describe a radiology housestaff-led quality improvement project to track radiation dose reporting a full year prior to state reporting mandates using a template-driven reporting system and our results over the first 12 months of its implementation. Effective July 2011, all radiology trainees were instructed to use a standard computed tomography (CT) report template that included a CT dose measurement derived from dose information routinely displayed on our picture archiving and communication system. Consecutive reports from July 1, 2011, to June 30, 2012, of patients who underwent CT examinations at our institution were then retrospectively reviewed. Compliance of each study with the reporting requirement was assessed based on the presence or absence of a radiation dose statement within the finalized report. A total of 36,217 eligible consecutive CT reports were identified within the review period. Of these, 91.9% reported the radiation dose for the examination, greatly exceeding the initial goal of 80% compliance with the dose reporting requirement. Successful reporting of CT radiation doses resulted from template-driven reporting, readily accessible calculation tools to facilitate dose calculation, and minimization of reporting burden on the radiologist a full year prior to state regulatory mandates.

Incidental detection of clinically unexpected breast lesions by computed tomography

Increased use of computed tomography (CT) has resulted in greater detection of incidental breast lesions unrelated to the primary diagnostic inquiry. To investigate the morphology and clinical significance of breast abnormalities detected incidentally by conventional CT. A total of 2945 female patients underwent CT examinations of the body, including the chest, from May 2006 to April 2010. Two radiologists interpreted these CT scans independently and pointed out a mass or non-mass-like lesion as abnormalities in the breast. Patients who incidentally showed breast lesions on CT scans were identified by a computer-based search of the diagnostic reports and were enrolled in this study. The morphology and enhancement patterns of CT-detected breast lesions were evaluated according to BI-RADS-MRI. In total, 32 clinically unexpected abnormal breast lesions were found in 31 (1.1%) patients. Twenty-nine of the 32 lesions were detected by contrast-enhanced CT and three by unenhanced CT. Ten breast cancers were found in 10 patients (0.34%), which yielded the prevalence for malignancy of 31% (10/32). Invasive ductal carcinomas accounted for eight lesions, while two were ductal carcinomas in situ (DCIS). Nine lesions were depicted as a mass and one DCIS was a non-mass-like lesion. Good morphological predictors of breast cancers for a mass were an irregular shape, a lobulated shape, and an irregular margin. Benign lesions accounted for 22 lesions from 21 patients (0.71%). Of these, 13 lesions in 13 patients were depicted as a mass and nine lesions in nine patients as a non-mass-like lesion. Unexpected breast lesions can be identified as a mass or non-mass-like lesion on conventional chest CT scans. Among these, breast cancers that are not clinically apparent occur with considerable prevalence. We suggest that careful interpretation of the breast should be a routine part of CT examinations.

Characteristic MR and CT imaging findings of hepatobiliary paragonimiasis and their pathologic correlations

Hepatobiliary paragonimiasis (HP) is not commonly encountered and may be confused with hepatobiliary tumors; however, computed tomography (CT) and magnetic resonance imaging (MRI) features of HP allow this entity to be distinguished from other diseases. To present the CT and MRI findings in patients with HP and to describe some specific imaging findings along with their pathological correlations. Imaging and clinical findings of 21 patients (9 boys/men and 12 girls/women; age range 3-67 years; mean age 40 years) who were diagnosed with HP were retrospectively evaluated. Among these patients, 16 underwent CT examination only, two had MR examination only, and three underwent both CT and MR. All patients underwent surgery, and the HP diagnosis was confirmed by the surgical and histopathologic results. Chronic abdominal pain or back pain was reported by 14 patients, severe abdominal pain with acute onset was reported by one patient, and six patients were asymptomatic and were discovered incidentally. Peripheral eosinophilia was present in 14 patients (14/21, 66.7%), and abnormal liver function tests were found in 16 patients (16/21, 76.2%). Of the 19 patients who underwent CT imaging, 17 patients showed multiple mixed hypodense lesions or multiple cysts with inlaying septation with separate irregular rims or circular enhancement on post-contrast CT images. Tunnel-shaped microabscesses and necrotic cavities were found in the lesions of 12 of those 17 patients. The other two patients showed smaller cystic masses. MRI showed faveolate T1 hypointense and T2 hyperintense areas in the liver parenchyma with rim or peripheral enhancement. Nodular or circular hyperintense materials were found scattered in the lesions on T1-weighted imaging. CT and MRI can reveal the radiological-pathological features of HP. Together with laboratory findings, MRI and CT findings may provide diagnostic clues, especially in endemic areas, that are very important for the selection of treatment methods.

SU-E-I-40: Effective Dose Normalized to Dose Length Product for Pediatric and Adult Reference Phantoms in Computed Tomography Examinations.

To develop a set of conversion factors from dose length product (DLP) to effective dose (E) for pediatric and adult reference individuals undergoing computed tomography (CT) examinations. This study used 12 hybrid computational phantoms representing reference pediatric and adult individuals in compliance with the International Commission on Radiological Protection (ICRP) reference data. The phantoms were combined with a model of the Siemens Sensation 16 scanner, to compute organ doses from CT examinations using a radiation transport code, MCNPX2.7. Effective doses based on ICRP 60 and 103 tissue weighting factors were calculated. The DLP was derived from the scan length and Computed Tomography Dose Index (CTDI)vol. The resulting DLP-to-E conversion factors were analyzed. The results consist in a set of DLP-to-E conversion factors for head, chest, abdomen, abdomen-pelvis, and chest-abdomen-pelvis CT examinations for newborn, 1-, 5-, 10-, 15-year-old and adult reference phantoms, for 80, 100 and 120 kVp and for ICRP 60 and 103 tissue weighting factors. The DLP-to-E factors decrease with smaller tube potential, with the greatest decrease for the head examinations for which values at 80 kVp are 20% smaller than at 120 kVp on average. The ICRP 103 weighting factors, compared to ICRP 60, Result in variations of DLP-to-E from 0.8 to 1.2-fold with a systematic increase for the chest, 1.14- fold on average, due to the increased breast weighting factor. The DLP-to-E factors for the body examinations are relatively similar to each other but 5 to 12-fold higher than for the head exam. The factors decrease with age until 15 years and then slightly increase for adult except for head. An updated set of DLP-to-E conversion factors were established based on more realistic human phantoms and provide an improved accuracy to obtain effective dose from DLP for patients undergoing CT examinations.

Differential diagnosis between benign and malignant ulcers: 320-row CT virtual gastroscopy

This study aims to assess the diagnostic accuracy of virtual gastroscopy obtained by 320-row computed tomography (CT) examination in differentiating benign from malignant gastric ulcers (GUs). 49 patients (30 M, 19 F, mean age 58.6) with endoscopic and histological diagnosis of GU underwent CT examination. A hypotonizing drug was administered and gastric walls were distended by air in order to perform virtual endoscopy. Based on morphological features, GUs were subdivided into benign or malignant forms by two blinded radiologists. Interobserver agreement was evaluated using Cohen’s kappa (κ) test. CT results were then compared with endoscopic and histological findings, having the latter as the reference standard. Thirty-five out of 49 patients (71%) were affected by malignant ulcers, while in the remaining 14 cases diagnosis of benign GU was made. Virtual gastroscopy showed diagnostic accuracy, sensitivity, and specificity values of 94%, 91%, and 100%, respectively, in differentiating benign from malignant ulcers. Almost perfect agreement between the two readers was found (κ = 0.86). CT virtual gastroscopy improves the identification of GUs and allows differentiating benign from malignant forms.

Trends of CT use in the pediatric emergency department in a tertiary academic hospital of Korea during 2001-2010.

ObjectiveWe wanted to assess the trends of computed tomography (CT) examinations in a pediatric emergency department (ED).Materials and MethodsWe searched the medical database to identify the pediatric patients who had visited the ED, and the number of CTs conducted from January 2001 to December 2010. We analyzed the types of CTs, according to the anatomic region, and the patients who underwent CT examinations for multiple regions. Data were stratified, according to the patient age (< 13 years and 13 ≤ ages < 18 years).ResultsThe number of CTs performed per 1000 patients increased by 92% during the 10-year period (per 1000 patients, increased from 50.1 CTs in 2001 to 156.5 CTs in 2006, and then decreased to 96.0 CTs in 2010). Although head CTs were performed most often (74.6% of all CTs), facial bone CTs showed the largest rate of increase (3188%) per 1000 patients, followed by cervical CTs (642%), abdominal CTs (474%), miscellaneous CTs (236%), chest CTs (89%) and head CTs (39%). The number of patients who had CT examinations for multiple regions in the same day showed a similar pattern of increase, to that of overall CT examinations. Increase of CT utilization was more pronounced in adolescents than in pediatric patients younger than 13 years (189% vs. 59%).ConclusionThe utilization of CTs increases from 2001 to 2006, and has declined since 2006. The increase of CTs is more pronounced in adolescents, and facial bone CTs prevail in increased number of examination followed by cervical CTs, abdominal CTs, miscellaneous CTs, chest CTs, and head CTs.

Comparison of computed tomography dose reporting software

Computed tomography (CT) dose reporting software facilitates the estimation of doses to patients undergoing CT examinations. In this study, comparison of three software packages, i.e. CT-Expo (version 1.5, Medizinische Hochschule, Hannover, Germany), ImPACT CT Patients Dosimetry Calculator (version 0.99×, Imaging Performance Assessment on Computed Tomography, www.impactscan.org) and WinDose (version 2.1a, Wellhofer Dosimetry, Schwarzenbruck, Germany), has been made in terms of their calculation algorithm and the results of calculated doses. Estimations were performed for head, chest, abdominal and pelvic examinations based on the protocols recommended by European guidelines using single-slice CT (SSCT) (Siemens Somatom Plus 4, Erlangen, Germany) and multi-slice CT (MSCT) (Siemens Sensation 16, Erlangen, Germany) for software-based female and male phantoms. The results showed that there are some differences in final dose reporting provided by these software packages. There are deviations of effective doses produced by these software packages. Percentages of coefficient of variance range from 3.3 to 23.4 % in SSCT and from 10.6 to 43.8 % in MSCT. It is important that researchers state the name of the software that is used to estimate the various CT dose quantities. Users must also understand the equivalent terminologies between the information obtained from the CT console and the software packages in order to use the software correctly.

Computed tomography indices and criteria for the prediction of esophageal variceal bleeding in survivors of biliary atresia awaiting liver transplantation

About 20% of biliary atresia (BA) survivors have attacks of esophageal variceal bleeding. We propose a method to evaluate the risk of esophageal variceal bleeding (EVB) using noninvasive indices by multislice computed tomography (CT). We reviewed 31 potential living-related liver recipients aged 99-5314 days (mean, 1474 days) who underwent CT examinations using a 64-slice multislice CT scanner. Of the 31 patients, 19 patients (Group A) with fecal occult blood had EVB on esophagogastroduodenoscopy; the rest belonged to Group B. Splenic diameters (mm) were divided by body heights (m) and platelet counts (1000/mm(3)) to produce standardized ratios of transverse splenic length/body height/platelet count (SLHPR). The transverse diameters of paraesophageal veins (PVs) and perigastric veins (PGVs) were measured adjacent to the lower thoracic esophagus and within the lesser sac, respectively. According to a receiver operating characteristic curve analysis, the SLHPRs (r=0.833), transverse PV (r=0.957), and PGV (r=0.987) diameters were better predictors of EVB than demographic and laboratory variables. However, the transverse diameters of PGVs and PVs were the most accurate predictors of the EVB. For candidates awaiting liver transplantation, screening by noninvasive SLHPR and the transverse diameters of PGVs and PVs by CT may help to identify BA patients with a high risk of EVB.

In-patient to isocenter KERMA ratios in CT

To estimate in-patient KERMA for specific organs in computed tomography (CT) scanning using ratios to isocenter free-in-air KERMA obtained using a Rando phantom. A CT scan of an anthropomorphic phantom results in an air KERMA K at a selected phantom location and air kerma K(CT) at the CT scanner isocenter when the scan is repeated in the absence of the phantom. The authors define the KERMA ratio (R(K)) as K∕ K(CT), which were experimentally determined in a Male Rando Phantom using lithium fluoride chips (TLD-100). R(K) values were obtained for a total of 400 individual point locations, as well as for 25 individual organs of interest in CT dosimetry. CT examinations of Rando were performed on a GE LightSpeed Ultra scanner operated at 80 kV, 120 kV, and 140 kV, as well as a Siemens Sensation 16 operated at 120 kV. At 120 kV, median R(K) values for the GE and Siemens scanners were 0.60 and 0.64, respectively. The 10th percentile R(K) values ranged from 0.34 at 80 kV to 0.54 at 140 kV, and the 90th percentile R(K) values ranged from 0.64 at 80 kV to 0.78 at 140 kV. The average R(K) for the 25 Rando organs at 120 kV was 0.61 ± 0.08. Average R(K) values in the head, chest, and abdomen showed little variation. Relative to R(K) values in the head, chest, and abdomen obtained at 120 kV, R(K) values were about 12% lower in the pelvis and about 58% higher in the cervical spine region. Average R(K) values were about 6% higher on the Siemens Sensation 16 scanner than the GE LightSpeed Ultra. Reducing the x-ray tube voltage from 120 kV to 80 kV resulted in an average reduction in R(K) value of 34%, whereas increasing the x-ray tube voltage to 140 kV increased the average R(K) value by 9%. In-patient to isocenter relative KERMA values in Rando phantom can be used to estimate organ doses in similar sized adults undergoing CT examinations from easily measured air KERMA values at the isocenter (free in air). Conversion from in-patient air KERMA values to tissue dose would require the use of energy-appropriate conversion factors.

Radiation Exposure from CT Examinations in Japan

BackgroundComputed tomography (CT) is the largest source of medical radiation exposure to the general population, and is considered a potential source of increased cancer risk. The aim of this study was to assess the current situation of CT use in Japan, and to investigate variations in radiation exposure in CT studies among institutions and scanners.MethodsData-sheets were sent to all 126 hospitals and randomly selected 14 (15%) of 94 clinics in Gunma prefecture which had CT scanner(s). Data for patients undergoing CT during a single month (June 2008) were obtained, along with CT scan protocols for each institution surveyed. Age and sex specific patterns of CT examination, the variation in radiation exposure from CT examinations, and factors which were responsible for the variation in radiation exposure were determined.ResultsAn estimated 235.4 patients per 1,000 population undergo CT examinations each year, and 50% of the patients were scanned in two or more anatomical locations in one CT session. There was a large variation in effective dose among hospitals surveyed, particularly in lower abdominal CT (range, 2.6-19.0 mSv). CT examinations of the chest and upper abdomen contributed to approximately 73.2% of the collective dose from all CT examinations. It was estimated that in Japan, approximately 29.9 million patients undergo CT annually, and the estimated annual collective effective dose in Japan was 277.4 *103 Sv person. The annual effective dose per capita for Japan was estimated to be 2.20 mSv.ConclusionsThere was a very large variation in radiation exposure from CT among institutions surveyed. CT examinations of the chest and upper abdomen were the predominant contributors to the collective dose.

SU-EE-A4-04: Organ Doses in the Reference Adult Male and Female Exposed to Computed Tomography Examinations: Monte Carlo Simulations and Experimental Validation

Purpose: To establish an organ dose database for adult male and female reference individuals undergoing computed tomography(CT) examinations by using the Monte Carlo(MC) method. Methods and Materials: We are using the MC method to estimate organ doses from CT examinations to support epidemiologic studies of the risk of second cancers associated with radiation exposure from CT examination. The fan‐shaped x‐ray beam of a SOMATOM Sensation 16 CT scanner was simulated by using a general purpose MC code, MCNPX v2.6. The bowtie filter was approximated based on beam profile measurements under service mode tube settings. To simulate the anatomy of patients, the University of Florida family of hybrid computational phantoms representing the adult male and female at their 50th percentile body weight and standing height were coupled with the CT scanner model. The reliability of the MC simulation system has been validated by comparing results with measurements from Computed Tomography Dose Index(CTDI) head and body phantoms. Organ absorbed doses were calculated for Head, Chest, Abdomen, and Pelvis examinations and compared with those from two commercial CT dose calculation programs (CT‐expo and CT‐Dosimetry). Results: Central and peripheral doses from the measurements using head and body CTDI phantoms were compared with those from MC simulation. The simulated doses showed good agreement with measured values with the largest percent difference of 8%. Normalized values of organ absorbed dose (mGy/100 mAs) were calculated for 25 organs in the adult male and female phantoms undergoing CT examinations. The dose results were compared with those from the commercial programs, and significant differences up to 200% were shown in major organs.Conclusion: The organ dose database developed in this study significantly improves the accuracy of organ dose assessments in CT examinations which have not been implemented in existing commercial CT dose evaluation programs.

Comparison of two types of adult phantoms in terms of organ doses from diagnostic CT procedures

The rapidly increasing number of diagnostic computed tomography (CT) procedures in the recent decades has spurred heightened concern over the potential risk to patients. Although an accurate organ dose assessment tool has now become highly desirable, existing software packages depend on stylized computational phantoms that were originally developed more than 40 years ago, exhibiting very large discrepancies when compared with phantoms that are anatomically realistic. However, past comparative studies did not focus on CT protocols for adult patients. This study was designed to quantitatively compare two types of phantoms, the stylized phantoms and a pair of recently developed RPI-adult male and adult female (RPI-AM and RPI-AF) phantoms, for various CT scanning protocols involving the chest, abdomen–pelvis and chest–abdomen–pelvis. Organ doses were based on Monte Carlo simulations using the MCNPX code and a detailed CT scanner model for the GE LightSpeed 16. Results are presented as ratios of organ doses from the stylized phantoms to those from the RPI phantoms. It is found that, for most organs contained in the scan volume, the ratios were within the range of 0.75–1.16. However, the stomach doses are significantly different and the ratio is found to be up to 1.86 in male phantoms and 2.29 in the female phantoms due to the anatomical differences between the two types of phantoms. Organs that lie near a scan boundary also exhibit a significant relative difference in organ doses between the two types of phantoms. This study concludes that, due to relatively low x-ray energies, CT doses are very sensitive to organ shape, size and position, and thus anatomically realistic phantoms should be used to avoid the dose uncertainties caused by the lack of anatomical realism. The new phantoms, such as the RPI-AM and AF phantoms that are designed using advanced surface meshes, are deformable and will make it possible to match the anatomy of a specific patient leading to further improvement in dose and risk assessments for patients undergoing CT examinations.

SU‐FF‐I‐52: Comprehensive CT Dosimetry Database for Pediatric and Adult Reference Males and Females: A Monte Carlo Study

Purpose: To establish an organ dose database for pediatric and adult male and female reference individuals undergoing computed tomography (CT) examinations and to develop software providing the dose information within a graphical user interface (GUI). Methods and Material: A series of hybrid computational human phantoms was developed at the University of Florida by using realistic patient CT images and flexible Non‐Uniform Rational B‐Spline (NURBS) surfaces. The phantoms include newborn, 1, 5, 10, 15, and adult male and female matched to the four reference data: reference organ mass from ICRP Publication 89, anthropometric data from CDC, tissue composition from ICRU Report 46, and intestine models of ICRP Publication 100. The 12 reference phantoms were ported into MCNPX2.5 code where helical fan beams from SOMATOM Sensation 16 helical multi‐slice CT scanner were modeled. Organ absorbed doses were calculated for Head, Chest, Abdomen, Pelvis, CAP examinations. Software was developed to provide the dosimetry database with GUI. The scanner matching algorithm was employed from the commercial software CT‐EXPO to take different scanner parameters from different scanner models into account. Results: Normalized values of organ absorbed dose (mGy/100 mAs) were calculated for 25 organs in the 12 phantoms undergoing CT examinations were calculated. The comprehensive CT dose database was incorporated into GUI‐supported software to provide realistic and consistent dosimetry information to end‐user. The dose results were compared with those from CT‐EXPO and significant differences were shown in major organ absorbed doses which were mainly caused by the anatomical difference between UF hybrid phantoms and limited stylized and old voxel phantoms in CT‐EXPO. Conclusion: The software developed in this study significantly improved accuracy and consistency of organ dose assessments in CT examinations which have not been implemented in a couple of previous CT dose evaluation software.This work is funded by the NCI Radiation Epidemiology Branch

Pancreatic metastases: CT and MRI findings

The pancreas is an unusual but occasionally favored site for metastases in patients with advanced malignancy. The pivotal role of computed tomography (CT) and magnetic resonance imaging (MRI) examination in detecting the pancreatic mass and providing guidance to obtain a definitive tissue diagnosis is emphasized in this study. Eleven patients with pancreatic metastases, 4 women and 7 men with a mean age of 62.45 years, were examined in a period of 5 years. All patients underwent CT examination and 3 patients were further evaluated by MRI. The primary malignancy was lung carcinoma in 7 patients, breast carcinoma in 3 patients and renal cell carcinoma in 1 patient. The pancreatic metastases were detected during initial staging in 4 cases and during follow-up in 7 cases. The type of metastases was solitary in 7 patients, multiple in 3 patients and diffuse in 1 patient, with rim or homogeneous enhancement. Seven patients had metastases to other organs. CT-guided biopsy was performed in 5 patients. Disparity in prognosis and management of patients with secondary pancreatic tumors makes detection and characterization of metastases to the pancreas an important goal of CT and MRI evaluation.