Abdominal CT Examinations Research Articles

Application value of total abdominal CT examination in elderly patients with acute intestinal obstruction

Objective To explore the necessities and clinical value of acute intestinal obstruction with computed tomography of whole abdomen in over 80 years old patients. Methods 50 patients with acute intestinal obstruction were diagnosed in department of emergency surgery and underwent the abdominal CT examinations.The clinical data, CT and surgery pathology of all patients were compared and analyzed. Results All cases were verified by surgical operation and pathological diagnosis, including colorectal cancer(n=21) and incarcerated abdominal external hernia(n=21), appendicitis(n=2), adhesive intestinal obstruction(n=2), intestinal volvulus (n=2), and intestinal intussusception(n=1) and stercoral intestinal obstruction(n=1), 12 cases were accompanied by bowel necrosis and perforation.12 patients were treated by laparoscope surgery, 38 cases by open laparotomy, 48 patients acquired good recovery, and 2 cases died from extensive bowel necrosis and multi-organ failure. Conclusion CT examination in whole abdomen could rapidly and accurately diagnose the cause of intestinal obstruction, evaluate complications and risks, so as to provide reasonable treatment choice and time, making patients acquired the effective effects as soon as possible, reducing the bad consequences. Key words: Intestinal obstruction; Tomography, X-ray computed; Aged, over 80 years old

The influence of low concentration iodinated contrast agent and low-dose CT scanning technique combined with body mass index on radiation dose and image quality of upper abdominal CT examinations

Objective To investigate the influence of double technology (low concentration iodinated contrast agent and low-dose scan) combined with body mass index (BMI) on radiation dose and image quality of contrast-enhanced upper abdominal CT examination. Methods One hundred and twenty patients who received upper abdominal enhanced CT examination were randomly divided into 4 groups: group A1, the iodinated contrast agent iodixanol (270 mg/ml), BMI<18.5 kg/m2 and 80 kVp; group A2, the iodinated contrast agent iodixanol (270 mg/ml), 18.5 kg/m2≤BMI≤24.9 kg/m2 and 100 kVp; group B1, the iodinated contrast agent ioversol (320 mg/ml), <18.5 kg/m2 and 120 kVp; group B2, the iodinated contrast agent ioversol (320 mg/ml), 18.5 kg/m2≤BMI≤24.9 kg/m2 and 120 kVp. Image quality was subjectively scored, the objective parameters (noise, CT values of abdominal aorta and liver parenchyma, contrast noise ratio of abdominal aorta and liver parenchyma) were evaluated and radiation dose was recorded. The differences of the indexes between A1 and B1 groups, A2 and B2 groups were compared with Mann-Whitney U test and pared-samples t test. Results All CT images were good. No images with 4 scores were obtained. No significant difference was found between group A1 and B1, between group A2 and B2 (P>0.05). There was no significant difference in contrast noise ratio of liver parenchyma (P>0.05), while significant differences existed in CT values of abdominal aorta and liver parenchyma, contrast noise ratio of abdominal aorta between group A1 and B1 (P<0.05). Significant differences existed in the parameters above mentioned between group A2 and B2, respectively (P<0.05). Radiation dose was lower in group A1 than in group B1 and in group A2 than in group B2 (P<0.05), respectively. Radiation dose was decreased by 40.1%(0.89/2.22) in group A1 than group B1 while radiation dose decreased by 56.9% (3.02/5.31) in group A2 than group B2. Conclusion According to BMI, the low concentration iodinated contrast agent and low-dose scan CT scanning technology could effectively reduce radiation dose and generate ideal images during the contrast-enhanced upper abdominal CT examination. Key words: Tomography, X-ray computed; Radiation dosage; Contrast media; Body weight

A Comprehensive Clinical Decision Support Application Software for dose Optimisation Procedure in CT

CT images are the most common imaging modality after conventional X-ray imaging. There are used in order to determine organ position, location and size in relation to treatment area for treatment planning and for diagnoses of diseases. The general aims of the study is to design a comprehensive clinical decision support application software for patients' dose optimization. The design of the GUI involve the use of mathematical modeling procedure where the modeled equations reduces the data from empirical measurements to real clinical application process for implementation. The final component of the modeling process is the GUI applications. This was done in two different process and procedures. The first was the coding process where a software was developed with written C++ code and integrated on the data capturing application platform for clinical application. The second was the visual indicators where the shape and size were modeled to represent the variation in age and gender that exist between the various model equations. The GUI are then used by radiographers to predict and plan the choice of input parameters for effective managements of doses to patient undergoing abdominal CT examination. Finally, a GUI and CAD models were designed to adequately reflect the comfortable working process of all the mathematical model equations. Reference effective abdominal and renal dose parameters have been established and developed in a data base for clinical application. In addition, the displayed interface on the DICOM interface enable the prediction of CTDI and DLP parameters with known kVp and mAs parameters before imaging.

Wilms Tumor-Follow-up Tailored Abdominal CT Examination

Purpose of Review Wilms tumor is the most common renal mass in infancy with peak incidence between 3 and 4 years old. Actual cure rates are around 90%. Current COG recommendations for imaging follow-up after treatment still include abdomino-pelvic CT for the first 18 months in a regimen that totals at least eight follow-up CTs before changing to US examinations. That represents a meaningful radiation exposure in patients who are more susceptible to stochastic effects, due to their low age.

A novel complete retroperitoneal laparoscopic nephroureterectomy via modified three ports approach

Objective To assess the clinical efficacy of a modified complete retroperitoneal laparoscopic nephroureterectomy via 3 port approach. Methods From August 2013 to February 2016, 23 patients with complete retroperitoneal laparoscopic renal and ureteral sleeve resection were treated with modified three port approach, including 15 males and 8 females. The average age was 67 years old (ranging 44-83 years old). All patients had complained about the hematuria before operation and urine exfoliated cells showed moderate to severe nuclear atypia. All patients accepted the abdominal CT and urography CTU examination, pre-operatively. All of them was diagnosed localized upper urinary tract malignant tumors based on those images, including 13 cases in the pelvis, and 10 cases in the upper segment of the ureter. No chemotherapy, radiotherapy or immunotherapy was performed before surgery. No patients have the history of severe basic disease or upper urinary procedure.The operations were performed under general anesthesia, patients take the contralateral back 30 degrees slope, low elevation head foot, waist bridge, side waist stretch. In the anterior superior iliac spine perpendicular to the line 2 cm parallel to the lower intersection of the rib border were disposed into the 12 mm trocar. Above the anterior superior iliac spine two cross finger level with the intersection of the anterior axillary node, we placed into the 10 mm trocar placement lens. Laparoscopic placement of third casing form an isosceles triangle with the first two casing. The renal fascia was incised with an ultrasonic knife from the renal dorsal side, and the renal hilum was isolated from the kidney by suction aspirator. The renal artery and vein were separated and closed by hem-o-lok. Along the psoas muscle surface to ureter, ureteral clipping by hem-o-lok but not to cut off the free distal ureteral, the lens is composed of first casing into, using ultrasonic knife to free ureter to the bladder wall segment, with 30 mm endoscopic stapler ureter and bladder wall cut off part. Operation time, blood loss and postoperative recovery were recorded in 23 cases. Results All 23 cases were successfully operated without related the operative complication. The operative duration ranged from 3.5 to 6.1 h (mean 4.8 h), the blood loss was 30-880 ml (mean 304 ml), and the postoperative stay was 8-30 d (mean 17.8 d). There are 3 cases of positive lymph node by postoperative pathological reports. Within 2 to 30 months following up, 2 patients died of tumor progression in 6 months after surgery. 4 patients were diagnosed with bladder cancer in 15 months, 15 months, 21 months, 24 months after surgery, respectively. And the transurethral resection of bladder tumor was performed. Conclusion The modified complete retroperitoneal laparoscopic nephroureterectomy via three ports is safe and reliable. Key words: Retroperitoneoscopic; Nephroureterectomy; Via three ports

セフトリアキソン投与が原因と考えられた偽胆石による急性膵炎の1成人例

The patient was a 74-year-old male. He started to have Epigastric pain 12 days after we started treating him for pneumonia by administrating ceftriaxone (CTRX) . Through an abdominal CT examination, we found gallbladder stones and common bile duct calculi, prompting us to diagnose him with acute biliary pancreatitis caused by pseudolithiasis, and then we urgently performed an endoscopic sphincterotomy. His pancreatitis improved afterward, and the gallbladder calculus completely disappeared two months later. Although it may not occur very frequently, we need to pay attention to the onset of pseudolithiasis when administering CTRX, even in adults.

Comparison of Measured Values of CTDI and DPL with Standard Reference values of Different CT Scanners for dose Management

The study is based on estimate of CTDI and DLP values for patients' dose optimization procedures. Technical parameters were obtained for three groups of randomly selected patients undergoing abdominal CT examinations of 320 patients of age 20-80 years. The measured values were obtained on image data and the standard reference values of various machines were obtained from service manual as part of QC/QA and the recommended values from ICRP publication 103. The mean CTDI and DLP parameters were; 6.33mGy and 936.25mGy respectively. Furthermore, the mean recorded values of CTDIVOL values were well within ICRP recommendation when the protocol was completed in one scan. On the other hand, in the case of multiscan the total CTDIVol was higher than the ICRP recommendations. While the mean DLP values were higher than the recommended value of 780 mGy-cm by ICRP publication 103. Finally, approximately 37% of the total varied CTDI and DLP values were higher than the recommended dose by ICRP publication 103.

Unborn children: Radiation protection in pregnancy

A diagnostic or interventional X-ray examination of a pregnant patient is sometimes considered to be necessary. In these cases, conceptus dose estimation is needed to assess radiogenic risks to the unborn child. During extra-abdominal examinations, the unborn child is exposed to scattered radiation and in most cases its dose is lower than 1 mGy. A detailed embryo/fetus dose evaluation is not needed for these examinations. Abdominal and/or pelvis X-ray examinations may deliver higher radiation doses to the conceptus. An abdominal CT examination performed on the mother is associated with an embryo/fetus dose of about 10–25 mGy. However, this is only a typical range of dose values. The actual dose depends on factors such as exposure parameters, x-ray tube filtration and use of dose reduction tools such as automatic exposure control. Doses to the unborn child below 100 mGy should not lead to therapeutic abortion. The risk to the embryo/fetus for stochastic effects is assessed on the basis of radiation dose using appropriate conversion coefficients provided by international organizations. Several methods have been developed to estimate doses to unborn children from X-ray examinations. CODE (COnceptus Dose Estimation) is a free web-based software tool (uploaded on embryodose.med.uoc.gr) developed for the estimation of conceptus radiation dose and risks in case of: a) pregnant patients subjected to radiological examinations and b) pregnant employees exposed during fluroscopically guided interventional procedures.

SU‐F‐I‐29: Investigating the Impact of the Amount of Contrast Material Used in Abdominal CT Examinations Regarding the Diagnosis of Appendicolith

Purpose:The purpose of this study is to report the case of a young adult in which the incomplete oral administration of contrast material led to diagnosis of an appendicolith, which cause acute appendicitis.Methods:A male 34 years old underwent CT examination due to acute abdominal pain in the upper abdomen. An ultrasound examination of the upper abdomen and kidneys, an x‐ray examination of the abdomen and a CT scan of the entire abdomen and pelvis after both oral and IV administration of contrast material were performed. In the ultrasound examination, both kidneys gallbladder and spleen appeared normal and the x‐ray examination did not show any pathological findings. As part of the CT examination, the patient received oral contrast material less than 500 ml due to lack of cooperation by the patient as a result of his abdominal pain.Results:The CT abdomen revealed a severely inflamed appendix that was significantly dilated at 1.1 cm. Moreover, it demonstrated a 1.4 cm appendicolith. The portion of the oral contrast material that was injected to the patient covered the upper abdomen and as a result an appendicolith could be revealed in the lower abdomen. If the patient had received the 1,000ml of contrast material, the whole abdomen would have been covered with the contrast in danger to lose the appendicolith, which caused the inflammation.Conclusion:Based on the findings of this study, in suspicion of acute appendicitis nephrolithiasis and ureterolithiasis, we propose to start the CT protocol with a CT scan without oral contrast material and then proceed with oral and IV contrast not only to succeed gastric intestinal differentiation but also to avoid covering the lower abdomen and obscure any small stones that may exist.

SU‐F‐I‐33: Estimating Radiation Dose in Abdominal Fat Quantitative CT

Purpose:To compare size‐specific dose estimate (SSDE) in abdominal fat quantitative CT with another dose estimate Dsize,L that also takes into account scan length.Methods:This study complied with the requirements of the Health Insurance Portability and Accountability Act. At our institution, abdominal fat CT is performed with scan length = 1 cm and CTDIvol = 4.66 mGy (referenced to body CTDI phantom). A previously developed CT simulation program was used to simulate single rotation axial scans of 6–55 cm diameter water cylinders, and dose integral of the longitudinal dose profile over the central 1 cm length was used to predict the dose at the center of one‐cm scan range. SSDE and Dsize,L were assessed for 182 consecutive abdominal fat CT examinations with mean water‐equivalent diameter (WED) of 27.8 cm ± 6.0 (range, 17.9 ‐ 42.2 cm). Patient age ranged from 18 to 75 years, and weight ranged from 39 to 163 kg.Results:Mean SSDE was 6.37 mGy ± 1.33 (range, 3.67–8.95 mGy); mean Dsize,L was 2.99 mGy ± 0.85 (range, 1.48 ‐ 4.88 mGy); and mean Dsize,L/SSDE ratio was 0.46 ± 0.04 (range, 0.40 ‐ 0.55).Conclusion:The conversion factors for size‐specific dose estimate in AAPM Report No. 204 were generated using 15 ‐ 30 cm scan lengths. One needs to be cautious in applying SSDE to small length CT scans. For abdominal fat CT, SSDE was 80–150% higher than the dose of 1 cm scan length.

Application of spectral CT in the differentiation of stage T3 and T4a gastric carcinoma

To investigate the application value of spectral CT in the differentiation of stage T3 and T4a gastric carcinoma. Data of 62 gastric cancer patients of stage T3 and T4a undergoing abdominal spectral CT examination in the First Affiliated Hospital of Zhengzhou University from December 2013 to December 2014 were collected retrospectively. There were 38 male and 24 female patients, with age of 33 to 77(58.6±10.4) years old. Abdominal double-phase enhanced scanning in gemstone spectral imaging mode was used to measure Iodine concentration (IC, 100 μg/ml) and water concentration(WC, 100 μg/ml) of perigastric fat tissue adjacent to the lesion during arterial phase(AP) and venous phase(VP), and normalized iodine concentration (nIC) was calculated respectively(nIC=IC/IC of aorta on the same slice). IC, WC, nIC of arterial phase and venous phase between stage T3 and T4a lesions were compared with double independent sample t test and compared with pathology. The diagnostic efficacy was evaluated using receiver operating characteristic (ROC) curve analysis. During arterial phase in stage T4a cases, IC (100 μg/ml) was -5.19±0.81 and nIC was -0.05±0.01, which was significantly higher than -3.44±1.54 (P=0.000) and -0.03±0.01 (P=0.000) in stage T3 cases. During venous phase in T4a cases, IC (100 μg/ml) was -3.78±0.94 and nIC was -0.04±0.01, which was significantly higher than -1.62±1.43 (P=0.000) and -0.02±0.02 (P=0.000) in stage T3 cases. As compared to arterial phase, IC and nIC of stage T4a and T3 of venous phase were more significantly different (all P<0.05). WC of stage T4a during arterial and venous phase was 955.72±15.68 and 949.86±17.36 respectively, while WC of stage T3 during arterial and venous phase was 947.77±18.43 and 942.46±18.53 respectively. There were no significant differences in WC between two stage cases during arterial and venous phase (P=0.106, P=0.143). ROC analysis showed that area under the ROC of IC and nIC during arterial phase was 0.829 and 0.867 respectively, and cut-off value of nIC was -0.039 for differentiation of stage T3 and T4a with corresponding 83.3% of sensitivity and 75.0% of specificity; area under the ROC of IC and nIC during venous phase was 0.873 and 0.905 respectively, and cut-off value of nIC was -0.031 for differentiation of stage T3 and T4a with corresponding 81.0% of sensitivity and 85.0% of specificity. Abdominal spectral CT scan is useful in the differentiation of stage T3 and T4a gastric carcinoma. The IC of perigastric fat tissue is significantly higher in stage T4a gastric carcinoma compared to stage T3 gastric carcinoma. Higher diagnostic efficacy can be obtained when taking -0.031 as the cut-off value of nIC during venous phase.

Radiologist-initiated double reading of abdominal CT: retrospective analysis of the clinical importance of changes to radiology reports

BackgroundMisinterpretation of radiological examinations is an important contributing factor to diagnostic errors. Consultant radiologists in Norwegian hospitals frequently request second reads by colleagues in real time. Our objective was to...

Prognostic value of carcinoembryonic antigen and carbohydrate antigen 19-9 in patients with stage II colorectal cancer

Objective To evaluate the significance of the expression of carcinoembryonic antigen (CEA) and carbohydrate antigen 19-9 (CA19-9) as prognostic indicators for patients with stage Ⅱ colorectal cancer. Methods A total of 285 patients with stage Ⅱ colorectal cancer who underwent potentially curative surgery were enrolled in the study. A high CEA level was defined as a level exceeding 5 ng/ml and a high CA19-9 level was defined as a level exceeding 37 U/ml. Patients were followed up every 3 months to review CEA and CA19-9 levels. Two years later, the chest and abdominal CT examination were performed every 3 months, and then every 6 months until 5 years. Results Out of these 285 patients, 99 (42.60 %) patients had high CEA levels, 25 (8.77 %) patients had high CA19-9 levels, and 12 (4.21 %) patients had both high CEA and CA19-9 levels. The overall survival rates of patients with both high CEA and CA19-9 levels were significantly worse than those of others (P < 0.05). During the study, 51 recurrences were diagnosed. There were 22 hepatic recurrences, 10 pulmonary recurrences, 9 local recurrences, 8 lymph node recurrences, and 2 peritoneal recurrences. CT, CEA and CA19-9 were the first abnormal examinations in 30, 5 and 8 recurrent patients, respectively. In 27 % of recurrent patients, the recurrence was detected earlier by CEA and CA19-9 than that by CT. Conclusions The detection of preoperative CEA and CA19-9 levels is useful for predicting the prognosis after potentially curative surgery in patents with stage Ⅱ colorectal cancer. For early detection of occult recurrence of colorectal cancer, tumor markers are relevant. Key words: Colorectal neoplasms; Carcinoembryonic antigen; Carbohydrate antigen 19-9; Prognosis

B.314 - Size-specific, scanner-independent organ dose estimates in multi-slice abdominal CT examinations of overweight and obese patients

B.314 - Size-specific, scanner-independent organ dose estimates in multi-slice abdominal CT examinations of overweight and obese patients

Hematemesis from Bleeding Pancreatic Pseudocyst Ruptured into the Duodenum

A 44-year-old alcoholic man with a history of multiple episodes of acute pancreatitis was transferred to our hospital with complaints of intense mid-epigastric pain and hematemesis for 3 h. He was diagnosed as pancreatic pseudocyst by abdominal CT examination (Figure 1a and 1b) 6 months ago. The abdomen was markedly tender, and an impulsatile mass measuring 10 cm × 15 cm was palpable. Emergent abdominal CT revealed giant hyper-attenuation cyst communicating with duodenum, suggestive of blood presence. Large amount of blood was also noted in stomach, duodenum and small bowel (Figure 1c). Conservative treatment, including parenteral nutrition and blood transfusion, was consecutively administered for 5 days. Follow-up CT show marked shrinkage of pancreatic pseudocyst and direct orifice of fistula (Figure 1d). Hemorrhagic complications are reported to occur in 6% to 31% of patients with pancreatic pseudocyst and bleeding into a pseudocyst may arise from a pseudoaneurysm or from vessels within its wall. Sequential CT can describe dynamic process of pancreatic pseudocyst complicating with gastrointestinal hemorrhage.

Retroperitoneal Air after ERCP with Sphincterotomy: Frequency and Clinical Significance &amp;lt;/br&amp;gt;—Retroperitoneal Air after Sphincterotomy

Background and Aim: After successful medical management of a patient with a clinical picture suggestive of post-sphincterotomy duodenal perforation, in which a computerized axial tomography (CAT) scan of the abdomen revealed the presence of subcutaneous emphysema and retroperitoneal air, concern arose as to the frequency of pneumoretroperitoneum following endoscopic retrograde cholangiopancreatography (ERCP) with sphincterotomy (ES) and if any procedure dependent factors were associated with this problem. Aim: To assess the frequency and clinical significance of retroperitoneal air after endoscopic retrograde cholangiopancreatography with sphincterotomy. Methods: Fifty consecutive patients, who had undergone ERCP with sphincterotomy, were submitted to abdominal CT examinations within 24 hours after completion of the procedure. One patient was with a large precut, but a failed ERCP was also included. The ERCP findings were unknown to the radiologist. Results: Seven (14%) of 50 patients showed CT findings of retroperitoneal air. All of them had uneventful post-procedural recovery. No clinical or laboratory abnormality was found in this group of patients. The presence of retroperitoneal air was not associated to the variables: precut, biliopancreatic disease type, endoscopic sphincterotomy length, additional endoscopic procedure (balloon exploration, gallstone extraction, stent insertion) or procedure duration. Conclusion: After ERCP with ES, retroperitoneal air is frequently found. In the absence of physical symptoms, retroperitoneal air is not clinically relevant and does not require specific treatment.

CT differentiation between tubo-ovarian and appendiceal origin of right lower quadrant abscess: CT, clinical, and laboratory correlation.

To investigate which clinical, laboratory, and CT findings potentially facilitate the differential diagnosis between tubo-ovarian abscess (TOA) and periappendicular abscess (PAA), we retrospectively reviewed abdominal CT examinations and medical records for all women who presented to our medical center with unilateral right pelvic abscess formation who underwent CT evaluation from 2004-2014. A wide spectrum of clinical data and imaging findings were recorded. CT diagnoses were made in consensus by two experienced body radiologists blinded to the final diagnosis. Findings associated with the infections were compared using the chi-square (χ(2)) or the Fisher exact test. Ninety-one patients were included; 58 with PAA (mean age 46 years) and 33 with TOA (mean age 37 years). Pain on cervical motion (67 %) and vaginal discharge (21 %) were significantly more common in TOA; other clinical signs were similar. The presence of right ovarian vein entering the mass on CT had 100 % specificity and 94 % sensitivity to TOA. Distended right fallopian tube (79 %), mass posterior to mesovarium (76 %), contralateral pelvic fat stranding (55 %), and thickening of sacrouterine ligaments (55 %) were significantly more common in TOA. Positive "arrowhead sign" (91 %), mesenteric lymphadenopathy (85 %), small bowel wall thickening (55 %), fluid in the right paracolic gutter (50 %), and cecal wall thickening (48 %) were significantly more common in PAA;internal gas was revealed only in PAA (33 %). Distinct CT features can increase diagnostic certainty regarding the origin of right lower quadrant abscess in women.

Medicare Policy Initiatives and the Relative Utilization of “Double-Scan” CT

PurposeCommonly called “double scans” by the media, combined pre- and postcontrast thoracic and abdominal CT examinations have been the focus of recent CMS policy initiatives. The aim of this study was to examine trends in the relative utilization of double-scan CT before and after 2006 legislation mandating relevant Medicare reporting initiatives. MethodsMedicare Physician Supplier Procedure Summary Master Files from 2001 through 2012 were used to identify claims for thoracic and abdominal CT examinations. Double-scan rates by billing physician specialty and place of service were analyzed over time. Rates of double-scan CT between radiologists and nonradiologists were compared using t tests. ResultsFrom 2001 to 2006, double-scan rates for thoracic and abdominal CT examinations declined by 1.7% and 7.5% for radiologists, respectively (from 6.0% to 5.9% and from 22.6% to 20.9%) but increased by 15.8% and 23.6% for nonradiologists (from 5.7% to 6.6% and from 28.8% to 35.6%). From 2006 through 2012, double-scan rates declined by 42.3% and 35.2% (from 5.9% to 3.4% and from 20.9% to 13.5%) for radiologists but only by 31.8% and 8.1% (from 6.6% to 4.5% and from 35.6% to 32.7%) for nonradiologists. Double-scan rates were significantly lower for radiologists than nonradiologists for all years for abdominal CT (P < .001) and for all years after 2006 legislation for thoracic CT (P < .05). ConclusionsReductions in thoracic and abdominal CT double-scan rates followed legislation mandating CMS initiatives designed to reduce costs and radiation. For nonradiologists, double-scan rates were consistently higher and declined more slowly than those for radiologists. Medicare policy initiatives directed toward imaging utilization seem to influence behavior differently for radiologists compared with nonradiologists.

TH‐EF‐BRA‐03: Size‐Specific, Scanner‐Independent Fetal Dose Estimates in Abdominal and Pelvic CT Examinations of Pregnant Patients

Purpose:The purpose of this work is to develop patient size‐specific, scanner‐independent CTDIvol‐to‐fetal‐dose conversion coefficients for abdominal and pelvic CT examinations of pregnant patients of various gestational ages.Methods:For 18 pregnant patients of gestational age ranging from 12 to 36 weeks who underwent clinically‐indicated CT examinations, models of maternal and fetal (or embryo) anatomy were created from the image data, and dose to the fetus was estimated using Monte Carlo simulations of fixed tube current helical scans of the abdomen and pelvis for 64‐slice MDCT scanners from four major manufacturers. Fetal doses were normalized by scanner‐specific 32 cm CTDIvol values and averaged across all scanners to obtain a scanner‐independent CTDIvol‐to‐fetal‐dose conversion coefficient for each patient. Patient size was described using water equivalent diameter (WED) measured at the image containing the three‐dimensional geometric centroid of the fetus. The coefficient of variation (CoV) across scanners for the simulated fetal dose was calculated before and after CTDIvol normalization to demonstrate the utility of scanner‐independent CTDIvol‐to‐fetal‐dose conversion coefficients for each patient. The relationship between the WED patient size metric and CTDIvol‐to‐fetal‐dose conversion coefficients was also examined to determine if a correlation exists.Results:The CoV across scanners for fetal dose in all patients before and after CTDIvol normalization ranged from 25.10%–30.16% and 5.60%–9.48%, respectively. An exponential relationship between CTDIvol‐to‐fetal‐dose conversion coefficients and patient size was observed with a coefficient of determination of 0.84.Conclusion:Strong correlation exists between CTDIvol normalized fetal dose and WED. These results indicate that fetal dose from abdominal and pelvic CT examinations of pregnant patients of various gestational ages may be accurately estimated with: (a) fetal dose normalized by CTDIvol to account for scanner variation and (b) a WED patient size metric to account for patient size variation.Disclosures — Michael McNitt‐Gray: Institutional Research Agreement, Siemens AG; Research Support, Siemens AG; Consultant, Flaherty Sensabaugh Bonasso PLLC; Consultant, Fulbright and Jaworski; Disclosures — Erin Angel: Employee of Toshiba America Medical Systems, Inc.

TU-F-CAMPUS-I-03: Preliminary Study of Size-Specific Dose Estimates in Adult Abdomenal CT Examinations in Taiwan

Purpose: This study was to investigate size-specific dose estimates (SSDE) for routine adult abdominal CT examinations in Taiwan. Methods: A national survey was conducted in Taiwan in 2014 to investigate SSDEs for routine adult abdominal CT examinations. The hospitals involved in this study provided CT images of their typical patients. The CT image in the level of the middle liver was selected to record the corresponding tube current, slice mAs or effective mAs. The image was also used to estimate the dimensions of patient as measuring the lengths in the anterior to posterior (AP) and lateral (LAT) directions. The effective diameter was then calculated from AP and LAT, and used to look up conversion factors in the AAPM 204 report. The volume CTDI (CTDIvol) for each CT unit was measured on sites using a 32-cm cylindrical standard dose phantom and a calibrated pencil-type ionization chamber. Individual patient’s SSDEs were then calculated from the corresponding SSDE conversion factor and the CTDIvol. Results: The study cohort included 111 CT units. The ratio of turning on automatic tube current modulation (ATCM) or not is 88:23. Effective diameters are 258.7±25.1 mm (167–366 mm). 99.3% of typical patients selected by each hospital have smaller effective diameter than the 32-cm dosimetry phantom. Adult abdomenal SSDE is 17.5 ± 8.8 mGy (1.9-58 mGy). The SSDE seems to decrease as the effective diameter increases as the ATCM turns off, and independent with the effective diameter as the ATCM turns on. Conclusion: The SSDE for typical patients in Taiwan was investigated. We continue to complete this investigation in 2015 to include more valid data to establish SSDE reference level in Taiwan. This study was financially supported by the Atomic Energy Council in Taiwan.