Mean Total Effective Dose Research Articles

Simultaneous indoor radon/thoron and in situ outdoor gamma dose measurements and estimation of annual effective dose in a tin mining area of Jos Plateau, Nigeria.

Radon, a radioactive gas can increase the risk of lung cancer when breathe in. Indoor Rn-222 and Rn-220 concentrations were determined using passive radon monitor in some dwellings in a Sn mining area of Jos Plateau. Outdoor gamma radiation was also measured with a hand-held survey meter. The range of Rn-222 and Rn-220 concentrations was from 7-53Bq m-3 to 41-267Bq m-3 with averages of 27±17 and 92±65Bq m-3, respectively. The mean total effective dose due to Rn-222+Rn-220 was estimated as 2.84±1.57mSv y-1. Rn-220 contributed between 50 and 95% to the total annual effective dose. There was no correlation between indoor Rn-220 and Rn-222 concentrations in the dwellings. Outdoor gamma radiation measured was between 0.31±0.06 and 0.62±0.08μSv h-1, and mean annual effective dose calculated was 1.14±0.21mSv y-1. It is concluded from this study that thoron should not be neglected in dose assessment.

Radiation Exposure from GEP NET Surveillance.

Neuroendocrine tumors (NET) are neoplasms that secrete peptides and neuroamines. For gastroenteropancreatic (GEP) NET, surgical resection represents the only curative option. Ten-year imaging surveillance programs are recommended due to long time-to-recurrence following resection. We performed retrospective chart review evaluating radiation exposure and practice patterns from surveillance of completely resected GEP NET. We performed a retrospective cohort study of cases with well-differentiated GEP NET from January 2005 to July 2020. Location of primary, modality of imaging, and duration of follow-up were collected. Dosimetry data was collected to calculate effective dose. 62 cases were included with 422 surveillance scans performed. Cross-sectional imaging was used in 82% and functional imaging was used in 18% of scans. Mean number of scans per year was 1.25 (0.42-3). Mean total effective dose was 56.05 mSv (SD 45.56; 0 to 198 mSv) while mean total effective dose per year was 10.62 mSv (SD 9.35; 0 to 45 mSv). Over the recommended ten years of surveillance the estimated total effective dose was 106 mSv. Surveillance of completely resected GEP NET results in cumulative radiation doses in the range associated with secondary malignancy development. Strategies to minimize radiation exposure in surveillance should be considered in future guideline development.

Modified Dynamic CT Myelography for Type 1 and 2 CSF Leaks: A Procedural Approach.

Dynamic CT myelography can identify spinal CSF leaks secondary to dural tears (type 1) and ruptured meningeal diverticula (type 2), but the radiation can be high secondary to multiple successive acquisitions. The purpose of this article is to discuss the procedural approach of a modified dynamic CT myelography technique with single scan acquisitions, reduced contrast volume, and condensed scan coverage and compare its radiation dose with that in traditional dynamic CT myelography. Retrospective review was performed for patients with spontaneous CSF leaks showing extradural collections on spine MR imaging who underwent traditional and modified dynamic CT myelography. The radiation doses between the 2 cohorts were compared. Thirty-seven patients (25 women, 12 men) had a type 1 or 2 CSF leak on dynamic CT myelography. Thirty-one patients had a type 1 CSF leak, and 6 patients had type 2 leaks. The traditional dynamic CT myelography was performed in 25 patients, and the average number of acquisitions per dynamic CT myelography was 3.6. The mean total effective dose per dynamic CT myelography was 31.3 mSv (range, 11.3-68.4 mSv). The modified dynamic CT myelography was performed in 12 patients, and the average number of acquisitions was 2.8. The mean total effective dose per dynamic CT myelography was 15.1 mSv (range, 4.8-24.6 mSv). The effective dose and dose-length product between the cohorts were statistically significant (P < .0001 and .01, respectively). Modified dynamic CT myelography performed with single scan acquisitions, smaller volume of contrast, and reduced scan coverage can reduce the radiation dose for type 1 and 2 CSF leak detection.

Oxidative Modification Status of Human Serum Albumin Caused by Chronic Low-Dose Radiation Exposure in Mamuju, Sulawesi, Indonesia.

The recently discovered high-level natural background radiation area (HBRA) of Mamuju in Indonesia provides a unique opportunity to study the biological effects of chronic low-dose radiation exposure on a human population. The mean total effective dose in the HBRA was approximately 69.6 mSv y-1 (range: 47.1 to 115.2 mSv y-1), based on a re-evaluation of the individual radiation exposure dose; therefore, proteomic analyses of serum components and oxidative modification profiling of residents living in the HBRA were reconducted using liquid chromatography-tandem mass spectrometry. The analysis of the oxidative modification sequences of human serum albumin revealed significant moderate correlations between the radiation dose and the modification of 12 sequences, especially the 111th methionine, 162nd tyrosine, 356th tyrosine, and 470th methionine residues. In addition, a dose-dependent variation in 15 proteins of the serum components was detected in the serum of residents exposed to chronic low-dose radiation. These findings suggest that the alterations in the expression of specific proteins and the oxidative modification responses of serum albumin found in exposed humans may be important indicators for considering the effects of chronic low-dose radiation exposure on living organisms, implying their potential utility as biomarkers of radiation dose estimation.

Estimation of Natural Radioactivity in some Popular Drinks in Nigeria and its Radiological Effect

The activity concentration on natural radionuclide in some samples of commonly consumed drinks have been determined using a gamma spectrometer, NaI detector. The mean activity concentration of 40K, 232Th, and 238U in the drink samples were estimated to be 23.76 ± 1.57, 1.55 ± 0.11, and 0.78 ± 0.16 Bq/L respectively. The mean effective dose equivalent of these natural radionuclides in food drinks are 5.77, 15.35, and 11.13 µSv/y respectively for 40K, 232Th, and 238U, while the mean total effective dose equivalent from all the natural radionuclides is 32.25 µSv/y. This value is less than the 0.1 mSv/y and 1 mSv/y recommendation of WHO and NCRP respectively for maximum permissible effective dose for public exposure. The excess lifetime cancer risk was estimated to be 1.13 x 10-4, which is lower than the world average. This is an indication that there is no significant cancer risk to humans as a result of the radionuclides consumption from these food drinks.

Recent Survey of Effective Doses of F-18 FDG Torso PET/CT in Korea and the Current Recommendations for CT Protocols of PET/CT.

This study aimed to construct a database of the effective doses (ED) from F-18 fluorodeoxyglucose (FDG) torso positron emission tomography/computed tomography (PET/CT) in Korea to provide data that supports the reduction of the CT dose of PET/CT and optimization of PET/CT protocols in Korea. We investigated data of ED and CT parameters of FDG PET/CT. The data were analyzed by body weight groups. A total of 31 hospitals participated in the survey (99 adults). The mean total EDs (± SD) were 8.77 ± 2.76, 10.93 ± 3.14, and 12.57 ± 3.79mSv for the 55-, 70-, and 85-kg groups, respectively. The FDG EDs were 4.80 ± 0.98, 6.05 ± 1.15, and 6.89 ± 1.52mSv, and the CT EDs were 4.00 ± 2.12, 4.88 ± 2.51, and 5.68 ± 2.89mSv, respectively. Of the enrolled hospitals, 54.5% used ultra-low-dose CT protocols, and their CT ED was significantly lower than low-dose CT group in all groups (2.9 ± 1.0, 3.2 ± 1.1, and 3.3 ± 1.0mSv vs. 6.6 ± 1.6, 7.2 ± 2.1, and 7.9 ± 2.2mSv, all p < 0.001, respectively). In the ultra-low-dose CT group, the CT ED with the iterative reconstruction was significantly lower than that of CT without iterative reconstruction in the 55-kg group (2.4 ± 0.9 vs. 3.3 ± 0.9, p = 0.04). These results and current recommendations can be helpful for optimizing PET/CT diagnostic reference level (DRL) and reducing unnecessary PET/CT radiation exposure.

PET-Based Human Dosimetry of 68Ga-NODAGA-Exendin-4, a Tracer for β-Cell Imaging.

68Ga-NODAGA-exendin-4 is a promising tracer for β-cell imaging using PET/CT. Possible applications include preoperative visualization of insulinomas and discrimination between focal and diffuse forms of congenital hyperinsulinism. There is also a significant role for this tracer in extending our knowledge on the role of β-cell mass in the pathophysiology of type 1 and type 2 diabetes by enabling noninvasive quantification of tracer uptake as a measure for β-cell mass. Calculating radiation doses from this tracer is important to assess its safety for use in patients (including young children) with benign diseases and healthy individuals. Methods: Six patients with hyperinsulinemic hypoglycemia were included. After intravenous injection of 100 MBq of the tracer, 4 successive PET/CT scans were obtained at 30, 60, 120, and 240 min after injection. Tracer activity in the pancreas, kidneys, duodenum, and remainder of the body were determined, and time-integrated activity coefficients for the measured organs were calculated. OLINDA/EXM software, version 1.1, was applied to calculate radiation doses using the reference adult male and female models and to estimate radiation doses to children. Results: The mean total effective dose for adults was very low (0.71 ± 0.07 mSv for a standard injected dose of 100 MBq). The organ with the highest absorbed dose was the kidney (47.3 ± 10.2 mGy/100 MBq). The estimated effective dose was 2.32 ± 0.32 mSv for an injected dose of 20 MBq in newborns. This dose decreased to 0.77 ± 0.11 mSv/20 MBq for 1-y-old children and 0.59 ± 0.05 mSv for an injected dose of 30 MBq in 5-y-old children. Conclusion: Our human PET/CT-based dosimetric calculations show that the effective radiation doses from the novel tracer 68Ga-NODAGA-exendin-4 are very low for adults and children. The doses are lower than reported for other polypeptide tracers such as somatostatin analogs (2.1–2.6 mSv/100 MBq) and are beneficial for application as a research tool, especially when repeated examinations are needed.

319. Effective Dose Assessment on an Hybrid Equipment: Results and challenges to integrate with MDCT

Purpose The aim of this study was to measure, monitor and report effective dose in nuclear medicine and to assess current challenges in integrating these measures with CT. Methods In 2014 we connected a CT-PET to a dose tracking software and started to collect dose data from CT modality; in late 2015 the software was upgraded to a version which includes a nuclear medicine module for dose tracking. Data from the PET part of the scanner, in terms of administered activity and effective dose, were also collected. Results Data from 12000 CT doses and 3700 PET doses were collected, mostly from: Whole Body (WB) 18F-FDG (63.2%), WB 11C-Choline (12.8%), WB 68Ga-DOTATOC (5.5%), Head 11C-Methionine for a total of 18.4% of the whole activity of the scanner. CT mean DLP (mGy∗cm) data values were (range between brackets): WB 18F-FDG 1486.3 (76.1-7700.9), WB 11C-Choline 2451.9 (290.9-5023.1), WB 68Ga-DOTATOC 1183.8 (41.0-3728.4) and Head 11C-Methionine 766.7 (52.3-2326.9). Mean effective doses (mSv) were: WB 18F-FDG 15.3 ± 4.7, WB 11C-Choline 26.5 ± 5.6, WB 68Ga 13.4 ± 3.7 and Head 11C-Methionine 1.2 ± 0.7. Mean administered activities (MBq) and effective doses (mSv) for radiopharmaceuticals used in PET were: WB 18F-FDG 335.9-6.4, Head 11C-Methionine 294.6-2.5, WB 68Ga-DOTATOC 168.3-3.5 and WB 11C-Choline 322.2–1.5. The mean total effective doses (mSv) due to both modality were: WB 18F-FDG 21.7 ± 4.9, Head 11C-Methionine 3.7 ± 0.8, WB 11 C-Choline 27.9 ± 5.6 and WB 68Ga-DOTATOC 16.9 ± 2.8. Conclusions The implementation of a dose tracking system to nuclear medicine is of great value for accurate and regular recording, reporting and analysis of patient’s effective doses. It can help to improve the evaluation of radiation exposures in the clinical practice.

265. Optimization of a three-phase computed tomography urography (CTU) protocol with retrospective and prospective study

Purpose To optimize a three-phase CTU in order to obtain the best trade-off between image quality and radiation dose. Methods and materials Considering the increase in CT examinations in our hospital, a high dose clinical protocols optimization program was undertaken. A CTU protocol was optimized, with 128-slice Siemens tomography, with CareDose4D for the real-time mA modulation. Starting from a retrospective analysis of a cohort of 43 patients (medium weight 66,9 kg), in terms of CTDIvol and SSDE (Size Specific Dose Estimates), we obtained a mean total effective dose of 26,7 mSv (estimated with CTExpo V2.0). Analyzing each protocol phase we realized to have a high margin to reduce dose. Taking as starting point AAPM indications [1] we identified a set of candidate protocols and used them for Catphan 600 Phantom acquisitions, all with automatic dose modulation and different mAs ref options. The quality reference mAs ref represents the effective mAs (mA x rotation time/pitch) value suitable for an average-sized patient weighing 70–80 kg. We analyzed image quality of the scans in terms of noise, spatial resolution and low contrast, and then we chose the protocol to be clinically validated. Finally we made a prospective analysis of 18 patients (medium weight 66,4 kg), again in terms of CTDIvol, SSDE and effective dose. Results Among all phantom acquisitions we chose a protocol with a noise decrease of 11% and a minimal loss of contrast (0,09% on 3 mm detail). The MTF50 value passes from 3,21 lp/mm to 3,08 lp/mm. The main radiological parameters of the protocol are summarized in the table below (gray for old protocol, white for the new one). The mean effective dose passed from 25,7 mSv to 14,1 mSv. Conclusions It was possible to reduce the dose by 45% without affecting the image quality.

P080] Assessment of effective dose in hybrid imaging

Purpose The aim of this study is to assess the typical doses associated with PET/CT examination in a large population and to evaluate the difference of effective dose estimation in fixed vs patient-adapted activity utilizing the same imaging protocols. Doses differences in the urinary bladder are also estimated for PET examination. Methods and materials DoseWatch™ tracking system was utilized to collect patient information and to measure effective dose (for WB 18 F-FDG PET/CT) and organ dose data (for PET only) associated with a fixed activity by retrospectively analyzing existing data. For CT examination DLP values and effective dose data was collected; for PET examination DoseWatch™ provides the administered activity, the effective and the organ doses, based on ICRP 106. Effective and organ dose (for PET only) in a PET/CT examination where the administered activity is adapted to the patient’s weight will be estimated from the same database using a theoretical calculation. The dose in the urinary bladder is also assessed on theoretical calculations. Results Dose data from 6900 CT and 1700 WB 18F-FDG PET were collected. CT mean DLP (mGy*cm) data values were: 1481.3 (76.1–7700.9) and mean effective doses (mSv): 15.2 ± 4.9. Mean administered activities (MBq) and effective doses (mSv) for 18F-FDG PET are: 333.9–6.4. The mean total effective doses (mSv) due to both modality are: 21.5 ± 5.2. equivalent doses (mSv) to urinary bladder are: 43.7 ± 5.8. Conclusions The implementation of a dose tracking system in nuclear medicine is of great value for accurate and regular recording, reporting and analysis of patient’s effective doses.

OA144] Measuring, monitoring and reporting effective dose on hybrid equipment: Results and challanges to integrate with MDCT in a large population study

Purpose The aim of this study was to measure, monitor and report the effective dose in nuclear medicine on s large population and to integrate these measurements with CT dose data. Methods and materials A dose tracking software (GE Dosewatch™) with a NM module was connected to a CT-PET and collected DLP and effective dose from CT modality and administered activity and effective from PET modality. The mean DLP and the mean effective doses with the ranges was assessed for CT. The mean administered activities and mean effective doses for the different radiopharmaceuticals used in PET were evaluated. Examinations were performed with a GE Discovery 690 which has a 64-detector CT scanner; PET scan is performed in stop and go imaging mode. Results Doses data from 11000 CT and 2700 PET were collected, mostly from: Whole Body (WB) 18F-FDG (63.2%), WB 11C-Choline (12.8%), Head 11C-Methionine (18.4%), WB 68Ga-DOTATOC (5.5%). CT mean DLP (mGy*cm) data values were (range between brackets): WB 18F-FDG 1486.3 (76.1-7700.9), WB 11C-Choline 2451.9 (290.9-5023.1), WB 68Ga-DOTATOC 1184.2 (41.0-3728.4) and Head 11C-Methionine 766.7 (52.3-2326.9). Mean effective doses due to CT modality (mSv) were: WB 18F-FDG 15.3 ± 4.7, WB 11C-Choline 26.5 ± 5.6, WB 68Ga-DOTATOC 13.4 ± 2.7 and Head 11C-Methionine 1.7 ± 2.9. Mean administered activity (MBq) and effective doses (mSv) for radiopharmaceuticals used in PET were: WB 18F-FDG 335.9-6.4, Head 11C-Methionine 294.4.6-2.5, WB 68Ga-DOTATOC 168.3-3.5 and WB 11C-Choline 322.2-1.5. The mean total effective doses (mSv) due to both modality were: WB 18F-FDG 21.7 ± 4.9, Head 11C-Methionine 4.3 ± 2.9, WB 11C-Choline 27.9 ± 5.6 and WB 68Ga-DOTATOC 16.9 ± 2.8. Conclusions The implementation of a dose tracking system in nuclear medicine is of great value for accurate and regular recording, reporting and analysis of patient’s effective doses. It can help to improve and optimize the evaluation of radiation exposures in the clinical practice.

Radiation dose reduction through combining positron emission tomography/computed tomography (PET/CT) and diagnostic CT in children and young adults with lymphoma.

Both [F-18]2-fluoro-2-deoxyglucose positron emission tomography/computed tomography (18F-FDG PET/CT) and diagnostic CT are at times required for lymphoma staging. This means some body segments are exposed twice to X-rays for generation of CT data (diagnostic CT + localization CT). To describe a combined PET/diagnostic CT approach that modulates CT tube current along the z-axis, providing diagnostic CT of some body segments and localization CT of the remaining body segments, thereby reducing patient radiation dose. We retrospectively compared total patient radiation dose between combined PET/diagnostic CT and separately acquired PET/CT and diagnostic CT exams. When available, we calculated effective doses for both approaches in the same patient; otherwise, we used data from patients of similar size. To confirm image quality, we compared image noise (Hounsfield unit [HU] standard deviation) as measured in the liver on both combined and separately acquired diagnostic CT images. We used t-tests for dose comparisons and two one-sided tests for image-quality equivalence testing. Mean total effective dose for the CT component of the combined and separately acquired diagnostic CT exams were 6.20±2.69 and 8.17±2.61mSv, respectively (P<0.0001). Average dose savings with the combined approach was 24.8±17.8% (2.60±2.51mSv [range: 0.32-4.72mSv]) of total CT effective dose. Image noise was not statistically significantly different between approaches (12.2±1.8 HU vs. 11.7±1.5 HU for the combined and separately acquired diagnostic CT images, respectively). A combined PET/diagnostic CT approach as described offers dose savings at similar image quality for children and young adults with lymphoma who have indications for both PET and diagnostic CT examinations.

How Does Patient Radiation Exposure Compare With Low-dose O-arm Versus Fluoroscopy for Pedicle Screw Placement in Idiopathic Scoliosis?

Intraoperative C-arm fluoroscopy and low-dose O-arm are both reasonable means to assist in screw placement for idiopathic scoliosis surgery. Both using pediatric low-dose O-arm settings and minimizing the number of radiographs during C-arm fluoroscopy guidance decrease patient radiation exposure and its deleterious biological effect that may be associated with cancer risk. We hypothesized that the radiation dose for C-arm-guided fluoroscopy is no less than low-dose O-arm scanning for placement of pedicle screws. A multicenter matched-control cohort study of 28 patients in total was conducted. Fourteen patients who underwent O-arm-guided pedicle screw insertion for spinal fusion surgery in 1 institution were matched to another 14 patients who underwent C-arm fluoroscopy guidance in the other institution in terms of the age of surgery, body weight, and number of imaged spine levels. The total effective dose was compared. A low-dose pediatric protocol was used for all O-arm scans with an effective dose of 0.65 mSv per scan. The effective dose of C-arm fluoroscopy was determined using anthropomorphic phantoms that represented the thoracic and lumbar spine in anteroposterior and lateral views, respectively. The clinical outcome and complications of all patients were documented. The mean total effective dose for the O-arm group was approximately 4 times higher than that of the C-arm group (P<0.0001). The effective dose for the C-arm patients had high variability based on fluoroscopy time and did not correlate with the number of imaged spine levels or body weight. The effective dose of 1 low-dose pediatric O-arm scan approximated 85 seconds of the C-arm fluoroscopy time. All patients had satisfactory clinical outcomes without major complications that required returning to the operating room. Radiation exposure required for O-arm scans can be higher than that required for C-arm fluoroscopy, but it depends on fluoroscopy time. Inclusion of more medical centers and surgeons will better account for the variability of C-arm dose due to distinct patient characteristics, surgeon's preference, and individual institution's protocol. Level III-case-control study.

Radiation dosimetry of 18F-FDG PET/CT: incorporating exam-specific parameters in dose estimates.

BackgroundWhole body fluorine-18 fluorodeoxyglucose positron emission tomography/computed tomography (PET/CT) is the standard of care in oncologic diagnosis and staging, and patient radiation dose must be well understood to balance exam benefits with the risk from radiation exposure. Although reference PET/CT patient doses are available, the potential for widely varying total dose prompts evaluation of clinic-specific patient dose. The aims of this study were to use exam-specific information to characterize the radiation dosimetry of PET/CT exams that used two different CT techniques for adult oncology patients and evaluate the practicality of employing an exam-specific approach to dose estimation.MethodsWhole body PET/CT scans from two sets of consecutive adult patients were retrospectively reviewed. One set received a PET scan with a standard registration CT and the other a PET scan with a diagnostic quality CT. PET dose was calculated by modifying the standard reference phantoms in OLINDA/EXM 1.1 with patient-specific organ mass. CT dose was calculated using patient-specific data in ImPACT. International Commission on Radiological Protection publication 103 tissue weighting coefficients were used for effective dose.ResultsOne hundred eighty three adult scans were evaluated (95 men, 88 women). The mean patient-specific effective dose from a mean injected 18F-FDG activity of 450 ± 32 MBq was 9.0 ± 1.6 mSv. For all standard PET/CT patients, mean effective mAs was 39 ± 11 mAs, mean CT effective dose was 5.0 ± 1.0 mSv and mean total effective dose was 14 ± 1.3 mSv. For all diagnostic PET/CT patients, mean effective mAs was 120 ± 51 mAs, mean CT effective dose was 15.4 ± 5.0 mSv and mean total effective dose was 24.4 ± 4.3 mSv. The five organs receiving the highest organ equivalent doses in all exams were bladder, heart, brain, liver and lungs.ConclusionsPatient-specific parameters optimize the patient dosimetry utilized in the medical justification of whole body PET/CT referrals and optimization of PET and CT acquisition parameters. Incorporating patient-specific data into dose estimates is a worthwhile effort for characterizing patient dose, and the specific dosimetric information assists in the justification of risk and optimization of PET/CT.

Radiation dosage in the urolithiasis population: Do we over-radiate our patients?

Introduction: There is increasing concern about the amount of radiation that patients with urolithiasis receive. Ensuring patients are exposed to the minimum necessary radiation is imperative. Here we review the radiation dosages that newly diagnosed urolithiasis patients received in the year following their presentation, both those presenting acutely and those referred electively. Patients and methods: A retrospective study of 95 treatment-naïve patients (47 acute, 48 elective) referred for management of urolithiasis was undertaken. The analysis included all imaging modalities related to stone disease for both patient groups within one year following presentation. The total effective dose (mSV) in one year was calculated by summing the dose for each individual radiation exposure. Results: An average of 5.6 radiological investigations (range 1–14) was carried out for acute patients and 4.57 for elective patients (range 1–11). The mean total effective dose was 14.45 mSV for the acute cases and 12.87 mSV for the elective cases. The maximum radiation dose reached 30.1 mSV in acute patients and 36.51 mSV in elective ones. None of the patients exceeded the maximal annual dose recommended by the International Commission on Radiological Protection (ICRP) of 50 mSV. Conclusion: Management of acute and elective urolithiasis patients can be achieved with acceptable radiation dose exposure. It is extremely important to keep the hazards of radiation in mind whilst managing patients with urolithiasis and clinicians need to remember adherence to the ALARA principle.

Characterization of uranium and its progenies in drinking water and assessment of dose to public around a NHBRA, Odisha, India

Present work deals with the distribution study of naturally occurring radioactive materials in drinking water samples around Orissa sands complex, Odisha, India and assessment of the comprehensive ingestion dose to members of the public. The mean total effective dose to member of public is found to be 67.1 µSv/y with a range of 13.2–198.5 µSv/y. The average effective dose is below the reference level of 100 µSv/y and also comparable with the range of global annual ingestion dose value reported worldwide. The activity concentration in drinking water reported here is due to natural distribution of radioanuclides.

The use of bedside chest radiography at a university hospital. Data on a two-week period

To evaluate the requests for bedside chest radiography (BCR) by clinicians. After IRB approval, we retrieved the patients' clinical records for demographics, unit, and duration for recovery in a two weeks period. For each BCR, exposure data and the reason for BCR were registered. The BCR results were categorized as one or more of the followings: negative, regular/irregular device position, known finding(s) unmodified/modified in respect with the previous BCR, new expected finding(s) (pleural effusion, low ventilation), or new unexpected findings (pulmonary edema, pneumothorax). As a utility indicator of BCR, we considered the rate of chest CT performed in these patients during the study period and the following week. We have estimated the effective radiation dose. A total of 337 BCRs (126 patients) entered the analysis, 74% of them being performed in post-surgery intensive care unit. Seventy-3 patients (58%) performed 1 or 2 BCRs, 53 (42%) 3 or more BCRs with a maximum of 13 BCRs performed on a newborn. The mean total effective dose was 0.2 mSv/patient (maximum 1 mSv). In post-surgery intensive care unit the mean daily BCR rate was 0.8/day (maximum 2/day). On 337 BCR requests, 49% showed no motivations at all, 42% reported the word "check" and in 9% a well-defined clinical query was specified. The rate of incorrect catheter position and new unexpected findings was 4%. One chest CT have been requested. BCR is often requested as a routine examination with a little rate of unexpected findings.

Radiation exposure during computed tomography-guided cryoablation of renal masses.

e15116 Background: Despite heightened awareness of risks from ionizing radiation, the use of image-guided therapy is rising. Our goal was to calculate the radiation effective dose (ED) received during computed tomography (CT)-guided percutaneous cryoablation (PC) of renal masses. Methods: A retrospective chart review from January 2008 to June 2009 found 21 patients had undergone CT-guided PC. Using radiation dose estimates from the procedures based on a standard anthropomorphic phantom, mean radiation ED was estimated. Fluoroscopy time and total ED were used to compute the learning curve which was assessed with correlation testing. Results: We performed PC on 24 masses ranging from 0.9-8.0cm. Mean patient age, body mass index, and lesion size were 65.8 years, 28.3, and 2.9 cm, respectively. For each mass ablated, mean fluoroscopy time was 46.4 seconds (range 11.4-143.4 sec), mean fluoroscopy ED was 8.2 mSv (range 1.9-28.0 mSv), and mean total ED was 21.6 mSv (range 10.1-37.5 mSv). We estimated the learning curve by dividing the 24 masses into quartiles and calculated the mean mass size, fluoroscopy time, and total ED per quartile. There was a 59.3% decrease in fluoroscopy time and a 39.4% decrease in total ED between the 1st and 4th quartile despite a 17.7% increase in mass size. Fluoroscopy time was moderately correlated with case number (R2=0.32). When plotting fluoroscopy time utilized per individual mass versus case number a decline was seen (R2=0.35). Fluoroscopy time alone was minimally correlated with mass size (R2=0.19) and not at all with BMI (R2=0.05). Conclusions: Fluoroscopy time declined as operator experience increased, subjecting patients to less radiation exposure. Mean total radiation ED was 21.6 mSv for all cases. For comparison, three-phase renal CT ED on our scanner was 23.7 mSv. While the greatest decline in fluoroscopy time (51.0%) occurred between the 1st and 2nd quartile, there was still an 11.0% time decrease between the 3rd and 4th quartile suggesting continued improvement in the learning curve. No significant financial relationships to disclose.

Effective Radiation Dose from Radiologic Studies in Pediatric Trauma Patients

Evaluation of the pediatric trauma patient frequently requires radiologic studies. Although low-dose radiation from diagnostic radiology is considered safe, lifetime risks per unit dose of radiation are increased in children compared to adults. The total effective dose of radiation to a typical pediatric trauma patient is unknown. We sought to estimate the total effective dose of radiation related to the radiologic assessment of injured children admitted to a pediatric Level I trauma center. We reviewed the radiology records of all children admitted directly to a trauma center in 2002 and tabulated all plain films, computed tomograms, angiographic/fluoroscopic studies, and nuclear medicine studies. Using age-adjusted effective doses (which incorporate biologic effects of radiation), we computed each patient's total effective dose of radiation. Of 506 admitted patients, 394 (78%) underwent at least one radiologic study. The mean total effective dose per patient was 14.9 mSv (median: 7.2 mSv; interquartile range: 2.2-27.4 mSv). On average, computed tomography accounted for 97.5% of total effective dose. Age and injury severity score did not predict total effective dose. We conclude that in pediatric trauma patients, the estimated total effective dose of radiation varied widely. Computed tomography contributed virtually the entire total effective dose. Regarding radiographic evaluation of pediatric trauma patients, the risks and benefits of current practices should continue to be evaluated critically, because lifetime risks associated with radiation exposure are inversely proportional to age at exposure.