Adult Computed Tomography Scans Research Articles

Impact of Implementing National Diagnostic Reference Levels on Radiation Dose Optimization in Adult Chest CT Scans: A Comparative Analysis

The management and optimization of radiation dose in computed tomography (CT) examinations is of paramount importance, especially when the safety of patients is concerned. This study evaluated the effect of implementing national diagnostic reference levels (NDRLs) for radiation dose optimization in 1,991 adult chest CT scans at a major Saudi hospital. Data was analyzed before and after NDRL implementation, with 21.5% of scans using contrast and 78.5% without. Before implementation, 11.1% used contrast and 36.7% did not; after implementation, 10.4% used contrast and 41.7% did not. The majority (83.5%) of scans passed NDRL criteria [CTDIvol and DLP are set at 12 (mGy) and 430 (mGy·cm)], with higher pass rates for contrast (91.8%) versus non-contrast (81.5%) scans. Effective dose (ED) was compared before and after NDRL implementation. For non-contrast scans, ED declined 2.43% from 12.37±5.25 mSv to 12.07±4.99 mSv after implementation (non-significant, p>0.05). For contrast scans, ED declined more substantially, 6.77% from 9.6±4.61 mSv to 8.95±4.44 mSv (non-significant, p>0.05). The findings highlight higher NDRL compliance in procedures with contrast and show areas for dose optimization improvement in procedures without contrast. Results suggest NDRLs provide guidance for optimizing radiation dose, but other factors like patient characteristics, protocol settings, and quality assurance programs should also be considered to ensure doses are as low as reasonably achievable (ALARA) without compromising diagnostic quality. Regular monitoring and review of CT protocols is recommended to avoid unintended consequences of dose reduction. Continued optimization is encouraged to reduce dose while ensuring quality.

Diagnostic Reference Levels of Radiographic and CT Examinations in Jordan: A Systematic Review.

A comprehensive search was performed to examine the literature on diagnostic reference levels (DRL) for computed tomography (CT) and radiography examinations that are performed routinely in Jordan. EBSCO, Scopus, and Web of Science were used for the search. The acronym "DRL" and the additional phrase "dose reference levels" were used to search for articles in literature. Seven papers that reported DRL values for radiography and CT scans in Jordan were identified. One study reported DRLs for conventional radiography, two studies reported CT DRLs in pediatrics, and the remaining four studies provided DRL values for adult CT scans. The most popular techniques for determining the DRLs were the entrance surface dose, volume CT dose index (CTDIvol), and dose-length product (DLP) values. Variations in Jordanian DRL values were noted across both modalities. Lower radiation doses and less variation in DRL values may be achieved by educating and training radiographers to better understand dose reduction strategies. To limit dose variance and enable dosage comparison, CT DRLs must be standardized in accordance with the guidelines of the International Commission on Radiological Protection (ICRP).

An observational study ascertaining the prevalence of bullae and blebs in young, healthy adults and its possible implications for scuba diving.

Introduction: Intrapulmonary air-filled cavities, e.g., bullae, blebs, and cysts, are believed to contribute topulmonary barotrauma (PBT) and arterial gas embolism (AGE) in divers. However, literature is unclear about the prevalence of bullae in healthy adults, ranging from 2.3-33.8%. While this could in part be explained due to increasing quality of radiologic imaging, such as computed tomography (CT) scans, other methodological factors may also affect these findings. This study aims to ascertain the prevalence of bullae in young and healthy adults. Methods: This single-center cross-sectional observational study re-assessed the CT scans of adults (aged 18-40) performed for a clinical suspicion for pulmonary embolism, from 1 January 2016 to 1 March 2020. Presence of bullae was recorded in an electronic database. Chi-square and Fisher exact tests were used for statistical analyses. Additionally, a multivariate logistic regression analysis was performed to study the independent predictive value of identified risk factors. Results: A total of 1,014 cases were identified, of which 836 could be included. Distribution amongst age groups (18-25, 26-30, 31-35, and 36-40) was almost equally, however, 75% of the population was female. Of the male proportion, 41% smoked, compared to 27% in females. In 7.2% (95% CI 5.6-9.1) bullae were identified. The prevalence increased with increasing age (p < 0.001), with odd ratios up to 5.347 (95% CI 2.164-13.213, p < 0.001) in the oldest age group. Males and smokers had higher odds ratios for bullae of 2.460 (95% CI 1.144-4.208; p = 0.001) and 3.406 (95% CI 1.878-6.157, p < 0.001), respectively. Similar results were seen in the multivariate logistic regression analysis, where age, male sex and smoking were all statistically significant independent risk factors for bullae. Discussion: Bullae were seen in 7.2% of a healthy population up to 40years old. Increasing age, smoking, and being male were identified as statistically significant risk factors, both in independent and in multivariate logistic regression analyses. Our observations may warrant a re-evaluation of the contribution of bullae to PBT and AGE, as the latter two occur very rarely and bullae appear to be more frequently present than earlier assumed.

Idiopathic pulmonary fibrosis is more strongly associated with coronary artery disease than chronic obstructive pulmonary disease

IntroductionPrevious studies have shown that the population attributable risk of low forced expiratory volume in one second (FEV1) for coronary artery disease (CAD) is substantial. FEV1 can be low either because of airflow obstruction or ventilatory restriction. It is not known if low FEV1 arising from spirometric obstruction or restriction are differently associated with CAD. MethodsWe analyzed high resolution computed tomography (CT) scans acquired at full inspiration in lifetime non-smoker adults with no lung disease (controls) and those with chronic obstructive pulmonary disease enrolled in the Genetic Epidemiology of COPD (COPDGene) study. We also analyzed CT scans of adults with idiopathic pulmonary fibrosis (IPF) from a cohort of patients attending a quaternary referral clinic. Participants with IPF were matched 1:1 by FEV1 %predicted to adults with COPD and 1:1 by age to lifetime non-smokers.Coronary artery calcium (CAC), a surrogate for CAD, was measured by visual quantification on CT using the Weston score. Significant CAC was defined as Weston score ≥7. Multivariable regression models were used to test the association of the presence of COPD or IPF with CAC, with adjustment for age, sex, body-mass-index, smoking status, hypertension, diabetes mellitus, and hyperlipidemia. ResultsWe included 732 subjects in the study; 244 with IPF, 244 with COPD, and 244 lifetime non-smokers. The mean (SD) age was 72.6 (8.1), 62.6 (7.4), and 67.3 (6.6) years, and median (IQR) CAC was 6 (6), 2 (6), and 1 (4), in IPF, COPD, and non-smokers, respectively. On multivariable analyses, the presence of COPD was associated with higher CAC compared to non-smokers (adjusted regression coefficient, β = 1.10 ± SE0.51; P = 0.031). The presence of IPF was also associated with higher CAC compared to non-smokers (β = 03.43 ± SE0.41; P < 0.001). The adjusted odds ratio for having significant CAC was 1.3, 95% CI 0.6 to 2.8; P = 0.53 in COPD and 5.6, 95% CI 2.9 to 10.9; P < 0.001 in IPF, compared to non-smokers. In sex stratified analyses, these associations were mainly noted in women. ConclusionAdults with IPF displayed higher coronary artery calcium than those with COPD after accounting for age and lung function impairment.

The Determination of Diagnostic Reference Range (DRR) Based on Clinical Indications in Head Computed Tomography (CT) Imaging

Diagnostic reference range (DRR) were introduced to help manage image quality as well as patient dose by providing minimum estimated dose that covers 25–75% range of dose distribution. The International Commission on Radiological Protection (ICRP) (2017) recommended 75th percentile as upper boundary and 25th percentile as lower boundary of DRR [1]. Dose below the lower range should compromised accurate interpretation of the image and dose above the upper range may be in excess and need to be reviewed. Meanwhile, Diagnostic Reference Levels (DRLs) also recommended by ICRP as a guidance to identify any uncommon high dose delivered by computed tomography (CT) scanner. DRLs are established at 75th percentile of dose distribution and should be implemented at international, regional, or local level for dose management.&#x0D;  &#x0D; This study aims to establish a local DRR based on five most common clinical indications for adult head CT scanning at Department of Radiology, Hospital Universiti Sains Malaysia (HUSM), Kelantan. This study involved a retrospective survey on adult patient data undergone head CT scan with two CT scanners, Toshiba CT scanner at Trauma Department and Siemens CT scanner at Radiology Department, HUSM. The related data regarding the scanning protocols and dose descriptor (dose length product, DLP) were recorded for the most common clinical indication in head CT scans.&#x0D;  &#x0D; Results showed the five most common clinical indication related to head CT scans were abscess, bleeding, stroke, trauma, and tumour. The DLP values were varied based on their clinical indications and CT scanner types.  Figure 1 shows boxplots representing the DRRs of dose length product (DLP) based on the five most common clinical indications in head CT scans for Toshiba and Siemens CT scanners. From the figure, the DLP ranges for Toshiba CT scanner were slightly higher than Siemens CT scanners. The lowest DLP value was observed for tumour indication and the highest DLP was bleeding and trauma indications. Clinical indication that requires higher image resolution and details and longer scan length, recorded higher DLP distribution.&#x0D; This study demonstrates that the dose descriptor values, CTDIvol and DLP were varied for similar anatomical region based on different image quality requirement for each clinical indication. Therefore, DRR and DRL should be established based on specific clinical indication and routine dose audit is essential to ensure patients safety. 

Poor practice and governance in Lebanese national diagnostic reference levels of adult head and body computed tomography: A nationwide study

Lebanon has one of the highest number of computed tomography (CT) scanners per capita in the world which could likely be one of the causative factors of its high cancer incidence. In this study, we aimed to establish a national diagnostic reference level (NDRL) in adult CT examinations of the head and body in Lebanon. Dose Length Product (DLP) (n = 2730) were recorded in 91 hospitals/centers in Lebanon for head, chest, and abdomen-pelvis CT. Data was obtained from adult patients (≥18 years) with a weight range of 75–80 kg, from January 2018 until December 2019. Then, the median, mean and 75th percentile of the DLP was calculated for each anatomical region. NDRL was reported as the 75th percentile. Then, the established NDRL was benchmarked with international countries as the USA, UK, and Australia. In our study, data were collected from imaging departments (n = 91), with a response rate of 65% of the national total. All CT scanners ranged from 1 to 256 slices. The 75th percentile for the DLP of the head, chest, and abdomen-pelvis CT scan in Lebanon was 1426, 646, and 967 mGy cm respectively. A significant difference in mean DLP of the chest and abdomen-pelvis CT in different governorates was noted with north Lebanon having the highest levels (604 and 882 mGy cm respectively) (p < 0.05). When benchmarked with 18 different countries, Lebanon ranked 2nd, 3rd, and 4th highest in 75th percentile DLP for head, chest, and abdomen-pelvis CT scans respectively. In conclusion, the established Lebanese NDRL for adult routine CT scans of head, chest, and abdomen-pelvis were significantly higher than the reported international radiation dose thresholds. This demonstrates a great scope for radiation dose reduction and the need for urgent intervention of DRL to optimize CT scanning procedures and protocols in Lebanon.

Radiation doses from head, neck, chest and abdominal CT examinations: an institutional dose report.

We aimed to obtain typical values for head, neck, chest, and abdominal computed tomography (CT) examinations from routine patients in 2018, and to review our data with national and international diagnostic reference levels (DRLs). Single-phase head, neck, chest, and abdominal CT scans of adults performed in 64-slice CT in 2018 were included in this study. Radiation dose parameters of CT scans were obtained from the picture archiving and communication system of our hospital. Volumetric CT dose index (CTDIvol) and dose length product (DLP) values were recorded. Effective dose (ED) and scan length was calculated. A 16 cm diameter phantom is referenced for head CT, and 32 cm diameter phantom is referenced for neck, chest, and abdominal CT. Descriptive statistics of the variables were given according to the normality testing. Median CTDIvol value was 53 mGy for the head, 13.1 mGy for the neck, 8.3 mGy for the chest, and 8.6 mGy for the abdomen. Median DLP value was 988 mGy.cm for the head, 299 mGy.cm for the neck, 314 mGy.cm for the chest, and 457 mGy.cm for the abdomen. Median ED value was 2.07 mSv for the head, 1.76 mSv for the neck, 4.4 mSv for the chest, and 6.8 mSv for the abdomen. Considering national DRLs, median CTDIvol values of head, chest, and abdomen were lower, whereas median DLP and ED values of head and chest were higher. For the abdomen, the median DLP and ED values were lower. Overall radiation dose parameters obtained in this study points out the need for optimization of head CT examinations in our institution.

EVALUATION OF IRRADIATION DOSES DELIVERED TO PATIENTS IN COMPUTED TOMOGRAPHY EXAMINATIONS IN 10 RADIOLOGY DEPARTMENTS IN DOUALA-CAMEROON.

Computed tomography (CT) scan is currently the most irradiating radio diagnostic procedure for the patients. The effective dose delivered by a CT-scan exploration corresponds to 1-20years of natural irradiation of an individual. Hence, there is need to evaluate this medical exposure, in order to provide indicators and propose guidelines for its daily practice. The purpose of this work was to assess patient exposure levels due to CT-scan exams and propose a local diagnostic reference levels for the most common CT examinations performed in the radiology units of Douala/Cameroon. Data from 1775 CT scans, amongst which 10 different types of common CT examinations on adults and children, were collected, of which 1378 were adult CT scans and 397 were pediatric CT scans. The dose-length product (DLP) values in the adult population for head, abdomen-pelvic and lumber spine CT scans were high as compared to the Institute for Radiological Protection and Nuclear Safety recommendations and previous local DRL with an increase of 36, 15 and 23%, respectively. A general decrease of the DLP for CT-scans examinations in the pediatric population was observed.

Evaluation of Impact of Factors Affecting CT Radiation Dose for Optimizing Patient Dose Levels

The dose metrics and factors influencing radiation exposure for patients undergoing head, chest, and abdominal computed tomography (CT) scans were investigated for optimization of patient dose levels. The local diagnostic reference levels (DRLs) of adult CT scans performed in our hospital were established based on 28,147 consecutive examinations, including 5510 head scans, 9091 chest scans, and 13,526 abdominal scans. Among the six CT scanners used in our hospital, four of them are 64-slice multi-detector CT units (MDCT64), and the other two have detector slices higher than 64 (MDCTH). Multivariate analysis was conducted to evaluate the effects of body size, kVp, mAs, and pitch on volume CT dose index (CTDIvol). The local DRLs expressed in terms of the 75th percentile of CTDIvol for the head, chest, and abdominal scans performed on MDCT64 were 59.32, 9.24, and 10.64 mGy, respectively. The corresponding results for MDCTH were 57.90, 7.67, and 9.86 mGy. In regard to multivariate analysis, CTDIvol showed various dependence on the predictors investigated in this study. All regression relationships have coefficient of determination (R2) larger than 0.75, indicating a good fit to the data. Overall, the research results obtained through our workflow could facilitate the modification of CT imaging procedures once the local DRLs are unusually high compared to the national DRLs.

Supracristal Plane: Is it an accurate predictor of the aortic bifurcation or the caval confluence?

An accurate knowledge of surface anatomy and anatomical planes are imperative to clinical practice. Traditionally anatomical planes are based on cadaveric studies. Radiological imaging creates an opportunity to re‐assess our current knowledge of surface anatomy. One commonly used landmark is the supracristal plane that can also be used to locate the position for needle insertion in the lumbar puncture. This study aimed to assess the location of the supracristal plane in relation to vertebral levels using Computed Tomography (CT) and to determine the structures located at this plane.Materials and MethodsAdult CT scans (n=191, mean age, 52 years; 59% male) in the supine position were analysed to determine the vertebral level of the supracristal plane, aortic bifurcation, inferior vena cava confluence and umbilicus. The incidence of these structures at each vertebral level was correlated with sex and age. Scans (n=31) with distorting pathology and an absence of consensus amongst reporters was excluded.ResultsThe supracristal plane, aortic bifurcation, IVC confluence and umbilicus were most frequently located at L4/5 intervertebral disc (47.5%), lower third of the L4 vertebra (38.1%), lower third of the L5 vertebra (30%) and at the level of the L4 vertebra (28.7%). In only 13% of patients was the aortic bifurcation located at the supracristal plane. Lumabrisation and sacralisation was present in 2 and 3 patients, respectively.ConclusionModern imaging has enabled an evidence‐based prediction of the location of abdominal organs in different populations. It is imperative that this information is assimilated and incorporated in surgical anatomy education.

Biological fingerprint using scout computed tomographic images for positive patient identification.

Management of patient identification is an important issue that should be addressed to ensure patient safety while using modern healthcare systems. Patient identification errors can be mainly attributed to human errors or system problems. An error-tolerant system, such as a biometric system, should be able to prevent or mitigate potential misidentification occurrences. Herein, we propose the use of scout computed tomography (CT) images for biometric patient identity verification and present the quantitative accuracy outcomes of using this technique in a clinical setting. Scout CT images acquired from routine examinations of the chest, abdomen, and pelvis were used as biological fingerprints. We evaluated the resemblance of the follow-up with the baseline image by comparing the estimates of the image characteristics using local feature extraction and matching algorithms. The verification performance was evaluated according to the receiver operating characteristic (ROC) curves, area under the ROC curves (AUC), and equal error rates (EER). The closed-set identification performance was evaluated according to the cumulative match characteristic curves and rank-one identification rates (R1). A total of 619 (383 males, 236 females, age range 21-92years) patients who underwent baseline and follow-up chest-abdomen-pelvis CT scans on the same CT system were analyzed for verification and closed-set identification. The highest performances of AUC, EER, and R1 were 0.998, 1.22%, and 99.7%, respectively, in the considered evaluation range. Furthermore, to determine whether the performance decreased in the presence of metal artifacts, the patients were classified into two groups, namely scout images with (255 patients) and without (364 patients) metal artifacts, and the significance test was performed for two ROC curves using the unpaired Delong's test. No significant differences were found between the ROC performances in the presence and absence of metal artifacts when using a sufficient number of local features. Our proposed technique demonstrated that the performance was comparable to that of conventional biometrics methods when using chest, abdomen, and pelvis scout CT images. Thus, this method has the potential to discover inadequate patient information using the available chest, abdomen, and pelvis scout CT image; moreover, it can be applied widely to routine adult CT scans where no significant body structure effects due to illness or aging are present. Our proposed method can obtain accurate patient information available at the point-of-care and help healthcare providers verify whether a patient's identity is matched accurately. We believe the method to be a key solution for patient misidentification problems.

Assessment of average radiation dose for abdominal computed tomography examinations in Aminu Kano Teaching Hospital, Kano

The demand for abdominal Computed Tomography (CT) scans has dramatically increased over the years due to its higher sensitivity in ruling out a wide range medical conditions as compared to other imaging modalities. However, this patronage is associated with high effective dose and hence attributable to the risk of radiation-induced injuries. Establishing an acceptable radiation dose level and designing a protocol of maintaining dose level within that range is a sure optimization practice that is recommended by most national and international radiation monitoring bodies. The study aims to assess the average radiation dose received by patients undergoing abdominal CT examinations in Radiology unit of AKTH Kano, Nigeria. Dose survey of 100 adult abdominal CT scans in Radiology department of AKTH from June-October 2018. CTDIvol and DLP were simply obtained from the CT machine as displayed on the console and recorded into an adapted IAEA survey form. Effective dose was estimated by multiplying DLP by the conversion factor, k-value for abdomen (0.015mSv/mGy.cm). A total of 100 patient’s radiation dose summary comprising 57 (57%) of females and 43 (43%) males with a mean age of 46 years. Determined 75th percentile CTDIvol, DLP and effective doses for abdominal CT were found to be 12 mGy, 2225.25 mGy.cm and 33.38 mSv respectively. The CTDIvol value was lower than most local and international established studies. The DLP and effective doses of the present study were significantly higher than other studies and calls for review of existing protocol to optimize practice. Keywords: Abdominal CT, DRL, Effective dose

[OA137] Adult radiation doses for computed tomography (CT) from an international dose registry

Purpose To contribute to the creation of CT radiation dose benchmarks for adults (>=15 years). We report the distribution of radiation dose metrics based on CT scans submitted in 2017 to a large international dose registry comprised of 139 institutions from 7 countries. The registry was supported through the US National Institutes of Health (NIH) and Patient Centered Outcomes Research Institute (PCORI). Methods We describe median (target) and 75th percentile (benchmark) doses for CT dose index volume (CTDIvol) and dose length product (DLP) by anatomic area across all institutions. Each institution was weighted equally when calculating targets and benchmarks. Results The US and Europe contributed 714,297 and 85,686 adult CT scans, respectively, during 2017, including examinations of the head (33%), chest (25%) abdomen (37%) and combined chest-abdomen (CAP) (5%). CTDIvol target (50%) and benchmark (75%) values (in mGy), respectively, in the US were: head (44 and 54), chest (9 and 13), abdomen (11 and 16), and CAP (10 and 14). Corresponding values in Europe were 4–52% lower: head (38 and 47), chest (4 and 7), abdomen (7 and 11), and CAP (9 and 14). Corresponding DLP values (in mGy-cm) for the US were: head (841 and 1075), chest (338 and 560), abdomen (669 and 1081), and CAP (918 and 1416). Corresponding values in Europe were 18–52% lower: head (685 and 789), chest (163 and 334), abdomen (425 and 675), and CAP (670 and 1045). The results changed minimally after accounting for patient size using circumference of the body part scanned. For CTDIvol, no value changed more than 2 mGy and for DLP no value changed more than 100 mGy-cm. Similar usage of multi-phase scanning in Europe (23%) and the US (22%) does not explain the large differences in DLP. Conclusions Dose metrics reported in a large number of patients can contribute to the creation of representative benchmarks that can be used for dose optimization efforts and institutional evaluation of CT radiation doses to know if their doses routinely exceed these benchmarks. Additional work should be undertaken to explore the reasons that doses are higher in the US than Europe.

Radiation Dose and Image Quality in Adult Computed Tomography Scans

Radiation Dose and Image Quality in Adult Computed Tomography Scans

Safety enhancement in adult body computed tomography scanning: comparison of iodixanol versus iohexol.

BackgroundThe aim of this study was to compare the safety and intra-individual contrast enhancement of low-osmolar monomeric iohexol and the iso-osmolar dimeric iodixanol in body computed tomography (CT) scanning.MethodsIn this single center, double-blind, prospective study, a total of 2000 consecutive patients undergoing adult body CT scanning were prospectively enrolled, with 1000 patients assigned to iodixanol and 1000 patients assigned to iohexol. In both groups, the contrast medium was injected at the rate of 3.5 ml/s. Subjective assessment of image quality for each image was determined using a 3-grading scale by three reviewers. Patients were monitored with questioning and vital signs before injection, immediately after injection, and at 24 and 48 h. Extensive laboratory evaluation also was performed.ResultsLaboratory results showed no significant difference across groups. There were also no detectable differences in image quality between the two contrast groups in this study. The total adverse reactions occurred in less than 1 % of individuals receiving iodixanol comparing to 2.5 % in iohexol group (P < 0.05). Among them, only 0.7 % patients injecting iodixanol suffered immediate events, comparing to 2 % patients in iohexol group. In all, 0.2 % patients with iodixanol and 0.5 % with iohexol had late allergic reaction. Further, No deaths occurred in any of the two groups.ConclusionsThe iso-osmolar iodixanol provides image quality compared with that of iohexol, with lower incidence of adverse events.

BODY SIZE-SPECIFIC EFFECTIVE DOSE CONVERSION COEFFICIENTS FOR CT SCANS.

Effective dose from computed tomography (CT) examinations is usually estimated using the scanner-provided dose-length product and using conversion factors, also known as k-factors, which correspond to scan regions and differ by age according to five categories: 0, 1, 5, 10 y and adult. However, patients often deviate from the standard body size on which the conversion factor is based. In this study, a method for deriving body size-specific k-factors is presented, which can be determined from a simple regression curve based on patient diameter at the centre of the scan range. Using the International Commission on Radiological Protection reference paediatric and adult computational phantoms paired with Monte Carlo simulation of CT X-ray beams, the authors derived a regression-based k-factor model for the following CT scan types: head-neck, head, neck, chest, abdomen, pelvis, abdomen-pelvis (AP) and chest-abdomen-pelvis (CAP). The resulting regression functions were applied to a total of 105 paediatric and 279 adult CT scans randomly sampled from patients who underwent chest, AP and CAP scans at the National Institutes of Health Clinical Center. The authors have calculated and compared the effective doses derived from the conventional age-specific k-factors with the values computed using their body size-specific k-factor. They found that by using the age-specific k-factor, paediatric patients tend to have underestimates (up to 3-fold) of effective dose, while underweight and overweight adult patients tend to have underestimates (up to 2.6-fold) and overestimates (up to 4.6-fold) of effective dose, respectively, compared with the effective dose determined from their body size-dependent factors. The authors present these size-specific k-factors as an alternative to the existing age-specific factors. The body size-specific k-factor will assess effective dose more precisely and on a more individual level than the conventional age-specific k-factors and, hence, improve awareness of the true exposure, which is important for the clinical community to understand.

Revisiting the surface anatomy of the sciatic nerve in the gluteal region.

The surface anatomy of the sciatic nerve (SN) in the gluteal region is clinically important (e.g., intramuscular injection). Anatomy texts describe the nerve in relation to the posterior superior iliac spine (PSIS), ischial tuberosity (IT), and greater trochanter (GT) but descriptions are inconsistent. The surface anatomy of the SN was determined in relation to these bony landmarks using computed tomography (CT) scans in living adults. One hundred consecutive adult pelvic CT scans (36 females, mean age 76 years) were available for dual consensus analysis. A further 19 adults (9 females, mean age 74 years) underwent pelvic CT scans in both prone and supine positions. The surface projection of the SN along a line between the PSIS and IT and between the IT and GT was measured. The SN was identified in 95% of scans at a mean of 5.2 ± 1.0 cm from the PSIS and 11.4 ± 1.1 cm from the IT. The SN was a mean of 5.8 ± 0.8 cm from the IT and 6.2 ± 1.0 cm from the GT. There were no significant differences in mean positions of the nerve between sides and sexes. A small but clinically irrelevant difference in the surface marking of the SN was found between supine and prone positions with respect to the GT and IT but not in relation to the PSIS and IT. In living adults, the SN lies approximately one-third of the way along a line between the PSIS and IT and half way between the GT and IT.

Design and optimization of an ultra wideband and compact microwave antenna for radiometric monitoring of brain temperature.

We present the modeling efforts on antenna design and frequency selection to monitor brain temperature during prolonged surgery using noninvasive microwave radiometry. A tapered log-spiral antenna design is chosen for its wideband characteristics that allow higher power collection from deep brain. Parametric analysis with the software HFSS is used to optimize antenna performance for deep brain temperature sensing. Radiometric antenna efficiency (η) is evaluated in terms of the ratio of power collected from brain to total power received by the antenna. Anatomical information extracted from several adult computed tomography scans is used to establish design parameters for constructing an accurate layered 3-D tissue phantom. This head phantom includes separate brain and scalp regions, with tissue equivalent liquids circulating at independent temperatures on either side of an intact skull. The optimized frequency band is 1.1-1.6GHz producing an average antenna efficiency of 50.3% from a two turn log-spiral antenna. The entire sensor package is contained in a lightweight and low-profile 2.8cm diameter by 1.5cm high assembly that can be held in place over the skin with an electromagnetic interference shielding adhesive patch. The calculated radiometric equivalent brain temperature tracks within 0.4°C of the measured brain phantom temperature when the brain phantom is lowered 10°C and then returned to the original temperature (37°C) over a 4.6-h experiment. The numerical and experimental results demonstrate that the optimized 2.5-cm log-spiral antenna is well suited for the noninvasive radiometric sensing of deep brain temperature.

A reappraisal of adult abdominal surface anatomy

Descriptions of clinically important surface landmarks often vary between and within contemporary anatomical texts. The aim of this study was to investigate the surface anatomy of major abdominal vessels, kidneys, spleen, gastroesophageal junction, and duodenojejunal flexure in living adults using computed tomography (CT). After excluding patients with distorting space-occupying lesions, scoliosis, abnormal lordosis, and obvious visceromegaly, 108 abdominal CT scans of supine adults (mean age 60 years, range 18-97 years; 64 female) at end tidal inspiration were available for analysis by dual consensus reporting. Intra-observer agreement was assessed by repeat blind assessment of a random sample of scans. The vertebral level of the aortic bifurcation and almost all of its major branches, and the origin of the inferior vena cava were consistent with current descriptions. Important differences from contemporary descriptions of surface anatomy were as follows: the renal arteries were most commonly at the L1 vertebral level (left 55%, right 43%); the midpoint of the renal hila was most frequently at L2 (left 68%, right 40%); the 11th rib was a posterior relation of the left kidney in only 28% of scans; and the spleen was most frequently located between the 10th and 12th ribs (48%) with its long axis in line with the 11th rib (55%). Although the majority of vascular surface landmarks are consistent with standard descriptions, the surface anatomy of the kidneys, renal arteries, and spleen needs to be revised in accordance with observations using modern imaging techniques in vivo.

Development of a database of organ doses for paediatric and young adult CT scans in the United Kingdom.

Despite great potential benefits, there are concerns about the possible harm from medical imaging including the risk of radiation-related cancer. There are particular concerns about computed tomography (CT) scans in children because both radiation dose and sensitivity to radiation for children are typically higher than for adults undergoing equivalent procedures. As direct empirical data on the cancer risks from CT scans are lacking, the authors are conducting a retrospective cohort study of over 240,000 children in the UK who underwent CT scans. The main objective of the study is to quantify the magnitude of the cancer risk in relation to the radiation dose from CT scans. In this paper, the methods used to estimate typical organ-specific doses delivered by CT scans to children are described. An organ dose database from Monte Carlo radiation transport-based computer simulations using a series of computational human phantoms from newborn to adults for both male and female was established. Organ doses vary with patient size and sex, examination types and CT technical settings. Therefore, information on patient age, sex and examination type from electronic radiology information systems and technical settings obtained from two national surveys in the UK were used to estimate radiation dose. Absorbed doses to the brain, thyroid, breast and red bone marrow were calculated for reference male and female individuals with the ages of newborns, 1, 5, 10, 15 and 20 y for a total of 17 different scan types in the pre- and post-2001 time periods. In general, estimated organ doses were slightly higher for females than males which might be attributed to the smaller body size of the females. The younger children received higher doses in pre-2001 period when adult CT settings were typically used for children. Paediatric-specific adjustments were assumed to be used more frequently after 2001, since then radiation doses to children have often been smaller than those to adults. The database here is the first detailed organ-specific paediatric CT scan database for the UK. As well as forming the basis for the UK study, the results and description of the methods will also serve as a key resource for paediatric CT scan studies currently underway in other countries.