Radiation dose analysis of computed tomography coronary angiography in Children with Kawasaki disease

BACKGROUND There is evolving role of computed tomography coronary angiography(CTCA)in non-invasive evaluation of coronary artery abnormalities in children with Kawasaki disease(KD).Despite this,there is lack of data on radiation dose in this group of children undergoing CTCA.AIM To audit the radiation dose of CTCA in children with KD.METHODS Study(December 2013-February 2018)was performed on dual source CT scanner using adaptive prospective electrocardiography-triggering.The dose length product(DLP in milligray-centimeters-mGy.cm)was recorded.Effective radiation dose(millisieverts-mSv)was calculated by applying appropriate age adjusted conversion factors as per recommendations of International Commission on Radiological Protection.Radiation dose was compared across the groups(0-1,1-5,5-10,and>10 years).RESULTS Eighty-five children(71 boys,14 girls)with KD underwent CTCA.The median age was 5 years(range,2 mo-11 years).Median DLP and effective dose was 21 mGy.cm,interquartile ranges(IQR)=15(13,28)and 0.83 mSv,IQR=0.33(0.68,1.01)respectively.Mean DLP increased significantly across the age groups.Mean effective dose in infants(0.63 mSv)was significantly lower than the other age groups(1-5 years 0.85 mSv,5-10 years 1.04 mSv,and>10 years 1.38 mSv)(P<0.05).There was no significant difference in the effective dose between the other groups of children.All the CTCA studies were of diagnostic quality.No child required a repeat examination.CONCLUSION CTCA is feasible with submillisievert radiation dose in most children with KD.Thus,CTCA has the potential to be an important adjunctive imaging modality in children with KD.

Low contrast medium and radiation dose for hepatic computed tomography perfusion of rabbit VX2 tumor

AIM:To evaluate the feasibility of low contrast medium and radiation dose for hepatic computed tomography(CT) perfusion of rabbit VX2 tumor.METHODS:Eleven rabbits with hepatic VX2 tumor underwent perfusion CT scanning with a 24-h interval between a conventional tube potential(120 k Vp) protocol with 350 mg I/m L contrast medium and filtered back projection,and a low tube potential(80 k Vp) protocol with 270 mg I/m L contrast medium with iterative reconstruction.Correlation and agreement among perfusion parameters acquired by the conventional and low dose protocols were assessed for the viable tumor component as well as whole tumor.Image noise and tumor-to-liver contrast to noise ratio during arterial and portal venous phases were evaluated.RESULTS:A 38% reduction in contrast medium dose(360.1 ± 13.3 mg I/kg vs 583.5 ± 21.5 mg I/kg,P < 0.001) and a 73% decrease in radiation dose(1898.5 m Gy·cm vs 6951.8 m Gy·cm) were observed.Interestingly,there was a strong positive correlation in hepatic arterial perfusion(r = 0.907,P < 0.001;r = 0.879,P < 0.001),hepatic portal perfusion(r = 0.819,P = 0.002;r = 0.831,P = 0.002),and hepatic blood flow(r = 0.945,P < 0.001;r = 0.930,P < 0.001) as well as a moderate correlation in hepatic perfusion index(r = 0.736,P = 0.01;r = 0.636,P = 0.035) between the low dose protocol with iterative reconstruction and the conventional protocol for the viable tumor component and the whole tumor.These two imaging protocols provided a moderate but acceptable agreement for perfusion parameters and similar tumorto-liver CNR during arterial and portal venous phases(5.63 ± 2.38 vs 6.16 ± 2.60,P = 0.814;4.60 ± 1.27 vs 5.11 ± 1.74,P = 0.587).CONCLUSION:Compared with the conventional protocol,low contrast medium and radiation dose with iterative reconstruction has no significant influence on hepatic perfusion parameters for rabbits VX2 tumor.

Paediatric computed tomography radiation dose: A review of the global dilemma

Computed tomography(CT)has earned a well-deserved role in diagnostic radiology,producing crosssectional and three-dimensional images which permit enhanced diagnosis of many pathogenic processes.The speed,versatility,accuracy,and non-invasiveness of this procedure have resulted in a rapid increase in its use.CT imaging,however,delivers a substantially higher radiation dose than alternative imaging methodologies,particularly in children due to their smaller body dimensions.In addition,CT use in children produces an increased lifetime risk of cancer,as children’s developing organs and tissues are inherently more vulnerable to cellular damage than those of adults.Though individual risks are small,the increasing use of CT scans in children make this an important public health problem.Various organizations have recommended measures to minimize unnecessary exposures to radiation through CT scanning.These include elimination of multiple or medically unnecessary scans,development of patientspecific dosing guidelines,and use of alternative radiographic methodology wherever possible.Another important factor in excessive CT exposures,however,is a documented lack of awareness among medical practitioners of the doses involved in CT usage as well as itssignificant potential dangers.This review examines the effects of paediatric CT radiation,discusses the level of medical practitioner awareness of these effects,and offers recommendations on alternative diagnostic methods and practitioner education.

Truncus arteriosus:Diagnosis with dual-source computed tomography angiography and low radiation dose

Truncus arteriosus is an uncommon congenital cardiac abnormality which is characterized by a single arterial trunk origin from the heart that supplies both the systemic,pulmonary and coronary circulation.We present a preterm newborn female patient with type 2 truncusarteriosus,left superior vena cava and aberrant subclavian artery diagnosed with low dose dual-source cardiac computed tomography(CT).We discuss that low dose dual-source cardiac CT has more advantages than other imaging methods and it is an important modality for assessment of patients with conotruncal anomalies such as truncusarteriosus.

Low-radiation and high image quality coronary computed tomography angiography in “real-world” unselected patients

AIM To determine the radiation dose and image quality in coronary computed tomography angiography(CCTA)using state-of-the-art dose reduction methods in unselected"real world"patients.METHODS In this single-centre study,consecutive patients in sinus rhythm underwent CCTA for suspected coronary artery disease(CAD)using a 320-row detector CT scanner.All patients underwent the standard CT acquisition protocol at our institute(Morriston Hospital)a combination of dose saving advances including prospective electrocardiogram-gating,automated tube current modulation,tube voltage reduction,heart rate reduction,and the most recent novel adaptive iterative dose reconstruction 3D(AIDR3D)algorithm.The cohort comprised real-world patients for routine CCTA who were not selected on age,body mass index,or heart rate.Subjective image quality was graded on a 4-point scale(4=excellent,1=non-diagnostic).RESULTS A total of 543 patients were included in the study with a mean body weight of 81±18 kg and a pre-scan mean heart rate of 70±11 beats per minute(bpm).When indicated,patients received rate-limiting medication with an oral beta-blocker followed by additional intravenous beta-blocker to achieve a heart rate below 65 bpm.The median effective radiation dose was 0.88 mSv(IQR,0.6-1.4 mSv)derived from a Dose Length Product of61.45 mGy.cm(IQR,42.86-100.00 mGy.cm).This also includes what we believe to be the lowest ever-reported radiation dose for a routine clinical CCTA(0.18 mSv).The mean image quality(SD)was 3.65±0.61,with a subjective image quality score of 3("good")or above for 93%of patient CCTAs.CONCLUSION Combining a low-dose scan protocol and AIDR3D with a 320-detector row CT scanner can provide high quality images at exceptionally low radiation dose in unselected patients being investigated for CAD.

Temporal Trends in Radiation Dose Associated with Coronary Computed Tomography Angiography

Background: In 2010, the International Atomic Energy Agency launched the “3A’s campaign” as an effective tool for primary cancer prevention. In 2011, the American Association of Physicists in Medicine recommended the size specific dose estimate (SSDE). Objectives: To audit doses of Coronary CT Angiography (Coronary CTA) in tertiary care referral center. Methods: We reviewed 998 consecutive Coronary CTA (from 2007 to 2012). Doses (CTDIvol mGy), DLP (mGy*cm), effective dose (DLP*0.014, mSv) were on-line archived. SSDE was estimated retrospectively. Appropriateness score was evaluated for exams performed from the 2010. Results: Overall median dose per Coronary CTA was 49.7 mGy for CTDIvol, 55.5 mGy for SSDE, 994.96 mGy*cm for DLP, 13.9 mSv for effective dose. Median DLP decreased over time (1452.94 in 2007, 1605.56 in 2008, 1113.49 in 2009, 759.99 in 2010, 448.61 in 2011 and 497.88 mGy*cm in 2012, p < 0.0001). SSDE was proportional to the size dependent factor (SDF);in patients with SDF > 1 (88%) CTDIvol underestimated SSDE (48.49 vs 57.19 mGy), whilst in patients with SDF < 1 (12%) CTDIvol overestimated SSDE (56.46 vs 50.3 mGy). Scans were appropriate in 58%, uncertain in 24%, and inappropriate in 18% of cases. Doses were similar in appropriate, uncertain or inappropriate examinations and in excellent-to-good (81%) vs. sufficient-to-poor (19%) image quality exams. Conclusions: Coronary CTA reference doses can be very misleading. SSDE can allow individual technique optimization. The dose is similar in appropriate and inappropriate examinations, and unrelated to image quality. The rate of inappropriate examinations is still too high even after dissemination of guidelines.

Computed tomography colonography and radiation risk:How low can we go?

Computed tomography colonography(CTC)has become a key examination in detecting colonic polyps and colorectal carcinoma(CRC).It is particularly useful after incomplete optical colonoscopy(OC)for patients with sedation risks and patients anxious about the risks or potential discomfort associated with OC.CTC's main advantages compared with OC are its non-invasive nature,better patient compliance,and the ability to assess the extracolonic disease.Despite these advantages,ionizing radiation remains the most significant burden of CTC.This opinion review comprehensively addresses the radiation risk of CTC,incorporating imaging technology refinements such as automatic tube current modulation,filtered back projections,lowering the tube voltage,and iterative reconstructions as tools for optimizing low and ultra-low dose protocols of CTC.Future perspectives arise from integrating artificial intelligence in computed tomography machines for the screening of CRC.

Study of Radiation Doses in Adult and Paediatric Patients Undergoing Computed Tomography Examination in Nigeria

The use of computed tomography (CT) has increased over the past decades and has resulted in a concurrent increase in medical exposure to ionizing radiation. Several recent studies have examined the link between medical radiation and the risk of cancer, especially in children. Results are presented in terms of the volumetric computed tomography dose index (CTDIvol) and dose length product (DLP) for head, chest and abdomen. The 75th percentile of adult CTDIvol for head, chest and abdomen are 85 mGy, 13.34 mGy and 13.29 mGy respectively and the corresponding DLP values 1437.47 mGy&middot;cm, 417.49 and 656.02 mGy&middot;cm. However, the paediatric head based on age group 0 - 1 yr, 1 - 5 yrs, 6 - 10 yrs and 11 - 15 years are 28.18 mGy, 32.12 mGy, 32.13 mGy and 28.20 mGy and corresponding DLP values 399.75 mGy&middot;cm, 514.38 mGy&middot;cm, 578.42 mGy&middot;cm and 487.11 mGy&middot;cm respectively and for paediatric abdomen from 1 - 5 years to 11 - 15 years are 3.98 mGy, 4.26 mGy and 5.92 mGy and the corresponding DLP 99.36 mGy&middot;cm, 160.84 and 235.85 mGy&middot;cm. The finding shows considerably high CTDIvol and DLP values for adult head comparable to the international standard thus optimization is required. Reduction in radiation doses for both adult and paediatric patients involve training of staff and optimize CT protocols.

Radiation and Differential Diagnosis of Computed Tomography (CT) Data for Coronavirus Infection “COVID-19” with Clinical Examples

This article is presenting data from a retrospective analysis of medical records and computed tomography (CT) scans of patients’ chests with coronavirus infection “COVID-19” who applied to the diagnostic center of URFA in Osh during the first wave of the pandemic in the Kyrgyz Republic, with a description of individual clinical cases and their differential diagnosis. Chest computed tomography is one of the main methods in visual diagnosis of pneumonia in COVID-19 in hospitalized patients, which allows determining signs, symptoms for effective treatment.

The Role of Artificial Intelligence (AI) in Radiation Protection of Computed Tomography and Fluoroscopy: A Review

Background: The medical imaging world is currently changing with the introduction of advanced modalities to help with diagnosis. There is then the need for the application of Artificial Intelligence (AI) in areas such as radiation protection to improve the safety as far as radiations are concerned. This review article discusses the principles, some of the challenges of radiation protection and the possible role of Artificial Intelligence (AI) regarding radiation protection in computed tomography and fluoroscopy exams. Methods: A literature search was done using Google Scholar, Science Direct and Pubmed to search for relevant articles concerning the review topic. Results: Some of the challenges identified were outdated and old X-ray machines, lack of QA programs on the machines amongst others. It was discovered that AI could be applied in areas like scan planning and positioning, patient positioning amongst others in CT imaging to reduce radiation doses. With fluoroscopy, an AI enabled system helped in reducing radiation doses by selecting the region of interest of pathology and exposing that region. Conclusion: The application of AI will improve safety and standards of practice in medical imaging.

Radiation Dose from CT-Scan of Childhood’s Head: Results of the First Ivorian Survey in a Single Study Site

Objectives: This study aims to evaluate the level of X-ray doses used in childhood’s head as Local Diagnostic Reference Levels (LDRLs) in computed tomography (CT) at a university hospital in Côte d’Ivoire. The Diagnostic Reference Level (DRL) have been set up and used to prevent unusually high radiation doses used in radiology departments and is therefore an optimization tool for practices and procedures in medical X-ray imaging for the radiation protection of patients. Methods: A prospective study of volume CT dose index (CTDIvol) and dose length product (DLP) was performed on images of childhood’s head obtained from a CT-scanner of 64 bars equipped with the tube current modulation capability and manufactured by Hitachi Medical System. 122 CT-scan data from 55 childhood’s head were analyzed. The scan data were stratified in four age groups: Results: The 75th percentile of CTDIvol and DLP (set as LDRL) obtained with respect to the stratified age groups are: 22.5 mGy and 452.5 mGy∙cm, 27.7 mGy and 690.6 mGy∙cm, 28 mGy and 722.4 mGy∙cm, 33.6 mGy and 736.8 mGy∙cm respectively. These outcome values increase with respect to the age of pediatric patients and are comparable to DRLs values obtained internationally. Conclusions: Obtaining good image quality while using low dose in children’s head computed tomography for radiation protection require to setup more surveys in Côte d’Ivoire for regional and national DRL. We proposed through this survey LDRLs in terms of CTDIvol and DLP, comparable to international DRLs values. This survey will be strengthened by additional surveys in order to obtain national DRLs for the radiation protection of the child patient in Côte d’Ivoire.

Effects of combining multiple dose reduction techniques on coronary computed tomography angiography

BACKGROUND Coronary computed tomography angiography(CCTA)is the preferred noninvasive examination method for coronary heart disease.However,the radiation from computed tomography has become a concern since public awareness of radiation hazards continue to increase.AIM To explore the value of multiple dose reduction techniques for CCTA.METHODS Consecutive normal and overweight patients were prospectively divided into two groups:Group A1,patients who received multiple dose reduction scans(n=82);and group A2,patients who received conventional scans(n=39).The scan parameters for group A1 were as follows:Isocentric scan,tube voltage=80 kV,and tube current control using 80%smart milliampere.The scan parameters for group A2 were as follows:Normal position,tube voltage=100 kV,and smart milliampere.RESULTS The average effective doses(EDs)for groups A1 and A2 were 1.13±0.35 and 3.36±1.30 mSv,respectively.There was a statistically significant difference in ED between the two groups(P<0.01).Furthermore,noise was significantly lower,and both signal-to-noise ratio and contrast signal-to-noise ratio were higher in group A2 when compared to group A1(P<0.01).Moreover,the subjective image quality(IQ)scores were excellent in both groups,in which there was no significant difference in subjective IQ score between the two groups(P=0.12).CONCLUSION Multiple dose reduction scan techniques can significantly decrease the ED of patients receiving CCTA examinations for clinical diagnosis.

Coronary computed tomography angiography in coronary artery disease

AIM: To investigate the research directions of coronary computed tomography (CT) angiography in the diagnosis of coronary artery disease (CAD) based on a systematic review of the literature.METHODS: A search of articles on coronary CT angiography in the diagnosis of CAD was performed during a 6-year-period between 2005 and 2010 from f ive main radiology journals namely, Radiology, American Journal of Roentgenology, European Radiology, European Journal of Radiology and British Journal of Radiology. Analysis of the references was focused on the research directions of coronary CT angiography with regard to the type of studies in terms of diagnostic value, application of dose-reduction strategies and resultant effective radiation doses with use of these techniques.RESULTS: One hundred and forty two studies were identified which met the selection criteria and were included in the analysis. 64-slice CT (single source anddual-source CT) dominated 78% of the coronary CT angiography studies. Prior to 2007, research was focused on the diagnostic value of coronary CT angiography, but since 2008 more attention has been paid to radiation dose reduction. Radiation dose was reported in 64 studies, representing 45% of total studies published in the f ive radiology journals. Various dose-saving strategies have been implemented and prospective electrocardiography-triggering and high pitch techniques were found to be the most effective approaches for radiation dose reduction, with the corresponding mean effective dose being 3.5 ± 1.9 mSv and 1.7 ± 0.6 mSv, respectively.CONCLUSION: This review shows that the current research in coronary CT angiography has shifted from the previous focus on diagnostic accuracy in CAD to more emphasis on radiation dose reduction.

Patient dose considerations in computed tomography examinations

Ionizing radiation is extensively used in medicine and its contribution to both diagnosis and therapy is undisputable.However,the use of ionizing radiation also involves a certain risk since it may cause damage to tissues and organs and trigger carcinogenesis.Computed tomography(CT) is currently one of the major contributors to the collective population radiation dose both because it is a relatively high dose examination and an increasing number of people are subjected to CT examinations many times during their lifetime.The evolution of CT scanner technology has greatly increased the clinical applications of CT and its availability throughout the world and made it a routine rather than a specialized examination.With the modern multislice CT scanners,fast volume scanning of the whole human body within less than 1 min is now feasible.Two dimensional images of superb quality can be reconstructed in every possible plane with respect to the patient axis(e.g.axial,sagital and coronal).Furthermore,three-dimensional images of all anatomic structures and organs can be produced with only minimal additional effort(e.g.skeleton,tracheobronchial tree,gastrointestinal system and cardiovascular system).All these applications,which are diagnostically valuable,also involve a significant radiation risk.Therefore,all medical professionals involved with CT,either as referring or examining medical doctors must be aware of the risks involved before they decide to prescribe or perform CT examinations.Ultimately,the final decision concerning justification for a prescribed CT examination lies upon the radiologist.In this paper,we summarize the basic information concerning the detrimental effects of ionizing radiation,as well as the CT dosimetry background.Furthermore,after a brief summary of the evolution of CT scanning,the current CT scanner technology and its special features with respect to patient doses are given in detail.Some numerical data is also given in order to comprehend the magnitude of the potential radiation risk involved in comparison with risk from exposure to natural background radiation levels.

Non-enhanced Low-tube-voltage High-pitch Dual-source Computed Tomography with Sinogram Affirmed Iterative Reconstruction Algorithm of the Abdomen and Pelvis

Objective To investigate the image quality, radiation dose and diagnostic value of the low-tube-voltage high-pitch dual-source computed tomography(DSCT) with sinogram affirmed iterative reconstruction(SAFIRE) for non-enhanced abdominal and pelvic scans. Methods This institutional review board-approved prospective study included 64 patients who gave written informed consent for additional abdominal and pelvic scan with DSCT in the period from November to December 2012. The patients underwent standard non-enhanced CT scans(protocol 1) [tube voltage of 120 k Vp/pitch of 0.9/filtered back-projection(FBP) reconstruction] followed by high-pitch non-enhanced CT scans(protocol 2)(100 k Vp/3.0/SAFIRE). The total scan time, mean CT number, signal-to-noise ratio(SNR), image quality, lesion detectability and radiation dose were compared between the two protocols. Results The total scan time of protocol 2 was significantly shorter than that of protocol 1(1.4±0.1 seconds vs. 7.6±0.6 seconds, P<0.001). There was no significant difference between protocol 1 and protocol 2 in mean CT number of all organs(liver, 55.4±6.3 HU vs. 56.1±6.8 HU, P=0.214; pancreas, 43.6±5.9 HU vs. 43.7±5.8 HU, P=0.785; spleen, 47.9±3.9 HU vs. 49.4±4.3 HU, P=0.128; kidney, 32.2±2.3 HU vs. 33.1±2.3 HU, P=0.367; abdominal aorta, 44.8±5.6 HU vs. 45.0±5.5 HU, P=0.499; psoas muscle, 50.7±4.1 HU vs. 50.3±4.5 HU, P=0.279). SNR on images of protocol 2 was higher than that of protocol 1(liver, 5.0±1.2 vs. 4.5±1.1, P<0.001; pancreas, 4.0±1.0 vs. 3.6±0.8, P<0.001; spleen, 4.7±1.0 vs. 4.1±0.9, P<0.001; kidney, 3.1±0.6 vs. 2.8±0.6, P<0.001; abdominal aorta, 4.1±1.0 vs. 3.8±1.0, P<0.001; psoas muscle, 4.5±1.1 vs. 4.3±1.2, P=0.012). The overall image noise of protocol 2 was lower than that of protocol1(9.8±3.1 HU vs. 11.1±3.0 HU, P<0.001). Image quality of protocol 2 was good but lower than that of protocol 1(4.1±0.7 vs. 4.6±0.5, P<0.001). Protocol 2 perceived 229 of 234 lesions(97.9%) that were detected in protocol 1 in the abdomen and pelvis. Radiation dose of protocol 2 was lower than that of protocol 1(4.4±0.4 m Sv vs. 7.3±2.4 m Sv, P<0.001) and the mean dose reduction was 41.4%. Conclusion The high-pitch DSCT with SAFIRE can shorten scan time and reduce radiation dose while preserving image quality in non-enhanced abdominal and pelvic scans.

Computed tomography and patient risk:Facts,perceptions and uncertainties

Since its introduction in the 1970s, computed tomography(CT) has revolutionized diagnostic decision-making. One of the major concerns associated with the widespread use of CT is the associated increased radiation exposure incurred by patients. The link between ionizing radiation and the subsequent development of neoplasia has been largely based on extrapolating data from studies of survivors of the atomic bombs dropped in Japan in 1945 and on assessments of the increased relative risk of neoplasia in those occupationally exposed to radiation within the nuclear industry. However, the association between exposure to low-dose radiation from diagnostic imaging examinations and oncogenesis remains unclear. With improved technology, significant advances have already been achieved with regards to radiation dose reduction. There are several dose optimization strategies available that may be readily employed including omitting unnecessary images at the ends of acquired series, minimizing the number of phases acquired, and the use of automated exposure control as opposed to fixed tube current techniques. In addition, new image reconstruction techniques that reduce radiation dose have been developed in recent years with promising results. These techniques use iterative reconstruction algorithms to attain diagnostic quality images with reduced image noise at lower radiation doses.

Low-dose computed tomography with 4th-generation iterative reconstruction algorithm in assessment of oncologic patients

AIM To compare radiation dose and image quality of lowdose computed tomography(CT) protocol combined with hybrid-iterative reconstruction algorithm with standarddose CT examinations for follow-up of oncologic patients. METHODS Fifty-one patients with known malignant diseases which underwent, during clinical follow-up, both standarddose and low-dose whole-body CT scans were enrolled. Low-dose CT was performed on 256-row scanner, with 120 kV and automated m A modulation, and iterative reconstruction algorithm. Standard-dose CT was performed on 16-rows scanner, with 120 kV, 200-400 m As(depending on patient weight). We evaluated density values and signal-to-noise ratio, along with image noise(SD), sharpness and diagnostic quality with 4-point scale.RESULTS Density values in liver, spleen and aorta were higher in lowdose images(liver 112.55 HU vs 103.90 HU, P < 0.001), as SD values in liver and spleen(liver 16.81 vs 14.41). Volumetric-Computed-Tomographic-Dose-Index(CTDIvol) and Dose-Length-Product(DLP) were significantly lower in low-dose CT as compared to standard-dose(DLP 1025.6 m Gy*cm vs 1429.2 m Gy*cm, P < 0.001) with overall dose reduction of 28.9%. Qualitative analysis did not reveal significant differences in image noise and diagnostic quality.CONCLUSION Automatic tube-current modulation combined with hybriditerative algorithm allows radiation dose reduction of 28.9% without loss of diagnostic quality, being useful in reducing dose exposure in oncologic patients.

Size-specific dose estimates: Localizer or transverse abdominal computed tomography images?

AIM: To investigate effect of body dimensions obtained from localizer radiograph and transverse abdominal computed tomography(CT) images on Size Specific Dose Estimate. METHODS: This study was approved by Institutional Review Board and was compliant with Health Insurance Portability and Accountability Act. Fifty patients with abdominal CT examinations(58 ± 13 years, Male: Female 28:22) were included in this study. Anteriorposterior(AP) and lateral(Lat) diameters were measured at 5 cm intervals from the CT exam localizer radiograph(simple X-ray image acquired for planning the CT exam before starting the scan) and transverse CT images. Average of measured AP and Lat diameters, as well as maximum, minimum and mid location AP and Lat were measured on both image sets. In addition, off centering of patients from the gantry iso-center was calculated from the localizers. Conversion factors from American Association of Physicists in Medicine(AAPM) report 204 were obtained for AP, Lat, AP + Lat, and effective diameter(√ AP * Lat) to determine size specificdose estimate(SSDE) from the CT dose index volume(CTDIvol) recorded from the dose reports. Data were analyzed using SPSS v19. RESULTS: Total number of 5376 measurements was done. In some patients entire body circumference was not covered on either projection radiograph or transverse CT images; hence accurate measurement of AP and Lat diameters was not possible in 11%(278/2488) of locations. Forty one patients were off-centered with mean of 1.9 ± 1.8 cm(range: 0.4-7 cm). Conversion factors for attained diameters were not listed on AAPM look-up tables in 3%(80/2488) of measurements. SSDE values were significantly different compared to CTDIvol, ranging from 32% lower to 74% greater than CTDIvol. CONCLUSION: There is underestimation and overestimation of dose comparing SSDE values to CTDIvol. Localizer radiographs are associated with overestimation of patient size and therefore underestimation of SSDE.

Computed tomography-based radiomic to predict resectability in locally advanced pancreatic cancer treated with chemotherapy and radiotherapy

BACKGROUND Surgical resection after neoadjuvant treatment is the main driver for improved survival in locally advanced pancreatic cancer(LAPC).However,the diagnostic performance of computed tomography(CT)imaging to evaluate the residual tumour burden at restaging after neoadjuvant therapy is low due to the difficulty in distinguishing neoplastic tissue from fibrous scar or inflammation.In this context,radiomics has gained popularity over conventional imaging as a complementary clinical tool capable of providing additional,unprecedented information regarding the intratumor heterogeneity and the residual neoplastic tissue,potentially serving in the therapeutic decision-making process.AIM To assess the capability of radiomic features to predict surgical resection in LAPC treated with neoadjuvant chemotherapy and radiotherapy.METHODS Patients with LAPC treated with intensive chemotherapy followed by ablative radiation therapy were retrospectively reviewed.One thousand six hundred and fifty-five radiomic features were extracted from planning CT inside the gross tumour volume.Both extracted features and clinical data contribute to create and validate the predictive model of resectability status.Patients were repeatedly divided into training and validation sets.The discriminating performance of each model,obtained applying a LASSO regression analysis,was assessed with the area under the receiver operating characteristic curve(AUC).The validated model was applied to the entire dataset to obtain the most significant features.RESULTS Seventy-one patients were included in the analysis.Median age was 65 years and 57.8%of patients were male.All patients underwent induction chemotherapy followed by ablative radiotherapy,and 19(26.8%)ultimately received surgical resection.After the first step of variable selections,a predictive model of resectability was developed with a median AUC for training and validation sets of 0.862(95%CI:0.792-0.921)and 0.853(95%CI:0.706-0.960),respectively.The validated model was applied to the entire dataset and 4 features were selected to build the model with predictive performance as measured using AUC of 0.944(95%CI:0.892-0.996).CONCLUSION The present radiomic model could help predict resectability in LAPC after neoadjuvant chemotherapy and radiotherapy,potentially integrating clinical and morphological parameters in predicting surgical resection.

Principle of diffraction enhanced imaging (DEI) and computed tomography based on DEI method

In the first part of this article a more general DEI equation was derived using simple concepts. Not only does the new DEI equation explain all the problems that can be done by the DEI equation proposed by Chapman, but also explains the problem that can not be explained with the old DEI equation, such as the noise background caused by the small angle scattering reflected by the analyzer. In the second part, a DEI-PI-CT formula has been proposed and the contour contrast caused by the extinction of refraction beam has been qualitatively explained, and then based on the work of Ando's group two formulae of refraction CT with DEI method has been proposed. Combining one refraction CT formula proposed by Dilmanian with the two refraction CT formulae proposed by us, the whole framework of CT algorithm can be made to reconstruct three components of the gradient of refractive index.