ALARA Principle Research Articles

TU‐PIS‐Exhibit Hall‐01: CT Dose Optimization Technologies II

Partners in Solutions is an exciting new program in which AAPM partners with our vendors to present practical “hands‐on” information about the equipment and software systems that we use in our clinics. The imaging topic this year is CT scanner dose optimization capabilities. Note that the sessions are being held in a special purpose room built on the Exhibit Hall Floor, to encourage further interaction with the vendors.Siemens‘ Commitment to the Right Dose in Computed Tomography Presentation Time: 11:15 – 11:45 AMProviding sustainable clinical results at highest patient safety: This is the challenge in medical imaging. Especially for Computed Tomography this means applying not simply the lowest, but the right dose for sound diagnostic imaging. Consequently, Siemens is committed to deliver the right dose in CT.In order to reduce radiation to the right dose, the first step is to provide the right dose technology. Through decades of research and development in CT imaging, Siemens CT has constantly introduced new ideas leading to a comprehensive portfolio of unique CARE technologies to deliver the right dose. For example automated kV adjustment based on patient size and the clinical question with CARE kV and three generations of iterative reconstruction.Based on the right dose technology, the next step is to actually scan at the right dose. For this, it is key to know the right dose targets for every examination. Siemens continuously involves CT experts to push developments further and outline how users can best adapt their procedures to the right dose. For users to know whether they met the right dose targets, it is therefore important to understand and monitor the actual absolute dose values. All scanners are delivered with defined default protocols which automatically use the available right dose technologies.Finally, to deliver the right dose not just in singular cases, but ideally to patients everywhere, organizations need then to manage dose across their institutions. Here Siemens offers the right dose management tools for administrations to analyze and document dose, to train their clinical staff and to continuously optimize the application of the right dose in clinical routine.Siemens CT is not only adhering to the ALARA principle, but is inspired by it.With CARE Right Siemens show their commitment to the right dose in CT.Toshiba Aquilion CT Dose Management ToolsPresentation Time: 11:45 – 12:15 PMA practical review of Toshiba’s CT dose management technologies from the physicist’s perspective. This presentation will include an overview of Toshiba’s CT dose reduction technologies and dose safeguards. Content will include answers to frequently asked questions relating to dose management, dose tracking, CTDI measurement, ACR accreditation, ACR QC, and protocol review on Toshiba CT systems.Specific topics will include the following: Toshiba’s mechanism of tube current modulation; Exposure record format and interpretation of the values; Dose reporting and dose safeguard tools; Use of AIDR 3D iterative reconstruction; The configuration of task specific image quality target and its integration with AIDR 3D; Tips for scanning the ACR phantom with wide beam geometry; Measuring CTDI for wide beam geometry; Discussion of daily QC procedures and specifications; Tips for annual QC evaluation; Protocol management tools

Diagnostic ultrasonography in neonates, infants and children—Why, when and how

Ultrasonography (US) has become the mainstay of paediatric imaging. This is not only due to considerations concerning radiation protection and ALARA principles, which of course implies shifting as many examinations as possible towards the non-irradiating modality which US constitutes. Ultrasound has undergone a remarkable evolution from its initial “orienting” images to a vast potential of a sophisticated modern imaging technique. Furthermore neonates, infants and children of specific conditions are perfectly suitable for performing US: Little fat and fibrous tissue, higher water content of the tissue and smaller structures enable not only good sound penetration and improved image quality but also application of higher frequencies that allow for higher special resolutions. Thus all the benefits of high-resolution US not only using high frequencies but also other modern techniques such as image compounding, harmonic imaging and speckle reduction filters, can – in paediatric patients – be applied to organs which often are not accessible with this techniques in adulthood, such as the kidney or the liver and spleen.

Intraoral Radiology in General Dental Practices – A Comparison of Digital and Film-Based X-Ray Systems with Regard to Radiation Protection and Dose Reduction

The purpose of this study was to gain insight into the distribution and application of digital intraoral radiographic techniques within general dental practices and to compare these with film-based systems in terms of patient dose reduction. 1100 questionnaires were handed out to general dental practitioners. Data was analyzed with respect to the type of system by using descriptive statistics and nonparametric tests, i.e. Kruskal-Wallis, Mann-Whitney and chi-square test (SPSS 20). 64% of the questioned dentists still use film-based radiology, 23% utilize storage phosphor plate (SPP) systems and 13% use a charge-coupled device (CCD). A strong correlation between the number of dentists working in a practice and the use of digital dental imaging was observed. Almost 3/4 of the film users work with E- or F-speed film. 45% of them refuse to change to a digital system. The use of lead aprons was popular, while only a minority preferred thyroid shields and rectangular collimators. A fourfold reduction of exposure time from D-speed film to CCD systems was observed. Due to detector size and positioning errors, users of CCD systems take significantly more single-tooth radiographs in total. Considering the number of radiographs per patient, there is only a slight tendency towards more X-rays with CCD systems. Up to image generation, digital systems seem to be as or even more difficult to handle than film-based systems, while their handling was favored after radiographic exposure. Despite a slight increase of radiographs taken with CCD systems, there is a significant dosage reduction. Corresponding to the decrease in exposure time, the patient dose for SPP systems is reduced to one half compared to film. The main issues in CCD technology are positioning errors and the size of the X-ray detectors which are difficult to eliminate. The usage of radiation protection measures still needs to be improved. ► Responsible use of digital intraoral radiology results in a significant dose reduction in everyday practice. ► The ALARA principle is only achieved by strict implementation of dose-reducing methods. ► The efforts to use dose-reducing devices must be increased.

Shut-Down Dose Rate analysis for ITER Diagnostic Equatorial and Upper Ports

The Shut-Down Dose Rate (SDDR) is an important criterion of radiation safety for the personnel access for maintenance operations in ITER ports after the cessation of the D-T 14MeV neutron fusion source. Therefore, the problem of the SDDR calculations attracts the attention of fusion neutronics community because SDDR in such a large and geometrically complicated fusion device as the ITER tokamak is challenging to compute. This challenge has been faced and overcome by applying dedicated methodological approaches explained in this paper. The results of the SDDR analysis allowed us to propose several design solutions for improvement of the radiation shielding of the ITER Generic Diagnostic Equatorial and Upper Port Plugs (EPP and UPP). The SDDR analysis was focused on the interspace area located between the ITER bioshield and port plugs where the personnel access is envisaged at ∼12 days after the ITER shut-down. By this analysis the radiation streaming pathways and dominant sources of decay radiation were revealed and the methods to mitigate the streaming and subsequent activation were found. The optimization of the port shielding was targeted on minimization of the SDDR in the interspace area following the ALARA principle and taking into account the feasibility to implement proposed shielding options with the actual hardware. Among them, wrapping the EPP walls with the B4C tiles improves the EPP shielding performance. While void around the ELM/in-vessel coils and blanket manifolds leads to the performance reduction. The SDDR inside the Generic UPP interspace depends mainly on the environment (blanket, manifolds, and gaps).

Monitoring of radiation dose rates around a clinical nuclear medicine site

Abstract The monitoring of radiation dose around the nuclear medicine site is an important study issue. In this study, TLD-100H radiation dosimeters were used to measure the ambient radiation dose rates around a clinical nuclear medicine site in order to investigate the latent hot zones of radiation exposure. Results of this study showed that the radiation doses measured from all piping and storage systems were comparable to the background dose. A relatively high dose was observed at the single bend point of waste water piping of the PET/CT. Another important finding was the unexpected high dose rates observed at the non-restricted waiting area (NRWA) of SPECT. To conclude, this study provides useful information for further determination of an appropriate dose reduction strategy to achieve the ALARA principle in a clinical nuclear medicine site.

Image quality and dose assessment in digital breast tomosynthesis: A Monte Carlo study

Abstract Mammography is considered a standard technique for the early detection of breast cancer. However, its sensitivity is limited essentially due to the issue of the overlapping breast tissue. This limitation can be partially overcome, with a relatively new technique, called digital breast tomosynthesis (DBT). For this technique, optimization of acquisition parameters which maximize image quality, whilst complying with the ALARA principle, continues to be an area of considerable research. The aim of this work was to study the best quantum energies that optimize the image quality with the lowest achievable dose in DBT and compare these results with the digital mammography (DM) ones. Monte Carlo simulations were performed using the state-of-the-art computer program MCNPX 2.7.0 in order to generate several 2D cranio-caudal (CC) projections obtained during an acquisition of a standard DBT examination. Moreover, glandular absorbed doses and photon flux calculations, for each projection image, were performed. A homogeneous breast computational phantom with 50%/50% glandular/adipose tissue composition was used and two compressed breast thicknesses were evaluated: 4 cm and 8 cm. The simulated projection images were afterwards reconstructed with an algebraic reconstruction tool and the signal difference to noise ratio (SDNR) was calculated in order to evaluate the image quality in DBT and DM. Finally, a thorough comparison between the results obtained in terms of SDNR and dose assessment in DBT and DM was performed.

Radiation protection aspects in the vicinity of TW class laser systems

Modern laser systems are able to generate ionizing radiation of significantly high energies by focusing ultra-short intense pulses onto targets. This study is focused on evaluating possible radiological hazards resulting from the fs high repetition rate laser, operating in a high intensity regime. Characteristics of radiation field generated within a typical experiment of electron acceleration are explored both theoretically and experimentally. The electron bunches with the charge of ~ pC, the pulse duration of ~fs, and 100 MeV energy in a single shot regime were chosen as a benchmark. First, the shielding capabilities of the civil structure surrounding the interaction chamber were examined. Second, responses of typical personal dosimeters (film, TLD, and electronic personal dosimeter), designed for usage in continuous fields, were studied in a pulsed radiation field. Measurements were performed at a Ti:Sapphire 25 TW laser system recently installed at PALS Research Centre in Prague. In accordance with the ALARA principle, the adequacy of an existing bulk shielding for the model electron acceleration experiment was verified and working regime was recommended.

A comparison of patient specific dosimetric calculations obtained by planar images and Monte Carlo simulation in 111In octreotide therapy

s / Physica Medica 30 (2014) e16ee44 e29 phase, as a function of the mean value of administered activity per patient treated each week was also acquired. Results: 675 patients were treated through 2011-2013. Mean administered activity 113,5±31.8mCi. Tank’s filling phase:42±4days.Rest decay duration:63±3days. I-131 activity,T, at the end of tank’s filling phase is given by the formula: T1⁄45.6*Aavg,[mCi] whereas Aavg[mCi] is the average amount of administered activity during tank’s filling time period. Tvalues:560-835 mCi and average monthly concentration 0.13mCi/lt. In accordance with Greek legislation, maximum limit of discharge is 110MBq /day. Liquid samples collected at releasing time documented radioactive releases of I-131, equal to those derived from estimations, much below recommended levels of once release. During the above time period a tank’s operation was interrupted twice as a consequence of clogging. Graphs that depict the measurements beyond are also provided. Conclusions: Above real practice data may be useful for further studies of environmental radiation protection from liquid waste of patients undergoing I-131 therapy for thyroid cancer. Physicists, taking into consideration ALARA principle, economic and social factors, must design in advance, emergency plan assuring that, any individual’s exposure is kept to the minimum practicable, in case of system’s mulfunction. A COMPARISON OF PATIENT SPECIFIC DOSIMETRIC CALCULATIONS OBTAINED BY PLANAR IMAGES AND MONTE CARLO SIMULATION IN 111IN OCTREOTIDE THERAPY Maria Argyrou , Maria Andreou , Nefeli Lagopati , Irini Baka , Ioannis Vamvakas , Maria Lyra . Radiation Physics Unit, A’ Radiology Department, Kapodistrian University of Athens, Aretaieion Hospital, 76 Vas. Sophias Ave, Athens, Greece; Medical Physics Department, Iaso Hospital,

Dosimetric Effects of Involuntary Motion for Total Marrow Irradiation With Volumetric Modulated Arc Therapy

Total marrow (and lymph nodes) irradiation (TMI and TMLI) by volumetric modulated arc therapy (VMAT) was shown to be possible. Many arcs with some isocenters are required to best cover the hematopoietic or lymphoid tissues target and to spare the neighbor healthy tissues according with ALARA principle. The direct consequence is the necessity of overlapping regions between neighbor arcs. In this study we evaluated the dosimetric effect of inaccurate isocenter positioning during the treatment of TMI and TMLI treatments using volumetric modulated arc therapy (VMAT).

Canadian Cardiovascular Society Position Statement on Radiation Exposure From Cardiac Imaging and Interventional Procedures

Exposure to ionizing radiation is a consequence of many diagnostic and interventional cardiac procedures. Radiation exposure can result in detrimental health effects because of deterministic (eg, skin reaction) and stochastic effects (eg, cancer). However, with the levels experienced during cardiac procedures these risks can be difficult to quantify. Healthcare providers and patients might not fully appreciate radiation-related risks. Though in many cases radiation exposure cannot be avoided, a practice of minimizing exposures to levels “as low as reasonably achievable” (ALARA principle) without compromising the utility of the procedure is encouraged. The purpose of this document is to inform health care providers on the key concepts related to radiation risk from common cardiac procedures and provide specific recommendations on ensuring quality of care.

Radiology patients dose mastering of Kirchberg hospital center

Medical irradiation is the primary exposure source, artificial origin, of the population in industrialized countries (1.3 mSv per year per capita on average according to the IRSN 2010). However, Radiation protection of persons exposed for medical purposes is a relatively recent concern (directives: 84/466 & 97/43 Euratom). The notion of regulatory dose limit is inappropriate in the context of medical examinations, in effect, reduce and maintain exposure to radiation at a dose as low as reasonably possible, in accordance with the ALARA principle (As Low As Reasonably Achievable), cannot be applied directly, the dose ‘‘mastering” through the justification and optimization of medical procedures. The dose mastering is a compromise: must firstly that the expected benefits outweigh the caused risks, and secondly that the dose is consistent with an interpretable medical image. Kirchberg Hospital Center (KHC) in Luxembourg, very aware of the problem of the doses delivered to patients during diagnostic examinations, has established a strategy evaluation and optimization of the dose which organizes around several axes: 1. standardization of procedures for conducting medical examinations, 2. the use of CT reconstruction algorithms in order to obtain interpretable images with low exposure, it is ASIR and VEO, 3. the acquisition of a dose management software connected with all services using radiology equipment (scanners, radiocontrolled table, mammography, surgical, etc.), it is DoseWatch, 4. the appointment of a DACS (Dose Archiving and Communication System) in order to follow exposure of patients in real time, manage alerts and publish monthly dose reports, 5. each actor in the radiological chain (manipulator, physician) is invited to regular meetings where the results are presented with DoseWatch. Following these meetings, he receives a sheet exposure showing the average and the 75th percentile of the dose for different examinations he has done. In this presentation we will discuss the items listed above through the experience of KHC and different conclusions.

SU‐E‐I‐12: Assessment of Absorbed Dose and Image Quality Using Cone Beam CT On An X‐Ray Angiography System

Purpose: Cone beam CT (CBCT) acquisitions using interventional X‐ray Angiography (XA) systems are becoming more prevalent. Patient dose should be considered when performing these studies. This work assesses absorbed radiation dose and image quality from CBCT acquisitions on an XA system. Methods: CBCT acquisitions of a CIRS tissue equivalent abdomen phantom and the Gammex ACR CT phantom were performed at 3 detector dose settings using a 90 kVp, 210 degree, 420 view, 8 second acquisition on a Siemens Artis Zee system. Radiation dose was measured using a Radcal 0.6cc ionization chamber positioned at central and peripheral locations in the abdomen phantom. Patient absorbed dose was estimated via a weighted average of the peripheral (2/3) and central (1/3) doses. Image quality was assessed via the standard deviation of the reconstructed image pixel values in a homogeneous region of the ACR CT phantom and contrast to noise ratio (CNR) measurements of the polyethylene rod to the background. For comparison, absorbed dose was measured with the same setup on a standard CT system using a clinical abdomen and pelvis protocol. Results: Estimates of patient absorbed dose for the CBCT acquisitions were 38, 26, and 15 mGy at detector dose settings of 540, 360 (default) and 200 nGy per view. The image noise at different dose settings was consistent with a 0.5 power law relationship. The absolute value of the CNR was determined to be 6.1 (540 nGy), 5.5 (360 nGy) and 3.7(200 nGy). The absorbed dose estimate for the abdomen and pelvis standard CT was 9 mGy. Conclusion: Absorbed dose from cone beam CT acquisitions on an interventional XA system is greater than that of a standard CT. The necessary image quality for a given CBCT imaging task and the potential for dose reduction should be assessed in accordance with ALARA principles. Research Grant: Siemens AG

SU‐E‐J‐35: Imaging Dose in Radiotherapy: An Institution‐Based Study

Purpose: Image‐guided radiotherapy (IGRT) has become an essential component in comprehensive radiation therapy. However, this method of localization also carries with it increased radiation dose to the patient. As a center with multiple imaging modalities for IGRT, the goal of this research was to quantify the imaging dose received by patients in different treatment and IGRT setups throughout the course of treatment. Methods: At our institution, the IGRT modalities used are MV port films, kV port films, ExacTrac, and kV cone‐beam CT (CBCT). There are currently two different IGRT‐equipped linear accelerators in use at our facilities. Each type of machine was tested for the imaging modalities it utilized. The exposure values for a single image were compared to the AAPM TG‐75 values to see whether the values fell within the previously published data. The exposure values were then converted to dose and multiplied by the conventional fractionation scheme for the associated area of treatment in order to compare the imaging dose to the total treatment dose for that site. Results: The majority of exposures fell within the guidelines of the AAPM TG‐75 report. Imaging doses, as a percentage of treatment dose, were all less than 1%. Conclusion: This study helped to establish baseline values for periodic imaging quality assurance and provided support that imaging doses in our facilities are reasonable in terms of previously published data and the ALARA principle. The exposure values for our institution align well with those listed in TG‐75, and as long as repeat imaging is kept to a minimum, imaging doses will remain only a small percentage of total treatment dose.

SU‐E‐J‐95: Increasing Soft Tissue Contrast by Combining New CT Technologies and Imaging Dose for Radiation Treatment Planning and Delivery Guidance

Purpose: CT dose is normally minimized based on ALARA principle. For radiation therapy (RT), a slightly increased CT dose in exchange for improved soft‐tissue contrast may be justified. In this work, we investigate the impact of CT imaging dose and other acquisition and reconstruction parameters on CT quality for RT planning and delivery guidance. Methods: CT data of various phantoms were acquired using a CT‐on‐rails (Somaton Definition AS Open, Siemens) with a series of acquisition parameters, such as tube voltage and current, rotation time, pitch, imaging dose control methods, and reconstruction algorithms, and were analyzed based on contrast‐to‐noise ratio (CNR) and dose‐weighted CNR (CNRD) to identify image quality enhancement protocols (IQEP). The IQEPs were then used to acquire CT during daily IGRT for selected patients with head and neck, prostate, and pancreas cancers. The impact of the improved CT images on RT was assessed with (1) accuracy and reproducibility of auto‐segmentation using ABAS (Elekta) and (2) intra‐and inter‐variability of manual contouring of the relevant organs by 10 observers. Results: As expected, the CNR generally increases with mAs from phantom CT data, while CNRD experiences a slow increase with mAs or reaches a plateau and then drops above certain mAs depending phantom size and relative electron density or contrast level. There is complicated interplay between kVp and mAs, particularly with regards to perception. Visual inspection of the patient CTs obtained with IQEPs showed clearer organ boundaries as compared to those from the standard CT protocols. This improvement was supported by the reduced intra‐and inter‐variability of manual contouring. The CT doses with IQEPs were 2–3 times higher than those from the standard protocols. Conclusion: CT quality can be improved by optimizing parameters in CT protocols for modern scanners, leading to improved accuracy of organ delineation for RT planning and delivery.

Effective Dose to Children during Cardiac Catheterization

The purpose of this study was to assess the effective dose received by children during cardiac procedures. 6 children from 3 to 14 years old who underwent coronary angiogram, cardiac catheterization and pulmonary valvuloplasty treatment were included in the present study. Measurement of effective doses of the paediatric cardiac patients was performed in four catheterization laboratories in three hospitals. Harshaw TLD badges (TLD-100, LiF: Mg, Ti) were used on patients to measure effective dose in the catheterization laboratory. The TLD badges were calibrated from Secondary Standard Dosimetery Laboratory. It is found that the highest dose was 2.01 mSv in 5.4 minute fluoroscopic time during peripheral angiogram and primary pace maker procedure and the lowest effective dose was 0.044 mSv in 1.2 minute fluoroscopic time during coronary angiography performed in the same hospital. The highest fluoroscopic time (18:14 min) was taken to perform a cardiac catheterization and pulmonary valvuloplasty procedure and the dose was 0.781 mSv. During cardiac catheterization children were exposed to high levels of radiation but there was a variant in dosage. Careful consideration should be given to minimize dosage by practicing ALARA principle. This type of study may lead cardiologist and scientist to improve necessary safety measures to be taken to reduce the exposure to patients and occupational worker. DOI: http://dx.doi.org/10.3329/bjmp.v4i1.14704 Bangladesh Journal of Medical Physics Vol.4 No.1 2011 145-147

Pediatric nuclear medicine and pediatric radiology

To improve clinical practice is our daily duty as specialists in radiology and in nuclear medicine. When a clinician asks us to perform an imaging examination, we have to advise that clinician about the best test or imaging strategy to study the clinical problem. Risk-to-benefit ratio and the ALARA principle have to be weighed, as well as modality and cost. Hybrid imaging is now the standard in nuclear medicine. The use of multimodality cameras such as SPECT/CT, PET/CT and PET/MR has been revolutionary [1–4]. The key is finding the exact location of functional or metabolic lesions. But adding CT increases the dosimetry [5–7], requires more detailed knowledge of imaging anatomy and depends on collaboration between radiologists and nuclear medicine specialists. The level of expertise among imaging specialists (at least in pediatric nuclear medicine) varies too much. In some countries nuclear medicine is an independent specialty, and in other countries radiologists are in charge of nuclear medicine tests. Physicians-in-training in radiology and in nuclear medicine have to receive multimodality training [8–12]. And continuing education in both specialties is vital to ensure that senior specialists are well-versed in the latest techniques. In any case, imaging specialists must be able to discuss the options with referring clinicians and to advise them on the appropriate technique for each clinical situation. Pediatric nuclear medicine can be performed in general nuclear medicine facilities or in dedicated pediatric nuclear medicine departments. The quality of the images has to be diagnostically excellent in pediatric nuclear medicine but superfluous scans must be avoided and doses must be as low as reasonably achievable and adjusted to each child according to international recommendations [7, 13–16]. These goals can be more easily reached in dedicated pediatric facilities. Dose reduction remains important. Contrary to general opinion the radiation dose of most nuclear medicine scans is lower than that of many comparable radiologic studies. The most typical example is abdominal CT, which has a higher dose than the most frequent nuclear medicine studies. Another example is that two-thirds of the radiation dose from PET/CT is from the CT component [12–14]. In the latter case it is possible to perform a diagnostic CT scan during the PET/CT examination rather than a separate diagnostic CT scan. Or a lower-dose CT scan could be performed in a patient who has recently undergone a diagnostic CT scan. The best option for the future in pediatric oncology, however, is PET/MR. In bone scintigraphy or an MIBG scan, performance of an SPECT/CT scan significantly increases the radiation dose [15–17]. A possibility is to use a lower-dose nondiagnostic CT scan in these cases. And the best practice is to report together with the radiologist, comparing the SPECT and the CT or MR images frame-by-frame. In many papers, correlative analysis of PET/CT images in children has been reported to be superior to separate analysis of CT and FDG/PET images. The term “correlative imaging” is the joint interpretation of different imaging modalities – CT, MR, US and scintigraphy [18]. This is the best example yet of why collaboration between radiologists and nuclear medicine physicians is so important.

Entrance Surface Dose from Pediatric Diagnostic X-ray Examinations in a Developing World Setting: Are We ‘ALARA Principle’ Compliant?

Background: Radiation protection in paediatric radiology requires special attention than in adult because children are more sensitive to radiation and at higher risk. This risk is explained by the longer life expectancy in children which allows for harmful effects of radiation to manifest and their developing organs and tissues being more sensitive to radiation. Hence, the need for determination of appropriate radiation dose for paediatric patients. Aims: To estimate entrance skin dose (ESD) received by paediatric patients during diagnostic x-ray examinations. Materials and Methods: A total of 253 paediatric patients undergoing various x-ray examinations between June 2011 and December, 2012 ia teaching hospital in the South West Nigeria were considered in this study. This hospital has no dedicated x-ray

Dose reduction methods for CT colonography

Patients, referring physicians, the media, and government agencies have all expressed concern over the risks of medical radiation, particularly as it relates to CT. This concern is particularly paramount when associated with a screening examination such as CT colonography. These theoretical risks must be weighed realistically against the substantial benefits of colon cancer screening as well as against the risks inherent in the major alternative screening option, optical colonoscopy. When put into perspective, the risk-benefit ratio is highly in favor of the performance of CT colonography. Nevertheless, in following the ALARA principle, there is an ever increasing armamentarium of options that can be employed in the pursuit of CT radiation dose reduction, all of which can be used in many synergistic combinations allowing for dose reduction while simultaneously preserving image quality and minimizing image noise. After a brief tutorial on estimating radiation dose, various strategies will be discussed including reductions in tube current and tube voltage as well as the use of automatic dose modulation and iterative reconstruction. Other practical considerations will also be reviewed including proper patient isocentering, optimization of colonic insufflation to minimize additional decubitus scans, proper choice of scan volumes to avoid overranging, and variation of slice thickness and window width to minimize perceived image noise. Finally, a strategy for how to incrementally introduce these methods as well as a way to compare dose reduction efforts across institutions throughout the country will be offered.

Dual source multidetector computed tomography coronary angiography in the surgical planning regarding the major coronary artery anomalies in children

Background: This study aims to demonstrate major coronary artery anomalies such as anomalous origin and coronary artery fistulas on dual-source multi detector computed tomography (MDCT) coronary angiography in children before surgical treatment. Methods: Six children (3 boys, 3 girls; mean age 6 years; range 2 days to 15 years) referred for a MDCT coronary angiography for evaluation of coronary anomaly between January 2010 and June 2011 were included in this study. Electrocardiography (ECG)-gated dual-source MDCT coronary angiography was performed on all patients. No beta-blockers were given prior to the procedure. The mean heart rate was 98±20 bpm (range 128 to 75 bpm). In all patients, ostium, course, and end-distal portion of coronary artery were inspected for anomalies. Exact opening point was carefully assessed in patients with fistulas. Dual-source MDCT examination was performed with low kilovolt dose reduction algorithm (80 kV, range 150-350 mA) compatible with ALARA principles. Results: Three anomalous origin (one ALCAPA, two anomalous left main coronary artery originated from right sinus of Valsalva) and three fistulas (two coronary-cameral fistula, one left main coronary artery -coronary sinus fistula) were clearly identified with dual-source MDCT angiography. Conclusion: Dual source MDCT angiography is a noninvasive and effective method as an alternative to conventional coronary angiography for the preoperative assessment of major anomalous origin of coronary artery or coronary artery fistulas.

EComment. Cardiac computed tomography angiography for evaluation of coronary artery bypass grafts

Sahiner and colleagues [1] demonstrate the comparative efficacy of 16- vs 64-slice cardiac computed tomography (CT) angiography when assessing coronary artery bypass grafts. One of the major concerns regarding the increased use of cardiac CT angiography is the effective radiation dose received by patients. The widening indications and applications of cardiac CT angiography may mean patients undergo multiple studies during their lifetime. The improved spatial and temporal resolution achieved by 64-slice cardiac CT over 16-slice cardiac CT comes at the expense of an increased effective radiation dose. In a study comparing 16- and 64-slice cardiac CT angiography, despite strategies to reduce radiation dose including reduction in tube voltage and changing gating strategies, the effective dose for cardiac CT was 6.4±1.9 and 11.0±4.1 mSv with 16- and 64-slice CT, respectively [2]. The Society of Cardiovascular Computed Tomography promotes the “ALARA principle“, which states that the radiation dose to a patient should be Low As Reasonably Achievable. In other words, we should use the lowest optimal radiation dose possible to achieve a diagnostic image [3]. In this study there was a similar diagnostic accuracy for graft patency between 16- and 64-slice cardiac CT although the 16 slice was less accurate for detecting graft stenosis. All proximal anastomosis could be visualized using both techniques. Therefore in certain clinical scenarios, where the question to be answered depends on identifying the origin of grafts or patency of grafts, the use of 16-slice cardiac CT will provide diagnostic information at a lower radiation dose. Conflict of interest: none declared