Radiation Exposure During Radiofrequency Catheter Ablation for Atrial Fibrillation

MACLE, L., et al. : Radiation Exposure During Radiofrequency Catheter Ablation for Atrial Fibrillation. RF catheter ablation of paroxysmal atrial fibrillation (PAF) is associated with prolonged fluoroscopy. The procedural duration and fluoroscopic exposure to patients and medical staff were recorded and compared among 43 ablation procedures for PAF, 20 for common atrial flutter, and 16 for accessory pathways. Patient radiation exposure was measured by dosimeters placed over the xyphoid, while that of physicians and nurses was measured by dosimeters placed outside and inside the lead apron. The mean fluoroscopy time was   57 ± 30   minutes for PAF,   20 ± 10   minutes for common flutter, and   22 ± 21   minutes for accessory pathway ablation. The patient median radiation exposure was 1110μSv for PAF, compared with 500 μSv for common flutter and 560 μSv for accessory pathway ablation (P < 0.01). The median radiation exposure to physician and nurse inside the lead apron were, respectively, 2 μSv and 3 μSv for PAF, 1 μSv and 2 μSv for common flutter, and <0.5 μSv and 3 μSv for accessory pathway ablations. RF catheter ablation for PAF was associated with prolonged fluoroscopy times and a twofold higher radiation exposure to the patient and physician compared with other ablation procedures. Assuming 300 procedures/year, radiation exposure to the medical staff was below the upper recommended annual dose limit. (PACE 2003; 26[Pt. II]:288–291)     

Coronary calcium scans and radiation exposure in the multi-ethnic study of atherosclerosis

With the increasing use of coronary artery calcium (CAC) scoring to risk stratify asymptomatic patients for future cardiovascular events, there have been concerns raised regarding the theoretical risk of radiation exposure to this potentially large patient population. Newer CT protocols have sought to reduce radiation exposure without compromising image quality, but the reported radiation exposures in the literature remains widely variable (0.7–10.5 mSv). In this study, we report the radiation exposure of calcium scoring from our MESA cohort across several modern CT scanners with the aim of clarifying the radiation exposure of this imaging modality. To evaluate the mean effective doses of radiation, using dose length product, utilized for coronary artery calcium scoring in the MESA cohort, in an effort to understand estimated population quantity effective dose using individual measurements of scanner radiation output using current CT scanners. We reviewed effective dose in milliSieverts (mSv) for 3442 participants from the MESA cohort undergoing coronary artery calcium scoring, divided over six sites with four different modern CT scanners (Siemens64, Siemens Somatom Definition, GE64, and Toshiba 320). For effective dose calculation (milliSieverts, mSv), we multiplied the dose length product by conversion factor k (0.014). The mean effective dose amongst all participants was 1.05 mSv, a median dose of 0.95 mSV. The mean effective dose ranged from 0.74 to 1.26 across the six centers involved with the MESA cohort. The Siemens Somatom Definition scanner had effective dose of 0.53 (n = 123), Siemens 64 with 0.97 (n = 1684), GE 64 with 1.16 (n = 1219), and Toshiba 320 with 1.26 mSv (n = 416). Subgroup analysis by BMI, age, and gender showed no variability between scanners, gender, ages 45–74 years old, or BMI less than 30 kg/m². Subjects over age 75 yo had a mean effective dose of 1.29 ± 0.31 mSv, while the <75 yo subgroup was 0.78 ± 0.09 mSv (p < 0.05). Effective doses in subjects with BMI > 40 kg/m² was significantly greater than other subgroups, with mean dose of 1.47 ± 0.51 mSv (p < 0.01). Using contemporary CT scanners and protocols, the effective dose for coronary artery calcium is approximately 1 mSv, an estimate which is consistently lower than previously reported for CAC scanning, regardless of age, gender, and body mass index.     

Human Radiation Dosimetry of [<Superscript>18</Superscript>F]AV-1451(T807) to Detect Tau Pathology

Purpose

[¹⁸F]AV-1451 is a positron emission tomography (PET) radioligand for detecting paired helical filament tau. Our aim was to estimate the radiation dose of [¹⁸F]AV-1451 in humans.

Procedures

Whole-body PET scans were acquired for six healthy volunteers (three male, three female) for 128 min after injection of [¹⁸F]AV-1451 (268?±?31 MBq). Radiation doses were estimated using the OLINDA/EXM software.

Results

The estimated organ doses ranged from 7.81 to 81.2 μSv/MBq. The critical organ for radiation burden was the liver. Radiation doses to the reproductive and blood-forming organs were 14.15, 8.43, and 18.35 μSv/MBq for the ovaries, testes, and red marrow, respectively. The mean effective dose was 22.47?±?3.59 μSv/MBq.

Conclusions

A standard single injection of 185 MBq (5 mCi) results in an effective dose of 4.7 mSv in a healthy subject. Therefore, [¹⁸F]AV-1451 could be used in multiple PET scans of the same subject per year.

     

Eye Lens Radiation Doses to Miscentering Patients and Health-Care Staff From Head Computed Tomography

The purposes of this study were to assess the effect of patient vertical miscentering on eye lens radiation doses in patients who have undergone head computed tomography (CT) and to measure the absorbed dose to the eye lens in health-care staff who remain in the CT room during the procedure. All measurements were performed in phantoms. Nanodot™ optically stimulated luminescence dosimeters were used to measure radiation doses. For the assessment of the effect of patient vertical miscentering, CT scans were obtained at six different table heights. The radiation doses in the eye lens of health-care staff received when working at three different locations in the CT room were measured. Correction coefficients were applied to determine equivalent dose, Hp(3), in the eye lens. The results revealed that the positioning of patients off the CT scan isocenter during head CT may result in a significantly increased eye lens dose. The phantom eye lens doses can be increased by 43.7% (70 mGy), and image noise increased when the table was 5 cm below the isocenter due to the effect of the bow tie filter and eyes being irradiated directly by the primary beam for a greater proportion of the tube rotation. An estimated eye lens dose of ≤0.1-0.2 mSv was found in phantoms simulating health-care staff, with the dose depending on positioning of the phantom. Health-care staff in the room during CT scans are at risk of a significant eye lens dose, particularly if positioned posterior to the gantry.     

Biodistribution and Radiation Dosimetry of [<Superscript>18</Superscript>F]Mefway in Humans

Purpose

[¹⁸F]Mefway is a positron emission tomography (PET) radioligand for quantification of the brain serotonin 1A (5-HT_1A) receptor density. The purpose of this study was to evaluate the radiation safety of [¹⁸F]Mefway in humans.

Procedures

Six healthy volunteers (three males and three females) were whole-body PET scanned for 114 min after injection of [¹⁸F]Mefway (226?±?35 MBq). Estimated radiation doses were determined by the OLINDA/EXM software.

Results

[¹⁸F]Mefway was safe and well tolerated by all subjects. Residence time ranges from 0 (gallbladder) to 0.822 h (urinary bladder wall). While the estimated radiation doses in the reproductive and blood-forming organs were below 13.35–22.87 μSv/MBq, radiation dose in the urinary bladder wall was 471 μSv/MBq. The mean effective dose was 40.23?±?6.63 μSv/MBq.

Conclusion

For a typical single injection of 185 MBq (5 mCi), the dose will result in 87.1 mSv for the urinary bladder wall. To reduce radiation burden, the bladder voiding can be used before [¹⁸F]Mefway PET scan.

     

Kyphoplasty and vertebroplasty in the treatment of osteoporotic fractures of the spine

This article presents the problem of spinal fractures and the application of vertebro- and kyphoplasty in their treatment. The techniques, outcomes, and complications involved in these procedures are described on the basis of current literature. The advantages and disadvantages of vertebro- and kyphoplasty are discussed.     

How do radiographic techniques affect image quality and patient doses in CT?

The radiation dose received by patients who undergo CT examinations has become a subject of considerable interest. Adult effective doses for head CT examinations are of the order of 1 to 2 mSv, and for single body examinations, patient doses are typically between 4 and 6 mSv. These doses are high in comparison to most other types of radiological examinations that use ionizing radiation. Patient CT doses may also be compared with natural background (3 mSv/year), dose limits to members of the public (1 mSv/year), and the highest level of occupational exposure, which is about 5 mSv/year. The advent of multi-slice technology will serve to increase CT utilization, as well as individual doses for any given examination. Radiologists are responsible for medical radiation doses to their patients, and it is imperative that they understand the relationship between radiation dose and image quality. In this review, we address the impact that variations in radiographic techniques (ie, selected values of X-ray kVp and mAs) have on patient doses as well as the quality of the resultant CT images.     

Estimation of Radiation Exposure to Workers During [18F] FDG PET/CT Procedures at Molecular Imaging Center,Oman

Positron-emission tomography (PET) is the imaging modality of choice in oncology. In addition, there are several indications for using PET in cardiology and neurology. The main radiotracer used is the radiolabeled glucose analog [¹⁸F] fluorodeoxyglucose ([¹⁸F] FDG). The high-energy annihilation radiation from positron emission may lead to significant radiation exposure to medical imaging professionals such as technologists and staff nurses, patients, and direct acquaintances of the patient. In this cross-sectional observational study, the effective dose to workers in the Molecular Imaging Center from patients injected with [¹⁸F] FDG is assessed. Dose rates were estimated by a calibrated, portable gamma-ray survey meter at 0.3, 0.5, 1.0, and 2.0 m from 70 patients who underwent whole body [¹⁸F] FDG PET/CT procedure immediately and 2 hours post-injection. Electronic personal dosimeters were used to determine the radiation doses per PET/CT imaging for the five staff who directly involved in handling of the injected patients. The staff includes two technologists, two staff nurses, and one medical physicist. The mean dose rates from patients after injection and standard deviation (μSv/h) for the four distances were 98.1 ± 20.0, 55.3 ± 20.0, 28.2 ± 10.0, and 10.8 ± 5.0, respectively. After 2 hours, the measurements significantly dropped to 45.7 ± 10.0, 23.6 ± 10.0, 9.9 ± 4.0, and 3.7 ± 1.0 μSv/h. The average effective dose values for a technologist from injected patients throughout the procedure of PET/CT study was 4.17 μSv per study or 5 mSv/y. This is less than the annual limit recommended by the International Commission on Radiological Protection of 20 mSv/y received in the medical imaging profession.     

Trauma team radiation exposure: the potential need for dosimetry monitoring

Objectives: Australian radiation regulations require routine monitoring of health‐care workers who might receive a whole‐body effective radiation dose in excess of 1 mSv/year. In Australian hospitals, routine monitoring with a dosimeter is recommended for levels beyond 300 μSv/year. We aimed to determine the potential radiation exposure to trauma team members and whether routine personal radiation dosimetry should be recommended. Method: An anthropomorphic mannequin with a radiation detector was placed at five locations around the resuscitation bed. Three sets of standard trauma‐series X‐rays were performed, and the exposure was measured and averaged at each location. These data were then extrapolated to estimate the potential radiation equivalence at the level of the thyroid gland for staff working in each of the locations over a 1 year period with and without personal protective equipment. Results: The total dose ranged from 1.2 to 20.5 μSv for a single trauma patient. The highest recorded dose was at the location of the circulation doctor during pelvic X‐ray. Based on these data, it would take only 15 trauma patients per year for a team member to be potentially exposed to the level at which routine dosimetry is usually recommended, should no personal protective equipment be used. The use of a lead gown and a lead gown with a thyroid collar reduced exposure by four‐ and ninefold, respectively. Conclusions: We have demonstrated the possibility of significant ionizing radiation exposure for unprotected trauma team members. Dosimeter use by trauma team personnel needs to be reviewed based on local protocols and patient numbers.     

High-definition computed tomography for coronary artery stents: image quality and radiation doses for low voltage (100 kVp) and standard voltage (120 kVp) ECG-triggered scanning

The noninvasive assessment of coronary stents by coronary CT angiography (CCTA) is an attractive method. However, the radiation dose associated with CCTA remains a concern for patients. The purpose of this study is to compare the radiation doses and image qualities of CCTA performed using tube voltages of 100 or 120 kVp for the evaluation of coronary stents. After receiving institutional review board approval, 53 consecutive patients with previously implanted stents (101 stents) underwent 64-slice CCTA. Patients were divided into three different protocol groups, namely, prospective ECG triggering at 100 kVp, prospective ECG triggering at 120 kVp, or retrospective gating at 100 kVp. Two reviewers qualitatively scored the quality of the resulting images for coronary stents and determined levels of artificial lumen narrowing (ALN), stent lumen attenuation increase ratio (SAIR), image noise, and radiation dose parameters. No significant differences were found between the three protocol groups concerning qualitative image quality or SAIR. Coronary lumen attenuation and in-stent attenuation of 100 kVp prospective CCTA (P-CCTA) were higher than in the 120 kVp P-CCTA protocol (all Ps < 0.001). Mean ALN was significantly lower for 100 kVp P-CCTA than for 100 kVp retrospective CCTA (R-CCTA, P = 0.007). The mean effective radiation dose was significantly lower (P < 0.001) for 100 kVp P-CCTA (3.3 ± 0.4 mSv) than for the other two protocols (100 kVp R-CCTA 6.7 ± 1.0 mSv, 120 kVp P-CCTA 4.6 ± 1.2 mSv). We conclude that the use of 100 kVp P-CCTA can reduce radiation doses for patients while maintaining the imaging quality of 100 kVp R-CCTA and 120 kVp P-CCTA for the evaluation of coronary stents.     

Occupational Radiation Exposure among the Staff of Departments of Nuclear Medicine and Diagnostic Radiology in Kuwait

Objectives

To investigate radiation exposure among the staff of departments of nuclear medicine (NM) and diagnostic radiology (DR) during 2008 and 2009 and to compare the mean doses received with the limit of 20 mSv/year of the International Commission of Radiological Protection (ICRP).

Materials and Methods

The whole-body dose or effective dose, i.e. Hp(10), and the skin dose, i.e. Hp(0.07), of the staff of departments of NM and DR in Kuwait for the period of 2008 and 2009 were taken from the national thermoluminescent dosimetry database. A total of 1,780 radiation workers, grouped as NM physicians, radiologists, NM technologists, and DR technologists, from 7 departments of NM and 12 departments of DR were included. The annual average Hp(10) and Hp(0.07) were calculated for each group and comparisons were made between the groups and the years. A two-sided Mann-Whitney test was carried out, at the p = 0.05 level, to compare the means. The mean Hp(10) was compared with the limits of the ICRP.

Results

Of the 16 distributions of Hp(10) and Hp(0.07), 10 were normal, with a mean annual Hp (10) in 2008 of 1.06, 1.03, 1.07, and 1.05 mSv for NM physicians, radiologists, NM technologists, and DR technologists, respectively. The corresponding Hp(0.07) values for 2008 were 1.03, 1.00, 1.05, and 1.03 mSv, respectively. Small but significant (p < 0.001) reductions in Hp(10) and Hp(0.07) were observed in 2009 for NM technologists and DR technologists. In all other cases, no significant (p > 0.072) differences were found.

Conclusion

The annual average Hp(10) was well below the limit of the ICRP.Key Words: Occupational exposure, Radiation dose, Nuclear medicine, Radiology     

Radiation Exposure of Patient and Physician during Implantation and Upgrade of Cardiac Resynchronization Devices

Background: Cardiac resynchronization therapy (CRT) is often associated with extended fluoroscopic exposure during placement of the devices. The objective of this study was to measure the radiation exposure sustained by different parts of the body of patients and operators during fluoroscopically guided cardiac resynchronization device implantation. Methods: Dosimetry data were prospectively recorded in a series of 104 consecutive patients, who underwent resynchronization device implantation or upgrade in our cardiac catheterization laboratory. Five Chipstrate dosimeters were fixed to the patient's skin around the thorax (right and left paravertebral, right and left parasternal, and sternal positions), one dosimeter was attached to the forehead, and one to the pubis. The operator was equipped with one dosimeter on the forehead at eye level and a ring dosimeter was worn on the right hand. Results: Based on the maximum radiation dose of 9.2 mSv measured at the operator's hand in a single implantation session, it might be recommended to conservatively limit the number of implantations to four per month (an annual limit value of 500 mSv). At a mean dose of 1.2 mSv, this number can be increased sevenfold. Conclusion: In patients, incipient deterministic radiation effects can theoretically be observed at dose area product >400 Gy?cm², a dose applied in 2.9% of CRT implantation procedures. Special follow‐up programs are considered necessary for these patients and for operators, as the latter may be exposed over many years given the unknown long‐term impact of chronic radiation exposure and the nature of current complex electrophysiology and device procedures. (PACE 2010; 1003–1012)     

Toward computer-assisted image-guided congenital heart defect repair: an initial phantom analysis

Purpose

Radiation exposure in interventional cardiology is an important consideration, due to risk of cancer and other morbidity to the patient and clinical staff. Cardiac catheterizations rely heavily on fluoroscopic imaging exposing both patient and clinician to ionizing radiation. An image-guided surgery system capable of facilitating cardiac catheterizations was developed and tested to evaluate dose reduction.

Methods

Several electromagnetically tracked tools were constructed specifically a 7-Fr catheter with five 5-degree-of-freedom magnetic seeds. Catheter guidance was accomplished using our image guidance system Kit for Navigation by Image-Focused Exploration and fluoroscopy alone. A cardiac phantom was designed and 3D printed to validate the image guidance procedure. In mock procedures, an expert clinician guided and deployed an occluder across the septal defect of the phantom heart.

Results

The image guidance method resulted in a dose of 1.26 mSv of radiation dose per procedure, while traditional guidance resulted in a dose of 3.33 mSv. Average overall dose savings for the image-guided method was nearly 2.07 mSv or 62 %.

Conclusion

The work showed significant (\(p<0.001\)) decrease in radiation dose with use of image guidance methods at the expense of a modest increase in procedure time. This study lays the groundwork for further exploration of image guidance applications in pediatric cardiology.

     

Effect of kVp on image quality and accuracy in coronary CT angiography according to patient body size: a phantom study

The aim is to investigate the effect of tube voltage and chest wall thickness on image quality, stenosis measurement, and radiation dose in coronary CT angiography (CCTA) in a phantom study. A phantom with tubes in a box at its center and concentric cylindrical plastic chambers of three layers at its periphery was constructed. The concentric cylinders were filled with oil or left empty to simulate different degrees of obesity. Retrospective CT scanning was performed at different kVps and mAs. Image noise, contrast to noise ratio (CNR), stenosis measurement, and radiation dose were obtained. A CNR higher than 10 was considered to be acceptable for clinical practice. Mean image noise was 51.7 at 80 kVp, 31.6 at 100 kVp, and 24.7 at 120 kVp (P < 0.001). A CNR greater than 10 could be achieved with all the images using 80 kVp as well as using 100 or 120 kVp. However, CNRs at 100 and 120 kVp were significantly higher than the CNR at 80 kVp (P < 0.001). There were no significant differences between 100 and 120 kVp. All stenosis measurements were overestimated. Accuracy of stenosis measurement was significantly correlated with CNR (P < 0.05), but not with kVps. Mean doses were 2.07 mSv at 80 kVp, 3.37 mSv at 100 kVp, and 5.17 mSv at 120 kVp (P < 0.001). CNR per radiation dose was highest at 80 kVp, regardless of chest wall thickness. For CCTA, using 80 kVp with high mAs is the best choice, regardless of chest wall thickness, for minimal radiation dose and sufficient image quality.     

Image quality in low-dose coronary computed tomography angiography with a new high-definition CT scanner

A new generation of high definition computed tomography (HDCT) 64-slice devices complemented by a new iterative image reconstruction algorithm—adaptive statistical iterative reconstruction, offer substantially higher resolution compared to standard definition CT (SDCT) scanners. As high resolution confers higher noise we have compared image quality and radiation dose of coronary computed tomography angiography (CCTA) from HDCT versus SDCT. Consecutive patients (n = 93) underwent HDCT, and were compared to 93 patients who had previously undergone CCTA with SDCT matched for heart rate (HR), HR variability and body mass index (BMI). Tube voltage and current were adapted to the patient’s BMI, using identical protocols in both groups. The image quality of all CCTA scans was evaluated by two independent readers in all coronary segments using a 4-point scale (1, excellent image quality; 2, blurring of the vessel wall; 3, image with artefacts but evaluative; 4, non-evaluative). Effective radiation dose was calculated from DLP multiplied by a conversion factor (0.014 mSv/mGy × cm). The mean image quality score from HDCT versus SDCT was comparable (2.02 ± 0.68 vs. 2.00 ± 0.76). Mean effective radiation dose did not significantly differ between HDCT (1.7 ± 0.6 mSv, range 1.0–3.7 mSv) and SDCT (1.9 ± 0.8 mSv, range 0.8–5.5 mSv; P = n.s.). HDCT scanners allow low-dose 64-slice CCTA scanning with higher resolution than SDCT but maintained image quality and equally low radiation dose. Whether this will translate into higher accuracy of HDCT for CAD detection remains to be evaluated.     

Prospectively gated low-dose CCTA: 24 months experience in more than 2,000 clinical cases

Cardiac CT exams have recently come under increased scrutiny because of their relatively high radiation dose. The most effective way to lower the dose of coronary computed tomography angiography (CCTA) exams is with the use of prospective gating. This allows for a significant reduction in effective radiation dose when compared to retrospective ECG gating while image quality is maintained or improved. We reviewed data from 2,124 consecutive cardiac CT exams, including 1,978 CCTA’s and 146 CCTA’s post CABG. With effective heart rate control, prospective gating was used for 92.1% of the CCTAs and 83.2% of CCTAs following CABG. The prospectively gated CCTAs had a mean effective dose of 3.1 ± 1.5 mSv, CCTAs following CABG had a mean dose of 6.4 ± 2.3 mSv. We review our experience using prospective gating in specific areas to include patient selection, patient preparation, use of β- and calcium-channel-blockers for heart rate control, selection of gating technique and scan parameters, radiation dose, and post-processing techniques.     

Adenosine-stress dynamic myocardial perfusion imaging using 128-slice dual-source CT: optimization of the CT protocol to reduce the radiation dose

The aim of this study was to compare the radiation dose and image quality of different adenosine-stress dynamic myocardial perfusion CT protocols using a 128-slice dual-source computed tomography (DSCT) scanner. We included 330 consecutive patients with suspected coronary artery disease. Protocols employed the following dynamic scan parameters: protocol I, a 30-s scan with a fixed tube current (FTC, n = 172); protocol II, a 30-s scan using an automatic tube current modulation (ATCM) technique (n = 108); protocol III, a 14-s scan using an ATCM (n = 50). To determine the scan interval for protocol III, we analyzed time-attenuation curves of 26 patients with myocardial perfusion who had been scanned using protocol I or II. The maximum attenuation difference between normal and abnormal myocardium occurred at 18.0 s to 30.3 s after initiation of contrast injection. Myocardial perfusion images of FTC and ATCM were of diagnostic image quality based on visual analysis. The mean radiation dose associated with protocols I, II, and III was 12.1 ± 1.6 mSv, 7.7 ± 2.5 mSv, and 3.8 ± 1.3 mSv, respectively (p < 0.01). Use of a dose-modulation technique and a 14-s scan duration for adenosine-stress CT enables significant dose reduction while maintaining diagnostic image quality.     

Prospective ECG-triggered sequential scan protocol for coronary dual-source CT angiography: initial experience

The exposure to ionizing radiation has raised concerns about coronary CT angiography (CCTA). Recently, prospective ECG-triggered sequential scan technique has been introduced in CCTA to significantly reduce radiation exposure. The purpose of this study was to analyze our experience with the sequential scan technique on a dual-source CT system with respect to image quality and radiation dose. Qualitative and quantitative image quality as well as radiation dose were assessed in 514 consecutive patients undergoing CCTA either with sequential or spiral image acquisition technique on dual-source CT. The selection of the applied scan technique was at the discretion of an experienced coronary CT angiographer. A multivariate logistic regression analysis was applied to identify predictors of diagnostic image quality. Diagnostic CCTA image quality was found in 1,395/1,429 (97.6%) versus 4,664/4,782 (97.5%) of the coronary segments in patients studied with sequential versus spiral scanning (P = 0.82). While the application of betablockers for CCTA was an independent factor for improved image quality in the multivariate regression analysis, heart rate variability and body mass index were indepentently associated with a deterioriated image quality. The scan technique had no independent impact on diagnostic image quality. Mean estimated radiation dose was reduced by 63% in patients studied with sequential scan technique (3.4 ± 2.2 vs. 7.6 ± 5.0 mSv, P < 0.01). In patients with a low and stable heart rate, the sequential scan technique is a promising method to effectively reduce radiation exposure in dual-source CCTA. Due to the comparable image quality in sequential and spiral dual-source CCTA, the sequential scan technique should be considered as the primary scan protocol in appropriate patients.     

Eliminating the stigma: A systematic review of the health effects of low-dose radiation within the diagnostic imaging department and its implications for the future of medical radiation

BackgroundLow-dose radiation exposure to Canadians is exponentially increasing due to the influx of diagnostic imaging and medical procedures that utilize radiation. Despite the use of medical radiation since 1896, the standardized acceptable dose for the Canadian public is still debated. The current annual dose limit for the public is set at 1 millisievert (mSv). This set dose limit intrinsically restricts the use of medical radiation for diagnosis due to concerns of public health.MethodsThis systematic review is in the form of a retrospective meta-analysis of previous experimental studies and observational reviews of low-dose radiation health effects. A database search using PubMed and Medscape identified 1,296 articles using the terms “low-dose radiation”, “radiation hormesis”, “radiation safety”, “dose exposure”, and “medical radiation”. Full text articles were excluded for the following reasons: radiation dose level not <100mSv, results of radiation effects not included, or no inclusion of biologic effects on living tissue. After screening, 15 studies were selected for inclusion.ResultsThe concerns of radiation exposure are based on epidemiological and experimental studies that have indicated that high-dose ionizing radiation has toxic effects and increases cancer risk. In contrast, low-dose radiation has experimentally demonstrated various beneficial effects through a combination of molecular and cohort studies, randomized control trials, and observational analysis. The limitation of radiation in medical imaging is founded on the assumption that low-dose radiation health risks are a linear extrapolation of high-dose radiation.Discussion/conclusionsThrough a systematic review of research, it is proposed that the current dose-response extrapolation for radiation-related health risks cannot be linearly based on the effects at high doses. By altering this knowledge, we could effectively improve patient diagnosis and public health by redefining the restrictions of current radiation limits within diagnostic imaging.     

Coronary CT angiography using the second-generation 320-detector row CT: assessment of image quality and radiation dose in various heart rates compared with the first-generation scanner

To assess the image quality and radiation dose reduction in various heart rates in coronary CT angiography using the second-generation 320-detector row CT compared with the first-generation CT. Ninety-six patients were retrospectively included. The first 48 patients underwent coronary CT angiography with the first-generation 320-detector row CT, while the last 48 patients underwent with the second-generation CT. Subjective image quality was graded using a 4-point scale (4, excellent; 1, unable to evaluate). Image noise and contrast-to-noise ratio were also analyzed. Subgroup analysis was performed based on the heart rate. The mean effective dose was derived from the dose length product multiplied by a conversion coefficient for the chest (κ = 0.014 mSv × mGy^?1 × cm^?1). The overall subjective image quality score showed no significant difference (3.66 vs 3.69, respectively, p = 0.25). The image quality score of the second-generation group tended to be higher than that of the first-generation group in the 66- to 75-bpm subgroup (3.36 vs 3.53, respectively, p = 0.07). No significant difference was observed in image noise and contrast-to-noise ratio. The overall radiation dose reduced by 24 % (3.3 vs 2.5 mSv, respectively, p = 0.03), and the reduction was substantial in patients with higher heart rate (66- to 75-bpm, 4.3 vs 2.2 mSv, respectively, p = 0.009; >75 bpm, 8.2 vs 3.7 mSv, respectively, p = 0.005). The second-generation 320-detector row CT could maintain the image quality while reducing the radiation dose in coronary CT angiography. The dose reduction was larger in patients with higher heart rate.