Overview of patient dosimetry in diagnostic radiology in the USA for the past 50 years

Role of contrast-enhanced serial/spot abdominal X-rays in perioperative follow-up of patients undergoing abdominal surgery: An observational clinical study

BACKGROUND

Many imaging methods such as ultrasonography, computed tomography (CT), magnetic resonance imaging, and endoscopy are used to identify the problems or complications that occur in the perioperative period and to determine the appropriate therapeutic approach. Specialists at surgical clinics and intensive care units sometimes need diagnostic procedures that can give quick results or reveal unexpected results. In particular, rapid on-site evaluation of patients followed under intensive care conditions has several advantages.

AIM

To determine the problems developing in patients in the perioperative period by contrast-enhanced abdominal X-ray (CE-AXR), revealing their current status or defining the effectiveness of CE-AXR.

METHODS

The files of the patients who underwent hepatopancreatobiliary or upper gastrointestinal surgery, whose CE-AXR film was taken, were reviewed retrospectively. Abdominal X-ray radiographs taken after ingestion of a water-soluble contrast agent (iohexol, 300 mg, 50 cc vial) and its application in a drain, nasogastric tube, or stent were evaluated. The contribution of the data obtained in patients who underwent CE-AXR to the diagnosis, follow-up, and treatment processes and the effectiveness of the application were investigated.

RESULTS

CE-AXR was applied to 131 patients in our clinic, most of whom underwent hepatopancreatobiliary or upper gastrointestinal surgery. It was determined that the data obtained from CE-AXR films taken in 98 (74.8%) of the patients contributed to the diagnosis, treatment, and follow-up expectations and positively affected the clinical processes.

CONCLUSION

CE-AXR is a simple procedure that can be applied anywhere, especially in intensive care patients and at bedside, with a portable X-ray device. The simplicity of the procedure, less radiation exposure for the patients, less time wastage, reduction in the CT and endoscopy procedure burden and costs, quick results, rapid assessment of the situation, and enabling the monitoring of processes with repetitive procedures are important advantages. X-rays taken will be useful in terms of being a reference value during the follow-up period of the patient and determining the situation in medicolegal processes.

Patient Radiation Doses in IR Procedures: The American College of Radiology Dose Index Registry-Fluoroscopy Pilot

PURPOSE

To update normative data on fluoroscopy dose indices in the United States for the first time since the Radiation Doses in Interventional Radiology study in the late 1990s.

MATERIALS AND METHODS

The Dose Index Registry-Fluoroscopy pilot study collected data from March 2018 through December 2019, with 50 fluoroscopes from 10 sites submitting data. Primary radiation dose indices including fluoroscopy time (FT), cumulative air kerma (Ka,r), and kerma area product (PKA) were collected for interventional radiology fluoroscopically guided interventional (FGI) procedures. Clinical facility procedure names were mapped to the American College of Radiology (ACR) common procedure lexicon. Distribution parameters including the 10th, 25th, 50th, 75th, 95th, and 99th percentiles were computed.

RESULTS

Dose indices were collected for 70,377 FGI procedures, with 50,501 ultimately eligible for analysis. Distribution parameters are reported for 100 ACR Common IDs. FT in minutes, Ka,r in mGy, and PKA in Gy-cm2 are reported in this study as (n; median) for select ACR Common IDs: inferior vena cava filter insertion (1,726; FT: 2.9; Ka,r: 55.8; PKA: 14.19); inferior vena cava filter removal (464; FT: 5.7; Ka,r: 178.6; PKA: 34.73); nephrostomy placement (2,037; FT: 4.1; Ka,r: 39.2; PKA: 6.61); percutaneous biliary drainage (952; FT: 12.4; Ka,r: 160.5; PKA: 21.32); gastrostomy placement (1,643; FT: 3.2; Ka,r: 29.1; PKA: 7.29); and transjugular intrahepatic portosystemic shunt placement (327; FT: 34.8; Ka,r: 813.0; PKA: 181.47).

CONCLUSIONS

The ACR DIR-Fluoro pilot has provided state-of-the-practice statistics for radiation dose indices from IR FGI procedures. These data can be used to prioritize procedures for radiation optimization, as demonstrated in this work.

Characterization of patient dose distributions and probabilistic risk analysis in cardiovascular catheterization laboratories

Purpose: Patient radiation doses in cardiovascular and interventional radiology are highly variable for similar procedures. This random nature may be better described by a distribution function, compared to a linear regression. This study develops a distribution function to characterize patient dose distributions and estimate probabilistic risk.Methods: Reference air kerma from 8647 patients over six years were retrospectively collected from an EP lab and two Cath labs. Data was first sorted into low dose (<100mGy) and high dose cases (>100mGy), and histograms of the data created. Dagum and Inverse gamma distributions were chosen to initially fit to both low and high dose cases. Fits between model and the data was optimized, and a linear regression analysis performed to obtain R squared values and standard errors for the correlation between model and data. Risk probabilities were estimated according to the modeled distribution function. BMI and time distributions were analyzed to understand their influence on the inverse gamma distribution error found in the data. 75th percentiles from both descriptive statistics and model were calculated.Results: The inverse gamma distribution can be used to characterize radiation dose distributions. Model predicted cases for radiation dose 3000mGy< x <5000mGy and >5000mGy are approximately 42 and 0 for 3651 cases for lab#1, and 14 and 1 for 3197 cases for lab#2, respectively, while the actual cases are 10 and 0, and 16 and 2. Descriptive and model statistics generated different 75th percentile levels for sorted data compared to unsorted data. Time has a greater influence on inverse gamma distribution function than BMI.Conclusion: This study creates a framework to understand the random error present in radiology practices that cause wide variations in patient radiation doses. It also provides an approach to evaluate different IR areas in terms of effectiveness of dose reduction measures.

Patient Radiation Doses in Interventional Radiology Procedures: Comparison of fluoroscopy dose indices from the American College of Radiology Dose Index Registry-Fluoroscopy (DIR-Fluoro) Pilot to the RAD-IR study

PURPOSE

To compare interventional radiology fluoroscopically-guided intervention (FGI) radiation dose index distributions from the American College of Radiology (ACR) Fluoroscopy Dose Index Registry (DIR-Fluoro) pilot to the Radiation Doses in Interventional Radiology (RAD-IR) study.

MATERIALS AND METHODS

Individual and grouped ACR Common IDs (procedure types) from the DIR-Fluoro pilot were matched to procedure types in the RAD-IR study. Fifteen comparisons were made. Distribution parameters including the 10^th, 25^th, 50^th, 75^th, and 95^th percentiles were compared for fluoroscopy time (FT), cumulative air kerma (K_a,r), and kerma area product (P_KA). Two derived indices were computed using median dose indices. The procedure-averaged reference air kerma rate (K_a,r¯) was computed as K_a,r / FT. The procedure-averaged X-ray field size at the reference point (A_r¯) was computed as P_KA / (K_a,r * 1,000).

RESULTS

Median FT was equally likely to be higher or lower in the DIR-Fluoro pilot compared to RAD-IR, while maximum FT was almost twice as likely to be higher in DIR-Fluoro than RAD-IR. Median K_a,r was lower in the DIR-Fluoro pilot for all procedures, as was median P_KA. The maximum K_a,r and P_KA were more often higher in the DIR-Fluoro pilot compared to RAD-IR. K_a,r¯ followed the same pattern as K_a,r, while A_r¯ was often greater in DIR-Fluoro.

CONCLUSIONS

Median dose indices have decreased since the RAD-IR study. Typical K_a,r rates are lower, a result of the use of lower default dose rates. However, opportunities for quality improvement exist, including a renewed focus on tight collimation of the imaging field of view.

Comparison of radiation exposure and surgery time between an intraoperative CT with automatic surface registration and a preoperative CT with manual surface registration in navigated spinal surgeries

PURPOSE

This retrospective matched case-control study was conducted to compare two CT based surgery techniques for navigated screw placement in spinal surgery, whether a reduction of radiation exposure and surgery time could be achieved.

METHODS

We matched cases treated with an intraoperative CT (iCT), regarding the type and number of implants, with cases treated with a preoperative CT (pCT) of one main surgeon. Outcome measures were radiation exposure due to intraoperative control x-rays, radiation exposure due to CT images, and the duration of surgery.

RESULTS

The required radiation exposure could be significantly reduced in the iCT group. For the intraoperative control X-rays by 69% (median (MED) 88.50/standard deviation (SD) 107.84 and MED 286.00/SD 485.04 for iCT and pCT respectively-in Gycm²; p < 0.001) and for the CT examinations by 25% (MED 317.00/SD 158.62 and MED 424.50/SD 225.04 for iCT and pCT respectively-in mGycm; p < 0.001) with no significant change in surgery time. The correlation between the number of segments fused and the necessary surgery time decreased significantly for the iCT group (Pearson product-moment-correlation: r = 0.569 and r = 0.804 for iCT and pCT respectively; p < 0.05).

CONCLUSION

The results show that spinal navigation using an intraoperative CT with automatic registration compared to a preoperative CT and intraoperative manual surface registration, allows a significant reduction of radiation exposure, without prolonged surgery time. A significant benefit regarding cut-to-suture-time can be gained with surgeries of a larger scale.

Patient-Based Dose Audit for Common Radiographic Examinations With Digital Radiology Systems: A Retrospective Cross-Sectional Study

This study aims to audit radiation doses of adult patients who underwent common diagnostic X-ray examinations and compare dose area product (DAP) values with the established International Diagnostic Reference Level (IDRLs). Retrospective cross-sectional records of 339-patients who underwent 699-radiographic examinations between October 2018 and March 2019 were obtained. Patient-related factors, exposure, and DAP data were recorded for the six most common examinations. The mean and 75th percentile of DAPs were recorded and compared to IDRLs values. The 75th percentiles of the locally measured DAPs were below IDRLs for all examinations except for lateral lumbar, AP, and lateral thoracic spine, in which DAP-75th-percentile exceeded all IDRLs by up to 40.7%, 2.8%, 365.5%, respectively. Considering the type of detector used, the mean of the locally measured DAPs significantly exceeded the UK DRLs for the lateral thoracic spine and lateral lumbar spine. Locally measured DAP values were below the IDRLs except for thoracic and lumbar spine projections, which significantly exceeded.

Noise Reduction in CT Images Using a Selective Mean Filter

Background

Noise reduction is a method for reducing CT dose; however, it can reduce image quality.

Objective

This study aims to propose a selective mean filter (SMF) and evaluate its effectiveness for noise suppression in CT images.

Material and Methods

This experimental study proposed and implemented the new noise reduction algorithm. The proposed algorithm is based on a mean filter (MF), but the calculation of the mean pixel value using the neighboring pixels in a kernel selectively applied a threshold value based on the noise of the image. The SMF method was evaluated using images of phantoms. The dose reduction was estimated by comparing the image noise acquired with a lower dose after implementing the SMF method and the noise in the original image acquired with a higher dose. For comparison, the images were also filtered with an adaptive mean filter (AMF) and a bilateral filter (BF).

Results

The spatial resolution of the image filtered with the SMF was similar to the original images and the images filtered with the BF. While using the AMF, spatial resolution was significantly corrupted. The noise reduction achieved using the SMF was up to 75%, while it was up to 50% using the BF.

Conclusion

SMF significantly reduces the noise and preserves the spatial resolution of the image. The noise reduction was more pronounced with BF, and less pronounced with AMF.

The skin dose of pelvic radiographs since 1896

OBJECTIVES

To derive conversions of antiquated exposure data into modern equivalents and to apply these in the assessment of the skin dose of pelvic radiographs since 1896.

METHODS

The literature 1896-2018 was searched for implicit and explicit dose information. The early implicit dose data contained now obsolete descriptions of radiation quality and quantity for long since disappeared X-ray systems of limited efficiency. Converting the old information into modern specifications was achieved using contemporary data and computer simulations. Final dose calculations were done with modern software. Explicit radiation doses of later date reported in old quantities and units were adapted according to current recommendations.

RESULTS

For the period before 1927 conversion algorithms for spark gap data and penetrometer hardnesses to high voltage could be derived. Electrical and X-ray efficiencies of several old röntgen systems were determined. Together they allowed reconstruction of 53 doses. After 1927 doses were generally explicitly specified; 114 were retrieved. Although an enormous spread was observed, the average skin dose was reduced by a factor of about 400.

CONCLUSIONS

Antiquated exposure data were successfully used for dose reconstruction. Extreme dose variability was a constant. Efforts to cut down doses were effective as skin doses went down from sub-erythema values to about one milligray.

Calculating Individual Lifetime Effective Risk from Initial Mean Glandular Dose Arising from the First Screening Mammogram

OBJECTIVES

The objective of the study was to use the initial mean glandular dose (MGD) arising from the first screening mammogram to estimate the individual total screening lifetime effective risk.

METHODS

Organ doses from full-field digital mammography (FFDM) screening exposures (craniocaudal and mediolateral oblique for each breast) were measured using a simulated approach, with average breast thickness and adult ATOM phantoms, on 16 FFDM machines. Doses were measured using thermoluminescent dosimeters accommodated inside the ATOM phantom; examined breast MGD was calculated. Total effective risk during a client's lifetime was calculated for 150 screening scenarios of different screening commencement ages and frequencies. For each scenario, a set of conversion factors were obtained to convert MGD values into total effective risk.

RESULTS

For the 16 FFDM machines, MGD contributes approximately 98% of total effective risk. This contribution is approximately constant for different screening regimes of different screening commencement ages. MGD contribution remains constant, but the risk reduced because the radiosensitivity of all body tissues, including breast tissue, reduces with age. Three sets of conversion factors were obtained for three screening frequencies (annual, biennial, triennial). Three relationship graphs between screening commencement age and total effective risk, as percentages of MGD, were created.

CONCLUSIONS

Graphical representation of total risk could be an easy way to illustrate the total effective risk during a client's lifetime. Screening frequency, commencement age, and MGD are good predictors for total effective risk, generating more understandable data for clients than MGD.

Radiation exposure for the surgical team in a hybrid-operating room

Hybrid-operating rooms enable the surgeon to acquire intraoperative high-resolution 2- and 3D images and use them for navigation. The radiation dose of the operating personal and the patient remains the major concern. In 9 months, 109 pelvic and spine cases were performed using a hybrid operating room. Radiation dose of the surgeon and the assisting nurse was recorded using real-time dosimeters. Lower radiation doses for the main surgeon in navigated dorsal instrumentations of the thoracic spine were recorded. Standing between the C-arm during screw placement increased the radiation dose sixfold. Lumbar dorsal instrumentation showed a similar radiation dose compared to the previous studies in traditional operating room settings. The use of a hybrid-operating room for dorsal spine instrumentation showed no increase in radiation dose compared to traditional settings. Intraoperative navigation can help to reduce the radiation dosage for the operating personnel.

Comparison of incident air kerma (ki) of common digital and analog radiology procedures in Kohgiluyeh and Boyer-Ahmad province

Introduction: Although in many developed countries, Analog radiography (AR) is replaced with digital radiography (DR) but AR is still widely used in many countries included Iran. Therefore, dosimetrically assessment of delivered dose is very important to avoid unnecessary patient dose.

Materials and Methods: In this study, all imaging centers in Kohgiluyeh and Boyer-Ahmad were selected. The initial information included the mean kVp and mAs used by the personnel to perform each radiological procedure were gathered through a questionnaire. Barracuda dosimeter was then used to measure Incident air kerma (ki). Data obtained from digital radiography (DR) and analogue radiography (AR) were then analyzed and compared to each other.

Results: The mean incident air kerma (ki) for five radiological procedures (chest AP&Lat, Skull AP&Lat, Lumbar spine AP&Lat, Thoracic spine AP&Lat and Pelvis) in digital devices were 0.38&1.34, 2.1&1.94, 4.99&7.83, 4.18& 6.41 and 4.33 mGy and those for analogue devices were 0.7&1.28, 3.05&3.02, 7.25&9.9, 7.125&8.36 and 5.36 mGy, respectively.

Discussion and Conclusion: The use of low kVp or high mAs is one of the reasons to increase the incident air kerma (ki) in analogue methods comparing to digital methods in all procedures except the chest (in Lateral view). Also the results, surprisingly, showed that in some of the analogue methods incident air kerma (ki) was less than digital methods which is most probably because of the auto-exposure conditions.

Radiation dose and magnification in pelvic X-ray: EOS™ imaging system versus plain radiographs

BACKGROUND

In plain pelvic X-ray, magnification makes measurement unreliable. The EOS™ (EOS Imaging, Paris France) imaging system is reputed to reproduce patient anatomy exactly, with a lower radiation dose. This, however, has not been assessed according to patient weight, although both magnification and irradiation are known to vary with weight. We therefore conducted a prospective comparative study, to compare: (1) image magnification and (2) radiation dose between the EOS imaging system and plain X-ray.

HYPOTHESIS

The EOS imaging system reproduces patient anatomy exactly, regardless of weight, unlike plain X-ray.

MATERIAL AND METHOD

A single-center comparative study of plain pelvic X-ray and 2D EOS radiography was performed in 183 patients: 186 arthroplasties; 104 male, 81 female; mean age 61.3±13.7years (range, 24-87years). Magnification and radiation dose (dose-area product [DAP]) were compared between the two systems in 186 hips in patients with a mean body-mass index (BMI) of 27.1±5.3kg/m² (range, 17.6-42.3kg/m²), including 7 with morbid obesity.

RESULTS

Mean magnification was zero using the EOS system, regardless of patient weight, compared to 1.15±0.05 (range, 1-1.32) on plain X-ray (P<10^-5). In patients with BMI<25, mean magnification on plain X-ray was 1.15±0.05 (range, 1-1.25) and, in patients with morbid obesity, 1.22±0.06 (range, 1.18-1.32). The mean radiation dose was 8.19±2.63dGy/cm² (range, 1.77-14.24) with the EOS system, versus 19.38±12.37dGy/cm² (range, 4.77-81.75) with plain X-ray (P<10^-4). For BMI >40, mean radiation dose was 9.36±2.57dGy/cm² (range, 7.4-14.2) with the EOS system, versus 44.76±22.21 (range, 25.2-81.7) with plain X-ray. Radiation dose increased by 0.20dGy with each extra BMI point for the EOS system, versus 0.74dGy for plain X-ray.

CONCLUSION

Magnification did not vary with patient weight using the EOS system, unlike plain X-ray, and radiation dose was 2.5-fold lower.

LEVEL OF EVIDENCE

3, prospective case-control study.

ESTABLISHMENT OF RADIATION DOSES FOR PEDIATRIC X-RAY EXAMINATIONS IN A LARGE PEDIATRIC HOSPITAL IN TURKEY

Pediatric patients are more sensitive to ionizing radiation when compared with adults. The aim of this study was to evaluate the radiation doses for some common pediatric x-ray examinations performed with various digital radiography systems. Quality control tests of the digital radiography systems were carried out according to international published protocols before the pediatric dose measurements. Radiation dose measurement was performed by using the x-ray tube outputs and thermoluminescent dosimeter dose measurement methods. In the present study, radiation doses were assessed for 247 chest, 230 pelvis, 194 skull and 73 abdomen x-ray examinations and in total 744 pediatric patients doses were measured. Pediatric patients were classified into four age groups 0-1, 1-5, 5-10 and 10-15 years as given by European Commission guidance. Effective doses were determined for each examination using a PCXMC 2.0 Monte Carlo program. The mean measured entrance skin doses for the age interval 1-5 years and AP projection by using tube output measurement methods were 149 µGy for chest, 304 µGy for pelvis, 387 µGy for skull and 199 µGy for abdomen examinations. The radiation dose results obtained in this study were in the range of the published results in the literature.

Two-dimensional breast dosimetry improved using three-dimensional breast image data

Conventional mammographic dosimetry has been developed over the past 40 years. Prior to the availability of high-resolution three-dimensional breast images, certain assumptions about breast anatomy were required. These assumptions were based on the information evident on two-dimensional mammograms; they included assumptions of thick skin, a uniform mixture of glandular and adipose tissue, and a median breast density of 50%. Recently, the availability of high-resolution breast CT studies has provided more accurate data about breast anatomy, and this, in turn, has provided the opportunity to update mammographic dosimetry. Based on hundreds of data sets on breast CT volume, a number of studies were performed and reported which have shed light on the basic breast anatomy specific to dosimetry in mammography. It was shown that the average skin thickness of the breast was approximately 1.5 mm, instead of the 4 or 5 mm in the past. In another study, 3-D breast CT data sets were used for validation of the 2-D algorithm developed at the University of Toronto, leading to data suggesting that the overall average breast density is of the order of 16-20%, rather than the previously assumed 50%. Both of these assumptions led to normalized glandular dose (DgN) coefficients which are higher than those of the past. However, a comprehensive study on hundreds of breast CT data sets confirmed the findings of other investigators that there is a more centralized average location of glandular tissue within the breast. Combined with Monte Carlo studies for dosimetry, when accurate models of the distribution of glandular tissue were used, a 30% reduction in the radiation dose (as determined by the DgN coefficient) was found as an average across typical molybdenum and tungsten spectra used clinically. The 30% average reduction was found even when the thinner skin and the lower average breast density were considered. The article reviews three specific anatomic observations made possible based on high-resolution breast CT data by several different research groups. It is noted that, periodically, previous assumptions pertaining to dosimetry can be updated when new information becomes available, so that more accurate dosimetry is achieved. Dogmatic practices typically change slowly, but it is hoped that the medical physics community will continue to evaluate changes in DgN coefficients such that they become more accurate.

Multicenter Comparison of 3D Spinal Measurements Using Surface Topography With Those From Conventional Radiography

INTRODUCTION

In pediatric spinal deformity the gold standard for curve surveillance remains standing full-column radiographs, but repeated exposure to ionizing radiation motivates us to look for nonradiographic solutions. This study tests a modern system of surface topography (ST) to determine whether it is reliable and reproducible.

METHODS

Patients from 6 pediatric spinal deformity clinics were recruited for enrollment. Inclusion criteria were age 8-18; diagnosis of scoliosis measuring ≥10 and <50 degrees or increased kyphosis of ≥45 degrees. Standing radiographs and ST scans (DIERS Formetric, Diers Medical Systems, Chicago, IL) were obtained on all patients and then measured and compared. A single investigator using a validated electronic measurement tool performed all radiographic measurements. Analysis of reproducibility and comparison of ST and radiographs were done.

RESULTS

A total of 193 patients were enrolled (148 F [77%]). The mean age was 13.25 years (range 8-18). The scoliosis magnitude was as follows: thoracic average 22.7 ± 10 degrees; lumbar average 19.6 ± 9 degrees. The kyphosis magnitude was 54.0 ± 11 degrees. The reproducibility for each ST parameter for 3 repeated scans was strong (interclass correlation = 0.855-0.944). Comparison to radiographic measurements was strong in the thoracic (r = 0.7) and moderate in the lumbar curve (r = 0.5). There was an average difference of 5.8 degrees in the thoracic spine and 8.8 degrees in the lumbar spine between ST Cobb angle estimates and radiographs. Thoracic kyphosis also had a strong correlation (r = 0.8) with radiographs.

CONCLUSIONS

Although the results are intended to measure similar aspects of deformity as the traditional Cobb angle, the measurement is not intended to be an exact estimation. The utility of ST is in the reproducible quantification of deformity after the initial radiograph has been taken. This has the potential to make longitudinal assessment of change in deformity without serial radiographs.

Exposure Risks Among Children Undergoing Radiation Therapy: Considerations in the Era of Image Guided Radiation Therapy

Recent improvements in toxicity profiles of pediatric oncology patients are attributable, in part, to advances in the field of radiation oncology such as intensity modulated radiation (IMRT) and proton therapy (IMPT). While IMRT and IMPT deliver highly conformal dose to targeted volumes, they commonly demand the addition of 2- or 3-dimensional imaging for precise positioning--a technique known as image guided radiation therapy (IGRT). In this manuscript we address strategies to further minimize exposure risk in children by reducing effective IGRT dose. Portal X rays and cone beam computed tomography (CBCT) are commonly used to verify patient position during IGRT and, because their relative radiation exposure is far less than the radiation absorbed from therapeutic treatment beams, their sometimes significant contribution to cumulative risk can be easily overlooked. Optimizing the conformality of IMRT/IMPT while simultaneously ignoring IGRT dose may result in organs at risk being exposed to a greater proportion of radiation from IGRT than from therapeutic beams. Over a treatment course, cumulative central-axis CBCT effective dose can approach or supersede the amount of radiation absorbed from a single treatment fraction, a theoretical increase of 3% to 5% in mutagenic risk. In select scenarios, this may result in the underprediction of acute and late toxicity risk (such as azoospermia, ovarian dysfunction, or increased lifetime mutagenic risk) in radiation-sensitive organs and patients. Although dependent on variables such as patient age, gender, weight, body habitus, anatomic location, and dose-toxicity thresholds, modifying IGRT use and acquisition parameters such as frequency, imaging modality, beam energy, current, voltage, rotational degree, collimation, field size, reconstruction algorithm, and documentation can reduce exposure, avoid unnecessary toxicity, and achieve doses as low as reasonably achievable, promoting a culture and practice of "gentle IGRT."

Is dosimetry still a necessity in current dental practice?

Today, dentists have a wide range of imaging modalities to choose from, the film based techniques, digital techniques, and the recent introduction of 3D volumetric or cone beam computed tomography (CBCT). The inherent design features of the new generation dental x-ray equipment has significantly improved over the years with no evidence of substandard x-ray units in operation. In dental facilities radiological workload is comparatively low, newer radiation equipments and accessories follow safety guidelines and employ better radiation protection measures for the patient and the operator. Dentists' knowledge and expertise in radiation protection measures is good, enabling them to carry out riskfree radiation procedures in their practice. Therefore, the present study is aimed at assessing the need for dosimeters in current dental scenario. 'Is there currently a significant risk from dental radiography to merit the use of personal dosimetery in dental practice. 'Dental health professionals (Oral radiologists) and radiographic assistants of fourteen dental colleges in Karnataka state participated in this questionnaire study. The questionnaire consisted of the following questions--the make, type, year of manufacture of radiographic machines used in their setup, number of radiographs made per day in the institution, type of receptors used, number of personnel at risk for radiation exposure, radiation protection measures used, regular monitoring by personal dosimeters, equivalent dosage readings for the past 12 months and whether the reading of thermoluminescent dosimeters (TLD) for any personnel had exceeded the recommended exposure value in the last 3 years. Dosimetry records of the radiology staff in the last three years shows doses no more than 1.50 mSv per year. The various institutions' dose (person mSv) was in the range of 3.70 mSv-3.90 mSv. Personal monitoring for Dentists can be omitted in the dental colleges since the estimated dose of oral radiologists contributed less than 0.01 mSv to the total average annual effective dose equivalent. Hence personal monitoring services (TLD Badges) for dentists employed in dental colleges should not be made mandatory.

In vitro dose measurements in a human cadaver with abdomen/pelvis CT scans

PURPOSE

To present a study of radiation dose measurements with a human cadaver scanned on a clinical CT scanner.

METHODS

Multiple point dose measurements were obtained with high-accuracy Thimble ionization chambers placed inside the stomach, liver, paravertebral gutter, ascending colon, left kidney, and urinary bladder of a human cadaver (183 cm in height and 67.5 kg in weight) whose abdomen/pelvis region was scanned repeatedly with a multidetector row CT. The flat energy response and precision of the dosimeters were verified, and the slight differences in each dosimeter's response were evaluated and corrected to attain high accuracy. In addition, skin doses were measured for radiosensitive organs outside the scanned region with OSL dosimeters: the right eye, thyroid, both nipples, and the right testicle. Three scan protocols were used, which shared most scan parameters but had different kVp and mA settings: 120-kVp automA, 120-kVp 300 mA, and 100-kVp 300 mA. For each protocol three repeated scans were performed.

RESULTS

The tube starting angle (TSA) was found to randomly vary around two major conditions, which caused large fluctuations in the repeated point dose measurements: for the 120-kVp 300 mA protocol this angle changed from approximately 110° to 290°, and caused 8%-25% difference in the point dose measured at the stomach, liver, colon, and urinary bladder. When the fluctuations of the TSA were small (within 5°), the maximum coefficient of variance was approximately 3.3%. The soft tissue absorbed doses averaged from four locations near the center of the scanned region were 27.2±3.3 and 16.5±2.7 mGy for the 120 and 100-kVp fixed-mA scans, respectively. These values were consistent with the corresponding size specific dose estimates within 4%. The comparison of the per-100-mAs tissue doses from the three protocols revealed that: (1) dose levels at nonsuperficial locations in the TCM scans could not be accurately deduced by simply scaling the fix-mA doses with local mA values; (2) the general power law relationship between dose and kVp varied from location to location, with the power index ranged between 2.7 and 3.5. The averaged dose measurements at both nipples, which were about 0.6 cm outside the prescribed scan region, ranged from 23 to 27 mGy at the left nipple, and varied from 3 to 20 mGy at the right nipple over the three scan protocols. Large fluctuations over repeated scans were also observed, as a combined result of helical scans of large pitch (1.375) and small active areas of the skin dosimeters. In addition, the averaged skin dose fell off drastically with the distance to the nearest boundary of the scanned region.

CONCLUSIONS

This study revealed the complexity of CT dose fluctuation and variation with a human cadaver.

Review of Kerma-Area Product and total energy incident on patients in radiography, mammography and CT

This study estimated the energy incident on patients in radiography, mammography and CT using data related to X-ray beam quantity and quality. The total X-ray beam quantity is the average Air Kerma multiplied by the X-ray beam area and expressed as the Kerma-Area Product (Gy cm(-2)). The X-ray beam quality primarily depends on the target material (and anode angle), X-ray voltage (and ripple) as well as X-ray beam filtration. For any X-ray spectra, dividing total energy (fluence × mean energy) by the X-ray beam Kerma-Area Product yields the energy per Kerma-Area Product value (ε/KAP). Published data on X-ray spectra characteristics and energy fluence per Air Kerma conversion factors were used to determine ε/KAP factors. In radiography, ε/KAP increased from 6 mJ Gy(-1) cm(-2) at the lowest X-ray tube voltage (50 kV) to 25 mJ Gy(-1) cm(-2) at the highest X-ray tube voltage (140 kV). ε/KAP values ranged between 1 and 5 mJ Gy(-1) cm(-2) in mammography and between 24 and 42 mJ Gy(-1) cm(-2) in CT. Changes in waveform ripple resulted in variations in ε/KAP of up to 15 %, similar to the effect of changes resulting in the choice of anode angle. For monoenergetic X-ray photons, there was a sigmoidal-type increase in ε/KAP from 2 mJ Gy(-1) cm(-2) at 20 keV to 42 mJ Gy(-1) cm(-2) at 80 keV. However, between 80 and 150 keV, the ε/KAP shows variations with changing photon energy of <10 %. Taking the average spectrum energy to consist of monoenergetic X rays generally overestimates the true value of ε/KAP. This study illustrated that the energy incident on a patient in any area of radiological imaging can be estimated from the total X-ray beam intensity (KAP) when X-ray beam quality is taken into account. Energy incident on the patient can be used to estimate the energy absorbed by the patient and the corresponding patient effective dose.

Characterization of calibration curves and energy dependence GafChromic™ XR-QA2 model based radiochromic film dosimetry system

PURPOSE

The authors investigated the energy response of XR-QA2 GafChromic™ film over a broad energy range used in diagnostic radiology examinations. The authors also made an assessment of the most suitable functions for both reference and relative dose measurements.

METHODS

Pieces of XR-QA2 film were irradiated to nine different values of air kerma in air, following reference calibration of a number of beam qualities ranging in HVLs from 0.16 to 8.25 mm Al, which corresponds to effective energy range from 12.7 keV to 56.3 keV. For each beam quality, the authors tested three functional forms (rational, linear exponential, and power) to assess the most suitable function by fitting the delivered air kerma in air as a function of film response in terms of reflectance change. The authors also introduced and tested a new parameter χ = netΔR·e(m netΔR) that linearizes the inherently nonlinear response of the film.

RESULTS

The authors have found that in the energy range investigated, the response of the XR-QA2 based radiochromic film dosimetry system ranges from 0.222 to 0.420 in terms of netΔR at K(air)(air) = 8 cGy. For beam qualities commonly used in CT scanners (4.03-8.25 mm Al), the variation in film response (netΔR at K(air)(air) = 8 cGy) amounts to ± 5%, while variation in K(air)(air) amounts to ± 14%.

CONCLUSIONS

Results of our investigation revealed that the use of XR-QA2 GafChromic™ film is accompanied by a rather pronounced energy dependent response for beam qualities used for x-ray based diagnostic imaging purposes. The authors also found that the most appropriate function for the reference radiochromic film dosimetry would be the power function, while for the relative dosimetry one may use the exponential response function that can be easily linearized.

Chest X-ray screening examinations among French uranium miners: exposure estimation and impact on radon-associated lung cancer risk

BACKGROUND

Medical surveillance of uranium miners can include periodic chest X-ray examinations. This study aimed to assess the X-ray exposure due to occupational health monitoring in the French cohort of uranium miners, and to test whether consideration of this additional radiation exposure impacts the excess risk of lung cancer death associated with radon exposure.

METHOD

X-ray exposure due to occupational health monitoring was estimated retrospectively based on review of a sample of miners' medical records and bibliographic data. Four exposure scenarios were designed, differing in their assumptions about the type of procedures performed, their frequency, and the lung dose delivered. Radon exposure and lung doses from exposure to α-particle emitters and external γ rays have previously been individually assessed. Exposure-risk and dose-risk relations were estimated by Poisson regression with a linear excess relative risk (ERR) model.

RESULTS

The cohort included 5086 miners with a mean follow-up duration of 30.1 years. The mean number of chest X-ray examinations ranged from 15.1 in the lowest to 34 in the highest-exposure scenario, and produced a mean cumulative lung dose ranging from 4.6 to 34.2 mGy. The role of occupation-related imaging screening X-ray procedures in total equivalent lung dose appeared insignificant compared to α-emitter exposure. X-ray exposure was not associated with lung cancer mortality risk. The ERR associated with radon remained significantly positive when X-ray exposure was included in the multivariate analysis.

CONCLUSIONS

X-ray exposure did not confound the exposure-risk relation between radon and lung cancer.

Radiation dose during coronary angiogram: relation to body mass index

OBJECTIVE

Ionising radiation based diagnostic and therapeutic cardiology and radiology procedures are very common in present day medical practice and are one of the largest medical sources of radiation to humans. The risk to health from radiation has been extensively documented. Obesity is becoming epidemic not only in the western world, but also in developing countries. In the present study we investigated if a patient's Body Mass Index (BMI) has an effect on the radiation dose received by the patient and operator during diagnostic coronary angiography (CAG).

METHODS

We analysed data of 3678 consecutive patients who underwent CAG from September 2007 to April 2010 in our cardiac catheter laboratory. Trans-radial access was used in 622 patients, whereas 3056 patients underwent CAG through trans-femoral route. We calculated the radiation dose in dose area product (DAP) units and correlated it with body mass index, screening time, procedure time, contrast volume, vascular access route and individual operator.

RESULTS

Among the explored parameters, body mass index had the most significant association with the radiation dose during the procedure. Despite having similar procedure times and contrast doses, patients with increased BMI received much higher radiation dose during CAG. We also found the left anterior oblique (LAO) caudal and LAO cranial views produced the biggest increase in radiation dose in patients with a high BMI. There was no inter-operator variability.

CONCLUSION

Obese patients require more than double the radiation dose in comparison to those with normal BMI. The operator should be aware of the increased dose of radiation required when performing CAG in patients with increased BMI, and especially in LAO cranial and caudal views.

Regional survey of image quality and radiation dose in computed tomography examinations in Saudi Arabia

This study is the first regional investigation in Najran, Saudi Arabia aimed at investigating radiation dose and image quality of computed tomography (CT) examinations. The survey data was collected from five scanners in four hospitals. For all CT scanners, a correction factor was calculated to measure the weighted computed tomography dose index (CTDIw) using standard dosimetry phantoms. The CTDIw were reported in this study and compared with other countries. It was found that most CTDIw values were close to the European reference levels and in line with the results of similar surveys in the other parts of world. Concerning image quality, 80 % of the scanners were found to be in compliance with the relative international guidelines for all the examined parameters.

Establishment of diagnostic reference levels in computed tomography for select procedures in Pudhuchery, India

Computed tomography (CT) scanner under operating conditions has become a major source of human exposure to diagnostic X-rays. In this context, weighed CT dose index (CTDI_w), volumetric CT dose index (CTDI_v), and dose length product (DLP) are important parameter to assess procedures in CT imaging as surrogate dose quantities for patient dose optimization. The current work aims to estimate the existing dose level of CT scanner for head, chest, and abdomen procedures in Pudhuchery in south India and establish dose reference level (DRL) for the region. The study was carried out for six CT scanners in six different radiology departments using 100 mm long pencil ionization chamber and polymethylmethacrylate (PMMA) phantom. From each CT scanner, data pertaining to patient and machine details were collected for 50 head, 50 chest, and 50 abdomen procedures performed over a period of 1 year. The experimental work was carried out using the machine operating parameters used during the procedures. Initially, dose received in the phantom at the center and periphery was measured by five point method. Using these values CTDI_w, CTDI_v, and DLP were calculated. The DRL is established based on the third quartile value of CTDI_v and DLP which is 32 mGy and 925 mGy.cm for head, 12 mGy and 456 mGy.cm for chest, and 16 mGy and 482 mGy.cm for abdomen procedures. These values are well below European Commission Dose Reference Level (EC DRL) and comparable with the third quartile value reported for Tamil Nadu region in India. The present study is the first of its kind to determine the DRL for scanners operating in the Pudhuchery region. Similar studies in other regions of India are necessary in order to establish a National Dose Reference Level.

Local reference dose evaluation in conventional radiography examinations in Iran

The goal of this study was to establish local diagnostic reference levels (LDRLs) for conventional radiography examinations in Sistan‐Baluchestan province of Iran, using dose area product (DAP) measurements followed by a comparison with international dose levels. DAP factor evaluation was carried out at eight radiography rooms in six public and one private health‐care centers. The study employed DAP, exposure, and demographic data (weight, age, height) for 1069 patients who presented for one of the 11 routine radiography examinations: chest (AP, PA, LAT), abdomen (AP), lumbar spine (AP, LAT), pelvis (AP), skull (AP/PA, LAT), and cervical spine (AP, LAT). The data were analyzed statistically and the minimum, median, mean, maximum, and third quartile DAP values were calculated. It was observed that LDRLs for chest PA (0.26 Gy.cm²) and chest LAT (0.66 Gy.cm²) projections were up to 136% and 113% higher, respectively, than their corresponding NRPB 2005 values. Other radiographic procedures had lower recommended reference doses compared with recently recommended national reference doses published in recent NRPB reports and other studies. Wide variations in DAP values and exposure parameters were observed for similar radiographic procedures between patients in different rooms and for different patients in the same room. These and other observations, such as poor radiographic techniques, high rate of radiographic reject/repeat, and lack of modern X‐ray machines and equipment, show that the need to carry out quality assurance programs is critical in Iran.

PACS numbers: 87.53.Bn, 87.59.B

Radiation dose reduction in intra-arterial chemotherapy infusion for intraocular retinoblastoma

BACKGROUND AND PURPOSE

Retinoblastoma (RB) is a rare malignancy affecting the pediatric population. Intravenous chemotherapy is the longstanding delivery method, although intra-arterial (IA) chemotherapy is gaining popularity given the reduced side effects compared with systemic chemotherapy administration. Given the sensitivity of the target organ, patient age, and secondary tumor susceptibility, a premium has been placed on minimizing procedural related radiation exposure.

MATERIALS AND METHODS

To reduce patient x-ray dose during the IA infusion procedure, customized surgical methods and fluoroscopic techniques were employed. The routine fluoroscopic settings were changed from the standard 7.5 pulses/s and dose level to the detector of 36 nGy/pulse, to a pulse rate of 4 pulses/s and detector dose to 23 nGy/pulse. The angiographic dose indicators (reference point air kerma (Ka) and fluoroscopy time) for a cohort of 10 consecutive patients (12 eyes, 30 infusions) were analyzed. An additional four cases (five eyes, five infusions) were analyzed using dosimeters placed at anatomic locations to reflect scalp, eye, and thyroid dose.

RESULTS

The mean Ka per treated eye was 20.1±11.9 mGy with a mean fluoroscopic time of 8.5±4.6 min. Dosimetric measurements demonstrated minimal dose to the lens (0.18±0.10 mGy). Measured entrance skin doses varied from 0.7 to 7.0 mGy and were 73.4±19.7% less than the indicated Ka value.

CONCLUSIONS

Ophthalmic arterial melphalan infusion is a safe and effective means to treat RB. Modification to contemporary fluoroscopic systems combined with parsimonious fluoroscopy can minimize radiation exposure.

Estimating the effective radiation dose imparted to patients by intraoperative cone-beam computed tomography in thoracolumbar spinal surgery

STUDY DESIGN

Observational.

OBJECTIVE

To estimate the radiation dose imparted to patients during typical thoracolumbar spinal surgical scenarios.

SUMMARY OF BACKGROUND DATA

Minimally invasive techniques continue to become more common in spine surgery. Computer-assisted navigation systems coupled with intraoperative cone-beam computed tomography (CT) represent one such method used to aid in instrumented spinal procedures. Some studies indicate that cone-beam CT technology delivers a relatively low dose of radiation to patients compared with other x-ray-based imaging modalities. The goal of this study was to estimate the radiation exposure to the patient imparted during typical posterior thoracolumbar instrumented spinal procedures, using intraoperative cone-beam CT and to place these values in the context of standard CT doses.

METHODS

Cone-beam CT scans were obtained using Medtronic O-arm (Medtronic, Minneapolis, MN). Thermoluminescence dosimeters were placed in a linear array on a foam-plastic thoracolumbar spine model centered above the radiation source for O-arm presets of lumbar scans for small or large patients. In-air dosimeter measurements were converted to skin surface measurements, using published conversion factors. Dose-length product was calculated from these values. Effective dose was estimated using published effective dose to dose-length product conversion factors.

RESULTS

Calculated dosages for many full-length procedures using the small-patient setting fell within the range of published effective doses of abdominal CT scans (1-31 mSv). Calculated dosages for many full-length procedures using the large-patient setting fell within the range of published effective doses of abdominal CT scans when the number of scans did not exceed 3.

CONCLUSION

We have demonstrated that single cone-beam CT scans and most full-length posterior instrumented spinal procedures using O-arm in standard mode would likely impart a radiation dose within the range of those imparted by a single standard CT scan of the abdomen. Radiation dose increases with patient size, and the radiation dose received by larger patients as a result of more than 3 O-arm scans in standard mode may exceed the dose received during standard CT of the abdomen. Understanding radiation imparted to patients by cone-beam CT is important for assessing risks and benefits of this technology, especially when spinal surgical procedures require multiple intraoperative scans.

Optimisation of performance for computed radiography in the West of Scotland

This paper describes experiences in the introduction of computed radiography systems to hospitals within the West of Scotland. Setting of automatic exposure control levels has enabled dose-area product values to be maintained at 160 cGy cm² for lumbar spine antero-posterior (AP), 250 cGy cm² for lumbar spine lateral, 210 cGy cm² for pelvis AP and 260 cGy cm² for abdomen AP. The study looks at dose levels achieved after 8 y in use and compares the dose levels found from surveys undertaken in 2007 and in 2010. The effects of raising tube potentials on image quality in terms of details and on contrast-to-noise ratio (CNR) were assessed. The results showed that CNR details seen in test images at tube potentials of 85-90 kV did not differ significantly from those with lower potentials and gave lower entrance surface doses.

Comparison of radiographic and surface topography measurements in adolescents with idiopathic scoliosis

Purpose:

In patients with adolescent idiopathic scoliosis (AIS), radiographic surveillance is the gold standard of assessing spinal deformity, but has negative long-term effects. The Formetric 4D surface topography system was compared to standard radiography as a safer option for evaluating patients with AIS.

Methods:

Fourteen volunteers with typical AIS patient stature had 30 repeated Formetric 4D measurements taken, and reproducibility was assessed. Sixty-four patients with AIS were then enrolled during routine clinic visits. Evaluation included standard radiographs and surface topography measurements. A comparison analysis was performed.

Results:

When assessing same-day repeated scans, a standard deviation of +/- 3.4 degrees for scoliosis curve measurements was determined, and the Reliability Coefficient (Cronbach) was very high (0.996). Cobb angles measured with the Formetric 4D differed from radiographic measurements by an average of 9.42 (lumbar) and 6.98 (thoracic) degrees, while the correlation between the two measurements was strong (95% confidence interval [CI]), 0.758 (lumbar) and 0.872 (thoracic) respectively.

Conclusions:

The Formetric 4D is comparable to radiography in terms of its test-retest reproducibility. Although this device does not predict curve magnitude exactly, the predictions correlate strongly with the Cobb angles determined from radiographs. It can be reliably used in the surveillance of patients with AIS.

Lodox/Statscan facilitates the early detection of commonly overlooked extracranial injuries in patients with traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) is a common diagnosis in the emergency department. Brain computed tomography (CT) has become a standard diagnostic tool with which to examine TBI patients. Conventional X-rays are ineffective for the evaluation of torso or extremity injuries. In the current study, we attempted to establish a diagnostic modality to evaluate systemically initially unconscious patients in the emergency department with a rapid screening technique characterized by sufficient information, low cost and low radiation exposure.

MATERIALS AND METHODS

From January 2008 to December 2009, patients with diminished level of consciousness received the Lodox/Statscan for evaluation of extracranial injuries were enrolled in this study. The accuracy of this diagnostic modality in detecting torso or extremity injuries in initially unconscious patients was analyzed by comparing the initial diagnosis (by the Lodox/Statscan) with the final diagnosis (confirmed by torso CT scan or after two weeks of follow-up).

RESULTS

There were 1,210 patients with TBI whose extracranial injuries were evaluated by the Lodox/Statscan. After excluding intra-abdominal injuries, the overall sensitivity rates of the Lodox/Statscan in diagnosing torso injuries and extremity injuries were 89.7% and 90.2%, respectively. No long bone fracture was missed by the Lodox/Statscan. The sensitivity and specificity of the Lodox/Statscan in diagnosing long bone fractures were both 100%. Most patients with torso injuries that were missed by the Lodox/Statscan could be managed conservatively without further treatment or complications. All of the missed extremity injuries were distal bone fractures.

CONCLUSION

The Lodox/Statscan can provide benefits for surveying extracranial injuries in patients with diminished level of consciousness. The Lodox/Statscan also emits a notably low dose of radiation and appears to be a relatively inexpensive adjunct to screen torso or extremity injuries in TBI patients.

Maltese CT doses for commonly performed examinations demonstrate alignment with published DRLs across Europe

This work recommends dose reference levels (DRLs) for abdomen, chest and head computerised tomography (CT) examinations in Malta as the first step towards national CT dose optimisation. Third quartiles volume CT dose index  values for abdomen: 12.1 mGy, chest: 13.1 mGy and head: 41 mGy and third quartile dose-length product values for abdomen: 539.4, chest: 492 and head: 736 mGy cm(-1) are recommended as Maltese DRLs derived from this first Maltese CT dose survey. These values compare well with DRLs of other European countries indicating that CT scanning in Malta is consistent with standards of good practice. Further work to minimise dose without affecting image quality and extending the establishment of DRLs for other CT examinations is recommended.

Peak skin and eye lens radiation dose from brain perfusion CT based on Monte Carlo simulation

OBJECTIVE

The purpose of our study was to accurately estimate the radiation dose to skin and the eye lens from clinical CT brain perfusion studies, investigate how well scanner output (expressed as volume CT dose index [CTDI(vol)]) matches these estimated doses, and investigate the efficacy of eye lens dose reduction techniques.

MATERIALS AND METHODS

Peak skin dose and eye lens dose were estimated using Monte Carlo simulation methods on a voxelized patient model and 64-MDCT scanners from four major manufacturers. A range of clinical protocols was evaluated. CTDI(vol) for each scanner was obtained from the scanner console. Dose reduction to the eye lens was evaluated for various gantry tilt angles as well as scan locations.

RESULTS

Peak skin dose and eye lens dose ranged from 81 mGy to 348 mGy, depending on the scanner and protocol used. Peak skin dose and eye lens dose were observed to be 66-79% and 59-63%, respectively, of the CTDI(vol) values reported by the scanners. The eye lens dose was significantly reduced when the eye lenses were not directly irradiated.

CONCLUSION

CTDI(vol) should not be interpreted as patient dose; this study has shown it to overestimate dose to the skin or eye lens. These results may be used to provide more accurate estimates of actual dose to ensure that protocols are operated safely below thresholds. Tilting the gantry or moving the scanning region further away from the eyes are effective for reducing lens dose in clinical practice. These actions should be considered when they are consistent with the clinical task and patient anatomy.

Global quality imaging: emerging issues

Quality imaging may be described as "a timely access to and delivery of integrated and appropriate procedures, in a safe and responsive practice, and a prompt delivery of an accurately interpreted report by capable personnel in an efficient, effective, and sustainable manner." For this article, radiation safety is considered as one of the key quality elements. The stakeholders are the drivers of quality imaging. These include those that directly provide or use imaging procedures and others indirectly supporting the system. Imaging is indispensable in health care, and its use has greatly expanded worldwide. Globalization, consumer sophistication, communication and technological advances, corporatization, rationalization, service outsourcing, teleradiology, workflow modularization, and commoditization are reshaping practice. This article defines the emerging issues; an earlier article in the May 2011 issue described possible improvement actions. The issues that could threaten the quality use of imaging for all countries include workforce shortage; increased utilization, population radiation exposure, and cost; practice changes; and efficiency drive and budget constraints. In response to these issues, a range of quality improvement measures, strategies, and actions are used to maximize the benefits and minimize the risks. The 3 measures are procedure justification, optimization of image quality and radiation protection, and error prevention. The development and successful implementation of such improvement actions require leadership, collaboration, and the active participation of all stakeholders to achieve the best outcomes that we all advocate.

AAPM/RSNA physics tutorial for residents: physics of flat-panel fluoroscopy systems: Survey of modern fluoroscopy imaging: flat-panel detectors versus image intensifiers and more

This article reviews the design and operation of both flat-panel detector (FPD) and image intensifier fluoroscopy systems. The different components of each imaging chain and their functions are explained and compared. FPD systems have multiple advantages such as a smaller size, extended dynamic range, no spatial distortion, and greater stability. However, FPD systems typically have the same spatial resolution for all fields of view (FOVs) and are prone to ghosting. Image intensifier systems have better spatial resolution with the use of smaller FOVs (magnification modes) and tend to be less expensive. However, the spatial resolution of image intensifier systems is limited by the television system to which they are coupled. Moreover, image intensifier systems are degraded by glare, vignetting, spatial distortions, and defocusing effects. FPD systems do not have these problems. Some recent innovations to fluoroscopy systems include automated filtration, pulsed fluoroscopy, automatic positioning, dose-area product meters, and improved automatic dose rate control programs. Operator-selectable features may affect both the patient radiation dose and image quality; these selectable features include dose level setting, the FOV employed, fluoroscopic pulse rates, geometric factors, display software settings, and methods to reduce the imaging time.

Comparison of radiation doses using weight-based protocol and dose modulation techniques for patients undergoing biphasic abdominal computed tomography examinations

Computed tomography (CT) of the abdomen contributes a substantial amount of man-made radiation dose to patients and use of this modality is on the increase. This study intends to compare radiation dose and image quality using dose modulation techniques and weight- based protocol exposure parameters for biphasic abdominal CT. Using a six-slice CT scanner, a prospective study of 426 patients who underwent abdominal CT examinations was performed. Constant tube potentials of 90 kV and 120 kV were used for all arterial and portal venous phase respectively. The tube current-time product for weight-based protocol was optimized according to patient's body weight; this was automatically selected in dose modulations. The effective dose using weight-based protocol, angular and z-axis dose modulation was 11.3 mSv, 9.5 mSv and 8.2 mSv respectively for the patient's body weight ranging from 40 to 60 kg. For patients of body weights ranging 60 to 80 kg, the effective doses were 13.2 mSv, 11.2 mSv and 10.6 mSv respectively. The use of dose modulation technique resulted in a reduction of 16 to 28% in radiation dose with acceptable diagnostic accuracy in comparison to the use of weight-based protocol settings.

Diagnostic accuracy, biohazard safety, and cost effectiveness-the Lodox/Statscan provides a beneficial alternative for the primary evaluation of patients with multiple injuries

BACKGROUND

Lodox/Statscan is a new digital X-ray machine with a low dose of radiation exposure that provides rapid, whole-body scans. In the setting of acute trauma management, the importance of image study is well recognized. Here, we report the accuracy of diagnoses made using Lodox/Statscan in patients with multiple injuries. We analyze the cost effectiveness, biohazard safety, and detection rate for treatment using the Lodox/Statscan and evaluate whether it is a viable alternative to the conventional trauma X-ray.

METHODS

We retrospectively reviewed patients who received a Lodox/Statscan between November 2007 and January 2009. All patients who had received both a Lodox/Statscan and a computed tomographic (CT) scan were enrolled. The CT scan was used to make the final diagnosis. The detection rate for treatment, sensitivity, and specificity of the Lodox/Statscan in diagnosis was analyzed.

RESULTS

One hundred eighty-four patients were eligible for the study during the 15-month study period. The detection rates for treatment using the Lodox/Statscan for pneumothorax, pelvic fracture, cervical spine injury, and thoracic-lumbar spine injury were 95%, 96.0%, and 57.1%, and 100%, respectively.

CONCLUSION

In our series, the Lodox/Statscan provided similar quality images and conventional series to the CT scans. Although the Lodox/Statscan missed some injuries, most of the subsequent treatments were not changed. Overall, there were several advantages to using this system, including the short interval of study, low-radiation exposure, and low cost. The Lodox/Statscan could therefore be used as an alternative to the traditional trauma X-ray for evaluation of acute trauma patients.

Can computer-assisted surgery reduce the effective dose for spinal fusion and sacroiliac screw insertion?

BACKGROUND

The increasing use of fluoroscopy-based surgical procedures and the associated exposure to radiation raise questions regarding potential risks for patients and operating room personnel. Computer-assisted technologies can help to reduce the emission of radiation; the effect on the patient's dose for the three-dimensional (3-D)-based technologies has not yet been evaluated.

QUESTIONS/PURPOSES

We determined the effective and organ dose in dorsal spinal fusion and percutaneous transsacral screw stabilization during conventional fluoroscopy-assisted and computer-navigated procedures.

PATIENTS AND METHODS

We recorded the dose and duration of radiation from fluoroscopy in 20 patients, with single vertebra fractures of the lumbar spine, who underwent posterior stabilization with and without the use of a navigation system and 20 patients with navigated percutaneous transsacral screw stabilization for sacroiliac joint injuries. For the conventional iliosacral joint operations, the duration of radiation was estimated retrospectively in two cases and further determined from the literature. Dose measurements were performed with a male phantom; the phantom was equipped with thermoluminescence dosimeters.

RESULTS

The effective dose in conventional spine surgery using 2-D fluoroscopy was more than 12-fold greater than in navigated operations. For the sacroiliac joint, the effective dose was nearly fivefold greater for nonnavigated operations.

CONCLUSION

Compared with conventional fluoroscopy, the patient's effective dose can be reduced by 3-D computer-assisted spinal and pelvic surgery.

LEVEL OF EVIDENCE

Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Imaging during pregnancy

The use of imaging techniques in women who are pregnant has increased greatly over the past decade. This focused review discusses the risks and indications of ultrasonography, magnetic resonance imaging, computed tomographic scanning, and fluoroscopy for the evaluation of the parturient with non-obstetric disorders. Diagnostic imaging of the pregnant woman for the evaluation of disorders not related to pregnancy is evolving, and protocols will vary from institution to institution. The potential benefit from indicated diagnostic radiological procedures in the parturient nearly always outweighs risk to the fetus because radiation exposure from a single procedure conveys little fetal risk.

Evolution of X-ray machine quality control acceptance indices

The quality assurance (QA) of radiographic images based on the operating conditions of X-ray equipment is essential for good image quality, accurate medical diagnostics and for the prevention of health professionals and patients to unnecessary doses of ionizing radiation. This paper presents a historical analysis of 1,635 Quality Assurance Technical Reports of Health Institutions in the state of São Paulo, Brazil, over a seven-year period. Based on acceptable limits for variations between nominal and measured parameters as the variable to determine the quality of X-ray equipment operating conditions, a significant improvement was found in the percentage of acceptance of the overall parameters described in the QA technical reports over this period. As expected, we found a strong concentration in the categories of conventional and portable X-ray equipment, which represent 72% and 84%, respectively, of the total number of equipments. A mechanical parameter such as half-value layer (HVL), which is important not only for image quality but also for radiation protection, showed significant improvements. Again, only 58% of portable X-ray equipment showed HVL values recommended for 80 kVp (above 2.3 mm Al), a percentage that improved to 76% in 2006. With regard to mammographers, which are newer machines, all the analyzed systems presented acceptable HVL values. Conventional X-ray machines showed an increase of this conformity index from 89% in 2000 to 94% in 2006. All this improvement was attributed to the continuous and extensive enforcement of Regulation Act 453 in the state of São Paulo. The improvement in equipment quality control standards is expected to result in the improvement of diagnostic quality, as well as in the reduction of exam repetitions, and thereby reducing the patient's exposure to radiation.

Rationale for National and Local Dose Reference Levels and Collective Effective Dose in CT

PURPOSE

This article is intended as a review of the methods of establishing dose reference levels (DRLs) in relation to computerized tomography (CT) and their role in the standardization and auditing of radiation dose in CT.

DISCUSSION

CT is considered a high radiation dose examination. The potential for dose reduction resulting from the establishment of DRLs is discussed. The rationale for the use of DRLs in relation to the use of appropriate radiation measurements and CT dose descriptors are discussed. The estimation of the radiation risk to the irradiated individual is given by the effective dose, which takes into consideration the type of radiation and the radiosensitivity of the irradiated tissues. The collective dose is used to describe the radiation exposure of a population from low doses of different sources of radiation.

CONCLUSION

Dose comparison between individual imaging sites is a vital part of DRL establishment and facilitates standardization of radiation dose levels for patients attending for a CT examination. Measurements of both effective and collective dose are difficult to achieve in practice. CT dose descriptors such as CT dose index and dose length product provide the means of comparing and monitoring the effect of optimized CT scanning protocols on the radiation dose.