Radiation risk is linear with dose at low doses

Intraoperative fluoroscopic radiation in orthopedic trauma: correlation with surgery type and surgeon experience

Background

While fluoroscopy is widely used in orthopedic trauma surgeries, it is associated with harmful effects and should, therefore, be minimized. However, reference values for these surgeries have not been defined, and it is not known how surgeon experience affects these factors. The aims of this study were to analyze the radiation emitted and exposure time for common orthopedic trauma surgeries and to assess whether they are affected by surgeon experience.

Methods

Data from 1842 trauma orthopedic procedures were retrospectively analyzed. A total of 1421 procedures were included in the analysis. Radiation dose and time were collected to identify reference values for each surgery and compared for when the lead surgeon was a young resident, a senior resident, or a specialist.

Results

The most performed surgeries requiring fluoroscopy were proximal femur short intramedullary nailing (n = 401), ankle open reduction and internal fixation (ORIF) (n = 141), distal radius ORIF (n = 125), and proximal femur dynamic hip screw (DHS) (n = 114). Surgeries using higher radiation dose were proximal femur long intramedullary nailing (mean dose area [DAP]): 1361.35 mGycm²), proximal femur DHS (1094.81 mGycm²), and proximal femur short intramedullary nailing (891.41 mGycm²). Surgeries requiring longer radiation time were proximal humerus and/or humeral shaft intramedullary nailing (02 mm:20 ss), proximal femur long intramedullary nailing (02 mm:04 ss), and tibial shaft/distal tibia intramedullary nailing (01 mm:49 ss). Senior residents required shorter radiation time when performing short intramedullary nailing of the proximal femur than young residents. Specialists required more radiation dose than residents when performing tibial nailing and tibial plateau ORIF and required longer radiation time than young residents when performing tibial nailing.

Conclusions

This study presents mean values of radiation dose and time for common orthopedic trauma surgeries. Orthopedic surgeon experience influences radiation dose and time values. Contrary to expected, less experience is associated with lower values in some of the cases analyzed.

Decreased Radiation Exposure Using Ultrasound-Assisted Reduction and Fixation of Femoral Shaft Fractures in Children: A Pilot Study

Elastic stable intra-medullary nail procedures have been used to treat femoral fractures in children for some time. Radiation exposure generated by intra-operative radioscopy may induce side effects in children and staff. This study introduces a method of ultrasound-assisted reduction and fixation of femoral fractures in children to decrease radiation exposure. We included 21 children and evaluated displacement of fractures using multi-section scanning. All fracture reductions were performed with ultrasonography. A hyperechoic point with a posterior acoustic shadow can be seen under the proximal and distal segments after the nail passes through the fracture site. Comparison with radioscopy suggests that this is a viable method of reduction and fixation of femoral shaft fractures in children, and can effectively decrease radiation exposure.

Improving patient and staff safety by minimising radiation exposure during trauma surgery: A simple and validated predictive model

INTRODUCTION

Minimising radiation exposure, from fluoroscopic equipment during trauma surgery is crucial to safe-guarding patients and staff. This aim of this study was to identify variables associated with increased radiation exposure for 3 of the most common trauma procedures. Secondly, we aimed to derive an internally and externally validated mathematical model for predicting radiation exposure for these procedures.

MATERIALS AND METHODS

We prospectively recorded radiation exposure from 270 sliding hip screw (SHS), ankle and wrist fixation procedures. Patient demographics, fracture severity, surgeon and radiographer grade were assessed using univariate and multivariate analyses. A mathematical model was then created and externally assessed for validity from another unit.

RESULTS

With regards to the analysis of radiation exposure when fixing wrist fractures, a significant regression equation was found (F (3, 86) = 62.2, p < 0.001), with an adjusted R² of 0.69. Patients' predicted radiation exposure (cGY/cm2) was therefore equal to the positive result of: 81.916(Fracture severity) + 43.426(Surgical grade) + 23.490 (radiographer grade)-203.89.With regards to the analysis of radiation exposure when fixing ankle fractures, a significant regression equation was found, (F (3, 83) = 15.49, p < 0.001), with an adjusted R² of 0.34. Patients' predicted radiation exposure (cGY/cm2) was therefore equal to the positive result of: 39.541(Fracture severity) + 51.937(Surgical grade) + 37.702 (radiographer grade)-124.558 SHS (F (3, 89) = 25.29, p < 0.001), R² of 0.44.61.338(Fracture severity) + 60.945(Surgical grade) + 35.491 (radiographer grade)-105.501. These predictive models were successfully externally validated.

CONCLUSION

This study has demonstrated a workable and externally validated model for accurately predicting the likely radiation exposure using common and easily collectable variables. These models could be used to modify practuce and minimise the radiation exposure to patients and staff.

The effect of surgical experience on the amount of radiation exposure from fluoroscopy during dynamic hip screw fixation

INTRODUCTION Dynamic hip screw (DHS) fixation for proximal femur fractures is one of the most common procedures in trauma that requires the use of fluoroscopy. Emphasis is often placed on producing the 'perfect picture', which may lead to excessive use of fluoroscopy, without added patient benefit. This study, the largest of its kind, aimed to determine the effect of surgical experience on the amount of radiation exposure from fluoroscopy during DHS fixation. METHODS All hospital admissions for extracapsular proximal femur fractures to our institution between 2007 and 2012 were analysed. Patient demographics, fracture configuration, grade of surgeon and the total radiation dose after fixation were recorded. Analysis of variance was performed to assess differences in radiation levels between different grades of surgeon. RESULTS A total of 1,203 patients with a mean age of 81.3 years (range: 21-105 years) were included in the study. The majority of the fractures were three-part (33.3%), followed by two-part (32.2%), four-part (25.7%) and basicervical (8.9%). Registrars (ST3-ST8) used a significantly higher radiation dose than consultants for all fracture types (p=0.009). When analysed separately by trainee group, the most junior registrars (ST3-ST4) and the most senior registrars (ST7-ST8) were found to use significantly higher radiation levels than consultants (p=0.037 and p<0.001 respectively). CONCLUSIONS The level of surgical experience does influence the amount of radiation exposure from fluoroscopy during DHS fixation. Surgical trainees should not ignore the potential harmful effects of radiation and should be equipped with the knowledge of how to keep the radiation exposure as low as possible.

Nanostructural Changes in the Cell Membrane of Gamma-Irradiated Red Blood Cells

The effect of gamma radiation on the ultrastructure of the cell membranes of red blood cells has been probed using a powerful tool, namely, atomic force microscopy. We used mice erythrocytes as a model. Blood samples withdrawn from mice were gamma-irradiated using a ⁶⁰Co source unit with doses of 10,15,20,25 and 30 Gy. Structural changes appeared in the form of nanoscale potholes, depressions and alterations of the cell membrane roughness. The roughness of the cell membrane increased dramatically with increasing doses, although at 10 Gy , the cell membrane roughness was less than that of normal red blood cells (controls). Therefore, such modifications at the nano-scale level may affect the biophysical properties of membranes, resulting in impairment of their function.

The primary determinants of radiation use during fixation of proximal femur fractures

OBJECTIVES

To establish the primary determinants of operative radiation use during fixation of proximal femur fractures.

DESIGN

Retrospective cohort study.

SETTING

Level I trauma centre.

COHORT

205 patients treated surgically for subtrochanteric and intertrochanteric femoral fractures.

MAIN OUTCOME MEASURES

Fluoroscopy time, dose-area-product (DAP).

RESULTS

Longer fluoroscopy time was correlated with higher body mass index (p=0.04), subtrochanteric fracture (p<0.001), attending surgeon (p=0.001), and implant type (p<0.001). Increased DAP was associated with higher body mass index (p<0.001), subtrochanteric fracture (p=0.002), attending surgeon (p=0.003), lateral body position (p<0.001), and implant type (p=0.05).

CONCLUSION

The strongest determinants of radiation use during surgical fixation of intertrochanteric and subtrochanteric femur fractures were location of fracture, patient body position, patient body mass index, and the use of cephalomedullary devices. Surgeon style, presumably as it relates to teaching efforts, seems to strongly influence radiation use.

Ionizing radiation doses during lower limb torsion and anteversion measurements by EOS stereoradiography and computed tomography

OBJECTIVES

To calculate and compare the doses of ionizing radiation delivered to the organs by computed tomography (CT) and stereoradiography (SR) during measurements of lower limb torsion and anteversion.

MATERIALS AND METHODS

A Rando anthropomorphic phantom (Alderson RANDO phantom, Alderson Research Laboratories Inc., Stanford, Conn) was used for the dose measurements. The doses were delivered by a Somatom 16-slice CT-scanner (Siemens, Erlangen) and an EOS stereoradiography unit (EOS-Imaging, Paris) according to the manufacturers' acquisition protocols. Doses to the surface and deeper layers were calculated with thermoluminiscent GR207P dosimeters. Dose uncertainties were evaluated and assessed at 6% at k=2 (that is, two standard deviations).

RESULTS

The absorbed doses for the principal organs assessed were as follows: for the ovaries, 0.1 mGy to the right ovary and 0.5 mGy to the left ovary with SR versus 1.3 mGy and 1.1 mGy with CT, respectively; testes, 0.3 mGy on the right and 0.4 mGy on the left with SR versus 8.5 mGy and 8.4 mGy with CT; knees, 0.4 mGy to the right knee and 0.8 mGy to the left knee with SR versus 11 mGy and 10.4 mGy with CT; ankles, 0.5 mGy to the right ankle and 0.8 mGy to the left with SR versus 15 mGy with CT.

CONCLUSION

The SR system delivered substantially lower doses of ionizing radiation doses than CT to all the organs studied: CT doses were 4.1 times higher to the ovaries, 24 times higher for the testicles, and 13-30 times higher for the knees and ankles. The use of the SR system to study the torsion of lower limbs makes it possible to reduce the amount of medical irradiation that patients accumulate.

Risk of leukaemia mortality from exposure to ionising radiation in US nuclear workers: a pooled case-control study

OBJECTIVE

To follow-up on earlier studies of the leukaemogenicity of occupational ionising radiation exposure.

METHODS

We conducted a nested case-control analysis of leukaemia mortality in a pooled cohort of US nuclear workers followed through 2005. Each case was matched to four controls on attained age. Exposures were estimated from available records. General relative risk models were used to estimate the excess relative risk (ERR) of leukaemia, excluding chronic lymphocytic (CLL), acute myeloid leukaemia, chronic myeloid leukaemia and CLL while controlling for potential confounders. Preferred exposure lags and time-windows of risks were calculated using joint maximum likelihood. Dose-response was also examined using linear, linear-quadratic, categorical and restricted cubic spline models.

RESULTS

There were 369 leukaemia deaths in 105 245 US nuclear workers. The adjusted ERR for non-CLL leukaemia was 0.09 (95% CI -0.17 to 0.65) per 100 mGy. Elevated non-CLL risks were observed from exposures occurring 6-14 years prior to attained age of cases (ERR per 100 mGy=1.9; 95% CI <0 to 8.0). Lagged models indicated non-linearity of risk at very low (<10 mGy) and high (>100 mGy) doses, which contributed to the imprecision of results in linear models. Similar risk attenuation was not evident in time-windows-based models.

CONCLUSIONS

Risk estimates were in reasonable agreement with previous estimates, with the temporality of non-CLL leukaemia risk as a dominant factor in dose-response analyses. Future research should focus on methods that improve evaluations of the dose-response, particularly in the low-dose range.

Can fluoroscopy radiation exposure be measured in minimally invasive trauma surgery?

Repeated use of X-rays in orthopedic surgery poses the problem of irradiation of patient and caregivers. Seven common minimally invasive bone trauma surgical procedures requiring image intensifier use were investigated: percutaneous K-wire fixation of the wrist, minimally invasive fixation plating of the wrist, percutaneous intramedullary nailing of the tibia and of the femur, short and long trochanteric nail fixation of trochanteric and sub-trochanteric fracture, and percutaneous fixation of thoracolumbar fracture. The study analyzed three parameters: dose area product (DAP), radiation duration, and skin entrance dose (SED). Data were collected from 15 successive implementations of each procedure. The aim of the study was to establish a database for this kind of bone trauma surgery and a hierarchy of the X-ray doses delivered. Percutaneous spinal osteosynthesis involved the highest dose, followed in decreasing order by long trochanteric nailing, femoral nailing, short trochanteric nailing, tibial nailing, wrist K-wire fixation and frontal wrist plate osteosynthesis. One short trochanteric nail procedure delivered the same DAP as 13 wrist K-wire fixation procedures, and one spinal osteosynthesis was equivalent to 13 short trochanteric nail or 174 wrist K-wire procedures. The anatomic area X-rayed appeared to be the main radiation dose factor. A database was established, but actual patient and staff radiation levels remained unknown.

A matter of life or death: modeling DNA damage and repair in bacteria

DNA damage is a hazard all cells must face, and evolution has created a number of mechanisms to repair damaged bases in the chromosome. Paradoxically, many of these repair mechanisms can create double-strand breaks in the DNA molecule which are fatal to the cell. This indicates that the connection between DNA repair and death is far from straightforward, and suggests that the repair mechanisms can be a double-edged sword. In this report, we formulate a mathematical model of the dynamics of DNA damage and repair, and we obtain analytical expressions for the death rate. We predict a counterintuitive relationship between survival and repair. We can discriminate between two phases: below a critical threshold in the number of repair enzymes, the half-life decreases with the number of repair enzymes, but becomes independent of the number of repair enzymes above the threshold. We are able to predict quantitatively the dependence of the death rate on the damage rate and other relevant parameters. We verify our analytical results by simulating the stochastic dynamics of DNA damage and repair. Finally, we also perform an experiment with Escherichia coli cells to test one of the predictions of our model.

Quantifying exposure to diagnostic medical radiation in patients with inflammatory bowel disease: are we contributing to malignancy?

BACKGROUND

While potential risks of diagnostic medical radiation are acknowledged, actual exposure of patients in routine clinical practice is poorly documented.

AIM

To quantify such exposure to vulnerable abdominal organs in patients with inflammatory bowel disease who are already at risk of intestinal cancer.

METHODS

All incidences of exposure to diagnostic medical radiation were documented in a consecutive series of 100 patients with inflammatory bowel disease (62 Crohn's disease, 37 ulcerative colitis, 1 indeterminate colitis) attending a hospital-based clinic. Total effective dose (mSv) was calculated using published tables. Predictors of high or no irradiation were evaluated by multivariate logistic regression analysis.

RESULTS

Thirteen patients had no documented diagnostic irradiation. Twenty-three patients received an effective dose greater than 25 mSv. An at-risk effective dose >50 mSv was received by 11 patients. Dosage was higher in patients with Crohn's disease than ulcerative colitis (P = 0.02) and in patients undergoing surgery (P = 0.004). However, no predictive factors for high radiation dosage or for no exposure were identified.

CONCLUSIONS

At-risk irradiation from diagnostic medical radiation is common in patients with inflammatory bowel disease, and might potentially contribute to the elevated risk of intra-abdominal and other cancers. The level of irradiation should be considered in clinical decisions regarding abdominal imaging.

What are the risks from medical X-rays and other low dose radiation?

The magnitude of the risks from low doses of radiation is one of the central questions in radiological protection. It is particularly relevant when discussing the justification and optimization of diagnostic medical exposures. Medical X-rays can undoubtedly confer substantial benefits in the healthcare of patients, but not without exposing them to effective doses ranging from a few microsieverts to a few tens of millisieverts. Do we have any evidence that these levels of exposure result in significant health risks to patients? The current consensus held by national and international radiological protection organizations is that, for these comparatively low doses, the most appropriate risk model is one in which the risk of radiation-induced cancer and hereditary disease is assumed to increase linearly with increasing radiation dose, with no threshold (the so-called linear no threshold (LNT) model). However, the LNT hypothesis has been challenged both by those who believe that low doses of radiation are more damaging than the hypothesis predicts and by those who believe that they are less harmful, and possibly even beneficial (often referred to as hormesis). This article reviews the evidence for and against both the LNT hypothesis and hormesis, and explains why the general scientific consensus is currently in favour of the LNT model as the most appropriate dose-response relationship for radiation protection purposes at low doses. Finally, the impact of the LNT model on the assessment of the risks from medical X-rays and how this affects the justification and optimization of such exposures is discussed.

Effective radiation doses in CT colonography: results of an inventory among research institutions

The purpose of this study was to estimate the effective dose that is currently used in CT colonography using scan parameters that were collected for this purpose, and to investigate trends in time. PubMed was systematically searched from 1996 until January 2004 for studies investigating CT colonography. Research institutions were contacted and asked for their current scan protocol. Thirty-six institutions published 74 studies. Twenty-eight of the 36 institutions provided their current protocol. The median effective dose in 2004 was 5.1 mSv (range 1.2-11.7 mSv) per position. Most institutions (93%) scan in both the supine and prone positions. The median mAs value was 67 mAs (range 20-200), median collimation was 2.5 mm (range 0.75-5). From 1996 until 2004 a significant decrease in mAs and collimation (P=0.006, P<0.0001, respectively) was observed, while institutions that used a multislice scanner increased (P<0.0001). The effective dose remained constant (P=0.76). In 2004 the median effective dose for a complete CT colonography was 10.2 mSv. Despite the increasing use of multislice scanners, which are slightly less dose-efficient, the median effective dose remained approximately constant between 1996 and 2004. This is mainly caused by the use of lower mAs settings.