Computed Tomography Scans in Patients With Young Adult Hip Pain Carry a Lifetime Risk of Malignancy.

PURPOSE: To calculate the lifetime risk of malignancy in young adult patients with hip pain using 5 different imaging and radiation dose protocols with or without pre- and postoperative computed tomography (CT). METHODS: Radiographic and CT patient radiation doses were retrospectively reviewed. Imaging protocols for hip pain composed of radiographs with or without pre- and postoperative CT scans were modeled and radiation doses were estimated using the PCXMC computer code. Based on these radiation doses, lifetime attributable risks of cancer and mortality for a 10- through 60-year-old male and female were calculated as published by the committee on the Biological Effects of Ionizing Radiation (BEIR) in the BEIR VII report. Relative risks and number needed to harm (NNH) were calculated for each protocol. RESULTS: Based on a review of our institutional database, 2 CT scan doses were used for this study: a high 5.06 mSv and a low 2.86 mSv. Effective doses of radiation ranged from 0.59 to 0.66 mSv for radiographs alone to 10.71 to 10.78 mSv for radiographs and CT both pre- and postoperatively at the higher dose. Lifetime attributable risk of cancer for radiographs alone was 0.006% and 0.011% for a 20-year-old male and female, respectively. Lifetime attributable risk of cancer for radiographs along with pre- and postoperative CT scans at higher dose was 0.105% and 0.177% for a 20-year-old male and female, respectively. Radiographs alone lead to an NNH of 16,667 for males and 9,090 for females, whereas the protocol with pre- and postoperative CT scans at the higher dose led to an NNH of 952 for males and 564 for females. The relative risk of this protocol compared to radiographs alone was 17.5 for males and 16.1 for females. CONCLUSION: Protocols with CT scans of the hip/pelvis pose a small lifetime attributable risk (0.034%-0.177% for a 20-year-old) but a large relative risk (5-17 times) of cancer compared with radiographs alone in the imaging evaluation for hip pain that decreases with increasing age. CLINICAL RELEVANCE: This study illustrates the need for clinicians to understand the imaging protocols used at their institution to understand the risks and benefits of using those protocols in their practice.

AAPM Task Group Report 272: Comprehensive acceptance testing and evaluation of fluoroscopy imaging systems.

Modern fluoroscopes used for image guidance have become quite complex. Adding to this complexity are the many regulatory and accreditation requirements that must be fulfilled during acceptance testing of a new unit. Further, some of these acceptance tests have pass/fail criteria, whereas others do not, making acceptance testing a subjective and time-consuming task. The AAPM Task Group 272 Report spells out the details of tests that are required and gives visibility to some of the tests that while not yet required are recommended as good practice. The organization of the report begins with the most complicated fluoroscopes used in interventional radiology or cardiology and continues with general fluoroscopy and mobile C-arms. Finally, the appendices of the report provide useful information, an example report form and topics that needed their own section due to the level of detail.

DNA double strand break (DSB) induction and cell survival in iodine-enhanced computed tomography (CT).

A multi-scale Monte Carlo model is proposed to assess the dosimetric and biological impact of iodine-based contrast agents commonly used in computed tomography. As presented, the model integrates the general purpose MCNP6 code system for larger-scale radiation transport and dose assessment with the Monte Carlo damage simulation to determine the sub-cellular characteristics and spatial distribution of initial DNA damage. The repair-misrepair-fixation model is then used to relate DNA double strand break (DSB) induction to reproductive cell death. Comparisons of measured and modeled changes in reproductive cell survival for ultrasoft characteristic k-shell x-rays (0.25-4.55 keV) up to orthovoltage (200-500 kVp) x-rays indicate that the relative biological effectiveness (RBE) for DSB induction is within a few percent of the RBE for cell survival. Because of the very short range of secondary electrons produced by low energy x-ray interactions with contrast agents, the concentration and subcellular distribution of iodine within and near cellular targets have a significant impact on the estimated absorbed dose and number of DSB produced in the cell nucleus. For some plausible models of the cell-level distribution of contrast agent, the model predicts an increase in RBE-weighted dose (RWD) for the endpoint of DSB induction of 1.22-1.40 for a 5-10 mg ml-1 iodine concentration in blood compared to an RWD increase of 1.07 ± 0.19 from a recent clinical trial. The modeled RWD of 2.58 ± 0.03 is also in good agreement with the measured RWD of 2.3 ± 0.5 for an iodine concentration of 50 mg ml-1 relative to no iodine. The good agreement between modeled and measured DSB and cell survival estimates provides some confidence that the presented model can be used to accurately assess biological dose for other concentrations of the same or different contrast agents.

How to report low-level laser therapy (LLLT)/photomedicine dose and beam parameters in clinical and laboratory studies.

BACKGROUND: Dose and beam parameters are critical for successful laser, LED, and other light therapy treatments; however, in our experience, researchers frequently make critical errors and omissions when submitting papers for publication. Journals frequently publish studies with missing data, mathematical errors, and no reported verification of beam parameters. This makes reproducibility impossible, and further confounds an already complex subject. OBJECTIVE: This article is intended to be a reference document for non-physicist researchers conducting low-level laser therapy (LLLT) laboratory studies and clinical trials to help them design and report the beam and dose aspects of their trials. RECOMMENDATIONS: It provides a checklist to help LLLT researchers understand and report all the necessary parameters for a repeatable scientific study. It includes the eight most important beam parameters to report, which are: wavelength, power, irradiation time, beam area at the skin or culture surface (this is not necessarily the same as the aperture size), pulse parameters, anatomical location, number of treatments, and interval between treatments. The three commonly used dose parameters are time, energy, and energy density. In addition, more thorough reporting would include coherence, application technique (contact, projection, scanning, pressure), beam profile, and spectral width, as these may also be considered important. Beam power often decreases as the device warms up and as the device ages; therefore, this should be checked routinely during an experiment/trial. Measurements of beam area and beam power require special instruments and trained technicians to operate them. Power measurements should be taken before, after, and at frequent intervals during research trials. CONCLUSION: Reviewers should insist that the minimum eight most important beam parameters are included, and authors should take care to measure and record these accurately before, during, and after an experiment or clinical trial.

Measurements of activation products associated with Havar foils from a GE PETtrace medical cyclotron using high resolution gamma spectroscopy.

Havar foils are specially engineered for beam-line windows used in the General Electric (GE) PETtrace medical cyclotron that can withstand the high pressure differentials and also temperatures developed near the target with proton bombardment. These foils effectively separate components along the beam line of the cyclotron. Various activation products are produced in the foils from the primary proton beam and other secondary radiations. An accurate estimate of the activation products is necessary for the disposal of these foils. The foils were assayed using two High Purity Germanium (HPGe) detectors calibrated over a wide energy range. These were positioned at different distances (0.10 m, 0.24 m, and 1.74 m) away from the detector faces to accommodate their high activities. A summary of the anticipated relative abundance of each activation product and a scatter plot of the average exposure rate per unit charge incident on the foil vs. time post-activation are provided. A detailed spectral analysis of the foils in the energy ranges between 12 keV to 300 keV and 12 keV through 2,500 keV revealed the residual activation products 56Co, 57Co, 58Co, 54Mn, and 183Re at 264 d post-irradiation. Spectral examinations of the different foils removed between 2003 and 2005 show the same activation products regardless of the irradiation time or foil position in the target assembly. The information presented in this paper can be used along with the integrated charge incident on the foils in estimating the activity of Havar foils for the purpose of disposal.

Evaluation of performance and stability of biocatalytic redox films constructed with different copper oxygenases and osmium-based redox polymers.

We are interested in investigating the applications of biocatalytic mediated reduction of oxygen by oxygenases in films on electrode surfaces, as such reactions can form the basis for biosensors or biocatalytic fuel cell development. Here we present approaches aimed at improving the stability and signal output of such films. These include selection of oxygen reducing biocatalysts which are active under physiological conditions and development of redox mediators which offer the opportunity to tailor the mediator to each enzyme. It was found that for each enzyme Melanocarpus albomyces laccase (MaL), Trametes hirsutus laccase (ThL) or bilirubin oxidase (MvBOD) it was the biocatalytic films mediated by Os(2,2'-bipyridine)(2)Cl.PVI that not only generated the highest current densities compared to Os(4,4'-dimethyl-2,2'-bipyridine)(2)Cl.PVI and Os(4,4'-dichloro-2,2'-bipyridine)(2)Cl.PVI, but also proved to be the most stable over 48 h. Under physiological conditions electrodes constructed from MvBOD generated the highest initial current densities for each of the osmium redox polymers, however these films proved to be the least stable over 48 h. Stability could be improved using surface pre-treatment.