Evaluation of Patient Effective Dose of Neurovascular Imaging Protocols of a C-arm Cone-beam CT & Estimation of Current Source Radioactivity of a Cs-137 Irradiator
Bibliographic record
Abstract
<p><bold>Purpose: </bold></p><p>(Project 1) The purpose of this study was three-fold: 1) to estimate the organ doses and effective dose (ED) for patients undergoing neurovascular imaging protocols, 2) to study the effect of beam collimation on ED for 3-D imaging protocols, and 3) to derive protocol-specific DAP-to-ED conversion factors.</p><p>(Project 2) The Cs-137 irradiator is one of the most commonly used irradiation device in radiobiological research. The purpose of this study is to develop a simple method to estimate the current source radioactivity of a Cs-137 irradiator (Mark I-68A, JL Shepherd). </p><p><bold>Material and Methods: </bold></p><p>(Project 1) A cone-beam CT system (Philips Allura Xper FD20/20) was used to measure the organ doses for seven 3-D (cone-beam CT and 3-D Rotational Angiography protocols) and eight 2-D (fluoroscopy and digital subtraction angiography) imaging protocols. Organ dose measurements were performed on an adult male anthropomorphic phantom (CIRS, Norfolk, VA) with 20 MOSFET detectors (Best Medical Canada, Ottawa, Canada) placed in selected organs. The dose area product (DAP) values were recorded from console. The ED values were computed by multiplying measured organ doses to corresponding ICRP 103 tissue weighting factors. The ED of four 3-D imaging protocols were also measured with standardized beam collimation to compare with the ED associated with the same protocols without beam collimation. </p><p>(Project 2) Three positions along the peak-dose irradiation direction within the irradiation chamber were picked as the reference dosimetry positions. Individual dose rate at each of these positions was measured by an ion chamber in "Gy/sec", as well as estimated by Monte Carlo simulation in "Gy/primary event". The source activity, "disintegration/sec", was then derived from these two sets of values and corrected by the branching ratio of the main 662 keV emission. </p><p><bold>Results: </bold></p><p>(Project 1) For the seven 3-D imaging protocols with uncollimated setting, the EDs ranged from 0.16 mSv to 1.6 mSv, and the DAP-to-ED conversion factors range from 0.037 to 0.17 mSv/Gy&#8729;cm<super>2</super>. For four protocols with beam collimation, ED was reduced approximately by a factor of 2, and the DAP-to-ED conversion factors by approximately 30%. For the eight 2-D imaging protocols, the ED rates ranged from 0.02 mSv/sec to 0.04 mSv/sec (for DSA) and from 0.0011 mSv/sec to 0.0027 mSv/sec (for fluoroscopy), and the DAP-to-ED conversion factors range from 0.045 to 0.068 mSv/Gy&#8729;cm<super>2</super> (for DSA) and factors range from 0.0029 to 0.059 mSv/Gy&#8729;cm<super>2</super> (for fluoroscopy).</p><p>(Project 2) For the irradiator in question, the source activity, as of Nov. 17, 2011, was estimated to be 2770 Curies. The current activity from the manufacturer was calculated to be 5900 Curies.</p><p><bold>Conclusion: </bold></p><p>(Project 1) We have measured ED for standard adult neuro imaging protocols in a C-arm cone-beam CT system. Our results provide a simple means of ED estimation using DAP values from console in the C-arm cone-beam CT system.</p><p>(Project 2) Our method offers a convenient means to estimate the source activity. The result was compared to the value computed from the manufacturer. We have found discrepancies between the two: 41%, 86%, and 97%, assessed at location 1, 2, and 3, respectively.</p>
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".