This week at University I attended a lecture on Radiobiology as part of our Intermediate Diagnostic Imaging studies. The lecture covered the effects of radiation within cells and resultantly the human body as a whole. The lecture also touched on the radiation doses that foetus’ can be exposed to, as part of our blog we have been given an article that is related to this topic to read over and critique.
The article that I am going to critique was written by Helen T. Winer-Muram, MD, in 2002 and is called “Pulmonary Embolism in Pregnant Patients: Fetal Radiation Dose with Helical CT” (Winer-Muram, 2002) it is a medical physics article and its purpose is to calculate mean foetal radiation doses reported by scintigraphy. Scintigraphy is a diagnostic test in which a two-dimensional picture of a body radiation source is obtained through the use of Radioisotopes (Medicinenet, 2014). The aim of this article is to give readers a detailed explanation of the methods of the experiment, how the experiment was ultimately carried out and the results and outcomes that were obtained on completion of the experiment.
This article was published in August 2002 and is now 12 years old; due to its age and with technology developing so rapidly may no longer be viewed as a creditable source. Due to the incredible amount of advancement it CT over the past years since the experiment was carried out, if the experiment were to be undertaken it may not be possible to obtain the same results.
Helen T Winer-Muram, MD is a practising Radiology Doctor with 41 years experience (WebMD, 2014), She specializes in Diagnostic Radiology and Cardiothoratic Radiology (WebMD, 2014). Helen T Winer-Muram, MD has contributed to 71 publications (Vitals, 2014). This makes her a creditable source. Other individuals that contributed to this article are John M. Boone, PhD, who is a professor of radiology (UC Davis Health System, 2014), Haywood L. Brown, MD who is a maternal-fetal medicine specialist (Duke Medicine, 2014), William C. Mabie, MD, who specializes in Obstetrics and Gynaecology, internal medicine and paediatrics (Vitals, 2014), Gerard T. Lombardo, MD who is a pulmonologist (Vitals, 2014) and S. Gregory Jennings, MD. All of these individuals have multiple publications and are all creditable sources adding to the value of this article.
This Experiment was carried out with 23 partcipants, certain test measures/protocols (CT parameters) were kept continuous throughout the study, these were:
- 120KkVp and 100Ma
- The scan time: 1second per scintillation
- Collimation: 2.5mm
- A pitch of 1
- Patient position: Craniocaudal
- Scan extent: 11 cm
With these protocols the mean foetal dose that would be received whilst undergoing a CT scan of the chest was calculated using Monte Carlo techniques. The Monte Carlo technique is a ‘problem solving technique used to approximate the probability of certain outcomes by running multiple trial runs, called simulations, using random variables’ (Palisade, 2014). Also the ‘Monte Carlo simulation is a method for exploring the sensitivity of a complex system by varying parameters within statistical constraints’ (The Mathworks inc, 1994-2014). The article then goes on to explain how the measurements were made and the differences between the cylindrical size that was used and an actual foetal shape and how this would affect the obtained results, ‘Differences in shape between a cylinder and the actual fetus have only a small effect on the fetal dose calculation, as long as the cylinder dimensions simulate the bounds of the fetus’ (Winer-Muram, 2002).
The experiment only used a small sample of pregnant patients, 23 in total, this could have been improved by using more pregnant patients, as ‘Increasing sample size can also give greater power to detect differences’ (Select Statistical Services, 2014) and also it is not specified as to how this sample of patients were picked. These 23 Pregnant Patients were all healthy women, of mixed ages – the mean age was 37 indicating that the patients were of a wide range of ages, mixed body mass indexes and in different stages of pregnancy. Eight of the patients were in the first trimester, nine in the second trimester and six in the third trimester, the results obtained from the experiment would have been more reliable if more pregnant patients were used in each trimester and if all of the patients were of similar age and body mass index.
The materials and methods section of the article was very detailed, it discusses how the experiment was implemented on the phantoms and the doses used.
In the conclusion all of the findings of this research are summarized, showing that helical CT scanning results in a lower foetal dose during all three trimesters.
The article is well presented and has diagrams, although I feel that the results section and the discussion section could have been elaborated on.
In conclusion this article and the data presented within it are relevant to the radiography world and also reinforce dose management and patient safety. There could have been certain improvements that could have been made to make the experiment more creditable and reliable, but it was extremely interesting.
Duke Medicine, 2014. Duke Medicine. [Online] Available at: http://www.dukemedicine.org/find-doctors-physicians/#!/haywood-l-brown-md [Accessed 6 October 2014].
Medicinenet, 2014. Medicine Net. [Online] Available at: http://www.medicinenet.com/script/main/art.asp?articlekey=9136 [Accessed 6 October 2014].
Palisade, 2014. Palisade. [Online] Available at: http://www.palisade.com/risk/monte_carlo_simulation.asp [Accessed 6 October 2014].
Select Statistical Services, 2014. Select Statistical Services. [Online] Available at: http://www.select-statistics.co.uk/article/blog-post/the-importance-and-effect-of-sample-size [Accessed 8 October 2014].
The Mathworks inc, 1994-2014. Mathworks. [Online] Available at: 2014 [Accessed 6 October 2014].
UC Davis Health System, 2014. UC Davis Health System. [Online] Available at: http://www.ucdmc.ucdavis.edu/radiology/faculty/boone.html [Accessed 6 October 2014].
Vitals, 2014. Vitals. [Online] Available at: http://www.vitals.com/doctors/Dr_Helen_Winer-Muram/credentials [Accessed 6 October 2014].
WebMD, 2014. WebMD Physician Directory. [Online] Available at: http://doctor.webmd.com/doctor/helen-winer-muram-md-8b6ad87c-92f7-4718-8187-ecb794657eca-overview [Accessed 6 October 2014].
Winer-Muram, H. T., 2002. Pulmonary Embolism in Pregnant Patients:Fetal Radiation Dose with Helical CT. Radiology, 224(2), pp. 487-492.