Lee Collins

Fetal umbilical artery flow velocity waveforms and placental resistance: clinical significance

Summary. Since the umbilical arteries carry fetal blood to the placenta we studied flow velocity waveforms in these vessels with a simple continuous wave Doppler system to assess placental blood flow. The ratio of peak systolic to least diastolic (A/B) flow velocity was measured as an index of placental flow resistance. In 15 normal pregnancies there was a small but significant decrease in this ratio through the last trimester. The A/B ratio was measured on 436 occasions in 168 high‐risk pregnancies. In 32 of 43 fetuses subsequently shown to be small for gestational age there was an increase in placental flow resistance with reduced, absent or even reversed flow in diastole. This finding was also present in the one fetus which died in utero. Serial studies in patients with fetal compromise indicated increasing flow resistance, a reverse of the normal trend. These results were not available to the clinician yet of 24 fetuses born before 32 weeks 13 had a high A/B ratio, and all of them were born electively. Maternal hypertension was associated with an increase in fetal placental flow resistance. The umbilical artery A/B ratio provides a new and non‐invasive measure of fetoplacental blood flow resistance.

Risk to Patients From Radiation Associated With Radiofrequency Ablation for Supraventricular Tachycardia

BACKGROUND Radiofrequency ablation may be associated with prolonged fluoroscopy times. Previous studies have calculated radiation risks by measuring the radiation dose at a limited number (6) of body sites. This is an inherently inaccurate measure. Our study aimed to quantify more precisely patient-related radiation risks associated with radiofrequency ablation for supraventricular tachycardia. METHODS AND RESULTS Nine female patients having radiofrequency ablation for supraventricular tachycardia were studied. The radiation dose was determined at 41 body sites in each patient with the use of thermoluminescent dosimeters and was correlated with that measured simultaneously with a Diamentor dose-area product meter. The estimated mean organ doses (mGy) per 60 minutes of fluoroscopy were: lungs 30.8; bone marrow 4.3; left breast 5.1; right breast 3. 5; and thyroid 2.4. From the average organ doses, the estimated mean total lifetime excess risk of a fatal malignancy was 294 per million cases (0.03%) per 60 minutes of fluoroscopy. The risk calculation from the Diamentor dose-area product and thermoluminescent dosimeters were similar, suggesting that radiation dose was measured accurately. The estimated risk of radiation-induced malignancy increased with increasing body mass index (P=0.03). CONCLUSIONS Prolonged fluoroscopy during radiofrequency ablation may potentially cause a small increase in the lifetime risk of fatal malignancy, with lung malignancy being most likely. This risk is small only with the use of techniques and x-ray equipment optimized to keep radiation as low as possible. The risk is increased in obese patients.

Applied imaging technology

This book, originally designed to be the notes to part 1 of the diploma course of the then RACR, has become a valuable reference, not only for budding radiologists, but also for medical physicists. There has always been a wealth of detail, including much which is not easily found in the common textbooks. The title is something of a misnomer, as the majority of the content is concerned with x-ray imaging. MRI, nuclear medicine and ultrasound are included, but the authors make no pretence to cover these topics as thoroughly. They are however kept up to date, and cover the RANZCR syllabus. The book is made up of 31 chapters, grouped into 6 logical parts – radiation biology and safety, basic physics of x-ray imaging, technology of x-ray imaging, magnetic resonance imagine, fundamentals of nuclear medicine, and ultrasound imaging. The 3 and now 4 editions have been reworked to be more like a textbook than a set of notes, although the primary purpose for the book remains the same. The 4 edition contains substantial revisions where technology has rapidly changed, in particular in digital imaging in all its forms, with a 15% overall increase in size. Multislice CT, CT fluoroscopy and computed and direct radiography are all new inclusions in an almost new digital radiography chapter. The currency is well illustrated by browsing through the references UNSCEAR 2000, ICRP Report 84, and a number of 2001 publications are included. The chapter covering protection of the patient and worker has been significantly reworked to reflect the increasing importance of this aspect as the use of radiology (especially CT) grows. The production values of the book have also been improved, and images are included for the first time. The soft cover binding has changed from glued to spiral, making it much easier to use. The publishing history gives a clue as to the frequency and timeliness of new editions – the first edition was only published in 1993. Many of the standard hardback texts are much slower to be updated, and this is one of the very few to be regularly revised (with revisions in the life of each edition as well). Like painting the Sydney Harbour Bridge, each new edition only appears to mean that the next revision is begun. One wonders how long the authors can keep it up. As in the previous edition, a large number (470) of searching multiple choice questions are included, grouped at the end of each part. No answers are provided, however with the publication of this edition, the reader may go to a web site at RMIT (www.life.rmit.edu.au/mrs/kpm/AIT/purchase.html), and test himor herself online with a selection of the questions. Purchasing information is also provided. Probably, given its original intended purpose, the highest praise I can give this book is to say that, if the trainee radiologist absorbed and understood all the content, there may be little need for medical physicists in radiology! Fortunately they concentrate on the medical aspects. As it is, this has long been one of the most used texts on my own bookshelf, and the new edition is welcomed. I can highly recommend it to both the reader who wishes to know more about the physics of imaging, and the regular practitioner in radiology physics.

Position paper: recommendations for a digital mammography quality assurance program V4.0

In 2001 the ACPSEM published a position paper on quality assurance in screen film mammography which was subsequently adopted as a basis for the quality assurance programs of both the Royal Australian and New Zealand College of Radiologists (RANZCR) and of BreastScreen Australia. Since then the clinical implementation of digital mammography has been realised and it has become evident that existing screen-film protocols were not appropriate to assure the required image quality needed for reliable diagnosis or to address the new dose implications resulting from digital technology. In addition, the advantages and responsibilities inherent in teleradiology are most critical in mammography and also need to be addressed. The current document is the result of a review of current overseas practice and local experience in these areas. At this time the technology of digital imaging is undergoing significant development and there is still a lack of full international consensus about some of the detailed quality control (QC) tests that should be included in quality assurance (QA) programs. This document describes the current status in digital mammography QA and recommends test procedures that may be suitable in the Australasian environment. For completeness, this document also includes a review of the QA programs required for the various types of digital biopsy units used in mammography. In the future, international harmonisation of digital quality assurance in mammography and changes in the technology may require a review of this document. Version 2.0 represented the first of these updates and key changes related to image quality evaluation, ghost image evaluation and interpretation of signal to noise ratio measurements. In Version 3.0 some significant changes, made in light of further experience gained in testing digital mammography equipment were introduced. In Version 4.0, further changes have been made, most notably digital breast tomosynthesis (DBT) testing and QC have been addressed. Some additional testing for conventional projection imaging has been added in order that sites may have the capability to undertake dose surveys to confirm compliance with diagnostic reference levels (DRLs) that may be established at the National or State level. A key recommendation is that dosimetry calculations are now to be undertaken using the methodology of Dance et al. Some minor changes to existing facility QC tests have been made to ensure the suggested procedures align with those most recently adopted by the Royal Australian and New Zealand College of Radiologists and BreastScreen Australia. Future updates of this document may be provided as deemed necessary in electronic format on the ACPSEM’s website (https://www.acpsem.org.au/whatacpsemdoes/standards-position-papers and see also http://www.ranzcr.edu.au/quality-a-safety/radiology/practice-quality-activities/mqap).

Recommendations for a technical quality control program for diagnostic X-ray equipment.

This position paper was produced by a working party set up by the Radiology Special Interest Group of the ACPSEM in 2001. It is designed to give the consensus view of College members in Australia and New Zealand on the nature and frequency of tests which should be performed on diagnostic x-ray equipment to maintain adequate quality control of imaging performance and radiation safety. Tests on mammographic equipment have been excluded having been covered in a previous ACPSEM position paper (Australas Phys Eng Sci Med, 24(3):107–131, 2001). Detailed descriptions of test procedures are not given but it is intended that a series of workbooks should be produced giving College recommended test methods for each imaging modality. The recommendations are produced here in an easy-toread, tabular form giving the nature and purpose of each test and the implications of non-compliance with regard to image quality and radiation safety.