Obesity is a massive public health issue and an increasing number of patients are obese, creating new challenges for imaging. Acquiring specific skills and knowledge and using appropriate equipment are the best strategies for dealing with this challenging population.
New information on radiation dose and dedicated technology have emerged that should enable radiologists and radiographers to better handle larger patients, experts will reveal today in a Special Focus session.
Larger patients present more challenges when it comes to radiological procedures, and appropriate solutions that tackle education and technology must be implemented, according to Jonathan McNulty, Associate Dean for Graduate Taught Studies at the School of Medicine, University College Dublin, Ireland, and president of the European Federation of Radiographers Societies.
“When radiologists and radiographers learn about imaging techniques and conventional radiography, we need to learn to adapt our techniques and optimise our protocols to make sure we get diagnostic images on larger patients. But because our patients are getting larger, it is starting to test our technology as well. It is not only about getting the highest quality diagnostic images but also making sure not to unnecessarily increase radiation doses to patients,” he said.
Today, most hospitals do not weigh and measure their patients when performing imaging studies, and radiologists and radiographers have to work without an accurate data set. No information is available as to exactly how much radiation dose obese patients receive when undergoing a CT examination.
A recent study1 has shed light in that area and shown that radiation dose in bariatric patients with a BMI of more than around 40 or 45 was increased by 130% compared with normal-weight patients. These results confirm long held suspicions that obese patients receive more dose than their normal-weight counterparts, according to Karen Knapp, Associate Professor in Musculoskeletal Imaging at Exeter University Medical School, UK. “I think this has quantified what a lot of us already knew. Clinically, you know you need to use additional radiation for this, but nobody had ever quantified it prior to this work,” she said.
Saeed Alqahtani, one of Knapp’s PhD students, reviewed bariatric patient imaging from the Musgrove Park Hospital in Taunton, UK, and found that radiation doses were increased up to 600% in bariatric patients, leading to roughly a 130% increase in the actual dose to the patient. “We have to increase our exposure factors when imaging extremely obese patients due to the increased tissue thickness, but when you translate that into a patient’s dose, it is comparatively lower than the required increase in exposure factors because fat is not radiosensitive,” Knapp said.
Patients who are very obese would therefore have a higher risk of cancer from having an abdomen x-ray compared to their normal-weight counterparts due to the increased exposure factors required to image them. This situation poses a public health issue, especially since these patients are already at an increased risk of developing cancer due to their obesity.
“However, on an individual basis, the increased risks are still very small, and all imaging is based on a risk-benefit judgement. Therefore, obese patients having radiographs should be assured that the risks are outweighed by the benefits for their health from the diagnosis the imaging will bring,” she concluded.
MRI is excellent at showing what is inside a patient’s abdomen and pelvis, thanks to the natural, built-in contrast between the organs and the fat that surrounds them. But obese patients are more likely to have a normal radiograph rather than an MRI scan because they cannot necessarily fit into the MRI scanner.
Manufacturers have built larger MRI bores and tables to sustain higher weights, and efforts have also been made to improve radiation protection and carefully optimise protocols when examining patients with CT.
In addition, post-processing of images can help keep radiation dose as low as possible and image reconstruction techniques can help overcome some of the image quality issues with larger patients.
“A lot of it is down to the hardware and the scanner design – but also the software and the algorithms we use for reconstruction. It is also crucial for radiographers to really understand how they can manipulate protocols to get the best quality image at the lowest dose. The combination of technology and professional expertise can really help us in all imaging modalities,” McNulty said.
Ultrasound of larger patients has long been disregarded, as intra-abdominal fat makes it harder for sound waves to penetrate through to the organs and obtain a good quality signal, which impacts image quality.
But healthcare providers have lately put a lot of pressure on the industry to develop solutions so that this non-ionising modality can be made available to obese patients, according to Barbara Kraus, MSc, a radiographer and researcher at the University of Applied Sciences in Vienna, Austria. “You need to answer clinical questions in your report. You often have to describe; you cannot see the lesion, or not in an adequate form. This is no longer acceptable. We must also achieve good resolution when the ultrasonic waves have to travel longer distances,” she explained.
Companies are working on increased ultrasound penetration to adapt the larger field of view in abdominal ultrasound, despite indication-related frequencies and required spatial resolution in the region.
Non-focal imaging, another strategy developed by the industry, enables automatic adjustment of the focus position, which saves time during examinations. Users can achieve higher frame rates and tissue penetration in combination with automatic focus.
Benefits of these new technologies include better spatial resolution and more time to focus on the patient, according to Kraus, who will present the latest products on the market during the session.
“With deeper penetration you get much more information from the signal coming back from the tissues. This was impossible with older equipment. This technology takes much more information from tissues and expands our field of examination. Not having to use the focus manually during the examination saves us a lot of time, which we can dedicate to obese patients, who have the same rights as other patients,” she concluded.
1 https://iopscience.iop.org/article/10.1088/1361-6498/aaf1dd/meta
LIVE
Special Focus Session, Saturday, July 18, 08:30–09:30
SF 7a Addressing challenges in imaging of larger patients
- Chairpersons’ introduction
Vibeke Logager; Copenhagen/DK
Jonathan McNulty; Dublin/IE - Key considerations in general radiography examinations of larger patients
Karen Knapp; Exeter/UK - Modification of ultrasound technique and protocols for larger patients
Barbara Kraus; Vienna/AT - Diagnostic image quality considerations for larger patients in computed tomography
Shane J. Foley; Dublin/IE - Optimal imaging of larger patients in magnetic resonance imaging
Elise Thiry; Strasbourg/FR - Live Q&A: How such patient diversity can impact on daily practice and how we can improve our services
FURTHER READING
Euler A, Heye T, Kekelidze M et al (2015) Assessment of image quality and low-contrast detectability in abdominal CT of obese patients: comparison of a novel integrated circuit with a conventional discrete circuit detector at different tube voltages. Eur Radiol. 25(3):687-93: european-radiology.org/3459
Cheng E, Hoskin S, Ridley L (2018) Clinician awareness, knowledge and attitudes towards radiation exposure, practical challenges and image interpretation in obese patients. 2018 ASM / R-0042: myESR.org/1842
Zhang HX, Fu JF, Lai C, Tian FY, Su XL, Huang K (2018) Feasibility of balanced steady-state free precession sequence at 1.5T for the evaluation of hepatic steatosis in obese children and adolescents. Eur Radiol. 28(11):4479-4487: european-radiology.org/5344
O’Brien CE, Duignan J, O’Brien AC, Heffernan EJ, Weir A (2018) Obesity in Radiology: Increasing incidence of obesity and its impact on diagnostic Ultrasound services. ECR 2018 / C-1250: myESR.org/181250
Cuccioli F, KARILA-COHEN P, El Sanharawi I, Arapis K, Marmuse JP, Schouman-Claeys E (2014) Optimisation of abdominal CT parameters in obese population BMI >40. ECR 2014 / C-1603: myESR.org/141603