Advances in paediatric imaging

Dr Sanjay P Prabhu

Recent advances in paediatric imaging can be broadly divided into the refinements of well-established techniques like radiography, fluoroscopy and CT, developments in the fields of MRI and ultrasound, advances in patient preparation like minimising the need for sedation, use of play therapy techniques and increased recognition for the need for child-friendly environments in radiology departments.

Refinements in radiography, fluoroscopy and CT

The widespread use of digital radiography has led to increased dose efficiency, and the greater dynamic range of digital detectors with possible reduction of radiation exposure to the young paediatric patient.

3D printed model of a brain with electrodes overlaid on the brain to simulate patient anatomy

Dependence on paediatric fluoroscopy has decreased over the years with the increased availability of alternative techniques like ultrasound, MRI, CT and endoscopy. However, in some conditions, fluoroscopy is a critical diagnostic tools. When fluoroscopy has to be used, it is imperative that optimised techniques, best summarised as ‘Pause and Pulse’ campaign sponsored by The Alliance for Radiation Safety in Pediatric Imaging are utilised. This includes always considering alternative means to image the patient and avoiding use of radiation, preparing the patient adequately, scanning only the area that is required, using last image hold, storing images acquired during screening with no additional dose, minimising use of magnification (which can increase dose) and scanning without the anti-scatter grid in place.

Advances in multi-slice CT technology including faster scanners with sub-millisecond rotation times now allow imaging of larger areas of the patient anatomy with less motion artefact and reduced need for sedation in children. Newer scanners have the capability to reduce radiation dose to account for the smaller size of the child. Paediatric imaging departments are implementing indication-based dosing (i.e. reducing tube current for certain indications where high detail is not needed).

Improvements in paediatric imaging contribute to the growth of non-invasive, radiation-free procedures. Even in conditions like intussusception, where fluoroscopy was the mainstay of the imaging during reduction, some centres are employing ultrasound to image the child, thereby avoiding radiation.

Advances in MRI

CT scan of the brain reconstructed with overlying electrodes in patient with seizures

The latest generation of higher field magnetic resonance imaging (MRI) scanners with improved coil technology allows for faster, non-invasive imaging of smaller, moving subjects and in many cases avoids the need for anaesthesia or radiation. In young children, use of ‘mock MRI’ where a play therapist helps the child acclimatise to the noises and closed space of the scanner on a non-working scanner replica before the real scan is another innovative method used in some paediatric centres. Motion compensation techniques combined with faster and higher strength MRI scanners allow imaging of neonates and young infants without sedation using a ‘feed and wrap’ technique and even moving foetuses in utero in greater detail than ever before.

The availability of ‘baby MRI’ scanners suitable for installation next to the neonatal unit and MRI-safe equipment allows young, sick and often very prematurely born infants to be transported to MRI scanner without disrupting vital treatment that the child needs.

Cardiac MRI has advanced in the last several years and most children with complex congenital heart disease are now imaged on MRI instead of CT in most specialised paediatric imaging centres.

The use of MRI for surgical planning has increased exponentially. Techniques like diffusion tractography which allows mapping of white matter tracts in the brain and functional MRI which allows mapping of eloquent areas involved in motor, sensory, language and visual function help guide the neurosurgeon during delicate surgical procedures and minimise damage to vital structures.

Use of three-dimensional reconstructions and in some cases, printing of 3D models using the patient’s imaging studies allows the surgeon to plan and simulate the procedure before going into the operative room.

The availability of intra-operative MRI (inside the operative suite) allows surgeons to confirm that a tumour has been completely removed or not before closing the surgical site. This is incredibly useful to avoid repeat procedures and ensure complete resection of tumours in many cases.

More recent innovations include use of MRI in children to guide minimally invasive therapeutic procedures like laser ablation of tumours and other lesions in various parts of the body. Real-time visualisation of the area being targeted allows effective treatment and at the same time, minimising patients discomfort and post-procedure stay in the hospital.

Advances in ultrasound

Tracts in the brain overlaid on a tumour using MRI

As mentioned in the section on fluoroscopy, the increasing use of ultrasound has been instrumental in significant reduction in radiation exposure. For example, in some centres contrast- enhanced ultrasound has replaced conventional radiologic methods used for vesicoureteral reflux, a condition in which urine refluxes back from the bladder into the ureters causing kidney infections and scarring. Introduction of harmonic imaging, which allows higher spatial and contrast resolution has resulted in improved image quality in areas like intestinal ultrasound. Use of three- dimensional [3D] ultrasound offers not only an improvement in diagnosis in selected cases, but also increases acceptance of ultrasound by clinicians and enhances parents’ understanding of the findings. 3D-ultrasound in paediatrics has been used in foetal scanning, brain ultrasound and volume measurement of the kidneys in children with suspected urinary tract abnormalities. Availability of smaller transducers and refinements in Doppler techniques allows very detailed study of flow and function even in small sized organs in the neonate and young infant.

Patient preparation, personnel training and environment modification

One of the aims of the imaging study is to ensure patient comfort and minimise pain.

Paediatric imaging centres are now designed with child-friendly colours and designed to make the place look less intimidating for the young child. Having dedicated personnel including radiation technologists, nursing staff and radiologists trained and experienced in dealing with children and well-versed in the most effective and optimal use of the technologies tailored for the paediatric patients is extremely important to ensure an overall improved experience for the child and family.

Many centres now try and minimise the number of needles that children require during their stay in the hospital by educating providers and instituting system practices that encourages use of dual-purpose catheters that can be used for multiple imaging procedures and administering medications.

Summary

Advances in paediatric imaging in the last few years have been exponential. It is imperative that medical personnel dealing with children acquaint themselves with these developments and parents should ask their medical providers for adequate measures to minimise risk to their child and choose the most optimal test to help diagnose the child’s illness. In many cases, this requires more of an attitudinal change towards the young child and his/ her family. Some of the changes can be accomplished with very little or no additional financial investment.

References:

1. Pause and Pulse: Ten Steps That Help Manage Radiation Dose During Pediatric Fluoroscopy- AJR:197, August 2011
2. Image Gently campaign- http://www.imagegently.org/
3. Neonatal Neuroimaging- Prabhu SP, Grant PE, Robertson RL, Taylor GA in Avery’s Textbook of the Newborn 9th Ed. Editors; Devaskar and Gleason