Look Ahead: The Future of Pediatric Radiology
Nationally recognized pediatric radiology expert Marilyn J. Siegel, MD, shares her insight on where technology is taking the subspecialty in coming years
The Nearer Future: Advances in Imaging Technologies
CT—New Methods Allow for Radiation Dose Reduction
Individualizing CT scanning techniques according to patient size and attenuation and the clinical indication for CT will result in further reductions of radiation exposures to the point where they may be comparable to those of conventional x-ray imaging.
Look for more use of low-dose scanning at 70 and 80 kilovoltage (kV) in cardiothoracic imaging in all pediatric patients, not only small children. The widespread use of low kV has been impeded by the limited power reserves of available x-ray tubes. Modern x-ray tubes provide substantial power reserves at low kV settings and thus enable dose-efficient low kV scans for all children, including those who are obese. To facilitate the lower kV selection, more automated kV selection technologies will emerge, offering the advantage of optimizing both milliamperages (mAs) and kV selection, maintaining both image quality and low dose. That makes CT a robust examination for reliable evaluation of cardiothoracic diseases in children.
Faster scanning with wide-beam or high-pitch scanners, which offer high temporal resolution and speed, thus limiting motion artifacts and reducing radiation exposure respectively, should become routine in clinical practice. CT scans will become so fast that the issues of motion and breath-holding may no longer be a major concern in pediatric CT. In addition, the benefits of better temporal resolution and speed will improve the practice of cardiac CT in young patients, where rapid heart rates and high radiation doses have been limiting factors.
In terms of technology, more research and eventually clinical use of phase-contrast CT imaging and photon-counting CT will improve image quality and lower radiation output. Both technologies may allow for more detailed tissue characterization and material discrimination at lower radiation doses than conventional scanners. Photon scanning will also offer the potential for “energy-selective” data, with multi-energy discrimination. Also look for low-dose scanning using optimized spectral shaping (tin filtration) to lower radiation dose.
Finally, look for changes in reporting radiation exposure. One can envision manufacturers reporting size-specific dose estimates (SSDE) at the scanner console and populating Digital Imaging and Communications in Medicine (DICOM) headers and structured reports, so that SSDE becomes an integral part of radiation dose tracking.
The Move to Material-specific Imaging: Dual-energy CT
Dual-energy CT will become an important tool in clinical pediatric imaging. In CT, materials with different elemental compositions can have identical CT numbers, making the differentiation and classification of different tissue types challenging. The ability of dual-energy CT to differentiate materials of different elemental compositions should lead to an evolution in the clinical applications of dual-energy CT in children. Also look for photon counting CT to take us from dual-energy CT to multi-energy CT in the future.
Benefits of CT Advances:
Monoenergetic images will improve image quality. The use of high kiloelectron voltage (keV) to decrease image noise and minimize artifacts in patients with metal implants will improve visualization of soft tissues and bone, and lead to more confident diagnoses (See image, this page). On the other hand, low keV will be used to visualize iodine, which will increase conspicuity of subtle lesions and compensate for poor venous access from slow injection rates in small intravenous catheters.
Automated bone subtraction in CT angiography can provide a bone-free view of the vascular system and deliver high-quality images for confident diagnoses.
Iodine maps will improve characterization and conspicuity of masses in solid organs. In the bowel, these maps can help in the diagnosis of bowel inflammation or ischemia by showing the iodine distribution. In oncology, this technology opens up the possibility of documentation of therapy response by quantification of tumor size and iodine uptake.
Lung perfusion will allow a comprehensive evaluation of the pulmonary vessels. Watch for its use in cyanotic congenital heart diseases to assess overall perfusion to the lungs before and after surgical repair and in the evaluation of perfusion defects in pulmonary embolism and pulmonary hypertension.
Ultrasound – Increases Roles for Elastography
Ultrasound continues to pull tricks out of a seemingly bottomless hat. In chronic liver diseases, elastography has shown great promise in noninvasively detecting fibrosis severity. Watch for more research on the impact of this technology on outcomes, including fewer biopsies and better identification of patients who may be candidates for interventional therapies.
In the musculoskeletal system, elastography is increasingly being used in the evaluation of acute tendon injuries, but look for increased use in inflammatory myopathies. Quantification of muscle stiffness at rest (passive findings) and over a course of gradual isometric contractions or following exercise (dynamic findings) opens a new frontier for monitoring treatment outcomes and predicting functional prognosis.
Future MR imaging will be faster and easier to perform while yielding exquisite image detail and multi-parametric characterization of anatomy and function. As a result, studies will be completed faster, reducing duration, depth and frequency of anesthesia for pediatric examinations.
New MRI methods are also poised to reduce examination times by generating multiple pulse sequence images from a single MRI exam. For example, a single brain exam that synthesizes six pulse sequences (e.g. short tau inversion recovery (STIR), T1-weighted fluid attention inversion recovery (FLAIR), T2-weighted FLAIR, T1-weighted, T2-weighted and proton-density) can be completed in one-third of the total time taken to use each sequence separately with conventional methods.
For cardiovascular MRI, 4-D flow imaging collects both time-resolved anatomic and blood velocity information at every location in a 3-D volume with a single free-breathing, 10-minute examination. Thus 4-D flow simultaneously provides in 10 minutes of imaging the key elements of a cardiac examination (anatomy, function and flow) that conventionally are acquired serially in over 60 minutes of imaging and patient breath-holding. For lung imaging, the potential of ultrafast sequences will allow dynamic assessment of lung anatomy and function during the entire respiratory cycle. MRI will likely become the preferred method of imaging children with chronic lung diseases, such as cystic fibrosis and lung transplantation-related bronchiolitis obliterans, replacing CT, which has been the standard modality.
3-D Printing Emerges into Clinical Practice
3-D printing is a rapidly growing technology for management of pediatric patients with cardiac and vascular malformations. 3-D printing aids understanding of complex 3-D relation-ships, and is being used increasingly for pre-surgical planning in congenital cardiovascular disease (See image, this page). This technology represents a new frontier of highly precise and personalized medicine, promising improved surgical and post-operative outcomes. Besides surgical planning, 3-D models are effective tools for education, procedure simulation and patient counseling.
Thus, 3-D printing is poised to revolutionize the practice of medicine in congenital heart disease. Also expect the technology to be increasingly used for planning craniofacial and maxillofacial surgery and in the musculoskeletal system for planning osteotomies, fracture fixations and arthroplasties.
Further into the 21st Century: Moving Toward Precision Imaging
In the era of precision or personalized medicine, pediatric radiology has the opportunity to help deliver the right treatment at the right time. By identifying which subgroups of patients have similar characteristics and are likely to benefit from the same therapies, more efficient clinical trials can be done with the goal of treating patients based on the precise characteristics of their disease. In the quest for precision imaging, a merger of morphologic and molecular information is likely to be critically important. Radiogenomics, linking imaging phenotypes to genotypes, and hybrid imaging using combined PET/MRI systems — which enable PET functional imaging to be anatomically co-registered with MRI — have already shown promise to characterize the molecular infrastructure, and should greatly contribute to patient-tailored care.
Optical imaging is the new kid in the imaging armamentarium. Optical spectroscopy for characterizing molecules via absorption and fluorescence spectra has been shown to be useful for tumor diagnosis in preclinical trials. In early clinical trials in adults it has been used to diagnose brain disorders, monitor treatment response, and guide intraoperative tumor biopsy. The future likely will include co-registration with 3-D imaging modalities, allowing rapid, whole-body fluorescence imaging. Its combination of high-detection sensitivity, real-time feedback of diagnostic information, and repeat measurement capability without harming healthy tissue holds great promise for imaging children in the age of precision medicine.
Disruption and Opportunities
As we transition from the era of depicting anatomy to the era of functional and molecular imaging, new technologies will create disruption and new responsibilities, including the need for increased learning and education. But they also will bring great opportunity. We will see a continued decrease of radiation exposure to the population, more accurate clinical diagnoses that will improve patient care, and more personalized healthcare. If pediatric radiologists embrace the challenges and build on the opportunities, our subspecialty — which has always been known for its innovation — will continue to grow and thrive in the years to come.