Medical Imaging is one of the most innovative and dynamic fields in the healthcare industry. It is crucial for disease diagnosis and has advanced remarkably over the last few years with widespread adoption of imaging systems like MRI, CT & USG and various modifications of these technologies. Some of the new trends in the medical imaging field include continued growth of various technologies such as:
Computed tomography (CT)
It is the workhorse of modern medical imaging. Today’s CT scanners include technological developments that enable us to better manage patient care, including high quality images, dose guidance and regulation, spectral and multi-energy imaging, and expansion of cardiac and brain imaging. Technology in CT has evolved from single slice scanner to ultra fast multidetector CT scanners reducing the acquisition time significantly, increasing the spatial resolution along with modifications to reduce patient radiation dose.
An exciting development that offers great promise to further increase the modality’s potential is dual energy CT (DECT), also known as ‘spectral imaging.’ It utilises two separate energy sets to examine the different attenuation properties of matter, having a significant advantage over traditional single energy CT. It can create virtual non-contrast images from contrast-enhanced imaging, eliminating the need of non-enhanced scan and thus reducing the radiation exposure to the patient. It can also delineate the composition of renal calculi and arterial plaques for appropriate management. It improves lesion detection and characterisation in sub-centimeter sized lesions in liver. DECT can enhance CT angiography protocols obt aining exquisite image quality and implementing calcium subtraction techniques at post-processing in case of significant wall calcifications, which can interfere with lumen assessment.
Perfusion blood volume maps acquired with DECT can be used to identify the segmental or sub-segmental areas of lung affected by a pulmonary thromboembolism and to detect areas of ischemia in the myocardium. It also allows to acquire better quality images in patients with metallic implants reducing the implants related artifacts.
Some of the newest CT scanners move fast enough to capture images that freeze cardiac motion and prevent motion blur or the need to stitch images from several heartbeats to reconstruct a complete cardiac image, also reducing the radiation exposure.
TAVR/structural heart planning software gives the clinicians the detailed and crucial information required for planning for transcatheter aortic valve replacement (TAVR) or other structural heart surgeries with the help of the CT scan acquired images. Similarly, extensive angiographic applications in the neuro-imaging including CT cerebral angiography, perfusion imaging, angiographic applications in body imaging have majorly revolutionised the patient care.
Tomosynthesis or 3D mammography
This cancer detection technology allows three-dimensional (3D) reconstruction of the breast tissue, which can then be viewed as sequential slices through the breast. This new technique reduces error and allows thorough examination of even dense tissue. Tomosynthesis facilitates detection of minute lung nodules and chest pathologies that can go undetected with conventional methods. This 3D imaging helps outline cancer morphology in patients and determine the stage of the disease with greater accuracy.
The most recent big advances in magnetic resonance imaging (MRI) technology have been on the software side. MR Elastography is a rapidly developing non-invasive technology for quantitatively assessing the mechanical properties of tissue and tissue stiffness. It works by combining MRI imaging with sound waves to create a visual map (Elastogram) showing the stiffness of body tissues.
Its applications are widely in use for assessment of hepatic stiffness and the stage of fibrosis in patients with liver disease. It can serve as a safer, less expensive, and potentially more accurate alternative to invasive liver biopsy which is currently the gold standard for diagnosis and staging of liver fibrosis.
Magnetic resonance-guided focussed ultrasound
This non-invasive, incisionless MRI-based therapeutic technique uses ultrasonic pulses to ablate the target tissue. It uses an MRI thermal imaging system to continuously measure temperature changes inside the body, pinpointing and guiding the treatment. It is gaining popularity as an alternative to medical and surgical interventions in the management of symptomatic uterine fibroids; other applications being treatments of adenomyosis, facetal arthropathy, bone tumours (both benign and malignant) for pain relief. Recently its applications in neurosurgery are also being explored for treatment of essential tremors and Parkinson’s disease.
Multimodality fusion or hybrid imaging
Anatomic imaging technologies like magnetic resonance imaging (MRI) and computed tomography (CT) clearly show morphologic features, such as size and shape, but not information on proliferation or inflammation. Functional imaging technologies, such as positron emission tomo-graphy (PET) or single-photon emission computed tomography (SPECT), use radiolabelled glucose or monoclonal antibodies to provide critical information on cellular activity, but cannot provide the anatomic detail needed for precise localisation. Physicians need both anatomic and functional data to make the definitive diagnosis that is so important to the patient. Bringing together anatomic and functional information with sensitivity and specificity is the true value of multimodal fusion imaging, examples are PET-CT, SPECT-CT imaging. Fused images can be used to plan surgical procedures, guide invasive or noninvasive therapeutic interventions, and monitor individual response to therapy.
Intraoperative imaging is a rapidly expanding field encompassing many applications that use a multitude of technologies. Some of these applications have been in use for many years and are firmly embedded in, and indispensable to, clinical practice (e.g. the use of X-ray to locate foreign bodies during surgery or oocyte retrieval under ultrasound guidance or intra-operative ultrasound for the lesion localisation and treatment.
Most spine surgeries today are done using minimally invasive techniques to spare muscle and healthy tissues. To do this as effectively as possible, some form of intraoperative imaging is typically used to verify surgical accuracy. The intraoperative images help make sure that a spinal implant is placed in the desired place or that a tumour is dissected to the desired outcome. While providing excellent imaging resolution and navigation to guide an operation, the mobile CT scanner also permits the surgeon to obtain immediate CT images at the completion of surgery. This allows for immediate intraoperative intervention if necessary before surgical closure.
Intraoperative MRIs or iMRIs, can move into the or during surgery, providing real-time images while the patient lies stationary on the table. These images are transferred to the frameless navigation system and allow up-to-date assessment of the brain’s position and shift, the degree of tumour resection and residual tumour. This enables the surgeon to maximally resect tumour while preserving normal structures and brain tissue. Though it has its own limitations in terms of cost and the technical difficulties, but it has wide applications in brain tumour surgery, epilepsy surgery and also for verification of electrode placement in surgeries for Parkinson’s disease and other disorders treated with deep brain stimulation.
3D printing and computer aided design
A 3D-printing technique allows clinicians to produce highly detailed models of human anatomy for better planning of complex surgical cases using the data acquired from CT images. While use of advanced visualisation in radiology is instrumental in diagnosis and communication with referring clinicians, this technology can render Digital Imaging and Communications in Medicine (DICOM) images as three-dimensional (3D) printed models capable of providing both tactile feedback and tangible depth information about anatomic and pathologic states.
The main applications are:
- Surgery preparation assisted by the use of 3D printed models
- 3D printing of surgical instruments.
- Custom-made prosthetics using 3D printing
Artificial intelligence (AI)
As AI technology is further developed, the possibility of a complete digitalised radiologist is a tangible reality. Although AI is being explored as an extra eye on imaging analysis, it is not likely to replace the human factor. The radiologists do much more than even the most advanced algorithm can because they don’t just look at images! Their scope includes communication, image quality assessment, image optimisation, education, procedures, policy making, and more.
Recently, Korean researchers proposed through a study that although AI was faster on its own in lesion detection than radiologist, the best results came from teamwork – humans utilising the AI algorithm as a second look. AI can support radiologists and radiographers by streamlining workflows and improving productivity.