In the past 100 odd years, radiology has progressed from simple X-rays to complex functional MRI’s and nuclear scans, informs Dr Shrinivas B Desai, Director- Department of Imaging & Interventional Radiology, Jaslok Hospital and Research Centre
There have been immense technological and scientific advances in radiology over the last decade. Similarly, our understanding about pathology and disease has increased exponentially.
Conventional radiography
Digital radiography has revolutionised the way we use radiographs in our daily practice. With portable direct radiography now being available, the radiograph is now displayed on the screen as soon as it is taken. Gone are the days when we had to check on the quality and exposure of the X-ray and probably repeat it if required.
CT
Dual Energy CT (DECT) has revolutionised cross sectional imaging and opened new vistas in the scope of CT imaging. DECT uses high and low tube potentials to detect the chemical composition of tissues, and subtract bone, iodine or any other component from the tissues to get an unparalleled informative image. It has been used to detect the composition of renal stones, diagnosis and management of gout, creating lung perfusion maps enabling better detection of subsegmental pulmonary thrombi and detecting overall clot burden. The virtual precontrast images can be obtained by subtracting iodine from post contrast CT, thereby completely omitting the need for plain CT. This has helped to reduce radiation dose, as there is no need to take a separate plain scan before giving iodinated contrast.
Advances in iterative reconstruction (algorithms that are used to produce a CT image from raw data) mean that the dose can be reduced by as much as 30-40 per cent without affecting the image quality on CT.
Improved quality and increased number of detector slices have made high quality CT coronary angiography a reality. Online subtraction of calcium in the coronary arteries will obviate the need for invasive coronary angiogram. The future CT scan may use a totally different substance like photon imaging for further technology breakthrough.
CT guided intervention
Biopsies, drainages, the ganglion ablations for a pain therapy, vertebroplasty for osteoporosis and RF/ microwave ablations of cancer tumours are routinely done under CT guidance, obviating the need for surgical treatments in the operation theatres. These procedures do not need general anesthesia and long hospital stay.
MRI
Better hardware, parallel imaging techniques, faster scan times, higher resolution and greater magnet strength had resulted in extracting better information in lesser amount of time. Whole body MRI with Dixon imaging has the potential to serve many indications of PET-CT for detection of distant metastases, without any radiation hazards.
Perfusion MRI (including Arterial Spin Labelling (ASL), a non-contrast perfusion technique) helps to diagnose and monitor therapy response in tumours.
MR Spectroscopy can detect the biochemical composition of tissues and is used to diagnose cancerous tumours and monitor their response to therapy.
Ultrasound
Today, ultrasound scanners produce much higher resolution with better image quality as a result of hardware improvements. Volumetric ultrasound probes have enabled us to acquire 3D data with multi-player capabilities, much like CT/ MRI scans. This has significantly enhanced fetal and gynecologic imaging. Ultrasound contrast agents are non-nephrotoxic and almost devoid of side effects. They have found applications in abdominal imaging, especially, liver imaging. Ultrasound elastography is a novel technique enabling us to objectively assess tissue hardness, thus enabling differentiation of benign from malignant breast masses and monitoring the progression of chronic liver disease, among other uses.
Digital subtraction angiography and interventional radiology
Rotational angiography with high resolution fat panel X-ray detectors have completely changed the image acquisition and data processing. The 3D road maps and large monitors are of tremendous help in complicated interventional radiological (brain and body) procedures, making endovascular surgery fairly safe and effective.
MR guided interventions
MR guided Focused Ultrasound Surgery (MRgFUS) is a non – invasive treatment modality, where different body tumours are destroyed and treated by high intensity focused ultrasound waves with thermal ablation and coagulated necrosis. This has emerged as an alternative and more effective treatment modality than invasive surgery in uterine tumours, bone metastasis, prostate and breast cancer, bone tumours, arthritis and many brain pathologies. This is a revolutionary cutting edge technology, which will have increasing applications in the future.
Other MR guided interventions:
MR guided biopsy (eg. breast and prostate) are now performed routinely.
Future trends
Switching over to techniques that would reduce ionising radiation and replace existing modalities with those that completely avoid radiation are increasingly the focus of scientific research. Photo acoustic imaging, newer contrast media, which do not have gadolinium or iodine is the way imaging may proceed. PET MR is emerging as a mainstay in cancer diagnosis. MR imaging has certainly assumed a central role in medical research.
In Winston Churchill’s famous words, “the farther back you can look, the farther forward you are likely to see”. In the past 100 odd years, radiology has progressed from simple X-rays to complex functional MRI’s and nuclear scans. The role of the radiologist has evolved from just providing the diagnosis to now being integral part of the management and treatment of the patient.