Trends in Diagnostic Imaging

The major drivers in Imaging Technology and Services as we look to the future are discussed below in general order of immediacy.

  1. PACS and related digital imaging systems. Most hospitals are at some stage of PACS planning and/or implementation. It will soon be an imperative in order to manage the exploding volumes of images created by the newest technologies (e.g. CT and MRI) and to provide enhanced quality and service. All specialized modalities are already digital: angiography, ultrasound, CT, MRI, and nuclear medicine. Most fluoroscopy systems purchased in the last 5-7 years are digital or digital capable. The last two “frontiers” are general radiography and mammography. Digital systems are available and in use for each, although equipment is 3-4 times more expensive than conventional equipment.

    Digital radiography is thus usually brought on line when full PACS is implemented. It is of two types: CR (computed radiography) and DDR (direct digital radiography).

    • CR uses cassettes loaded into the table like a film cassette. The image is captured digitally and “discharged” from the CR plate into electronic format using a CR reader (a process akin to film developing). This is slightly more efficient than conventional film. In the long run, CR is a transition to DDR for most providers, although in will continue to be more cost-effective in lower volume providers.
    • DDR has electronic sensors built into the table. As soon as an image is taken, it appears on a monitor in the room. There is thus no manipulation or “development” of cassettes, which can be the most time consuming parts of many exams. DDR equipment is also highly automated with preprogrammed table/tube manipulations. DDR will significantly improve patient throughput, if the support systems are in place to move patients in and out of rooms as rapidly as practical (change/waiting spaces close to rooms and support staff to manage patient flows).

    Adoption of digital mammography is in the early stages; however it will be the standard in 5-8 years. Computer assisted diagnosis (CAD) will become prominent as an adjunct, providing a second read for screening mammography. Tomosynthesis will provide 3D breast images from digital mammography.

  2. CT. CT was introduced over 30 years and has undergone numerous advances, but no time period has seen changes as rapid and profound as the last few years and looking ahead at least ten more. Procedure volumes have been growing at least 10% per year, a trend that may accelerate in the next five years. Multi-slice CT (MSCT) was introduced in 1998 and has rapidly evolved from 2>4>8>16>32>64 slices with 128 and 256 on the horizon. The end point is flat panel detectors which provide "infinite" slices.

    16 MSCT changed the paradigm since it permits volumetric (3-D) reconstruction with high resolution. Radiologists no longer just read slices. This capability has opened the door to CTA vascular studies (peripheral, carotid, neuro, renal, and aorta) and virtual “oscopies” (e.g. colonoscopy, bronchoscopy).

    64 MSCT is opening the door to cardiac CT and coronary artery imaging (and improving all 3D studies). It is likely to replace diagnostic cardiac caths and expand the patient population being tested.

    Areas most affected by MSCT are:
    • Emergency medicine. Because of the speed of MSCT and the ability to scan multiple areas of interest in one exam, use will grow rapidly in the ED. It will be necessary to “dedicate” one MSCT to ED in larger hospitals and to make if very convenient in others. With three scans performed as a single procedure, it will be possible to triage chest pain between MI, pulmonary embolism, and dissecting aneurysm. Similarly, abdominal and pelvic scans can be used to triage an acute abdomen.
    • Stroke. A major element in the ED is rapid assessment of stroke in order to differentiate between occlusive and hemorrhagic stroke and to optimize therapy. CT perfusion and diffusion studies will provide the information needed.
    • Vascular disease, including carotid disease. CT angiography (CTA) will become the early diagnostic tool of choice impacting ultrasound and angiography. Angiography will be used primarily for interventions with known disease.
    • Coronary artery disease. CTA will be used early in assessment of early heart disease, and cardiac cath will be used for subsequent treatment. CTA will also be used to monitor patients post treatment (CABG, angioplasty/stent). The role of cardiac nuclear medicine will decline (due to MR as well).
    • Virtual colonoscopy. Although not quite as accurate as conventional colonoscopy today, problems will be overcome. More patients will opt for CT colonoscopy, and thus more patients will be diagnosed with disease and receive interventions using traditional methods.
    • Virtual bronchoscopy. This will be the procedure of choice for assessment of lung and other thoracic diseases. CAD will be important.

    These advances in CT are negatively impacting conventional imaging including radiography and fluoroscopy as well as emergency ultrasound and nuclear medicine.

  3. MRI. MRI came into clinical use about 25 years ago. It has experienced rapid growth at rates of 8-12% per year. Such trends will continue due to new applications resulting from magnet and gantry design, coils, and greatly increased computing speed. The clinical areas that are currently most significant for MRI are neurosciences, orthopaedics, oncology, and ENT. Newer areas of growth in the next 5-10 years are breast, cardiology, vascular, and interventional/minimally invasive procedures.

    • Breast MRI will become prominent, initially for high risk patients and ultimately prior to interventions. It will guide breast interventions for lesions that can only be detected by MRI.
    • MRI could become the gold standard in assessing cardiac function, having further negative impacts on nuclear cardiology.
    • MRI will complement CT in assessing brain function post-stroke and will be standard of care for all white matter brain diseases.
    • MRA will complement CTA for plaque/wall characterization.

    Currently the technical standard for general imaging service is a 1.5T magnet. Higher field strength magnets are moving into some community hospitals. Within 10 years, 3.0T will be the standard of care in larger community hospitals due its greater speed, higher resolution, and ability to perform functional studies. Specialized systems will become more prevalent including orthopaedic, breast, and head (3T).

  4. Fusion Imaging. Fusion imaging is the “marriage” of two modalities to provide a combined image. The general advantage is to combine structural and functional information into a single output. Fusion can be done with hardware or software. Software fusion requires that the two modalities establish several common reference points so that a program can overlay one image on the other. Hardware fusion produces both types of images sequentially on a single equipment platform.

    The most common examples are in nuclear medicine with SPECT-CT and PET-CT. PET/SPECT provides functional information about tissue properties/function/ viability. CT provides anatomical orientation.

    The most common applications for PET-CT are oncology for staging tumors, planning therapy, and monitoring recurrence. In the future it will be used mid-therapy (systemic) to determine response. At this time, there are virtually no sales of PET-only systems, and existing systems will soon be replaced.

    Some PET-CT systems are being used for treatment planning by smaller cancer centres with the CT component also used simulations. However as the utilization of PET-CT grows, the role in treatment planning will become one role for PET-CT systems in general.

    Future PET-CT growth will occur in neurology and cardiology. New markers are in development for SPECT-CT. The major impacts will likely be in cardiac imaging, but they could impact oncology and neurosciences as well.

    There continues to be significant debate about the role of CT and/or MRI in conjunction with Angiography, especially for newly developing neuro-interventional procedures. There are designs for suites with both modalities provided internally and others with CT and/or MRI adjacent to angiography. If these combinations develop, they will be located primarily in centers with major neuroscience services.

  5. Treatment. Imaging guided interventions have grown rapidly in recent years involving multiple imaging modalities. CT, ultrasound, angiography, and fluoroscopy are the primary ones. This has been part of the movement to less-invasive procedures performed in (hospital) outpatient settings. We will see continued growth in such procedures with some interesting new approaches.

    A combined MRI/ultrasound system has been in use in Europe for at least 5 years and was recently approved in the US. A continuous MRI image is used to guide a focused ultrasound probe (external) which heats and destroys tissue non-invasively. The initial application is for uterine fibroids, replacing hysterectomy. The procedure could be done in imaging in a room similar to conventional MRI.

    Other ablation therapies will continue to expand, including radiofrequency (RFA), cryo-ablation, laser-ablation, etc. Some will performed in imaging and some will be performed in procedural areas.

    Treatment planning will move to a new level with 3-D images generated by CT and MRI guiding more focused radiation, various types of surgical instruments, and robotics systems. Some will be real time; some will be off-line. Another variation will be surgical suites with CT or MRI scanners in close proximity so that surgical progress/outcomes can be evaluated in the peri-operative environment.

  6. Functional imaging. Most of imaging provides information about structure, the exception being nuclear medicine. Looking 8-15 years out, imaging will provide information at the tissue and molecular level in a variety of ways. Functional MRI and MRS (spectroscopy) are the clearest examples. However CT and ultrasound will also be used to characterize tissue. New types of functional studies will involve new imaging agents that are injected and activated in the presence of target cells or molecules. Cancer will probably be the earliest application, but neurology, cardiology, and other areas will follow. Current imaging modalities will see increased utilization, mostly CT, MRI, PET, and nuclear medicine. Entirely new modalities may emerge. Of all the trends identified herein, this will probably take the longest to devolve to the community setting.