STATE OF THE ART AND TRENDS

Clinical Imaging has always played a crucial role in patient care. There is a compelling need today for early diagnosis of pathologies and personalised treatment. The key to meet this demand lies in the effective use of technologies and efficient interactions between various actors involved in the imaging process.

ACTORS

An imaging cycle begins when an individual presents oneself to the physician with a complaint or problem with his / her body. After some relevant clinical examinations, if the cause of the problem is not definitive, the physician refers the patient to obtain one or more medical scans to examine the internal anatomy and / or their functioning. Depending on the nature of the problem, the imaging exam may be performed using one or more of the following technologies

• Radiography (Fluoroscopy, XRAY (XR or DR for Digital XRAY))

• Ultrasound (US)

• Tomography (Linear Tomography, Poly Tomography, Computed Tomography (CT))

• Magnetic Resonance Imaging (MRI)

• Nuclear Medicine (Scintigraphy, Single Photon Emission Computed Tomography (SPECT), Positron Emission Tomography (PET))

• Echocardiography (ECG)

• Thermography

  These exams are generally performed by qualified technologists who are trained to operate the medical equipments. The results are provided to the radiologists for interpretation and then subsequently to the referring physician. After analysis the diagnosis and possible remedies are suggested back to the patient. These medical equipments are designed and created by various manufactures which employs experts in the required technologies.

  Key actors in the imaging cycle include patient, physician, technologists, radiologists and manufacturers

  ACTOR INTERACTIONS

  In order to provide the best care to the patients, interactions between these actors in the imaging cycle are very critical. An overview of the actor tasks and their interactions is shown in the form a sequence chart below in figure 1. A few important interaction scenarios are further discussed as follows:

• Patient – Physician: The communication and understanding between the patient and physician is very crucial in identifying and treating the problem. It is important for the patient to mention all relevant symptoms and be clear about his or her situation. The physician’s responsibility is to ask the necessary questions and study the patient well. There is an increasing interest among patients to understand the details about the diagnosis as well as all available treatment options. Thus keeping the patient in the loop at every stage of the cycle is important. This need also has created a requirement that links with equipment manufactures in order to provide result reports that may be interpreted or communicated easily to the patients.

• Technologist – Radiologist: The technologist is very well qualified in operating the medical equipment in order to obtain the required results. The radiologist on the other hand is best in interpreting the results (generally medical images). In order to obtain results that can be best used for diagnosis, the radiologist and technologist need proper interactions.

• Radiologist – Physician: The interpretation of results / images obtained from the medical equipments can sometimes be very complex. It is the responsibility of the radiologist to analyze all the available data and communicate the probable diagnosis with relevant evidence. This is critical for the physician to create and plan an appropriate treatment for the patient.

• Manufacturer – Technologist, Radiologist and Physician: It is extremely important for the medical equipment to generate high quality reliable results to facilitate appropriate diagnosis and treatment. It is thus very critical for the manufacturer to extensively communicate with the equipment users. The information shared by the technologists, radiologists and physicians help the manufactures design and the equipments to suit the need.

Figure 1

TECHNOLOGY TRENDS

The current state of medical imaging would not have been possible without the intelligent use of various technologies. This comprises of various hardware equipments, imaging concepts and software algorithms. Each imaging modality has its own bounded strengths and a complete diagnosis / treatment can be precisely defined after analyzing complimentary data from multiple modalities. Three key technological trends along with their clinical use are highlighted hereby:

• Multi-Modality Analysis: Various clinical and research studies have now shown that data combined from multiple imaging modalities add significant value and confidence towards differential diagnosis and appropriate treatment. Some commonly used modality combinations are XRAY / CT, PET / CT, SPECT CT and more recently MRI / US and PET / MRI. Images may either be obtained combined scanning equipment that houses multiple technologies or they may be combined through software post separate acquisitions. Such fusions are able to provide insights into pathologies in different anatomical and / or functional perspectives. An example use case of a recent study of brain tumor using PET and MRI is shown in figure 2. The fusion images give a better perspective about both the anatomical regions affected by tumor as well as the clear boundaries of the tumor region.

Figure 2 [Ref: http://medicalphysicsweb.org/cws/article/research/43526]

• Quantitative Imaging: Quantitative imaging is the extraction of quantifiable features from medical images for the assessment of normal or the severity, degree of change, or status of a disease, injury, or chronic condition relative to normal [Ref: http://www.rsna.org/QIBA_.aspx]. Representing the area of observation using quantitative parameters extracted from the images provides improved ability to characterize the pathology. Deviation from known normal parameter values can provide clearer indication of the underlying problem when compared to looking visually at images purely qualitatively. There is an increasing trend today in the field of imaging to identify key quantitative imaging markers for various pathologies. Some examples of quantitative parameters that are becoming common clinical practice include volume information, diffusion / perfusion characteristics of tissues, rate of blood flow etc.
• Computer Aided Diagnosis (CAD): As the name suggests, this is a technology in the field of medical imaging that involves the use of smart computer algorithms and visualisation techniques to assist in the process of diagnosis. Given the volume of data that is being generated today due to increased computational capabilities, there is a growing challenge to humanly analyse and interpret them. This is where CAD tools can potentially play an important role. They attempt to simplify the data, provide better presentation and / or bring focus to a subset of the data that is more relevant to the pathology of interest. There is an increasing interest in the imaging community to use such CAD tools for data interpretation and analysis. Sophisticated diagnostic tools are being created that focus on specific pathologies and provide great insights into interpreting the corresponding data. The efficacy and reliability of CAD tools / devices though, is still not proven to completely rely on their results. The radiologist / physician still hold the complete responsibility for making the diagnosis and devising treatments. The computer algorithms that are predominantly of use in the CAD tools can be largely classified as ones that work on analysing and evaluating patterns. After all a radiologists inherently does the same task. In essence CAD tools are an attempt to bring artificial intelligence into the software. The primary anatomical areas that have currently been subject to CAD are chest, breast and colon. Few clinical applications where CAD has started to make a positive difference are Breast Mammography, detection of colonic polyps and lung nodules, cancer screening etc. [Ref: http://radiology.rsna.org/content/225/2/606.full]. The number of papers related to CAD research presented at RSNA (Radiological Society of North America) conference between the year 2000 and 2005 is shown below in table 1.

Table 1 [Ref: K. Doi, Computerized Medical Imaging and Graphics 31 (2007) 198–211]

More recent trends in CAD include Coronary Artery Disease, Oncologic applications, therapy response monitoring etc. There is also a great need and interest in integrating quantitative imaging along with CAD tools. CAD is also being considered and evaluated to be integrated with PACS (Picture Archival and Communication Systems). Overall in the next few years CAD is expected to be utilized for all routine evaluations thus aiding physicians to concentrate on more complex scenarios where their expertise and experience is most needed.

TAKE HOME MESSAGE

Clinical imaging today has become a key tool towards patient care. The future is moving towards performing imaging as a part of routine check-ups in order to assist in early diagnosis and personalized treatment. The actors in this field are not only embracing various technologies but also integrating them to add great clinical value. The field has come a long way but there is still potential for a lot more it can provide. The collaboration amongst the actors and advancement in technology is paving the path to bring to reality the popular quote “Prevention is better than cure by Desiderius Erasmus”.