CT imaging has come a long way since its introduction in the field of medicine as a diagnostic modality. While imaging in the past was confined to radiographic assessments only, the advent of CT led to improvements in the diagnostic capabilities of the physicians. The first in the series of the CT scans were the conventional collimation scans, which although were a good addition to diagnostics; remained a small part in the diagnostic planning. It was later with the addition of the high resolution CT scanning that true possibilities of this diagnostic were realized.
High resolution CT for the first time enabled the physician to discriminate between parenchyma and various tissues of the organ, and thereby diagnose with accuracy various diseases. It was later on that the introduction of spiral and multi detector CT scanners further improved the diagnostic value of the CT scan. (Muller, 2002) This was many steps ahead of the conventional radiographic techniques in use. For radiographs were not able to differentiate body structures beyond hard tissues and soft tissues, and could not assess accurately the densities of the various organs.
CT imaging became one of the widely used modalities in the cases of brain and body scans. It especially became a method of choice for cancer patients, where detection and metastasis were known with increased accuracy. CT then found its way into the brain scans especially in patients suffering from stroke or brain occupying lesions. Later on CT became a good method to study the lungs and the thoracic region. However, the introduction into the cardiac CT was delayed considerably.
There were many reasons why early CT systems were not used in cardiac imaging. The first challenge was the small size of the coronary arteries that were aimed for imaging, along with the tortuous path as well as movement due to cardiac and respiratory motion. (White and Reed, 2004) The tortuous course of the arteries makes it very difficult to locate and much less trace them with accuracy. This technique virtually became useless due to this draw back for heart cases, as coronary artery blockages could not be viewed.
The technique factors that made this procedure difficult at the earlier stages included the lack of speed and poor temporal resolution in the initial CT models. The heart is especially difficult to view and scan due to the continuous motion of the heart. This makes viewing of the coronary arteries even more difficult due to their small size. The introduction of the first models of electron beam tomography was not successful due to its expensiveness and therefore was not employed in many hospitals for a long time.
The multi-detector and the spiral CTs were the next in line in the evolution of the CT scans. This method was in many ways superior as it gave high details of the small coronary structures. Indeed the diagnostic and detail value of the spiral CT has been compared to that of conventional angiography, making it a good diagnostic procedure for various heart conditions as well. The only problem that the physicians encountered with CT was the lack of resolution in the images. Again this was attributed to the constant movement of the heart, and the changes that took place due to breathing.
These problems still cause difficulty in the imaging with the current models. With increased advancements in the diagnostics, it is hoped that this problem will also be taken care of. (Muller, 2002) The concept behind the CT scan is the acquisition of multiple radiographs of an area under review. These radiographs are taken at different angles around the organ to be viewed, and therefore aims to collect as much radiographic images within one sitting. These multiple x-ray images are combined together to create multiple cross sectional views of the organ or area under study.
These methods can either use a contrast or not, depending upon the type of procedure. The contrast used is generally iodine, but others are also used albeit occasionally. Now with the recent advancements in the procedure, the use of multi-detector scanning is undertaken, which result in high resolution and quality images of the heart. (History of Innovations, 2006) These scans with the contrast are able to provide very high resolution images and two dimensional and three dimensional views, thereby revolutionizing the imaging process of the diagnostics.
The CT scan has made it possible to fuse the visual as well as virtual demonstration of the organs on to a screen and thereby giving accurate assessment of the various body functions and organs. The areas where these diagnostics are seeking improvement include improvements in speed, quality and dimensions of the display, and improved access to the data provided. Another area of development includes the reduction in the intensity of the X-ray beams to reduce adverse effects.
Since the anatomical information of the individual patient is reproduced exactly, the treatment plan is more accurate and in lieu with the patient needs. In many respects, the current methods of CT and MRI can be termed as virtual dissection of the body, as it is able to provide visualization of the organs, possible only through anatomical dissection in the past. (Robb, 2006) This technique has been found to be especially useful in emergency cases of cardiac pathologies, where rapid scanning can help save lives. CT scanning had introduced three new advantages to the radiographic imaging of the past.
The image produced was digital, which made it possible to manipulate it, and magnify it considerably to understand the pathosis. The differences of tissue density were well understood which was not possible with conventional radiographs, and various cross sectional views help establish a 3 dimensional view which was limited to one dimension with radiographs. These developments have taken years to take place. However now, thanks to these technologies, it is possible to image a beating heart, and blood flow in the heart, brain, lungs and the extremities. (Robb, 2006)