One of the biggest concerns in the use of CT cardiac is the high dose of radiation that the patient is subjected to. These doses have been recorded to be as high as 15mSv. For the reduction of these high doses, many strategies are employed. These include X-Ray beam filtration, X-ray beam collimation, X-ray beam current modulation and adaptation for body habitus. The most common method however, is the dose modulation procedure where the X-ray tube output is changed during the various stages of the cardiac cycle. This dose is increased to 100% in diastole, while is minimized to 20% in systole.
The effect is the reduction of the total radiation dose by almost 50%. (Fishman, 2006) One of the recent researches have put many others in concern about the false positive results of the CT scans. A report in Science Daily has claimed that the new PET-CT scanners along with their soft wares are predicting as high as 40% false positive in patients and is indicating coronary disease in them. (Science Daily, 2007) According to the report the researcher K Lance Gould claims that there are many false negatives regarding coronary artery diseases due to this procedure.
Similarly in 23 percent of the cases, the PET-CT scanner has shown high abnormalities in the structure of the heart. Many factors are considered to be the cause of this faulty detection. The inability of the software to identify the changes due to breathing and heart rhythm can cause false positive results, which can be dangerous in an inexperienced physician’s hands. Gould claims that only a perfectly conducted technique results in accurate results. PET is a recent intervention in diagnostics of the heart, and has been predominantly used for brain, lungs and body imaging.
Failure to appreciate the differences in the cardiac imaging is the reason for faulty results. However, Gould does admit that there are certain advantages of the technique. Again, if done properly, the technique is highly accurate. It is also a fast way of obtaining information and has a short time for the procedure. It has been very much credited for good diagnosis of the heart. Until the doctor or the physician is able to identify the technological aberrations in the technique, Gould recommends not using it or consulting with more experienced personnel. (Science Daily, 2007) The new directions in ct imaging of the heart:
With improved hardware and software systems being introduced in the market, the evolutions in the CT imaging of the heart are rapid. The newer MDCT systems consist either of 40 unit or 64 unit detector systems. This increase is leading to creation of more than 5000 images, which in turn is improving the outcomes of imaging and visualization even better. (White and Reed, 2004) A current problem faced is the imaging in the motionless views, where temporal resolution is still inadequate. There are many initiatives being taken to address this part of the CT scanning, however, the achievements in this area are still slow.
(White and Reed, 2004) The introduction of the 64-slice CT has been a breakthrough in the diagnosis of the cardiac modalities. The high sensitivity along with high detail acquisition has made it one of the best methods for cardiac diagnosis, in all clinical setups. This has not however, absolved the technicians or the physicians from their duty to correctly diagnose the condition. Contrast delivery and data acquisition must be synchronized properly in order to improve the data acquisition. Researches are giving out results that show that 64-slice CT imaging is far more superior to conventional coronary angiography.
In a recent study by Das et al in 2007, 53 patients had their CT heart carried out. The finding of the CT imaging was then compared with the conventional angiographs of the patient. The detection was being carried out for stent restenosis. Both methods gave comparable results of above 95% accuracy in the detection of the restenosis. Coronary CT in fact helped in identification of restenosis in many cases that were below 50%. The research was able to prove that it has the capability to depict in-stent-low-attenuation filling defects, which was comparable to that of angiography procedures.
(Das et al, 2007) Ultrafast cardiac imaging is another modality that has been introduced for cardiac CT purposes. This technique can take multiple images of the heart in a single heart beat, which not only speeds up the process, but also is able to provide accurate detail about the functioning of the heart. It is a good modality to detect calcium in the coronary arteries, and can be used as a diagnostic as well as a preventive tool for heart conditions. This procedure can be carried out along with ECG and EKG. (Ultrafast CT Scan, 2007)