Despite the many advantages of MHCT, one should be aware of the relative limitations of this emerging technology. The combination of narrow collima-tion and a large area of coverage (e.g., CT angiography studies) can result in very large data sets that are not practical to view on standard films. Such data sets are ideally viewed in a ''filmless'' environment with cineviewing at a workstation. Moreover, the cost of filming such large data sets can be prohibitive. Subsequently, many departments have chosen either to only film selected images or to completely forego producing hardcopy images. Even in a ''film-less'' PACS environment, however, this new technology may create challenges regarding how best to manipulate and store the large amount of data generated by MHCT studies. Rubin has recently proposed several alternative visualization techniques in order to tackle the ''data explosion'' produced by MHCT studies . Before such alternative techniques can be introduced into daily practice, we will have to await the development of substantial improvements in automated processing, processing speed, and user interface .
Other relative limitations of MHCT include the increased complexity of imaging protocols, the increased importance of proper timing for optimal enhancement in vascular studies, and the potential to increase the radiation dose, depending on the specific scanning parameters employed. With regard to radiation exposure, if MHCT is performed with equal slice thickness to single-detector CT, MHCT actually results in a slightly decreased dose to the patient due to better dose efficiency of the detector; however, this advantage is lost or reversed if thinner slices are routinely employed with MHCT . Importantly, preliminary investigations suggest that one may perform MHCT of the lungs with a ''low-dose'' technique for some clinical indications . Future research in this area is necessary.
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