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This is with reference to the original article titled “Three Dimensional Spiral CT Imaging of Musculoskeletal System: Application & Advantages” (MJAFI 2005; 61:133-8). Comparison of application of Three dimensional spiral CT imaging with MRI in imaging of Musculoskeletal System continues to evoke mixed response. However, at present, the scale is clearly tilted towards Magnetic Resonance Imaging in most musculoskeletal conditions except in skeletal trauma. In view of this, following comments are offered on this article:
The authors have used 3-D CT Imaging in evaluation of bone tumors. The authors’ contention is that CT is not only as efficacious but is superior to MRI in detection of cortical destruction of calcification. However, it is brought to the attention of the readers that the main aim of imaging studies in bone tumors is to establish the extent of lesion, detect the bone marrow involvement, skip lesions, satellite lesions, to define aggressive nature of lesion and to establish extent of soft tissue involvement. For all these aims, MRI remains the imaging modality of choice and is superior to 3-D CT Scan. With exception of densely sclerotic lesions e.g. osteoid osteoma, MRI has replaced CT scan for the assessment of skeletal tumors .
The authors have also used 3-D CT for evaluation of avascular necrosis of femoral head while accepting at the same time that MRI is considered as the gold standard. MRI can detect stage-I avascular necrosis of the femoral head whereas 3-D CT detects from stage – II onwards only [2,3]. The reason for 3-D CT imaging preference is not clear.
Last but not the least, the often ignored issue of radiation exposure and safety needs to be considered. In this study, every patient underwent radiation exposure to obtain 180 to 320 CT images. Some of these patients also underwent repeat imaging studies. This is a highly significant level of radiation. Doing a 3-D CT imaging study in a patient with a skeletal tumor or avascular necrosis of femoral head (where MRI is the established gold standard) raises safety issues as well as ethical issues. It is hoped that patients undergoing these studies were fully informed of these issues and necessary informed consent was obtained for undergoing a relatively less revealing imaging study with very high radiation exposure. As the authors have not declared this study to be either experimental or comparative (with MRI), ethical issues regarding patient safety and relevance of investigations need due consideration. As the study was conducted at a tertiary care centre, it is not likely that facilities of MRI were not available locally (In service hospital/in local civil medicare set up).