Computed Tomography (CT) is the mainstay of diagnostic imaging evaluation of thoracic disorders. However, there are a number of CT protocols ranging from a simple non-contrast CT at one end of the spectrum, and CT perfusion as a complex protocol available only on high-end scanners. With the growing diversity, there is a pressing need for radiologists, and clinicians to have a basic understanding of the recommended CT examinations for individual indications. This brief review aims to summarise the currently prevalent CT examination protocols, including their recommended indications, as well as technical specifications for performing them.

SummaryBackgroundTo evaluate the role of diffusion weighted imaging (DWI) and apparent diffusion coefficient (ADC) values at 3 Tesla in characterizing sinonasal masses.Material/MethodsAfter ethical clearance, 79 treatment naive patients with head and neck masses underwent magnetic resonance imaging (MRI), including DWI at 3 Tesla using the following b values – 0, 500 and 1000 s/mm2. Thirty-one patients were found to have sinonasal tumours and were subsequently analysed. Image analysis consisted of a morphological evaluation of conventional MR images, qualitative evaluation of DW trace images and quantitative assessment of mean ADC values. Receiver operating characteristic (ROC) curve was drawn to determine a cut-off ADC value for the differentiation between benign and malignant masses.ResultsSinonasal masses showed an overlapping growth pattern on conventional imaging, irrespective of their biological nature. The mean ADC value of benign lesions was 1.948±0.459×10−3 mm2/s, while that of malignant lesions was 1.046±0.711×10−3 mm2/s, and the difference was statistically significant (p=0.004). When a cut-off ADC value of 1.791×10−3 mm2/s was used, sensitivity of 80% and specificity of 83.3% were obtained for characterization of malignant lesions, which was statistically significant. Juvenile nasopharyngeal angiofibroma (JNA) showed distinctly high ADC values, while meningioma was the only benign lesion with restricted diffusion. Atypical entities with unexpected diffusion characteristics included: adenocarcinoma, adenoid cystic carcinoma, meningioma, chondrosarcoma and fibromyxoid sarcoma.ConclusionsDWI in conjunction with conventional imaging can potentially enhance the diagnostic accuracy in characterizing sinonasal masses as benign or malignant. Some specific entities such as JNA and meningioma showed distinctive diffusion characteristics.

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Purpose:To evaluate the diffusion weighted (DW) magnetic resonance imaging (MRI) features of the extracranial schwannomas of head and neck.Materials and Methods:The MRI (including DWI) of 12 patients with pathologically proven head and neck schwannomas (4 men, 8 women, with mean age of 32.6 years; age range 16–50 years) were retrospectively evaluated. Images were analyzed for signal intensity and morphology on conventional sequences followed by the qualitative evaluation of DW images (DWI) and measurement of apparent diffusion coefficient (ADC) values.Results:Majority of the tumors were located in the parapharyngeal space (8/12). All but one showed heterogeneous appearance, with 10 tumors showing scattered areas of hemorrhage. Eight out of 12 tumors showed intensely hyperintense core surrounded by intermediate signal intensity peripheral rim (reverse target sign) on T2-weighted (T2W) images. On DWI, these eight tumors showed a distinctive appearance, resembling target sign on trace DWI and reverse target on ADC map. Out of the remaining four tumors, one showed uniformly restricted diffusion whereas three showed free diffusion. Mean ADC value in the central area of free diffusion was 2.277 × 10−3 mm2/s (range of 1.790 × 10 −3 to 2.605 × 10−3 mm2/s) whereas in the peripheral area was 1.117 × 10−3 mm2/s (range of 0.656 × 10−3 to 1.701 × 10−3 mm2/s). Rest of the schwannomas showing free diffusion had a mean ADC value of 1.971 × 10−3 mm2/s.Conclusion:Majority of the head and neck schwannomas showed a characteristic appearance of free diffusion in the centre and restricted diffusion in the periphery of the mass.