<prompt> Investigation of choice for detection char-acterization of interstitial lung disease isMRIChest X-rayHigh Resolution CT scanVentilation perfusion scan  <response>: C i.e. HRCT High Resolution CT HRCT is investigation of choice for interstitial lung disease parenchymal lung disease and bronchiectasisQ as it can delineate the lung parenchyma upto the level of secondary pulmonary lobule. Principles of HRCT are: 1.Narrow beam collimation leading to thin section r:: 1.5 mm 2.Small field view 1t increased resolution. 3. High spatial reconstruction algorythm edge enhancing or sharp algorythmQ eg. Bone algorythm, that makes structure visible sharper reduce smoothing, but it makes image noise more obvious. 