The photoelectric effect is an interaction between a low to intermediate energy X-ray beam and the inner shell electron. Inner shell electron is ejected, the outer electron goes into inner orbit to occupy the space, and the extra energy is ejected as characteristic radiation and is called the photoelectric effect. The photoelectric effect is of fundamental importance in diagnostic radiography since it is the primary method by which contrast is developed in radiographs. It allows for the differentiation of different types of tissues on the X-ray film. Very low-energy X-rays are not capable of producing the photoelectric effect. High energy X-rays are also not capable of photoelectric effect due to random scattering of electrons from the outer shell. This is known as the Compton effect and it can lead to distortion of the image. The goal of X-ray imag...
CT is the initial investigation for aortic dissection as it is more widely available and takes a shorter time when compared to MRI. MRI, though highly accurate for acute aortic disease evaluation, is usually confined to cases of severe renal insufficiency or when the use of iodinated contrast medium is absolutely contraindicated. The image below depicts CT chest showing Type A aortic dissection from the aortic root. (A) Axial view and (B) sagittal view. The arrows indicate the intimal flap. The image below shows the classification systems used for aortic dissection.
Rapid accumulation of fluid or blood in the pericardial space causing increase in the intrapericardial pressure is called as cardiac tamponade. This results in Compression of cardiac chambers. ↓ ↓ venous return ↓ ↓ cardiac output Causes Trauma Progressive pericardial effusion due to tuberculosis, viral, bacterial infections Often, uraemia can cause significant pericardial effusion Features Hypotension. Widened cardiac dullness. Muffled or decreased heart sounds. Increased venous pressure with raised jugular veins. Pulsus paradoxus (pulse becomes weaker on inspiration than expiration). In severe cases, heart is unable to expand causing shock and often sudden death. Beck’s triad Hypotension Muffled heart sounds Raised jugular venous pressure Investigation Chest X-ray and US confirms the diagnosis. Differential diagnosis: Tension pneumothorax. Treatment Pericardial tap is done for immediate temporary relief under US g...
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