“What can a CT scan detect in the lungs?”
I am a 38 year old female. I want to know what can a CT scan detect in the lungs?
2 Answers
A Chest CT can evaluate many things. Certainly all the anatomy from the front to the back of the person evaluated from the top slice (often including the low neck) to the bottom slice (including the lower lung which allows imaging of some of the liver, spleen, and adrenal at that level. The lungs themselves and the nearby structures such as the heart, pleural lining, mediastinum are key t areas that can be evaluated. Different CT methods are used for more specific findings desired by the requesting physician. Talk to the ordering doctor to know what they are asking to find out.
A CT scan is an X-ray of the chest. The X-ray machine circles around you when you are inside the doughnut. It shoots X-rays into your body. It measures how many come out the other side. So what a CT scanner 'sees' (counts really) is how many X-rays get stopped by your body, and how many come all the way through. So a CT scanner can tell how much each part of the body absorbs X-rays. That is a measure of the density of the tissue. The scanner then uses all these density measurements, to generate pictures.
For example, a lung is usually filled with air. Hence, it is not very dense. Most X rays go all the way through the lung. If a lung fills with fluid, the fluid is denser than air. So a fluid-filled lung stops more X rays. The CT scanner doesn't count as many X-rays coming out the other side. It registers the higher density of the fluid-filled lung. The CT scanner can't tell if the fluid is infected fluid from pneumonia, sterile fluid from heart failure, or swallowed fluid that went down the wrong pipe. It just sees density.
A specialist in Radiology reviews the CT scan. They have spent years studying different patterns and distributions of different densities, in different parts of the body. They issue a report on what the CT shows. This report is made available to the Doctor that ordered the CT scan. This report, along with your complaints, medical history, labs, and physical exam helps your doctor figure out what is going on.
So when a disease causes parts of the body to be a different density than normal, a CT scan will show that disease. Like fluid in a lung, or a break in a dense bone. When the diseased tissue is the same density as healthy tissue, a CT scan is not as helpful. For example, a tumor inside a kidney is often the same density as normal kidney tissue. So to register that tumor, a CT scanner would not be great. Additional steps like injecting contrast into the vein may be needed, or other techniques like MRI or Ultrasound. In a different way, a stomach with an ulcer can have the same density as a stomach without an ulcer. In those cases, an endoscope would be a better way to make a diagnosis. So CT scanners see density. Radiologists use those density measurements to infer what disease is the cause.
For example, a lung is usually filled with air. Hence, it is not very dense. Most X rays go all the way through the lung. If a lung fills with fluid, the fluid is denser than air. So a fluid-filled lung stops more X rays. The CT scanner doesn't count as many X-rays coming out the other side. It registers the higher density of the fluid-filled lung. The CT scanner can't tell if the fluid is infected fluid from pneumonia, sterile fluid from heart failure, or swallowed fluid that went down the wrong pipe. It just sees density.
A specialist in Radiology reviews the CT scan. They have spent years studying different patterns and distributions of different densities, in different parts of the body. They issue a report on what the CT shows. This report is made available to the Doctor that ordered the CT scan. This report, along with your complaints, medical history, labs, and physical exam helps your doctor figure out what is going on.
So when a disease causes parts of the body to be a different density than normal, a CT scan will show that disease. Like fluid in a lung, or a break in a dense bone. When the diseased tissue is the same density as healthy tissue, a CT scan is not as helpful. For example, a tumor inside a kidney is often the same density as normal kidney tissue. So to register that tumor, a CT scanner would not be great. Additional steps like injecting contrast into the vein may be needed, or other techniques like MRI or Ultrasound. In a different way, a stomach with an ulcer can have the same density as a stomach without an ulcer. In those cases, an endoscope would be a better way to make a diagnosis. So CT scanners see density. Radiologists use those density measurements to infer what disease is the cause.
