Pulmonology
A Cough That Will Not Go: When to Worry and What Causes It
In Pakistan a cough lasting two weeks or more should be tested for tuberculosis. What else causes a long cough, and the signs that mean see a doctor now.
27 Aug 202610 min read
X-ray
Also known as Radiograph, Plain film
An X-ray uses a small dose of radiation to produce an image, and it is best at showing bone and the chest. It is quick, widely available and usually the first imaging test requested.
X-rays pass through the body and are absorbed to different degrees on the way. Dense tissue such as bone absorbs a great deal and leaves the detector unexposed, appearing white; air absorbs almost none and appears black; soft tissue and fluid fall in between. The image is a shadow, and everything in the path is superimposed in one plane — which is both why it is fast and why it has limits.
| X-ray | {{ct-scan}} | {{ultrasound}} | {{mri}} | |
|---|---|---|---|---|
| Radiation | Low | Higher | None | None |
| Best at | Bone, chest | Cross-sections, bleeding, trauma | Soft organs, pregnancy, live imaging | Brain, spine, joints |
| Speed | Immediate | Minutes | Immediate | 20–45 minutes |
Because a plain film superimposes everything, a normal X-ray does not exclude much. A fracture can be invisible in the first days, and soft tissue injury is largely unseen — which is when a or follows.
Where this comes up
General Medicine
Fever in Adults: What It Means and When to Worry
Most fevers settle within three days. In Pakistan a fever that lasts longer needs testing for dengue, typhoid or malaria — and a few need help the same hour.
27 Aug 20269 min read
Cardiology
Chest Pain: When to Worry and When to Call for Help
Chest pain lasting more than a few minutes with sweating, breathlessness or pain spreading to the arm or jaw is an emergency. Call Rescue 1122 now.
25 Aug 202611 min read
Pulmonology
Asthma: Symptoms, Inhalers and How to Stay in Control
Wheeze, night cough and breathlessness that come and go. What asthma actually is, why the preventer matters more than the blue inhaler, and when an attack is an emergency.
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Related terms
- CT scanComputed tomography, CAT scanA CT scan uses X-rays taken from many angles and reassembled by computer into cross-sectional images of the body. It is fast and detailed, which makes it the scan of choice in emergencies, and it delivers a meaningfully higher radiation dose than a plain X-ray.
- MRIMagnetic resonance imagingAn MRI scan uses a strong magnetic field and radio waves to build detailed images of soft tissue. It involves no X-rays and no radiation.
- UltrasoundSonography, Ultrasound scanAn ultrasound scan builds images from high-frequency sound waves reflected back off the body's tissues. It uses no radiation, which is why it is the scan used in pregnancy.
- OsteoporosisBrittle bone disease, Thin bonesOsteoporosis is loss of bone density that leaves bones fragile enough to break from a minor fall or even a cough. It causes no symptoms until a fracture happens, which is what makes it dangerous.
- ScreeningScreening testScreening is testing people who feel well, to find a condition earlier than symptoms would. It is only worth doing when finding the condition early genuinely changes what happens next.