Chest X-ray: What makes a good image?

This is an important topic that I feel we need to cover before moving any further in our chest X-ray series. I wish I had more time to learn from radiologic technologists (RT), the real pros. Here is my quick and dirty assessment of the image.

Rest In Peace. Don’t die, but just enjoy a relaxing moment today and marvel at how wonderful and amazing life has been. RIP for the rest of this talk will be used to remind us of rotation, inspiration, and penetration. I’m not sure this is coming out right.

Rotation refers to patient alignment for the exam. Is the patient centered? The easiest way radiologists are first taught is to look at the clavicles. They should appear relatively symmetric. We look at the clavicular heads which is the bump where it connects to the bone in the center of your chest/sternum.

CXR labeled
The left clavicular head near the aortic knob is not as close to the midline as the head of the right clavicle. This patient is ever so slightly rotated to the left.

While this patient may be rotated, it is entirely acceptable. This is a good exam. Reshooting an X-ray to correct for this degree of “rotation” would be inappropriate.

Inspiration reflects the patient’s lung expansion and breath hold capability. Remember chest X-rays can be done in the radiology department with a standard PA view or portably. The portable view generally does not enable a patient to have as good an inspiratory effort. Take a deep breath slouched in your couch. Now with good posture standing up straight and tall. Your chest can get much larger with your ribs elevating up and out as your lungs fully expand. As a resident I was taught being able to visualize 8-10 ribs was considered a good inspiration. Since your ribs curve they are higher posteriorly where they join to your spine and lower anteriorly near your front where they connect through cartilage to your sternum. Eight anterior ribs and/or ten posterior well-visualized ribs is the goal.

PA chest
PA chest with a good inspiration.

 

We already talked about how the heart will appear larger in size/cardiomegaly on portable chest X-rays. Well the blood vessels in the lungs look different too! With a small inspiration the vessels appear larger, more closely packed and crowded, and can seem a little more hazy overall. To inexperienced readers this gives the appearance of increased fluid in the lungs, so called pulmonary edema. So a portable chest can make the heart look bigger and the lungs appear to have more fluid. We’ve just described the findings of congestive heart failure (CHF), cardiomegaly with pulmonary edema.

chest x-ray -portable
Portable chest X-ray where the heart looks big and the lungs look hazy

So how can you tell the difference between CHF and a low inspiration? Well, I try to cheat as much as possible. I’m either stupid or smart, but I use whatever information I can obtain to help me out. If I am perplexed I grab my cell phone and text or call my colleague to discuss the case, but it usually doesn’t come to this. RTs can make or break a radiologist. We are a team. They always see the patient and I don’t get to see patient’s enough. I read every single RT note. They will often let me know if the patient has a history of CHF. In fact many outstanding technologists will relay pertinent clinical information that is extremely valuable to the appropriate interpretation of most X-rays, whichever body part.

Penetration refers to the appearance of the film. Is it too dark and burned out looking blackened? This is called overpenetrated. Is it too bright and the heart and mediastinum are all a bright white and it’s hard to separate the two? This is called underpenetrated.

chest x-ray - exposure levels
mAs is referring to the amount of radiation dose. 6 mAs was perfect for this body type, but maybe not every person.

The goal is to be able to see the lung markings/blood vessels well. But you must also be able to “see through” the heart following the contour of the aorta and able to detect the subtle behind the heart/retrocardiac pneumonia.

This is part of the art of radiography. Sure there are autotimers and preset technique settings for different body parts, but everyone is different. A bigger patient has more soft tissue which stops X-rays from getting to the plate/detector (used to be film) in which case the image will appear bright. So larger people require more radiation exposure/dose to obtain a similar appearing image to a smaller patient. Do not freak out. You probably had more radiation exposure on your last airplane flight than this small dose adjustment, seriously.

Radiologists can use their computers to adjust the brightness and contrast of an image, but you can only adjust the source material so much. So again, it is up to the radiologic technologist to ultimately acquire the best possible images. We work together as a team. As a patient, please be kind and do your best to work with the technologist when they adjust your position and ask you to TAKE IN A GOOD BREATH AND HOLD IT. They care about you and are trying to provide you the best healthcare possible.

Thanks,

Ron

 

 

Image Credits:

portable chest X-ray

penetration chest X-ray

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I am an American Board of Radiology certified Diagnostic Radiologist with a certificate of additional qualification in Neuroradiology. I absolutely love my job. I have learned a tremendous amount about the human body, including its’ expected complications given our extraordinary complexity, and get to use that knowledge to help people. I personally have experienced emotional devastation and loss, which has made me compassionate and empathetic. I really care about people, and I hope I can use this site to help you. I graduated medical school in 2004 from New York Medical College. My wife and I had our first son in NY where we bought our 900 sf two bedroom one bath starter home. I stayed at Westchester Medical Center for radiology residency, where we had our second son. I obtained a neuroradiology fellowship position at Yale New Haven Medical Center commuting about an hour and a half each way for a year while we had our third boy. Upon graduation I was fortunate to return to Westchester Medical Center to work in Neuroradiology, Body Imaging, and Women’s Imaging departments, a rarity in academic medicine. Almost a decade later and I am living in a larger home in Reno working in a private practice community based outpatient radiology group which contracts with a rural hospital in Elko, Nevada. My wife and I now have four boys and gave up on the girl. We also have a male Bernese mountain Dog named Helmut and female Newfoundland named Lucy. Despite all its hardships and tremendous struggles, I have an absolutely amazing life, which is a gift I cherish. It’s down to my philosophy. I am a firm believer in teamwork. So much comes down to communication. When healthcare providers talk to each other one-on-one, the patient care is always improved, every time! We might not find an answer to your problem, but our collective knowledge sure can help improve your chances. At Yale the best conference I ever regularly attended was a head and neck tumor board. The head and neck surgeon (otolaryngologist = ENT) presented the patient’s clinical history, the radiologist showed the images, the oncologist discussed the tumor and chemotherapy options, and the patient came to the conference and we all did a physical exam looking into their mouth to directly visualize a tumor. It was incredible! Patients came from far and wide to see this highly trained, world-renowned, humble, Japanese, gentleman surgeon. It was also an epiphany. I found that when I see the patient, talk to them, listen to their story, examine them and discuss the patient with my colleagues, the patient felt better and I had a lot of fun. It’s weird but reminds me of seeing a comedy where it is always funnier in a packed theater with everyone laughing. Knowledge and compassion are both infectious and contagious. My greatest days are helping patients deal with some of their most difficult days, and I am good at it.

2 thoughts on “Chest X-ray: What makes a good image?

  1. Wow, thank you, thank you, thank you for this series, Dr. Swanger! CXRs (particularly portables) are about 80%-90% of what I do at the hospital. It’s like our bread & butter here, but image quality can vary widely due to a number of factors (i.e. high volume, pt acuity, varying body habituses). It is invaluable for me to gain insight into how you Rads diagnose pathologies, and helps me critique and improve my image quality, making me a better technologist in the long run. Keep writing!

    Like

    1. No, THANK YOU! You are providing me with the RIGHT motivation to continue. Knowing that what I am writing is helping improve your image quality, increasing the diagnostic capabilities for radiologist’s, which ultimately translates into better patient care is what it is all about!

      Like

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