Pareidolia

I love words. Radiology has reminded me of one of my favorite words, pareidolia. A type of apophenia, it refers to that common habit of seeing, hearing, or perceiving something random and interpreting it as significant. How many times have you looked at a weird cloud or listened to a song backwards and found meaning where it was not intended? Even the image shown above, taken by a NASA Viking mission to Mars in 1976 jumps out as a face, but it turns out to be a trick of the sunlight on a random rock formation.

Human psychology is wired to identify patterns, faces, sequences, and shapes even in random data. We are biased to find things, and it's more pronounced when we're looking for something in particular. We see what we expect to see. Thus, the best clinical studies are blinded. If you are conducting a study to see whether a drug does better than a placebo, if you know which patients are taking the drug, you are more likely to get a positive result. Subjects and interpreters should be blinded to what arm of the study patients are assigned to. This takes away bias.

We must keep this in mind in radiology. I am much more likely to call a chest X-ray normal if it's in a reading room rather than a lecture because I know and expect that images shown in lecture will be abnormal. I also think radiologists should know the clinical information regarding the studies they interpret. Sometimes clinicians will hold back on giving the history because they don't want to bias the radiologist. This is silly. Giving a radiologist more information only changes their pre-test probability. If they expect something to be wrong, they are more likely to identify it, especially if it is subtle. The good radiologist will then hit all the other boxes in the checklist to make sure nothing else is wrong. We see what we want to see. If radiologists know what the clinician expects, he changes his pre-test probability and is more likely to make the right diagnosis.

Image is in the public domain, from Wikipedia.

Rorschach

The Rorschach inkblot test (example shown above) is a psychological test where a subject is asked to interpret an inkblot. His response reveals something about his personality, emotional state, and thought process. What do you see in the image? What aspects of the image do you focus on? How easy is it to create a shape or figure or description? And what could this possibly reveal to an outside observer about your psychological state?

In some ways, and perhaps unfairly so, radiology to a beginner feels like an inkblot test. We look at complex images with an overwhelming amount of information and it's hard to know where to begin. What's normal? What's abnormal? Often, findings are subtle yet significant. CTs and MRIs have hundreds of slices to look through, and watching experienced radiologists scroll through this wealth of data is both intimidating and impressive.

For example, the CT angiogram above shows a life-threatening pulmonary embolus. But it can also be "windowed" (adjusting the contrast/display) to examine the bones, soft tissues, vessels, heart, and lungs. How do you pick up on what stands out? How do you know you aren't just imaging a finding in a Rorschach inkblot test?

The residents always seem to return to a systematic method to ensure they look at everything. It's really easy for me to identify an outrageously abnormal finding and forget to examine everything else in the image. I think the other element is simply practice. After looking at enough normal and abnormal pictures, the differences start to become instinct. Radiology in some ways reminds me of that game in childhood of examining two images and finding the differences.

Image of Rorschach ink blot is in the public domain, from Wikipedia. Image of the CT angiogram is also in the public domain, from Wikipedia.

Poem: Rorschach

Rorschach

Somehow we've lost the pen's scritch-scratch,
fountain trailing ink like dewdrops, blossoming texture on paper,
lost it in favor of tap dancing fingers, a piano without sound.
And in the same way, light box engineers have gone
out of service, and no one knows the satisfaction of the flick
of film, the snap of plastic, that illume of X-ray, no--
we instead camp indoors in rooms whose bulbs never go out,
in the hum of computers and dictation, the coalescence of shadow
in some challenge of imagination-- and I imagine a trickle
of breeze in this basement, a peek of sunshine through the blinds
because technology should not make obsolete that dream of lying
in a field tall as grain, making animals out of clouds in the sky.

Image of the Rorschach ink blot is in the public domain, from Wikipedia.

Radiologist as Consultant

The radiologist acts as a true consultant; physicians rather than patients are the direct clients of radiologists. Whereas nearly all other doctors see and treat patients directly, radiologists and pathologists are once removed; they take the patient's data but interpret it for other doctors. On this rotation, I've realized that this role means radiologists know an impressive amount about general medicine and surgery. Simply from images, they can generate a rich differential diagnosis of what might be going on, offer opinions on what treatment modalities may be most appropriate, and make suggestions on further studies to better define the problem. They have knowledge about every part of the body in a way that few other specialties do, from bone to brain to bowel to bladder. I've really been struck by the amount of stuff that a radiologist needs to know.

Image of a magnetic resonance imaging angiography shown under GNU Free Documentation License, from Wikipedia.

Interventional Radiology

We got a lecture from Ernest Ring, one of the true pioneers of interventional radiology. Interventional radiology is a subspecialty which involves minimally invasive procedures done under image guidance such as ultrasound, CT, or fluoroscopy. Common procedures include injecting dye into a vessel (angiogram), putting a balloon and stent into a vessel, draining an infection, biopsying a lesion, and connecting different blood vessels (TIPS). In any case, Ernest Ring is an emertius professor here who did the first embolization to stop bleeding in a pelvic fracture and the first embolization to stop a diverticular bleed. He practically defined the field, conducting the original studies on applications of needles and catheters and coming up with new ways to treat recalcitrant diseases. He watched the field blossom and change over the last four decades. I really have a great respect for history, and it was simply inspiring to hear from someone who strode into the unknown and created around him such an exciting, brilliant, and innovative field.

Image of cerebral angiography is in the public domain, taken from Wikipedia. This beautiful image of the brain's blood vessels shows an injection in the left vertebral artery and flow in the contralateral vertebral artery, the basilar artery, and the posterior circulation of the circle of Willis.

Radiology

This month I'm in radiology at San Francisco General Hospital. The radiology elective is a mix between didactics and practical reading of radiographs. We have regular daily medical student lectures which have been outstanding, focusing on relevant intern-year problems such as the acute abdomen, chest X-rays, thoracic trauma, lines and tubes, etc. Radiology has become so much more relevant after my clinical rotations. When we were first exposed in anatomy, radiology baffled me; even the basics such as right and left confused me and I simply did not have the spatial resolution capacity to reconstruct CTs in my head. But after my neurology, surgery, and medicine rotations, I've gotten much more comfortable with common radiologic appearances and studies. So now that I can make clinical correlates of the images, these lectures have much more relevance.

This learning is paired with reading room experiences where we shadow residents as they read studies. Real images, unlike teaching files, are often confusing, vague, complicated, or indeterminate. Often, clinical teams will come down to ask for help; it's always useful for me to hear the clinical presentation of the patient. So far, I've found myself reviewing a lot of basic anatomy that I've forgotten such as the blood supply of the gut. I hope this will prepare me to read my own studies as an intern next year.

Image is in the public domain, taken from Wikipedia.

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This highest-grossing epic science fiction Pocahontas story features blue humanoids and extraordinary visual effects. In talking to one of my friends, a pharmacy resident, we realized the blue skin made us think of an unfortunate side effect of the antiarrhythmic drug amiodarone which can cause bluish-slate gray discoloration of the skin in 1-3% of patients on chronic therapy. Alas, the things medical knowledge does to us.

Image shown under Fair Use, taken from Wikipedia.