K.E.M. Radiology

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Department of Radiology 

  Seth G.S. Medical College and K.E.M. Hospital, Mumbai , India

Radiography of an ovum - Armchair research

Since many centuries, man has been fascinated by the supernatural powers. Initially, things which weren’t comprehensible to the simple human mind were considered divine, or more often evil. But in human history there have been few remarkable discoveries that have opened new paradigms and expanded haorizons of humanity. One such awakening happened when man for the first time could see through objects, the discovery of roentgen rays! It is no surprise that Prof Roentgen’s wife exclaimed – “I have seen death!” after looking at the radiograph of her own hand, a picture sans flesh. 

Expectedly, X-rays evoked great interest in the general public and X-ray booths were a common site in cities where one could get themselves photographed using roentgen rays. 

Taking inspiration from this history, we decided to study the structure of an egg using roentgen rays. Both boiled and unboiled eggs were studied to delineate the changes in radiographic appearance due to boiling.

The comparative radiographic anatomy – simplified for a radiologist

1. Outermost covering of an egg is the hard shell, which an enthusiastic cook likes to break effortlessly and a novice struggles. It is made up of calcium carbonate crystals. It acts like a semipermeable membrane, such that air and moisture can pass through its thousands of tiny pores. On a radiograph it appears as a thin radiopaque layer encircling the egg. The outline of the egg is well demarcated when it is having an intact shell. On radiographs of a boiled egg with its shell removed the margins are less distinct. This reminds us of the radiographic principle- The more the difference in radiodensity of two tissues adjacent to each other, better is the definition of its margins. Objects of similar density abutting each other, lead to loss of the interface- silhouette. 

2. Just like the brain, the egg contains two layers of membranes. One closely adherent to the egg shell and one in close contact with the contents of the egg. It can be compared to the meninges of brain, especially the two layers of dura.

These two layers can’t be seen radiographically, albeit they are clearly visible to a keen naked eye. Between these two membranes lies a pocket of air- called the air cell.

3. The air cell is visible as a biconvex radiolucency near the broad end of an unboiled egg.  It stays in that region despite changing the position of the egg- horizontal or upside down, indicating that it is bound between the layers and is “extraaxial”. The term extraaxial here means that it is outside the inner membrane which contains the egg white and yolk, bit inside the outer membrane adherent to the outer shell.

4. In case of a boiled egg, such lucency is not seen. Indicating the process of heating might have lead to escape of air through the micropores of shell, after it becomes hot. A boiled egg has an area  of coagulated proteins – egg white around a relatively radiolucent center- the yolk. This could be due to relatively higher fat content of the yolk.

5. The next radiograph shows a punctured egg with a part of the egg white drained out. It shows an air fluid level as the atmospheric air replaces the “intraoval” air and the effect of atmospheric pressure creates a horizontal level. This is akin to the differences in the shape of pleural effusion and hydro-pneumothorax which show different shapes due to the influence of intrapleural and atmospheric pressures respectively.

These series of radiographs might not mean much to a busy radiologist or the treating physician in their day to day practice. But its implications go much beyond in planting a seed of zeal and persistence in the process of learning in our lives. And what better time to imbibe these ideas of inquisitiveness when you are young- water it, nurture it and grow it. As Clay Bedford said “You can teach a student a lesson for a day; but if you can teach him to learn by curiosity, he will continue the learning process as long as he lives.”


Acknowledgment : I am thankful to my colleague Dr. Harshitha Shetty and radiographers in my department for help with obtaining these images.

Fig1. Both eggs with their shells intact. The air cell is visible as a biconvex radiolucency near the broad end  of an unboiled egg.

Fig1. Both eggs with their shells intact. The air cell is visible as a biconvex radiolucency near the broad end  of an unboiled egg.

Fig 2. The air cell retains its shape on changing position.

Fig3. Air fluid level in a broken egg.

Fig. 4 : All in one.

Fig. 5 : from : https://www.mannapro.com/homestead/the-anatomy-of-an-egg

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