I had the opportunity to see some interesting cases in last week´s clinic hours. Dr. VanKoevering, whom I shadow, specializes in tumors of the skull base and sinonasal cavity, mostly sees adult patients. I would say the majority of his patients have or have had cancer, and many of them are heavy smokers, which is often a causal factor for this type of disease. 

This time, I was particularly interested in understanding computerized tomographies of the skull base. Previously, I had studied CT scans, but from a medical perspective. Now, I have been reading more about the science behind this essential imagining technique, which consists of sending x-rays across multiple planes of an anatomic structure, such as the skull, producing a three-dimensional image. X-rays, like gamma rays, alfa and beta particles, are a kind of ionizing radiation, able to knock out electrons from atomic nuclei with its high energy (the wavelength of most X-rays lies in the range of 0.01 nm up to 10 nm. This corresponds to an energy range of 100 keV down to 100 eV). Therefore, the CT scan is like a set of multiple planar radiographies taken of a body part, and as such creates a considerably higher amount of ionizing radiation. In excess, this radiation can alter atoms and produce changes in cellular DNA. Therefore, its use must be minimized as much as possible. 

The release of electrons from the atoms x-rays collide with rely on the photoelectric effect, described by Einstein (who won the Nobel Prize for discovering that photon energy is quantized). X-rays occur when electrons are liberated from a heated filament, or cathode, thanks to thermiomic emission. Then, with the help of a high voltage, the liberated electrons move towards a metal target, which acts as the anode. When short-wave electromagnetic radiation reaches its binding energy level and collides with surfaces, it produces the emission of electrons. When these high-energy electrons collide with the atoms of the metal target (anode), X-rays are produced. 

But this science doesn’t yet explain how images are actually imprinted on an x-ray film. A traditional x-ray detector consists of a film based on a silver iodide emulsion. The exposure and development of this film isn’t that different from how photographic films are developed. In the case of digital x-ray detector arrays (in use since the early 2000’s), a scintillator layer converts x-rays to visible light, which is then detected by a pixel array. 

The types of CT scans include sequential, spiral, electron beam tomography, dual energy CT, CT perfusion imaging, and the PET CT. CT scanning of the head is usually used for detection of stroke, tumors, cysts, trauma and hemorrhage. In these images of the head, it is possible to identify dark (hypodense) structures, which indicate the presence of edema and infarction. Often, cancerous tumors are accompanied by peripheral edema and tissular death (infaction). Bright (hyperdense) images could mean either calcifications or the presence of a hemorrhage. 

I think it is fascinating to have the opportunity to understand CT scans both as a physician and as an engineer. Having both a medical and technical understanding of an imaging study such as the CT scan, can give more ideas to the scientist, to improve existing technologies and develop new ones.     

Since mid-January this year, I’ve had the pleasure of shadowing Dr. VanKoevering, an otolaryngologist at The James Cancer Hospital, one of the best medical centers of its kind in the United States, as ranked by U.S. News & World Report. I’m thrilled by this new experience, for which I think writing about is very much worth it.  

As a medical student, and later, as an international medical graduate, I’ve shadowed multiple surgeons in the past, in large hospitals in Vienna, Austria, Aarhus, Denmark, Samara, Russia, and, of course, the US. However, this rotation is different due to the fact that I am able to see patients in surgeries and medical rounds from the perspective of a biomedical engineer, something I’ve never experienced on past rotations. 

As all engineers do, the biomedical engineer applies natural science and math to solve problems in our society and improve already-existing technologies, but, unlike the others, focuses on biological sciences and medicine in a unique manner that addresses human health and disease. As an IMG and future biomedical engineer and researcher, I want to acquire a round understanding of the human body, in order to provide better treatments and develop more efficient medical devices. 

During this ENT surgery rotation, I’ve seen several types of craniofacial cancer, including sinonasal undifferentiated carcinoma, low grade sinonasal adenocarcinoma, sinonasal malignant mucosal melanoma, nasopharyngeal carcinoma. Often, these cancers are highly aggressive and have very poor prognosis. Also, many of these patients (a large portion of them heavy smokers) require partial removal of their larynx, including their vocal chords, which leaves them unable to speak. 

One of the medical procedures I’ve seen thus far in this rotation is the tracheoesophageal puncture, TEP, which allows patients to speak again by connecting the esophagus with the trachea, causing vibrations in the esophagus that mimic the function of the vocal cords as air passes through them. 

Another device I’ve seen during my rotation, which has called my attention, is the flexible nasopharyngoscope, which uses fiberoptic or digital chip-on-the-tip technology. Its scope diameter varies from 1.9 mm (pediatric model) to 6 mm (adult model). It is possible to attach a high-resolution camera to the scope’s viewing port, allowing the health provider to visualize the area of interest as seen from the tip lens of the device. The tip which carries the lens is flexible, providing a field of view of up to 90 degrees by maneuvering the angulation control knobs located in the control body of the device. It is primarily a diagnostic device (e.g. evaluation of sleep apnea, venopharyngeal insufficiency, fiber endoscopic evaluation of swallowing, FEES, done by a speech therapist) with assistive therapeutic applications (e.g. visual tool for excision and debridement of nasopharyngeal cancerous tumors and their biopsy, removal of easily accessible foreign bodies, tracheostomies, and vocal cord injections for vocal cord palsies). It is generally a safe device which doesn’t generate complications; however, it is not totally exempt from them. These include mucosal tearing, bleeding, sneezing, laryngospasm (in less than 1% of procedures), gagging, and damage to anatomical structures, which is extremely rare with the use of flexible scopes, as opposed to rigid ones. The two main contraindications for its use include acute epiglottitis and croup. 

This is the first of four entries I intend to make on this subject. In doing so, I look forward to encouraging people to learn more about this exciting topic.