# A Review of Medical Diagnostic Video Analysis Using Deep Learning Techniques
## 3 Taxonomy of Deep-Learning-Based Medical Video Analysis
### Types of Medical Videos  
Echocardiography, endoscopy, and ultrasound procedures generate three types of videos for diagnosing diseases, such as the presence of polyps in body organs and cardiomyopathy. There are also a few other types of videos, such as surgery and training videos, that are used for analysis and teaching purposes. As this study only deals with diagnostic videos, such videos are out of the scope of our research. Further details about these videos are given in the following subsections.  
_(1) Echocardiography:_ Echocardiography is a noninvasive and affordable imaging technology that helps doctors diagnose a heart's pumping strength, blood flow, the presence of a tumor, the functionality of valves, and the physiology of the heart [10]. Echocardiography uses sound waves by passing a probe called a transducer over the chest. Anatomical structures of the heart are displayed on the screen of the echocardiography machine as sequential frames over time. For echocardiography videos, temporal resolution plays a vital role. Temporal resolution is the time from starting one frame to the next; it shows the ultrasound system's ability to capture structures with rapid movements, such as the cardiac cycle. Low temporal resolution can cause data loss, resulting in an incorrect diagnosis. Another challenge medical practitioners face is poor video quality caused by improper probe handling and loss of signals. Figure 2a depicts the echocardiography frame showing a two-chamber view of the heart.  
_(2) Endoscopy:_ Endoscopy is a procedure in which an endoscope is passed inside the human body to examine an organ, such as the intestine, colon, or stomach. Endoscopy is the preferred test for various types of cancer, polyps, and lesion detection [11]. The technique for capturing endoscopy and echocardiography videos is different; hence, the results are dissimilar. The endoscopy videos are colorful and usually of good quality compared with the echocardiography videos. The presence of interference, such as food and gastric juices, in the digestive system makes it challenging for medical staff to analyze the regions of interest. The presence of uninformative frames in endoscopy videos makes the diagnosis process time-consuming and inefficient in terms of computational resources. Figure 2b depicts the endoscopy frame showing a polyp in the colon area of the body.  
Figure 1: Taxonomy of literature review.  
(3) Ultrasound: Ultrasound is extensively used for diagnosing the causes of pain, swelling, and infection in any part of the body (e.g., kidney, liver, and gallbladder) in a cost-effective manner [12]. Ultrasound imaging uses high-frequency sound waves and can be performed on various organs to examine them internally. Ultrasound can also guide surgeons during surgery regarding the area of interest. The relatively low-energy acoustic waves used during ultrasound imaging cannot penetrate thick layers of human tissue; for example, in obese people, the liver and other vital abdominal organs can lie four to five centimeters below the surface. Such cases present more physical strain on sonographers and radiologists. Figure 2c depicts the ultrasound frame showing a benign breast tumor.