Devices for imaging body cavities or passages in vivo are known in the art and include endoscopes and autonomous encapsulated cameras. Endoscopes are flexible or rigid tubes that pass into the body through an orifice or surgical opening, typically into the esophagus via the mouth or into the colon via the rectum. An image is formed at the distal end using a lens and transmitted to the proximal end, outside the body, either by a lens-relay system or by a coherent fiber-optic bundle. A conceptually similar instrument might record an image electronically at the distal end, for example using a CCD or CMOS array, and transfer the image data as an electrical signal to the proximal end through a cable. Endoscopes allow a physician control over the field of view and are well-accepted diagnostic tools.
Capsule endoscope is an alternative in vivo endoscope developed in recent years. For capsule endoscope, a camera is housed in a swallowable capsule, along with a radio transmitter for transmitting data, primarily comprising images recorded by the digital camera, to a base-station receiver or transceiver and data recorder outside the body. The capsule may also include a radio receiver for receiving instructions or other data from a base-station transmitter. Instead of radio-frequency transmission, lower-frequency electromagnetic signals may be used. Power may be supplied inductively from an external inductor to an internal inductor within the capsule or from a battery within the capsule.
An autonomous capsule camera system with on-board data storage was disclosed in the U.S. Pat. No. 7,983,458, entitled “In Vivo Autonomous Camera with On-Board Data Storage or Digital Wireless Transmission in Regulatory Approved Band,” granted on Jul. 19, 2011. The capsule camera with on-board storage archives the captured images in on-board non-volatile memory. The capsule camera is retrieved upon its exiting from the human body. The images stored in the non-volatile memory of the retrieved capsule camera are then accessed through an output port on in the capsule camera.
When the endoscope is used for imaging the human GI tract, one of the primary purposes is to identify any possible anomaly. If any anomaly is found, it is further of interest to determine characteristics of the anomaly, such as the size of the anomaly. For example, the polyp size is an important clinical factor associated with surveillance interval decision making for the colonoscopy procedure. Usually, a large polyp size is associated with a higher probability of malignancy. Furthermore, for cancerous tumor, the size will affect the probability of lymphovascular invasion and metastasis, and also impact prognosis substantially. For example, in a technical paper by Warren et al., (“Comparison of One-, Two-, and Three-Dimensional Measurements of Childhood Brain Tumors”, Journal of National Cancer Institute, pp. 141-145, Vol. 93, No. 18, Sep. 19, 2001), it shows that the tumor lymphovascular metastasis is more closely related to tumor area or volume, i.e. multiple dimensional measurement than a dimensional measurement. Similar observation has also be noted by Kikuchi et al., (“A new staging system based on tumor volume in gastric cancer”, Anticancer Research, pp. 2933-2936, Vol. 21, No. 4B, July-August 2001).
However in the colonoscopy standard procedure, the polyp size is always measured by its longest dimension. For example, in a technical article by Chaptini et al, (“Variation in polyp size estimation among endoscopists and impact on surveillance intervals”, Gastrointestinal Endoscopy, pp. 652-659, Volume 80, No. 4: 2014), the polyp size is determined by measuring the size of the open forceps from the printed photograph or images displayed on a display device. Similar size measuring technique has also been mentioned by Plumb et al., (“Terminal digit preference biases polyp size measurements at endoscopy, computed tomographic colonography, and histopathology”, Endoscopy, pp. 899-908, Vol. 48, October 2016).
It is desirable to develop techniques that can easily measure or estimate the physical area or physical volume of an object of interest.