Imaging Chain
The current standard surgical endoscopy imaging system consists of a light source, light‐transmitting cable, endoscope, camera head and camera control unit (CCU), and monitor (Figure 3.1). Each part is critical, and the resulting surgical image can only be as good as the weakest component in the chain. For example, if a surgeon has a full high‐definition (HD) camera, HOPKINS® telescope and light cable, but incorporates into the chain a standard‐resolution monitor, the resulting image quality will be limited by the quality of the screen. Even an old, damaged, or dirty light cable can degrade the image quality of an otherwise high‐end endoscopic imaging system [1–5]. An image troubleshooting guide is presented in Table 3.1.
Figure 3.1 The basic endoscopic imaging chain.
Source: © KARL STORZ SE & Co. KG, Germany.
The light generated by the light source is transmitted via optical fibers in the fiberoptic light cable and the telescope, to illuminate the anatomical space being observed. The image is transmitted through a series of lenses from the distal tip of the telescope to the eyepiece. Next, the chip in the video camera head senses the image and transmits it to the CCU, which processes the endoscopic image and transmits it to a monitor for viewing. This video projection enables the surgeon to maintain an ergonomic posture and to share this visual information with other participants. Furthermore, video imaging facilitates documentation of procedures, in several formats, valuable for medical records, teaching, client education, or consultation purposes [1–5]. Video imaging also enables remote access to view the procedure via live streaming through an integration platform [6].
Telescopes
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General Concepts
Rigid endoscopes are more convenient than flexible endoscopes for examining and performing procedures in body cavities [7–9]. Rigid scopes (i.e., telescopes) are also much simpler in design and less expensive than flexible endoscopes. Despite their lens system and fiber optics, they do not contain flexible materials, are easier to clean and maintain, and have a longer working lifespan [10]. Some models may include a working channel, integrated instrument, or a variable viewing angle, which allows a wider viewing field, in narrow deep anatomical regions. State‐of‐the‐art rigid telescopes are constructed with high‐quality optical glass rod lenses (HOPKINS® rod lenses), producing high‐quality images that are bright, magnified, wide angle, and of high resolution and contrast [1–5, 9]. No single model of rigid endoscope is universally suitable. The appropriately sized telescope should be selected based on the surgical procedure, size, and morphology of the patient and ultimately by the preference and experience of the surgeon. Although smaller scopes tend to be more versatile, they are also more prone to breakage, and their illumination capacity is limited when used in larger, more light‐absorptive cavities such as the abdomen or thorax of large breed dogs.
Table 3.1 Image troubleshooting guide.
| Problem | Possible cause | Resolution |
|---|---|---|
| Image is not clear | Fogged or dirty lens | Blot distal lens of telescope on live tissue or apply antifog agent to lens. |
| Fogged distal lens | Immerse telescope in warm sterile water or apply antifog agent to lens. | |
| Dirty eyepiece, camera, or adapter | Clean using cotton swab moistened with sterile water. | |
| Lens not adjusted to operator's eyesight | Rotate focus adjustment ring on camera head until image is clear. | |
| Internal fluid damage or cracked rod lens | Moisture within telescope will permanently cloud lens in distal end or eyepiece (repair by manufacturer). | |
| Misconnected camera on telescope eyepiece | Check for proper coupling and positioning of camera head to telescope by adjusting adapter. | |
| Image is too dark or too bright | Dirty light guide | Clean light‐guide connector and distal tip using gauze moistened with sterile water. |
| Improper light source or camera settings | Adjust brightness control knob, camera gain, or manual aperture setting. | |
| Old or improperly installed lamp | Properly install lamp; replace old lamp. | |
| Image is too blue | White balance improperly done or not done before telescope insertion into patient | Remove telescope from patient, clean distal lens, and perform white balance correctly. |
| Deficient illumination | Bulb lifespan ending | Check working hours on light source; replace bulb or activate alternate bulb inside light source. |
| Improperly connected light cable | Check for correct and full insertion of light‐transmitting cable. | |
| Worn light cable (broken fibers) | If >30% of light‐transmitting capacity is lost, then substitute cable. | |
| Light source on stand‐by mode | Check and press stand‐by button to activate light output. | |
| Light source is turned down | Increase light source output. | |
| Loss of pneumoperitoneum | Empty tank or closed valve from gas supply | Check gas remaining in tank; replace tank; open valves of general gas supply. |
| Open Luer‐lock on one or more trocars, leaking gas | Check and close all stopcocks except the one coming from the insufflator. | |
| Blockage of line going to patient | Be sure the tip of the Veress needle is not blocked by tissue and that the valve on the Veress needle or gas input cannula is open to incoming gas. | |
| Leaky cannula valve or sealing cap |
Assure proper assembly and functioning of each cannula and replace any worn sealing caps.
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