There are several methods for external registration of physiological and pathological processes. Some of the capabilities and drawbacks of telemetryTelemetry Measurement at a distance (e.g., body temperature, heart rate, blood pressure, etc.), generally by means of wireless technology. A transmitter is attached to or implanted into the animal, which can then move about freely. are discussed. In addition, different registration technologies are reviewed, including transponderTransponder A radio receiver that responds to a specific signal by emitting its own signal. use and biophotonic imagingBiophotonic imaging A technique which makes use of a luciferase gene, incorporated into for instance, microorganisms or cancerous cells. After these modified organisms or cells have been introduced into an experimental animal, their presence can be quantitatively detected by the light which the organisms/cells emit, and which can be measured non-invasively..

Telemetry

Telemetry is a way of making physiological and behavioral measures on an animal that is free to move in its cage. Telemetry involves implanting a transmitter into the abdominal cavity of the animal. This allows prolonged registration of physiological parameters such as body temperature, heart rate, and blood pressure, outside the body, without further handlingHandling Manipulating the animal, picking it up, holding it, and restraining it. of the animal. Telemetry is widely used in pharmacological research. Data gathered by means of telemetry can also be used for assessing the health status of an animal and for determining a humane endpointHumane endpoint The moment in the experiment at which pain and/or distress experienced by the investigational animal is ended or alleviated by either killing the animal humanely or by discontinuing the procedure.. Finally, it can help reduce the number of animal procedures, since an animal can be monitored over time and it can serve as its own control (see picture).

On the other hand, telemetry has drawbacks which have to be considered before one decides to set up experiments utilizing this technology. Technical possibilities combined with a desire for efficient animal use, often actually lead to an increase in the number of measurements per animal (e.g., by reusing animals), which may increase discomfortDiscomfort A state of pain and distress in laboratory animals.. The presence of the transmitter in the abdominal cavity and the (frequent) necessity of individual housing, can exert a negative influence on the animal’s welfareWelfare A complex and dynamic internal state that includes: successful biologic functioning, positive experiences, and absence of negative conditions. The animal adapts effectively to internal needs and external stimuli and maintains a good mental state. and on its behavior and physiological functions.

Transponder

Body temperature can also be recorded by means of a transponder, which can be implanted subcutaneously. This method relies on external induction technology, which allows the use of tiny injectable transmitters. Body temperature is read by holding a scanner close to the animal’s body.

Biophotonic imaging

This technology makes it possible to track microorganisms or cancerCancer A general term for a collection of diseases characterized by abnormal, uncontrolled growth of tissue cells or blood cells. Cancer may develop in specific tissues or cells, or it may spread from the original tumor to other parts of the body, where it can cause growth of secondary tumors (metastases). cells inside the body (see picture). It makes use of a luciferase gene, incorporated into microorganisms or cancer cells respectively. The luciferase gene causes photons to be emitted that can be detected outside the animal with special cameras. The resulting photographs reveal the spread of the microorganisms or the growth or metastasisMetastasis Seeding of cancer cells to locations in the body distant from the site of the original tumor. The capacity to give rise to metastases is a specific sign of malignancy. The prognosis will usually be poor. of the tumorTumor Neoplasm, new growth. Is predicated upon autonomous growth of cells or tissues into benign or malignant tumors. cells (see picture). Prior to biophotonic imaging the animal must be anesthetised.

In addition, we currently have many different options for non-invasive animal monitoring. These technologies include functional magnetic resonance imaging (fMRI), by which functional information , e.g. images of the beating heart or brain activity, can be gathered from a living laboratory animal.
Positron Emission Tomography (PET), PET scanningScanning 1) Probing using some form of imaging; e.g., encephalography (recording the activity and structure of the brain). 2) As a behavioral concept: alert posture in a fight/flight situation. Slow sideways swaying of the head and anterior part of the body. is based on the biodistribution of imaging substances. These are radio nucleotides that release positively charged particles or positrons. PET scans are used mostly to visualize biological processes in organs and tissues, and to follow them over time. Reviews on non-invasive or minimally invasive bioimaging technologies can be found in the ILAR Journal issue “Noninvasive Bioimaging of Laboratory Animals” (Volume 49, Issue 1, 2008).