Abstract

There are currently 4 institutions in Florida involved with the rehabilitation of fibropapilloma green sea turtles. These facilities dedicate a great deal of time, effort and expense in the diagnosis, treatment and support of these individuals. Clinicians at these locations may be limited in the clinical options available for diagnostic imaging with each technique having advantages and disadvantages in terms of availability, patient costs, the need for anesthesia, and the knowledge for proper interpretation. Fibropapillomatosis typically involves growths of varying sizes on the skin and eyes, but may also involve the plastron, carapace, cloaca, and oral cavity. In some cases the tumors may be found internally with a prevalence for the lungs and kidneys, but may also include other organs such as the intestinal mucosa. Surgical excision of the external growths has utilized a number of techniques including standard scalpel removal, electrosurgery, and CO₂ laser. Prior to excision of tumors, a turtle undergoes a clinical evaluation that may include a CBC, chemistries, glucose, body weight, and when available radiography. Turtles with extensive tumor growth may also be further evaluated with MRI or CT to detect the presence of internal tumors. Rapid, exuberant regrowth of tumor tissue post surgery may indicate an increased likelihood of internal tumor involvement. These animals may undergo additional diagnostic scans to avoid ineffective follow up surgery.

Previous reports have investigated the use of MRI for the detection of normal anatomic structures and fibropapilloma tumors.¹ Imaging with MRI has also been used in sea turtles with the advantage of more detailed soft tissue evaluation than CT but the scanning time required can result in patient movement and incomplete scans.² Heavy sedation or anesthesia may be needed to complete the scan without movement requiring additional trained personnel to provide support for the anesthetized patient during transport, maintenance and recovery. While CT may not result in the soft tissue detail of MRI, it may be the modality available to clinicians in a geographic area or more likely to be offered because of the short scanning times involved. CT still provides excellent evaluation of the pulmonary tissue when looking for tumors or pulmonary compromise. It may also provide visualization of kidney tissue with larger tumors and its effectiveness is directly related to the clinicians knowledge of sea turtle anatomy and the information provided to the scanning personnel on what is desired.³ Many clinicians will not pursue these techniques because of their lack of comfort on what to expect and what to ask for when dealing with willing hospital technicians. The main disadvantage of CT for the patient is radiation exposure. Pulmonary tumors may vary in size from 0.1 to over 2 cm, so the CT protocol is to slice the patient transversely at 2mm thickness and 2mm increments to enhance detection of small tumors. Let the technician know you would like to have 3D reconstruction on the patient which will then support 3D volume rendering when you receive the data. The data set can be reconstructed at thinner intervals with post processing software.

Software for 3D volume rendering may be available from the personnel on-site, but again requires additional time for the technician and may decrease their desire to cooperate if too much is asked of their busy schedule. One example of software used for 3D rendering is OsiriX® which is available for Apple computers over the web.

Products Cited

OsiriX® http://www.osirix-viewer.com/

References

1.  Croft LA, Graham JP, Schaf SA, Jacobson ER 2004. Evaluation of magnetic resonance imaging for the detection of internal tumors in green turtles with cutaneous fibropapillomatosis. 2004. J Am Vet Med Assoc 225:1428-1435.

2.  Valente AL, Curnca R, Zamora MA, Parga ML, Lavin S, Alegra F, Marco I 2006. Sectional anatomic and magnetic resonance imaging features of coelomic structures of loggerhead sea turtles. Am J Vet Res 67:1347-1353.

3.  Wynecken J. The anatomy of sea turtles. NOAA Tech Mem NMFS-SEFFC- 4700, 2001.Pp 1-172.