The Museum's spectacled porpoise specimen undergoes an MRI at the Royal National Orthopaedic Hospital in Stanmore. Image: Jan Letocha/ Royal National Orthopaedic Hospital

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Taking a spectacled porpoise to hospital

The Museum's spectacled porpoise specimen recently made a rather unusual trip, undergoing MRI, CT and X-ray scans at the Royal National Orthopaedic Hospital in Stanmore. 

A trip to hospital may seem a little late for the Museum's spectacled porpoise (Phocoena dioptrica).

But mammal curators Richard Sabin and Roberto Portela Miguez were on a data-collecting mission, intending to find out as much as possible about a species that is practically unknown to science. 

A unique opportunity

The Museum's spectacled porpoise specimen has spent several months in the freezer since its scientific debut in October 2017. But the cetacean was fully defrosted for the first time since its arrival in the UK from the Falkland Islands. It was then packed in a van in the very early hours, ready for a road trip to Stanmore in northwest London.

The Royal National Orthopaedic Hospital generously offered use of their imaging centre to perform MRI, CT and X-ray scans on the specimen. These scans provide a record of the porpoise before more intrusive research takes place.

Museum scientists were kindly offered the opportunity to scan the spectacled porpoise specimen at the Royal National Orthopaedic Hospital. (L-R: Hospital imaging manager Andrew Turner, Museum mammal experts Richard Sabin and Roberto Portela Miguez) © Jan Letocha / Royal National Orthopaedic Hospital

Richard Sabin, Principal Curator of Mammals, says, 'We're trying to grab as much data as we can non-invasively before we start to do the dissection.

'This specimen is probably going to yield so much new scientific data, which is what makes it so exciting, but means that we have to go slowly and methodically.'

Why is this porpoise important?

Spectacled porpoises are seldom seen in the wild and very little is known of the strikingly counter-shaded animals. The International Union for the Conservation of Nature currently lists them as data-deficient. 

The porpoise was an unusual sight as it was manoeuvred through the hospital's corridors

An opportunity to find out more about this elusive species was not one to be missed. Every effort is being made to find out as much as possible about spectacled porpoises from the Museum specimen.

Richard says, 'They could be quite abundant in the wild, but they live in the circumpolar region around the Antarctic and they're very hard to observe, making assessments of their abundance extremely difficult. When they die out at sea, their remains tend to be scavenged and sink instead of washing up on beaches where they can be collected for examination.

'What we're hoping to achieve with our studies is to provide data that we can contribute to the current, very limited scientific knowledgebase for the species. Hopefully, these data will be of use to conservation groups and governments in the southern hemisphere, helping with the protection of the species. '

A full-body MRI

First for the porpoise was a full-body MRI, giving an outside-in view of the animal's anatomy - although were it a male specimen, squeezing the cetacean into the machine would likely have been a challenge.

Richard explains, 'The males have a disproportionally large dorsal fin compared to their overall body size. There is little sexual dimorphism between the male and the female other than the dorsal fin.'

Three hospital staff prepare the porpoise and MRI machine for scanning

The porpoise specimen is prepared for the move from MRI to CT © Jan Letocha / Royal National Orthopaedic Hospital

The MRI provided an in-depth look at the porpoise's structure, including the boneless tail fluke's complex system of blood vessels, used in life to help regulate body temperature.

Porpoises swim and feed almost constantly. As they do, heat builds up in their bodies - a testament to the effectiveness of their insulating blubber. The water that flows over their dorsal fin and tail fluke cools their blood, which then lowers their temperature as it circulates in their body.

CT and X-ray

At a weight of around 70 kilogrammes, lifting the dead weight of the porpoise to move her from one scanner to another was not the easiest of tasks. Otherwise she was a model patient.

The porpoise's second scan of the day was a CT, which provides a cross-sectioned view of the body

But the team pulled through and the cetacean began her second scan of the day - a CT that gave a cross-section look at the animal's body. Despite still having plenty of room width-ways owing to the female's smaller dorsal fin, at 192 centimetres long the porpoise was almost the maximum length for this machine.

Following CT, she was taken on a short trip down the corridor to the X-ray department, where a series of overlapping images were captured.

Antony Turner, imaging manager at the Royal National Orthopaedic Hospital, explained, 'With the X-ray, we'll be able to stitch the images together, so you have an image of the whole spine.'

The porpoise was transferred to X-ray, which offered a clear image of the specimen's skeleton © Jan Letocha/ Royal National Orthopaedic Hospital

This scan showed skeletal details such as the typically mammalian bone structure of the pectoral flippers.

'You think it's going to be weird and wonderful, but it's not all that different from human anatomy,' says Antony.

Using MRI, CT and X-ray, the Museum scientists now have a detailed record of the animal's internal organs, soft tissues and bone structure.

The next step for the porpoise project is careful dissection. This is a destructive process, so digital imaging offers a lasting look back at the untampered-with body.

The data collected using the hospital scans and 3D structured light scans undertaken by the Museum's Imaging and Analysis Centre will help experts learn more about the little-known species.