First localizer image of Callie.
(Gregory Berns)
Robert and Sinyeob were smiling and giving the thumbs-up sign through the window.
Sure enough, there on the scanner console was a blurry but clearly recognizable image of Callie in profile. Her brain and spinal cord were unmistakable. Everyone gazed in amazement at what was surely the first MRI image of a dog in a natural position. Every other image like this had been obtained in anesthetized dogs who had been intubated and who had their necks hyperextended unnaturally. It was eerie seeing Callie’s brain transition into her spinal cord and how it ran down her neck just behind her trachea.
Next up were the functional scans. Robert opened a box on the screen to set the field of view. We oriented the FOV so that it was as if Callie’s head were a loaf of bread; the MRI would digitally slice her brain face-on, in what is called the coronal plane. Each slice would be 3.5 millimeters thick and, with twenty-five slices, that meant the depth of the box would be 87.5 millimeters—just under 3.5 inches. It didn’t leave much margin for error. If Callie placed her head in a different location, her brain would be out of the FOV, even if she held it perfectly still. I hoped the chin rest would do its job.
I looked at the clock. It was three o’clock. We had already burned up two hours just to get to this point, and we hadn’t even done anything with McKenzie yet. I made a mental note to switch to McKenzie at three thirty.
Callie’s energy level had noticeably decreased. She trotted up the stairs into the magnet, but now she wasn’t wagging her tail as much. This was actually a good thing. When she wagged her tail in the magnet, the fishtailing motion caused her head to move in rhythm with her tail.
Andrew took up his position at the rear of the magnet. He held a small box with four buttons. The button box was connected to a computer in the control room. Each time Andrew pressed a button, the computer would log the exact time after the beginning of the scan. One button represented the beginning of each trial, when Callie placed her head in the chin rest. Andrew would push a second button when I put up the hand signal for hot dogs, and he would push a third button when I gave the signal for peas. A fourth button would be pushed when I actually delivered the reward. By logging the time of each of these events, we would be able to match them up to the corresponding scan number.
Callie had settled in and looked at me expectantly. I gave her a hot dog and yelled, “Good girl!” I nodded to Andrew to indicate she was ready.
The scanner emitted a few clicks and then launched right into the jackhammer sounds of the functional scans. This was the sequence Callie had been practicing with for the last month, but it was much louder than the localizer. She lifted her head up from the chin rest and started to retreat, but then she paused. Half in and half out, she stared at me. I held up a piece of hot dog. Callie thought about this for a second, and then scooted forward to lick the treat out of my hand. Satisfied that nothing bad was going to happen, she settled into the chin rest.
Out of the corner of my eye, I could see Andrew hit the first button. He was holding up one finger—the sign for hot dogs.
In my head, I counted two Mississippis and put up the hot dog sign. Callie’s eyes dilated. I tried to count another six Mississippis before giving her the treat. It was just like practicing at home.
We kept at it. Not every repetition was a success, though. One time, I bumped the patient table as I reached in to give Callie her food. The slight jarring spooked her, and she backed out. Amazingly, she retreated only partway and came back when I held up the food.
After what seemed like an eternity, the scanner stopped.
Callie was waiting for me at the end of the patient table. I gave her a big hug and a handful of hot dog before escaping to the control room, where Robert was scrolling through a series of images on his screen. Most had snow. Occasionally something doglike would appear at the bottom of the screen, only to disappear a few images later.
Nothing.
“She wasn’t in the field of view,” Robert said.
My heart sank. Callie had performed so well, but her position during the localizer had been different. Without knowing it, we had programmed the scanner for the wrong location. Callie’s brain was nowhere to be seen.
We had come too far to give up, and Callie showed me that she could do this.
“Let’s switch to a dorsal orientation,” I said.
Staring at Callie’s localizer image, I realized what should have been obvious all along. The dog brain is longer front to back than it is from top to bottom. To better match the flattened shape of the brain, it made sense to take slices from top to bottom, which is called the dorsal orientation. Unless we took very thick slices or a lot of them, the FOV is a rectangular brick that is larger in the plane of the slices. By rotating the FOV to better match the flattened shape of Callie’s head, we would be much more likely to capture her brain regardless of where she put her head down.
Using the cursor, Robert rotated the FOV ninety degrees. It was now aligned parallel to Callie’s brain.
Between the scan and the fiddling at the console, we had burned up another thirty minutes. I broke my internal vow to switch to McKenzie. “Let’s try this one more time. Then we’ll give McKenzie a shot.” Callie was lying on her side next to me. She was tired. I reached down to stroke her. Her tail thwacked the floor, indicating that she still had some juice left.
By now the team had settled into a routine. Rebeccah secured the earmuffs and Andrew took up his position at the rear of the scanner. Callie, now either bored or depleted of energy, sauntered into the magnet. She didn’t so much as flinch when the sequence started.
Peas and hot dogs.
This time we blazed through the repetitions. After about ten of each type, I turned to Andrew.
“She’s doing really well,” I said. “Let’s see if the new orientation worked.” He nodded and gave the “cut” signal to Robert. Callie and I both ran to the control room. Everyone was already staring at the console.
Brains. We had brains.
As Robert scrolled through the sequence of images, you could plainly see cross sections through Callie’s brain. We had captured sixty scans, and more than half of them contained an image of a brain.
McKenzie wearing her wrapped-up earmuffs.
(Bryan Meltz)
I was elated. We had surpassed my hope of getting ten good images.
Everyone cheered and high-fived.
Lisa bent down to embrace Callie. “You did it!”
Callie licked her face.
Sinyeob just shook his head in disbelief, while Andrew summed it up: “Wow.”
While everyone crowded around the computer, I sank into a chair, utterly exhausted. I hadn’t realized how intense the last several hours had been. But now the adrenaline that had kept me going drained away, and I crashed. Same for Callie. She had already made her way to Melissa’s pup tent for some quiet time and was sacked out.
But we weren’t done. Now it was McKenzie’s turn.
Callie had forged the way. Based on what we had learned about the noise and the earmuffs, we wouldn’t have to waste any time with McKenzie.
Rebeccah worked her magic with the earmuffs. While Callie wore the small size, McKenzie had to wear mediums. Fully wrapped, McKenzie looked like she was wearing a turban.
Because every dog is a different size and shape, the scanner would again need to go through the shimming and localizer sequence for McKenzie. Melissa and Mark got her settled in the scanner and gave a thumbs-up to start the scan.