Human Brown Adipose Tissue Depots Automatically Segmented by Positron Emission Tomography/Computed Tomography and Registered Magnetic Resonance Images

The goal of this procedure is to use both thermo neutral and cold activated PET CT to automatically segment depots of brown adipose tissue and apply to Coregistered MRI scans of the same subject. This is accomplished by first acquiring both thermo neutral and cold activated MRI and PET CT scans on the same subject. The second step is to spatially register all four scans of one subject.

Due to the difficulty of registering whole body images focus should be placed on accurate registration of the supraclavicular region. Next, the registered cold activated and thermo neutral PET CT scans for one subject are used to define the BAT regions for that specific subject. The final step is to apply the BAT regions of interest to the MRI scans that have been registered to the PET CT scans of the same subject.

Ultimately, this procedure provides quantitative MRI metrics in brown adipose tissue using automatically generated BAT regions of interest instead of manually defined regions. The main advantage of this technique over existing methods used in studies of human brown adipose tissue is that this technique acquires and combines MRI and PET CT scans under both thermo neutral and cold activated conditions on the same subject. Using the MRI metrics yielded by this approach, it may be possible to answer key questions such as the prevalence and spatial distribution of human brown adipose tissue using only MRI To prepare the temperature controlled room.

For MRI use a small room for cooler temperatures, maintain the room temperature with a portable air conditioning unit and a rotating floor fan to keep the cool air circulating. When warmer temperatures are desired, use a programmable portable heater, which oscillates to circulate the warm air around the room. Prior to entering the temperature controlled room, have the subject change into standard medical shorts and a standard medical shirt.

Remove socks and shoes. Measure the subject's height, weight, and waist circumference after changing into the standard clothing. Also, measure the subject's body temperature using a sublingual thermometer.

Then direct the subject to enter the temperature controlled room. Ask the subject to sit quietly and not perform any activity that could change body temperature such as exercising, typing, or falling asleep. After sitting in the room for one hour, measure the body temperature again using a sublingual thermometer.

After the second hour of sitting in the temperature controlled room, measure the body temperature a third time using a sublingual thermometer. If performing the cold MRI place the cold vest on the subject prior to the subject, leaving the temperature controlled room. After two hours in the temperature controlled room, transport the subject in a wheelchair to the MRI scanner.

Acquire MRI scans using a three Tesla MRI scanner, equipped with two channel parallel transmit capability. An extra large 16 channel torso Receive coil and a modified tabletop hang. The anterior portion of the torso.

Receive coil from the top of the scanner bore. In a fabric sling, allow the sling to hang low enough to slide against the subject's body. In order to maximize the signal to noise ratio.

Place the posterior portion of the torso received coil in a rolling coil wagon, sandwiched between two layers of the tabletop as the table moves through the scanner bore. Hold the coil wagon at ISO center by straps attached to the scanner covers at the front and back of the scanner war so that the posterior coil element remains stationary. Position the subject on the bed to enter the scanner feet.

First in a supine position, remove the vest prior to the subject lying down. Then have the subject place both arms inside a bag similar to a pillowcase and lower the arms to either side of the body. To minimize differences between subject positioning in MRI and PET CT scans, it is important to allow the subject to lie down naturally on the scanner bed, to use the same amount of cushioning under the head during each scan, and to use the pillowcase bag to support the arms.

Any support used for the subject during one scan, for example, a pillow under the knees or lower back should always be used in the same way for that subject. Once the subject is in place, acquire fat water MRI using a multi-stack multis slice, multi-facet field echo acquisition with seven stacks of 20 axial slices. Covering from the crown of the head to upper thigh slices are contiguous with a zero millimeter gap between slices.

Have a pet CT technologist place an IV port in the subject's hand or arm vein. This IV port allows the radiology technician to inject the radio tracer later when the subject is sitting in the temperature controlled room. After setting up the temperature controlled room as before, direct the subject to enter.

Ask the subject to sit quietly and not perform any activity that could change body temperature. After sitting in the room for one hour, measure the body temperature again using a sublingual thermometer. After the first hour in the temperature controlled room, have the radiology technician administer the injection of fluoro deoxy glucose through the IV port.

Inject 0.14 milli per kilogram of F 18 FDG. Calculate the exact dosage based on the subject's specific weight. After the second hour of sitting in the temperature controlled room, measure the body temperature again using a sublingual thermometer.

After two hours in the temperature controlled room, transport the subject in a wheelchair to the PET CT scanner. Acquire PET CT scans on a discovery C and treat lead PET CT scanner. Position the subject on the bed to enter the scanner headfirst in a supine position.

Once lying down, have the subject place both arms inside a bag similar to a pillowcase and lower the arms to either side of the body. This helps ensure the shoulders are positioned in a similar manner during both MRI and PET CT exams, which makes image co-registration easier. The PET CT imaging field of view covers from the crown of the head to mid-thigh in seven to nine bed positions depending on subject height.

Acquire the PET CT images using the recommended pet CT parameters listed in the text protocol. Proceed with processing and analysis as detailed in the text protocol. Acquiring both MRI and PET CT scans on the same subject and performing co-registration on all scans enables reliable measurement of quantitative MRI.

Metrics of BAT shown here are unprocessed, warm and cold PET CT and MRI scans from one subject. By acquiring both warm and cold PET CT data, it is possible to clearly distinguish the cold activated bat depots by the increased 18 FFDG uptake. Shown here is the clavicular level axial slice post reregistration.

The increased 18 FFDG uptake seen in the cold PET scan occurs in the supraclavicular region of adipose tissue. The MRI fat signal fraction in this region falls in the 50 to 80%range, similar to that of previous research. After coregistering all four scans, it is possible to create a subject specific bat mask using criteria derived from the PET CT images.

This mask can then be applied to the four coregistered scans to acquire image metrics in the bat depots, as is shown here for one subject. Applying the BAT mask to the registered scans results in numerical values from the acquired data presented as a mean N 95%confidence interval. While attempting this procedure, it's important to remember to always position the subject in the same manner for each of the four scans, as this greatly improves the co-registration of the images Following this procedure.

With the addition of other MRI methods, such as diffusion weighted imaging, perfusion and thermometry, it should be possible to study the spatial distribution and prevalence of brown adipose tissue in humans.