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Concept of an upright wearable positron emission tomography imager in humans

View Article: PubMed Central - PubMed

ABSTRACT

Background: Positron Emission Tomography (PET) is traditionally used to image patients in restrictive positions, with few devices allowing for upright, brain‐dedicated imaging. Our team has explored the concept of wearable PET imagers which could provide functional brain imaging of freely moving subjects. To test feasibility and determine future considerations for development, we built a rudimentary proof‐of‐concept prototype (Helmet_PET) and conducted tests in phantoms and four human volunteers.

Methods: Twelve Silicon Photomultiplier‐based detectors were assembled in a ring with exterior weight support and an interior mechanism that could be adjustably fitted to the head. We conducted brain phantom tests as well as scanned four patients scheduled for diagnostic F18‐FDG PET/CT imaging. For human subjects the imager was angled such that field of view included basal ganglia and visual cortex to test for typical resting‐state pattern. Imaging in two subjects was performed ~4 hr after PET/CT imaging to simulate lower injected F18‐FDG dose by taking advantage of the natural radioactive decay of the tracer (F18 half‐life of 110 min), with an estimated imaging dosage of 25% of the standard.

Results: We found that imaging with a simple lightweight ring of detectors was feasible using a fraction of the standard radioligand dose. Activity levels in the human participants were quantitatively similar to standard PET in a set of anatomical ROIs. Typical resting‐state brain pattern activation was demonstrated even in a 1 min scan of active head rotation.

Conclusion: To our knowledge, this is the first demonstration of imaging a human subject with a novel wearable PET imager that moves with robust head movements. We discuss potential research and clinical applications that will drive the design of a fully functional device. Designs will need to consider trade‐offs between a low weight device with high mobility and a heavier device with greater sensitivity and larger field of view.

No MeSH data available.


Related in: MedlinePlus

Top Left: One min PET scan with the head turning back and forth about 45 degrees (Patient 1). Image resolution after software filtering is about 1 cm in this case, and slice thickness is 4 mm. Top Left Center: 10 min PET scan while the patient remains still (Patient 1). Spatial resolution and slice thickness are the same as in the top left panel. Top Right Center: Helmet_PET image of the brain once imported into the MIM software (Patient 1). For comparison purposes, this image is 2‐mm thick with greater than 4‐mm spatial resolution. Top Right: The same slice of the participant as in the top right center panel, but using the clinical Siemens mCT PET/CT system. Bottom: Six different ROIs which were compared between the Helmet_PET images and the clinical PET/CT images for two patients. The comparison is expressed as the mean voxel value of the specified ROI divided by the mean voxel value of the whole slice, resulting in the reported percentages. The first five ROIs were two dimensional from 2‐mm brain slices. The final ROI was an experimental test of a three‐dimensional ROI encompassing a portion of the medial cingulate cortex. It is worth noting that the three‐dimensional ROI was still normalized to a 2D longitudinal slice, just as in the two‐dimensional ROIs
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brb3530-fig-0004: Top Left: One min PET scan with the head turning back and forth about 45 degrees (Patient 1). Image resolution after software filtering is about 1 cm in this case, and slice thickness is 4 mm. Top Left Center: 10 min PET scan while the patient remains still (Patient 1). Spatial resolution and slice thickness are the same as in the top left panel. Top Right Center: Helmet_PET image of the brain once imported into the MIM software (Patient 1). For comparison purposes, this image is 2‐mm thick with greater than 4‐mm spatial resolution. Top Right: The same slice of the participant as in the top right center panel, but using the clinical Siemens mCT PET/CT system. Bottom: Six different ROIs which were compared between the Helmet_PET images and the clinical PET/CT images for two patients. The comparison is expressed as the mean voxel value of the specified ROI divided by the mean voxel value of the whole slice, resulting in the reported percentages. The first five ROIs were two dimensional from 2‐mm brain slices. The final ROI was an experimental test of a three‐dimensional ROI encompassing a portion of the medial cingulate cortex. It is worth noting that the three‐dimensional ROI was still normalized to a 2D longitudinal slice, just as in the two‐dimensional ROIs

Mentions: Two patients included in the analysis were imaged with Helmet_PET more than 4 hr after their clinical PET/CT scan. The obtained images were then compared with the PET/CT images of the patient's head. We estimate, based on the half‐life of F18‐FDG (~110 min) that the activity level after the 4 hr wait period in the second two patients was 25% the amount during their clinical scan. The selected results of this comparison are presented in Figure 4.


Concept of an upright wearable positron emission tomography imager in humans
Top Left: One min PET scan with the head turning back and forth about 45 degrees (Patient 1). Image resolution after software filtering is about 1 cm in this case, and slice thickness is 4 mm. Top Left Center: 10 min PET scan while the patient remains still (Patient 1). Spatial resolution and slice thickness are the same as in the top left panel. Top Right Center: Helmet_PET image of the brain once imported into the MIM software (Patient 1). For comparison purposes, this image is 2‐mm thick with greater than 4‐mm spatial resolution. Top Right: The same slice of the participant as in the top right center panel, but using the clinical Siemens mCT PET/CT system. Bottom: Six different ROIs which were compared between the Helmet_PET images and the clinical PET/CT images for two patients. The comparison is expressed as the mean voxel value of the specified ROI divided by the mean voxel value of the whole slice, resulting in the reported percentages. The first five ROIs were two dimensional from 2‐mm brain slices. The final ROI was an experimental test of a three‐dimensional ROI encompassing a portion of the medial cingulate cortex. It is worth noting that the three‐dimensional ROI was still normalized to a 2D longitudinal slice, just as in the two‐dimensional ROIs
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brb3530-fig-0004: Top Left: One min PET scan with the head turning back and forth about 45 degrees (Patient 1). Image resolution after software filtering is about 1 cm in this case, and slice thickness is 4 mm. Top Left Center: 10 min PET scan while the patient remains still (Patient 1). Spatial resolution and slice thickness are the same as in the top left panel. Top Right Center: Helmet_PET image of the brain once imported into the MIM software (Patient 1). For comparison purposes, this image is 2‐mm thick with greater than 4‐mm spatial resolution. Top Right: The same slice of the participant as in the top right center panel, but using the clinical Siemens mCT PET/CT system. Bottom: Six different ROIs which were compared between the Helmet_PET images and the clinical PET/CT images for two patients. The comparison is expressed as the mean voxel value of the specified ROI divided by the mean voxel value of the whole slice, resulting in the reported percentages. The first five ROIs were two dimensional from 2‐mm brain slices. The final ROI was an experimental test of a three‐dimensional ROI encompassing a portion of the medial cingulate cortex. It is worth noting that the three‐dimensional ROI was still normalized to a 2D longitudinal slice, just as in the two‐dimensional ROIs
Mentions: Two patients included in the analysis were imaged with Helmet_PET more than 4 hr after their clinical PET/CT scan. The obtained images were then compared with the PET/CT images of the patient's head. We estimate, based on the half‐life of F18‐FDG (~110 min) that the activity level after the 4 hr wait period in the second two patients was 25% the amount during their clinical scan. The selected results of this comparison are presented in Figure 4.

View Article: PubMed Central - PubMed

ABSTRACT

Background: Positron Emission Tomography (PET) is traditionally used to image patients in restrictive positions, with few devices allowing for upright, brain‐dedicated imaging. Our team has explored the concept of wearable PET imagers which could provide functional brain imaging of freely moving subjects. To test feasibility and determine future considerations for development, we built a rudimentary proof‐of‐concept prototype (Helmet_PET) and conducted tests in phantoms and four human volunteers.

Methods: Twelve Silicon Photomultiplier‐based detectors were assembled in a ring with exterior weight support and an interior mechanism that could be adjustably fitted to the head. We conducted brain phantom tests as well as scanned four patients scheduled for diagnostic F18‐FDG PET/CT imaging. For human subjects the imager was angled such that field of view included basal ganglia and visual cortex to test for typical resting‐state pattern. Imaging in two subjects was performed ~4 hr after PET/CT imaging to simulate lower injected F18‐FDG dose by taking advantage of the natural radioactive decay of the tracer (F18 half‐life of 110 min), with an estimated imaging dosage of 25% of the standard.

Results: We found that imaging with a simple lightweight ring of detectors was feasible using a fraction of the standard radioligand dose. Activity levels in the human participants were quantitatively similar to standard PET in a set of anatomical ROIs. Typical resting‐state brain pattern activation was demonstrated even in a 1 min scan of active head rotation.

Conclusion: To our knowledge, this is the first demonstration of imaging a human subject with a novel wearable PET imager that moves with robust head movements. We discuss potential research and clinical applications that will drive the design of a fully functional device. Designs will need to consider trade‐offs between a low weight device with high mobility and a heavier device with greater sensitivity and larger field of view.

No MeSH data available.


Related in: MedlinePlus