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Techniques and Equipment

PET

PET CT machine

PET scans are acquired following administration of a radiotracer. The radiotracer accumulates in the tissue to be studied, and its radionuclide decays by emission of a positron (anti-electron). After travelling at most a few millimetres, a positron will collide with an electron, simultaneously releasing two gamma rays (photons) with an energy of 511 keV into opposite directions. These two photons are detected by the PET camera and simultaneously localized within a fixed period of time by a series of opposing detectors, which correspond to multiple rings of scintillation crystals. By collecting a statistically significant number of radioactive events, mathematical algorithms reconstruct a three-dimensional image that shows the distribution of the positron-emitting molecules in the brain. 

Animation of accumulation of radioactive tracer

PET imaging uses isotopes which decay by β+, these usually have short half-life. This technique is advantageous for shorter processes and can also be used by multiple administrations of the tracer.

To the right you see accumulation of the PET-tracer FE-PE2I in the striatum of a rat brain.
Courtesy of Deniz Kirik.

SPECT 

SPECT CT Machine

Gamma-ray photons emitted from the internal distributed radiopharmaceutical penetrate through the animal’s or patient’s body and are detected by a single or a set of collimated radiation detectors. Most of the detectors used in current SPECT systems are based on a single or multiple NaI (TI) scintillation detectors. In SPECT, projection data are acquired from different views around the animal/patient.

SPECT image of mouse

SPECT imaging uses photons emitted from radioactive decay, for photon energies 25-350 keV. These isotopes usually have longer half-life, and the technique is advantageous for long processes as well as radiotherapy studies. Due to the difference in photon energy from different isotopes, more than one process can be monitored simultaneously.

CT

Schematic principle of CT
Schematic principle of CT

X-ray Computed Tomography (CT) is a non-invasive technique for visualizing interior features within solid objects, and for obtaining digital information on their 3-D geometries and properties.

CT is a non-invasive technique that provides a detailed 3-D image. The same object can be imaged multiple times on different occasions to study the development of your treatment/disease model. CT uses the density difference in the object to create images of resolution down to 10 µm.

Animation of caput femuralis

To the the right you see micro-X-ray imaging.
The head of a hip-joint (caput femoralis) from a mouse.
Diameter of the head is 1.3 mm.
CT images: slice thickness 0.01 mm, voxel-size 0.01 x 0.01 mm.

Using a radioactive tracer, physiological phenomena can be followed and functional images are created. The biomolecule of interest, labelled with a radioactive nuclide, is injected into the object to follow where it accumulates and how fast. The acquired intensity maps are then superimposed on the CT picture for easier image analysis. 

 

Instrument specifications

CT (Mediso)

Detector

Gd2O2S

Spatial resolution

0.01-0.425 mm

Transaxial FOV

35-120 mm

Multimodality

PET or SPECT

Bore size

150 mm

NanoSPECT/CT (Mediso)

Detector

NaI(Tl)

Spatial resolution

>0.5 mm

Collimation

36 pinholes

Energy range

25-350 keV

Multimodality

CT

Bore size

70 mm

NanoPET/CT (Mediso)

Detector

LYSO

Spatial resolution

>1 mm

Transaxial FOV

12.4 cm

Multimodality

CT

Bore size

150 mm

 

Radiochemistry

We offer a fully equipped radiochemistry where we can label everything from liposomes, antibodies and proteins all the way down to small molecules. Please inquire the platform coordinator if you have a project in mind and want to know more.

SPECT tracers are generally synthesized on request. PET tracers that are available or can be made available with minimum set-up time are:

PET tracer

Delivery/provider

Used for

18F-NaF

SUS/LBIC

Bone imaging, retained by calcium

18F-FDG

SUS

Glucose metabolism, oncology

18F-Choline

SUS

Accumulates in tumors due to malignancy-induced overexpression of choline kinase, cancer

18F-FLT

SUS

Active cellular proliferation of malignant tumours, oncology

18F-FET

SUS

Accumulates in cerebral gliomas and in extracranial squamous cell carcinomas owing to increased transport (amino transporter system), oncology

18F-AV-1451

SUS

Tau pet imaging agent, neurology

18F-MISO

LBIC

Hypoxia, oncology

18F-FES

LBIC

Fluoroestradiol, breast cancer estrogen-receptor (ER) expression, oncology

18F-MPPF

LBIC

Specific serotonin 5-HT1A antagonist, abnormalities in the serotoninergic system, neurology

18F-MFES

LBIC

Estradiol, breast cancer estrogen-receptor (ER) expression, oncology

18F-FDHT

LBIC

Prostate tumours, androgen receptor (AR) levels, oncology

18F-DOPA

LBIC

Dopamine transport, neurology/oncology

18F-FMT

LBIC

Dopamine production, neurology

18F-tyrosine

LBIC

Brain tumours, glioma, oncology

68Ga-DOTATATE

SUS

Somostatin receptors, neuro-endocrine tumours, oncology

11C-Raclopride

SUS

Selective antagonist on D2 dopamine receptors, neurology