PXMOD Implementation

Acquisition and Data Requirements

Image Data

A data set representing the autoradiographical slices in arbitrary units. Select 1/1 as the loading units as the values are transformed into nCi/g during the model calculations. An appropriate translation table must be derived from the image representation of the reference sheets and supplied as the TAC1 curve in the model preprocessing panel. Note that the duration of the acquisition must be specified as the time from injection until sacrificing the animal.

Blood Data

Plasma activity of blood sampled at a peripheral artery from the time of injection until sacrificing the animal.

Important: Select 1/1 as the units and ensure that the values in the data file are already in nCi/g.

Blood Preprocessing

PXMOD C14 Autroradiography Blood Pre-Processing

Model Preprocessing

The parameters applied in the autoradiographic calculation of MRGlu must be entered in the model pre-processing dialog

PXMOD C14 Autroradiography Model Pre-Processing

Plasma glucose	Plasma glucose measured with a blood sample of the animal.
Lumped constant	It is used to account for the difference in uptake between normal glucose and DG.
K1	Unidirectional transfer of DG into tissue.
k2	Clearance of DG from the tissue.
k3	Phosphorylation rate in tissue.
k4	Dephosphorylation of glucose-phosphate in tissue.

As mentioned before it is assumed that the input images are in arbitrary units and must be converted to radioactivity. This is done by the application of a translation table which must be specified as shown in the Model pre-processing dialog above (C14translation.crv). The contents of this text file should look like :

Graphic[1/1] Activity[1/1]
46 0
48 34
57 84
66 126
72 157
82 233
86 270
95 323
95 391
102 433
111 497
121 549
126 585
136 688
159 916

So in the above example the image pixel values have an original range up to 159, and the resulting activity values range up to 916nCi/g as determined by the reference sheets. Note that linear interpolation is applied between the specified time points.

The translation curve is shown in the preprocessing Result area as

PXMOD C14 Autroradiography Translation Curve

Map Parameters

PXMOD C14 Autroradiography Model Pre-Processing

MRGlu	Metabolic Rate of Glucose in [mmol/min/100ml], the actual result of the model. It is calculated according to eq. (8) in [13].
nCi/g	This is just a utility parameter showing the activity in the pixels after application of the conversion table.