Page 62 - ARNM-3-2

Advances in Radiotherapy
& Nuclear Medicine 18 F-FDG uptake and hypercholesterolemia

information at the first 2 min, segmented similarly to (HC, n=8; mean age=69.25±3.96 years), and SA patients
the CT images. The arterial wall calcification on CT was (SA, n=6; mean age=70.00±1.50 years).
defined visually by attenuation values ≥130 Hounsfield The clinical variables and the estimated MRGlu values
units. Calcium density was divided into four groups (K1 for all three groups are presented in Table 1, expressed as
– K4) from the lowest to the highest density, following mean ± SD. These measurements were collected before the
the Agatston et al. scoring strategy. Calcium area was 18 F-FDG-PET examinations.
27
defined as at least two adjoining pixels within the CT
arterial ROI with attenuation ≥130 Hounsfield units, and The average glucose levels for all participants were
was normalized to the artery area to yield the calcium area within the recommended range, as detailed in Table 1
ratio. This ratio was then divided into two groups based on (expressed in mmol/L). 25
whether the value was below or above the mean calcium The standard irreversible two-tissue compartment
area ratio (20%). 28 model for F-FDG consists of two compartments and
18
Arterial and tissue F-FDG activity curves as a function four rate constants that describe the transport and
18
of time were extracted using factor analysis of dynamic metabolism of 18 F-FDG (Figure 1A). After cellular
sequence (FADS) in dynamic PET data. Partial volume uptake, F-FDG is phosphorylated by hexokinase into
18
correction was performed using the modified Müller- 18 F-FDG-6-phosphate, which is metabolically trapped, as
Gartner method. The transport rate constants K , K , and it cannot be further degraded or easily dephosphorylated;
29
2
1
K were calculated using a two-tissue-compartment model the metabolized tracer ( F-FDG) compartment (MTC)
18
3
implemented in MATLAB R2024b (The MathWorks, is assumed to be irreversible with K =0. The goodness
4
USA). Detailed descriptions of this model can be found of fit between the raw data and model-fitted curves
elsewhere. 30 is represented by the squared Pearson’s correlation
2
The net influx rate (K ) of F-FDG was calculated using coefficient (r ), shown in Figure 1B, ranging from 0.8 to
18
n
Equation I. 0.997, with a mean value of 0.94 ± 0.04. Figure 1C displays
decay-corrected time-activity curves for the arterial input
K K function (arterial input function, extracted from FADS,
1
K K K 3 3 (I) solid line), tissue signal (star markers), and model-fitted
n
2
MTC, respectively).
where K , K , and K are transport rate constants; K is curves for free and metabolized compartments (FTC and
1
n
3
2
expressed in mL/g/min assuming a tissue density of 1 g/mL. 31
Table 1. The clinical variables for CL, HC, and SA groups
The MRGlu per ROI was then calculated using
Equation II. Parameters CL HC SA p
Age (years) 70.00±3.91 69.25±3.96 70.00±1.50 >0.05
Glucose
MRGluK n Lumpedconstant 100 (II) Weight (kg) 63.50±5.52 76.92±10.02 80.06±25.60 <0.05
Total cholesterol
(mmol/L) 3.43±0.60 5.47±1.29 3.74±0.96 <0.05
where K is the net influx rate; MRGlu is expressed in
n
µmol/100 g/min, with the lumped constant set at 0.89. High-density 1.36±0.37 1.32±0.21 1.27±0.30 >0.05
32
lipoprotein cholesterol
MRGlu values were assessed in the aorta and iliac arteries (mmol/L)
to estimate inflammatory activities. Low-density 1.44±0.69 3.46±1.26 1.85±0.53 <0.05
Continuous data were tested for normality using the lipoprotein cholesterol
D’Agostino-Pearson omnibus test. The goodness of fit (mmol/L)
was evaluated using Pearson’s correlation coefficient. Triglyceride (mmol/L) 1.40±0.59 1.50±0.63 1.36±0.63 >0.05
Parametric variables were expressed as mean ± standard Glucose (mmol/L) 5.23±0.61 4.58±0.86 5.16±0.33 >0.05
deviations (SD) and compared using the Mann–Whitney C-reactive protein 2.75±0.12 6.82±7.85 3.93±0.04 <0.05
U test. A non-significant threshold was set at p>5%. All (mg/L)
statistical analyses were conducted in MATLAB R2024b. MRGlu 12.50±8.45 15.14±9.89 14.70±8.93 <0.05
(µmol/100 g/min)
3. Results Notes: All data expressed as mean±standard deviations; p was derived
Participants were classified into three groups based on from a statistical comparison among groups using the Mann–Whitney
U test.
clinical characteristics: Control subjects (CL, n=4; mean Abbreviations: CL: Control; HC: Hypercholesteremia; SA: Stable
age=70.00±3.91 years), hypercholesteremia subjects angina; MRGlu: Metabolic rate of glucose.
Volume 3 Issue 2 (2025) 54 doi: 10.36922/arnm.8540