Tracer uptake

Plate 6.2 A patient has received two PET scans with [nC]DASB (3-amino-4-[(2-dlmethylaminomethyl) phenylsulfanyll benzonitrilet. a tracer selective for the serotonin transporter. The first was obtained prior to treatment and the sec raid after treatment with citalopram, 20 mg/day for 4 weeks. Tracer uptake has been reduced in the striatum by approximately 90l ot suggesting that 80 o of the serotonin transporters are occupied by citalopram with that level of exposure (Meyer etal, 2001)... 

Cell studies were carried out in three different cell lines. Experimental parameters such as cell number, tracer concentration (5nM of Lu-DOTATATE per tube) and incubation parameters (pH, time and temperature) were identical for all experiments. Table 8.3 shows the extent of tracer uptake in the different cell lines. AR42J cells showed the highest uptake of the three cell lines studied. No significant inhibition in binding due to the addition of cold peptide was observed. The results depicted in Table 8.3 are indicative of the higher somatostatin receptor expression on AR42J cells than on HT-29 and MCF-7 cells. 

Cell type Tracer uptake (%) DOTATATE (cold) ... 

A binding of 13.2 0.8% ( = 3) was observed with 5 x 10 MCF-7 cells for 1 gg of the Lu-p-NCS-benzyl-DOTA-estradiol complex. With SepPak purification, the cell uptake improved to 17.1 1.6% (n = 3). No further increase in cell uptake was observed with HPLC purification. It was observed that the tracer uptake in the cells decreased to 8.3 2.0% (n = 3) with the addition of 100 gg of cold estradiol. Similar results were observed when these experiments were carried out on 24 well plates where cells were plated 1 d prior to the experiments. The decrease in cell uptake with the addition of estradiol indicated the specificity of the radiolabelled conjugate for the MCF-7 cell lines. Blank experiments were carried out with Lu labelled BFCA under similar experimental conditions. No retention of the activity in the cell pellet was observed, ruling out the possibility of carrier mediated uptake. 

In normal human subjects the agent allowed an excellent delineation of the cortical gray matter, the basal ganglia, the thalamus and cerebellar hemispheres as regions of relatively increased tracer uptake. White matter displayed substantially less uptake than gray matter. The primary route of excretion of the tracer is through the kidneys. TcO-L.L-E( ID I" SPECr shows particular promise for the evaluation of patients with stroke [ 70],... 

Level 1 Fixed low-dose ablation, 1850-4625MBq (50—125mCi), is performed following surgery for solitary tumors under 4.0 cm in diameter without pre- or post-surgical evidence of spread to local-regional lymph nodes or extension to extra-thyroidal soft tissue. Administered activity is based on age, patient size, tumor characteristics and tracer uptake within the gland remnant. 

Fig, 4.2a-e. Biliary atresia (BA), a Slightly inhomogeneous echo texture of the liver, prominent wall of common bile duct (CBD) arrows), b Tiny gallbladder. c,d Tracer uptake in liver, both kidneys, and bladder, but not in a gallbladder or duodenum. e Transhepatic cholangiography reveals atretic CBD arrow)... 

The results of these studies could open new perspectives for radiation treatment planning. They demonstrated the feasibflity of in vivo PET studies performed with tracers which in experimental models were closely related to tissue hypoxia. Furthermore, they showed, even in a small number of patients, a significant correlation between hypoxia-tracer uptake and treatment response. However, clinical trials analyzing the impact of FHV as a target for radiation treatment planning in lung cancer have not been done so far. 

Another essential question addresses the reproducibility of the intratumoral distribution of hypoxia. In a recent study Nehmeh et al. (2008) evaluated the dynamics of the FMISO uptake in PET over 3 days in 14 patients with untreated head and neck tumors. The authors describe variability in spatial hypoxia tracer uptake. Only 6/13 patients had well-correlated intratumoral distributions of FMISO, suggestive of chronic hypoxia. 

Fig.33.1a-c. I -PET in a patient with differentiated thyroid cancer following thyroidectomy (a). There is no anatomical background, as 1 is highly specific for thyroid tissue. Fusion with anatomical data is mandatory for correct localization of iodine uptake (b). FDG as a nonspecific radionuclide provides some limited anatomical data, which allows localization of the area of increased tracer uptake (arrow) within the left base of the tongue (c). 

Image evaluation of PET is performed both qualitatively and quantitatively. The reader assesses the PET data for regions of focally increased tracer uptake (qualitative image analysis). A region of interest is drawn around a hot spot on PET, offering quantitative analysis of the tracer activity in that area. Quantitative PET data are typically reported as standardized uptake values (SUV) ... 

Fig. 33.5a-d. Contrast-associated PET artifact apparent focal tracer uptake in the left axilla on PET (arrow in a). The corresponding CT demonstrates high-attenuation contrast material... 

Antoch G, Freudenberg, LS etal. (2002) Focal tracer uptake a potential artifact in contrast-enhanced diml-modality PET-CT scans. J Nucl Med 43 1339-1342 Antoch G, Stattaus J et al. (2003) Non-small cell lung cancer dual-modality PET-CT in preoperative staging. Radiology 229 526-533... 

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