Impact of disposable syringes type choice on myocardial perfusion imaging procedures with [99mTc]Tc-tetrofosmin

BACKGROUND

Residual activity in dispensing syringes is a problem that has been sporadically reported with various radiopharmaceuticals. Studies with [99mTc]Tc-tetrofosmin are non-consistent so far. The aim was to quantify the residual activity of [99mTc]Tc-tetrofosmin in different syringes in a clinical setting and to assess its impact on the clinical imaging procedure.

METHODS

The residual activity of [99mTc]Tc-tetrofosmin was measured in 3 types of syringes: 3-part lubricated and non-lubricated syringes and 2-part syringe (n ≥ 30 for each syringe). The residual activity was located and quantified using a CzT SPECT camera and radio-counting then was correlated with different clinical parameters and processed by multiple linear regression analysis.

RESULTS

Residual activity was different in all syringe types but lubricated syringes showed significantly higher levels with a mean ± SD of 26.12 ± 10.21% (P < .001). For these syringes, the residual activity was mainly located on the lubricated body. They also have a positive and significant impact on the standardized counting duration of patients' acquisitions.

CONCLUSION

Lubricated syringes with high residual activity should be avoided as they increase the risk of prolonging patient acquisition time and potentially increasing the risk of poor image quality.

Revisiting detection of in-transit metastases in melanoma patients using digital 18F-FDG PET/CT with small-voxel reconstruction

AIM

To evaluate the use of digital ¹⁸F-FDG PET/CT with small-voxels reconstruction for detecting in-transit metastases in melanoma patients with primary lesion located on the upper or lower limbs, in comparison with standard reconstruction and European Association of Nuclear Medicine Research limited (EARL)-compliant reconstruction mimicking former generation PET systems.

METHODS

Forty-six PET examinations acquired in list mode on a Vereos digital PET/CT system were reconstructed with (1) the standard reconstruction [2 iterations, 10 subsets (2i10s), point-spread function (PSF) modelling and time-of-flight enabled, no post-filtering and voxel size of 2 mm], (2) a small-voxel reconstruction using 1 mm voxels otherwise using the same parameters, (3) an EARL-compliant reconstruction mimicking a former generation system. Comparison of results across these reconstructions was made for a blind randomized review using a 3-point scale for the presence of in-transit metastases and image quality as well as for tumour-to-background (T/B) ratios and noise level in reference organs.

RESULTS

Seven of the thirty-two EARL-compliant images classified as negative moved to positive on 1mm_PSF images, and 5 of the 6 EARL-compliant images classified as indeterminate moved to positive on 1mm_PSF images (P = 0.01). Amongst a total of 20 PET examinations classified as positive using the 1mm_PSF reconstruction, fifteen were considered true positive, five false positive results occurred. Twenty-four patients with 1 mm PSF images were classified as negative, none of those under active surveillance experienced in-transit metastases during the 17 months following their PET examination. The positive likelihood ratio for the 1 mm reconstruction was much higher than that observed for EARL-compliant images (14.7 vs 7.82). Importantly, negative likelihood ratios for the 1 mm and 1mm_PSF reconstruction were almost perfect. Compared to EARL-compliant data, T/B ratios extracted from the 1mm_PSF showed a 2.84-fold increase (P < 0.001). A similar pattern of statistically significant increase was observed for noise level in organs of reference. Image quality for the torso was found to be significantly lower for 1mm_PSF reconstruction (P = 0.03). Image quality for the limbs was found to be better for 1mm_PSF (P < 0.001).

CONCLUSION

Digital PET with small-voxel reconstruction brings an additional value for the detection of in-transit metastases by reducing the number of indeterminate findings and making up for falsely negative scans using former generation PET systems. An acquisition encompassing lower or upper limbs as appropriate should be performed.

Increased myogenic tone and diminished responsiveness to ATP-sensitive K+ channel openers in cerebral arteries from diabetic rats

Diabetes mellitus has profound adverse effects on vascular and, in particular, endothelial function. Although pressure-induced constriction ("myogenic tone") is a major contributor to the regulation of blood flow, little is known about the effects of diabetes on this response. Diabetes has been shown to diminish the dilation of cerebral arteries to synthetic ATP-sensitive K+ (KATP) channel openers. In this study, we explored the effects of diabetes induced in rats by streptozotocin on cerebral artery (250 to 300 microns) myogenic tone and on vasodilations to the synthetic KATP channel openers pinacidil and levcromakalim. Elevation of intravascular pressure caused a graded membrane potential depolarization and constriction, which was greater in arteries from diabetic rats compared with normal rats (at 60 mm Hg, 5 mV more depolarized and 22 microns more constricted). Pressurized arteries (at 60 mm Hg) from diabetic rats were 5- to 15-fold less sensitive to pinacidil and levcromakalim than were control arteries (EC50 values for pinacidil and levcromakalim were 1.4 and 0.6 mumol/L, respectively, in diabetic animals and 0.3 and 0.04, respectively, in control animals; P < .05). Removal of the endothelium or addition of a NO synthase inhibitor, NG-nitro-L-arginine (LNNA), in control arteries decreased the sensitivity to KATP channel openers and depolarized and constricted control arteries to levels similar to those observed in arteries from diabetic animals. Sodium nitroprusside caused a membrane potential hyperpolarization and enhanced the response to pinacidil in arteries from diabetic animals. Removal of the endothelium or LNNA had little effect on the apparent KATP channel opener sensitivity, the membrane potential, and pressure-induced constrictions of arteries from diabetic animals. The results are consistent with the hypothesis that this type of diabetes leads to a decrease in tonic NO release from the endothelium, which in turn causes membrane potential depolarization and vasoconstriction, resulting in a diminished response to KATP channel openers.

Extracellular K(+)-induced hyperpolarizations and dilatations of rat coronary and cerebral arteries involve inward rectifier K(+) channels

1. The hypothesis that inward rectifier K(+) channels are involved in the vasodilatation of small coronary and cerebral arteries (100-200 microm diameter) in response to elevated [K+]o was tested. The diameters and membrane potentials of pressurized arteries from rat were measured using a video-imaging system and conventional microelectrodes, respectively. 2. Elevation of [K+]o from 6 to 16 mM caused the membrane potential of pressurized (60 mmHg) arteries to hyperpolarize by 12-14 mV. Extracellular Ba(2+) (Ba2+(o)) blocked K(+)-induced membrane potential hyperpolarizations at concentrations (IC(50), 6 microM) that block inward rectifier K(+) currents in smooth muscle cells isolated from these arteries. 3. Elevation of [K+]o from 6 to 16 mM caused sustained dilatations of pressurized coronary and cerebral arteries with diameters increasing from 125 to 192 microm and 110 to 180 microm in coronary and cerebral arteries, respectively. Ba2+(o) blocked K(+)-induced dilatations of pressurized coronary and cerebral arteries (IC50, 3-8 microM). 4. Elevated [K+]o-induced vasodilatation was not prevented by blockers of other types of K(+) channels (1 mM 4-aminopyridine, 1 mM TEA+, and 10 mu M glibenclamide), and blockers of Na(+)-K(+)-ATPase. Elevated [K+]o-induced vasodilatation was unaffected by removal of the endothelium. 5. These findings suggest that K+(o) dilates small rat coronary and cerebral arteries through activation of inward rectifier K(+) channels. Furthermore, these results support the hypothesis that inward rectifier K(+) channels may be involved in metabolic regulation of coronary and cerebral blood flow in response to changes in [K+]o.

Esophageal prothesis for neoplastic stenosis. A prognostic study of 77 cases

Esophageal prothesis (EP) is a palliative treatment for inoperable neoplastic stenosis. Ninety-one patients were candidates for EP placement between 1978 and 1983. EP placement was successful in 77 patients. Of these: 85% had primary esophageal cancer; 15% had bronchial or mediastinal carcinoma; 83% had stenosis in the middle third. Dysphagia was the main symptom in 84%, and tracheoesophageal fistulae in 16%. The observed median survival was 3.2 months +/- 1.9 (2 standard deviations [SD]), and the survival rate at 1 year was 7%. With the single-factor analysis method, not one of 12 factors presented any significance (age, sex, general status, anterior treatment, lesion site, endoscopic feature, stenosis diameter, histologic features, metastasis, tracheal involvement, symptoms, and type of prothesis). Two factors had a P value approaching significance: there were slightly longer survival rates in patients with a stenosis diameter less than 7 mm (P less than 0.07), and with stenosis located in the lower third and cardia (P less than 0.07). By multivariate analysis (Cox model), prognostic significance was found in only one factor: the location in the lower third and cardia (P = 0.002, relative risk = 3). The quality of life after EP placement was briefly improved: 80% of 73 evaluable patients had improvement in dysphagia for a mean duration of 3.7 months +/- 2 (2 SD), especially patients with a good general status (0 and 1; P less than 0.01); and 45% of patients had improvement of their general status for a mean duration of 4.1 months +/- 2 (2 SD). Minor complications related to EP placement were observed in 40% of patients (pain, obstruction, and mobilization), and severe complications were observed in 20% (perforation, 11 cases; fistulae, 5 cases, with death in 3 cases; hemorrhages, 4 cases). In conclusion, EP is a good palliative treatment, although complications are frequent, and evaluation of patient comfort is required to compare this procedure with other available techniques.