Mean Count Values Research Articles

99m Technetium-pyrophosphate bone scan: A potential biomarker for the burden of transthyretin amyloidosis in skeletal muscle: A preliminary study.

Transthyretin amyloidosis (ATTR) proteins can infiltrate skeletal muscle and infrequently cause a myopathy. 99m Technetium-pyrophosphate (99m Tc-PYP) is a validated biomarker for cardiac involvement in variant and wild-type ATTR (ATTRv and ATTRwt, respectively). The aim of this study was to test the hypothesis that 99m Tc-PYP is a biomarker for muscle burden of ATTR. Radioisotope uptake in the deltoid muscles of patients with ATTR was compared to uptake in control subjects without amyloidosis in a retrospective study. 99m Tc-PYP scans were evaluated in 11 patients with ATTR (7 ATTRv, 4 ATTRwt) and 14 control subjects. Mean count (MC) values were measured in circular regions of interest (ROIs) 2.5-3.8cm2 in area. Tracer uptake was quantified in the heart, contralateral chest (CC), and deltoid muscles. Tracer uptake was significantly higher over the deltoids and heart but not the CC, in patients with ATTR than in control subjects. MC values were 120.1± 43.7 (mean ± SD) in ATTR patients and 78.9± 20.4 in control subjects over the heart (p= 0.005), 73.3± 21.0 and 63.5± 14.4 over CC (p= 0.09), and 37.0± 11.7 and 26.0± 7.1 averaged over both deltoid muscles (p= 0.014). 99m Tc-PYP is a potential biomarker for ATTR amyloid burden in skeletal muscle.

A multicenter phantom study on noise structure in [F-18] FDG-PET imaging

Introduction Point-spread-function (PSF) modelling seem to be very attractive to obtain superior image quality in [F-18] FDG oncological studies, nonetheless it is known to significantly increase noise variability. Purpose To evaluate the impact of PSF/TF on noise structure of iterative reconstructed (IR) images. Materials and methods An anthropomorphic phantom with [F-18] FDG clinical concentrations was acquired on Biograph-mCT (Siemens) and Discovery690 (General Electric) PET/CT scanners. Overall, 96 datasets were obtained by varying reconstruction modalities (RM = IR, TF, PSF, TF+PSF), frame (128,256), equivalent iterations number (IT = 63,270), and Gaussian filter (GF = 2, 4, 6 mm). To limit noise correlation in PET imaging, 6 groups of concentric ROIs (r = 8;10;13;16;19 mm) were drawn on 3 slices at liver level. Fixing slice and ROI size, the signal variation was defined: SV% = 100∗SD/M, were SD,M are standard deviation, mean among the mean count values found for the ROIs, respectively. Results SV decreases with ROI size and GF, and increases with IT. Moreover, SV depends on RM, but in different ways on the two PET scanners. For Biograph-mCT, highest and lowest SV were observed for PSF and TF and for GF = 2, 4, 6 mm mean(range) values were: 7.8%(5.1–10.6), 5.7%(3.1–8.5), 4.5%(2.5–6.7) and 4.5%(2.7–6.4), 3.8%(2.4–5.4), 3.2(2.2–4.5), respectively. For Discovery690, highest and lowest SV were observed for PSF+TF and IR and for GF = 2, 4, 6 mm the mean(range) values were: 8.3%(6.8–10.5), 8.1%(6.7–10.2), 7.9%(6.6–9.7) and 5.1%(3.5–8.2), 4.5%(3.1–7.0), 4.2%(3.2–6.2), respectively. Same trends are observed for the range of SV values. Conclusions The PET scanners of this study showed different behaviors of SV in relation to RM. Increased SV could lead to degradation of precision in quantitative oncological studies with [F-18] FDG for monitoring treatment response. Point-spread-function (PSF) modelling seem to be very attractive to obtain superior image quality in [F-18] FDG oncological studies, nonetheless it is known to significantly increase noise variability. To evaluate the impact of PSF/TF on noise structure of iterative reconstructed (IR) images. An anthropomorphic phantom with [F-18] FDG clinical concentrations was acquired on Biograph-mCT (Siemens) and Discovery690 (General Electric) PET/CT scanners. Overall, 96 datasets were obtained by varying reconstruction modalities (RM = IR, TF, PSF, TF+PSF), frame (128,256), equivalent iterations number (IT = 63,270), and Gaussian filter (GF = 2, 4, 6 mm). To limit noise correlation in PET imaging, 6 groups of concentric ROIs (r = 8;10;13;16;19 mm) were drawn on 3 slices at liver level. Fixing slice and ROI size, the signal variation was defined: SV% = 100∗SD/M, were SD,M are standard deviation, mean among the mean count values found for the ROIs, respectively. SV decreases with ROI size and GF, and increases with IT. Moreover, SV depends on RM, but in different ways on the two PET scanners. For Biograph-mCT, highest and lowest SV were observed for PSF and TF and for GF = 2, 4, 6 mm mean(range) values were: 7.8%(5.1–10.6), 5.7%(3.1–8.5), 4.5%(2.5–6.7) and 4.5%(2.7–6.4), 3.8%(2.4–5.4), 3.2(2.2–4.5), respectively. For Discovery690, highest and lowest SV were observed for PSF+TF and IR and for GF = 2, 4, 6 mm the mean(range) values were: 8.3%(6.8–10.5), 8.1%(6.7–10.2), 7.9%(6.6–9.7) and 5.1%(3.5–8.2), 4.5%(3.1–7.0), 4.2%(3.2–6.2), respectively. Same trends are observed for the range of SV values. The PET scanners of this study showed different behaviors of SV in relation to RM. Increased SV could lead to degradation of precision in quantitative oncological studies with [F-18] FDG for monitoring treatment response.

SEASONAL ERYTHROCYTE COUNT VARIATIONS IN LABORATORY RAISED NEWTS

SUMMARY The variations in erythrocyte concentration throughout the year were followed in 192 specimens of the newt Triturus cristatus camifex (Laurenti), sampling 16 specimens per month. The laboratory conditions, with temperatures ranging between 10 and 22 °C, revealed a marked increase in mean count values in the winter which—at lower temperatures—would have been masked by the state of hibernation. The mean concentration varies from a summer low of about 120,000 erythrocytes/mm3 to a winter high of more than 160,000. During the transitional months of March-April and November-December, the standard deviation reach the highest values of about 30,000.

Small average differences in attenuation corrected images between men and women in myocardial perfusion scintigraphy: a novel normal stress database

BackgroundThe American Society of Nuclear Cardiology and the Society of Nuclear Medicine state that incorporation of attenuation-corrected (AC) images in myocardial perfusion scintigraphy (MPS) will improve image quality, interpretive certainty, and diagnostic accuracy. However, commonly used software packages for MPS usually include normal stress databases for non-attenuation corrected (NC) images but not for attenuation-corrected (AC) images. The aim of the study was to develop and compare different normal stress databases for MPS in relation to NC vs. AC images, male vs. female gender, and presence vs. absence of obesity. The principal hypothesis was that differences in mean count values between men and women would be smaller with AC than NC images, thereby allowing for construction and use of gender-independent AC stress database.MethodsNormal stress perfusion databases were developed with data from 126 male and 205 female patients with normal MPS. The following comparisons were performed for all patients and separately for normal weight vs. obese patients: men vs. women for AC; men vs. women for NC; AC vs. NC for men; and AC vs. NC for women.ResultsWhen comparing AC for men vs. women, only minor differences in mean count values were observed, and there were no differences for normal weight vs. obese patients. For all other analyses major differences were found, particularly for the inferior wall.ConclusionsThe results support the hypothesis that it is possible to use not only gender independent but also weight independent AC stress databases.

Three-dimensional Gaussian model to define brain metastasis limits on 11C-methionine PET

Purpose Since 11C-methionine (MET) heavily accumulates in brain tumors, PET with MET (MET—PET) is proposed for the image-guided planning of their targeted therapy. Determination of bulk tumor limits is therefore a crucial component of MET—PET image analysis. We aimed at validating a Gaussian model of tumor delineation on MET—PET. We choose MET—PET and MRI data obtained in brain metastases to adjust the model. Indeed, MRI limits of these non-infiltrative hypermetabolic brain lesions are efficiently used for their curative treatment. Methods and materials We developed a three-dimensional (3D) Gaussian model that relates the tumor-limit-defining threshold to maximum and mean count values in the defined tumor volume and to mean count values in a reference region. To adjust the model to experimental data, we selected 25 brain metastases following these criteria: (i) no surgery or classical radiotherapy within 6 months, (ii) no previous radiosurgery, (iii) MET—PET and MRI acquired within a 48-h interval, (vi) necrosis representing less than 25% of tumor volume on MRI. We applied a progressive thresholding procedure on MET—PET so as to match tumor limits on contrast-enhanced co-registered MRI. Results In 22 tumors, a match could be reached between tumor margins on MET—PET and MRI. The relation between mean, maximum and threshold values closely fits the 3D-Gaussian model function. We found a quadratic relation between the mean-to-threshold ratio and the maximum-to-cerebellum activity ratio. Conclusions A 3D-Gaussian model may describe the limits of MET uptake distribution within brain metastases, providing a simple method for metabolic tumor delineation.

Technetium-99m Hexamethylpropylene Amine Oxime Lung Scintigraphy Findings in Low-Dose Amiodarone Therapy

Amiodarone (AD)-induced pulmonary toxicity is one of the major complications of long-term AD therapy. Technetium-99m-labeled D: ,L: -hexamethylpropylene amine oxime (Tc-99m HMPAO) scintigraphy has been used to assess lung injury. We designed this study to clarify lung uptake changes of Tc-99m HMPAO using low doses of AD (5 mg/kg/day) during long-term therapy in a rabbit model. Group 1 consisted of 7 rabbits fed with AD by gavage for 6 months. To investigate the effect of ketamine on Tc-99m HMPAO uptake, 5 rabbits were included in Group 2 as a control group. Tc-99m HMPAO scintigraphy was performed in both Group 1 and Group 2 at baseline and after 2, 4, 6, 8, and 12 weeks of AD intake. After 16, 20, and 24 weeks of drug intake, Tc-99m HMPAO scintigraphy was repeated only in group 1. One-min anterior images were acquired 30 min after the injection of 37 MBq of Tc-99m HMPAO. For semiquantitative evaluation, the mean count values were obtained and lung/background and liver/background ratios were calculated. Histopathologic evaluation was performed. No increase in lung and liver uptake of Tc-99m HMPAO was found 2, 4, 6, 8, and 12 weeks after drug intake. There was no significant increase in L/B and H/B ratios of Tc-99m HMPAO in Group 1 compared with Group 2. Both scintigraphic studies and histopathologic examinations showed nonspecific changes. Longitudinal studies investigating Tc-99m HMPAO lung uptake may be planned in patients carrying risk factors for AD-induced lung toxicity.

Semi-quantification of methionine uptake and flair signal for the evaluation of chemotherapy in low-grade oligodendroglioma

11C-Methionine (MET) is a useful positron emission tomography (PET) tracer for the evaluation of low-grade gliomas. Among these tumors, a high percentage of low-grade oligodendrogliomas (ODG) are sensitive to chemotherapy with procarbazine, CCNU, and vincristine (PCV). We aimed at: (1) objectively assessing ODG response to PCV by a metabolic index (the Activity Volume Index or AVI) generated from an automated semi-quantification of PET with MET (PET-MET); (2) comparing AVI and quantitative magnetic resonance imaging (MRI) measurements of response to PCV. seven patients with ODG were followed for a period of 19.9+/-6.6 months after the completion of PCV chemotherapy. Regions of interest (ROI) were generated by covering all voxels with count values above a threshold level set at 120% of the mean cerebellar activity. On each slice, ROI volume and mean count values were calculated. AVI was calculated as the sum over all ROI of tumor volumex(tumor mean count/cerebellum count). Tumor volume measurements on MRI, were based on signal abnormalities visually detected on fluid-attenuated inversion recovery (FLAIR) sequences. PCV therapy was associated with a drastic decrease in AVI (mean+/-SD, cm3): AVI post-PCV=0.80+/-1.45 vs. AVI prior PCV=12.94+/-11.46 (P=0.03). Likewise, we observed a decrease in tumor volume estimated from the FLAIR signal (31.37+/-11.99 post-PCV vs. 67.95+/-39.96 prior PCV, P=0.03) although AVI decrease after PCV was significantly more pronounced (P=0.015). This study, based on limited number of patients and follow-up period indicates that AVI may be a sensitive and observer-independent method applicable to the assessment of ODG responsiveness to PCV treatment and may offer a major added value to both clinical assessment and MRI evaluation of chemotherapeutic outcomes.