A robust method, based on a novel source, for performance and diagnostic capabilities assessment of the positron emission tomography system.

The aim of our work was to provide a robust method for evaluating imaging performance of positron emission tomography (PET) systems and particularly to estimate the modulation transfer function (MTF) using the line spread function (LSF) method. A novel plane source was prepared using thin layer chromatography (TLC) of a fluorine-18-fluorodeoxyglucose ((18)F-FDG) solution. The source was placed within a phantom, and imaged using the whole body (WB) two dimensional (2D) and three dimensional (3D) standard imaging protocols in a GE Discovery ST hybrid PET/CT scanner. Modulation transfer function was evaluated by determining the LSF, for various reconstruction methods and filters. The proposed MTF measurement method was validated against the conventional method, based on point spread function (PSF). Higher MTF values were obtained with 3D scanning protocol and 3D iterative reconstruction algorithm. All MTF obtained using 3D reconstruction algorithms showed better preservation of higher frequencies than the 2D algorithms. They also exhibited better contrast and resolution. MTF derived from LSF were more precise compared with those obtained from PSF since their reproducibility was better in all cases, providing a mean standard deviation of 0.0043, in contrary to the PSF method which gave 0.0405. In conclusion, the proposed method is novel and easy to implement for characterization of the signal transfer properties and image quality of PET/computed tomography (CT) systems. It provides an easy way to evaluate the frequency response of each kernel available. The proposed method requires cheap and easily accessible materials, available to the medical physicist in the nuclear medicine department. Furthermore, it is robust to aliasing and since this method is based on the LSF, is more resilient to noise due to greater data averaging than conventional PSF-integration techniques.

Increased breast density correlates with the proliferation-seeking radiotracer (99m)Tc(V)-DMSA uptake in florid epithelial hyperplasia and in mixed ductal carcinoma in situ with invasive ductal carcinoma but not in pure invasive ductal carcinoma or in mild epithelial hyperplasia.

The purpose of this study was to assess the relationship of mammographic breast density (BD) and cell proliferation/focal adhesion kinase activation-seeking radiotracer technetium 99m pentavalent dimercaptosuccinic acid (99mTc(V)-DMSA) uptake in women with different breast histologies, that is, mild epithelial hyperplasia (MEH), florid epithelial hyperplasia (FEH), mixed ductal carcinoma in situ with invasive ductal carcinoma (DCIS + IDC), and pure IDC. Fifty-five women with histologically confirmed mammary pathologies were submitted preoperatively to mammography and 99mTc(V)-DMSA scintimammography. The percentage and intensity of 99mTc(V)-DMSA uptake and the percentage of BD were calculated by computer-assisted methods and compared (t-test) between the breast pathologies. In breasts with increased BD, FEH and DCIS + IDC were found. On the contrary, pure IDC and MEH were identified in breasts with significantly lower BD values. In breasts with increased 99mTc(V)-DMSA area and intensity of uptake, FEH was the main lesion found compared to all other histologies. Linear regression analysis between BD and 99mTc(V)-DMSA uptake area and intensity revealed significant coefficients of correlation (r  =  .689, p < .001 and r  =  .582, p < .001, respectively). Increased BD correlates with the presence of FEH and mixed DCIS + IDC but not with pure IDC or MEH. Its close relationship to 99mTc(V)-DMSA, which also showed an affinity to FEH, indicates that stromal microenvironment may constitute a specific substrate leading to progression to different subtypes of cancerous lesions originating from different pathways.

Renin-angiotensin system dysregulation in fetuses with hydronephrosis.

OBJECTIVES: To evaluate if fetal hydronephrosis is associated with dysregulation of the renin-angiotensin system (RAS), and if it could represent an early predictor of future renal damage or arterial hypertension. STUDY DESIGN: The study consisted of 26 pregnant women and their fetuses. Ultrasound scans were performed to evaluate the renal pelvis in fetuses. Four fetuses with hydronephrosis were included in the study, while the rest were found to have normal renal pelvis. Active and inactive renin was calculated by IRMA method in fetal and maternal blood, during the second trimester of pregnancy. RESULTS: A comparison of plasma active and inactive renin levels was made between pregnant women and their fetuses, as well as between fetuses with and without hydronephrosis. Active and inactive renin levels obtained from fetuses with hydronephrosis were significantly higher compared to those obtained from fetuses with normal kidneys. CONCLUSIONS: Dilatation of renal pelvis in the second trimester of pregnancy seems to up-regulate the renin and prorenin system in fetal blood. Both factors are indicative of possible future renal pathology.