18F-4FMFES and 18F-FDG PET/CT in Estrogen Receptor-Positive Endometrial Carcinomas: Preliminary Report.

This article reports the preliminary results of a phase II clinical trial investigating the use of the estrogen receptor (ER)-targeting PET tracer 4-fluoro-11ß-methoxy-16α-18F-fluoroestradiol (18F-4FMFES) and 18F-FDG PET in endometrial cancers. In parallel, noninvasive interventions were attempted to slow progression of 18F-4FMFES metabolites in the intestines to reduce abdominal background uptake. Methods: In an ongoing study, 25 patients who received prior pathologic confirmation of an ER-positive endometrial cancer or endometrial intraepithelial neoplasia agreed to participate in the ongoing clinical trial. Patients were scheduled for 18F-FDG and 18F-4FMFES PET/CT imaging in random order and within 2 wk. Patients were administered either 4 mg of loperamide orally before 18F-4FMFES tracer injection or repeated intravenous injection of 20 mg of hyoscine N-butylbromide during 18F-4FMFES PET/CT. Regions of interest covering the whole abdomen and excluding the liver, bladder, and uterus were drawn for the 18F-4FMFES PET images, and an SUV threshold of more than 4 was applied. The volume of the resulting region was compared between the different interventions to estimate the extent of the intestinal background uptake. Results: Repeated injection of hyoscine N-butylbromide substantially reduced the intestinal background volume, whereas loperamide had a significant but moderate effect. 18F-4FMFES tumor SUVmax ranged from 3.0 to 14.4 (9.4 ± 3.2), whereas 18F-FDG SUVmax ranged from 0 to 22.0 (7.5 ± 5.1). Tumor-to-background ratio was significantly higher for 18F-4FMFES (16.4 ± 5.4) than for 18F-FDG (7.4 ± 4.6). Significant differences were observed between grade 1 and higher-grade tumors concerning 18F-4FMFES uptake and contrast, 18F-FDG uptake, and the 18F-FDG/18F-4FMFES uptake ratio. Conclusion: It is possible to improve 18F-4FMFES abdominal background using hyoscine N-butylbromide. Both 18F-FDG and 18F-4FMFES PET are suitable for detection of ER-positive endometrial cancers, although 18F-4FMFES yielded a better tumor contrast than did 18F-FDG.

The regional effect of serum hormone levels on cerebral blood flow in healthy nonpregnant women.

Sex hormones estrogen (EST) and progesterone (PROG) have received increased attention for their important physiological action outside of reproduction. While studies have shown that EST and PROG have significant impacts on brain function, their impact on the cerebrovascular system in humans remains largely unknown. To address this, we used a multi-modal magnetic resonance imaging (MRI) approach to investigate the link between serum hormones in the follicular phase and luteal phase of the menstrual cycle (MC) with measures of cerebrovascular function (cerebral blood flow [CBF]) and structure (intracranial artery diameter). Fourteen naturally cycling women were recruited and assessed at two-time points of their MC. CBF was derived from pseudo-continuous arterial spin labeling while diameters of the internal carotid and basilar artery was assessed using time of flight magnetic resonance angiography, blood samples were performed after the MRI. Results show that PROG and EST had opposing and spatially distinct effects on CBF: PROG correlated negatively with CBF in anterior brain regions (r = -.86, p < .01), while EST correlations were positive, yet weak and most prominent in posterior areas (r = .78, p < .01). No significant correlations between either hormone or intracranial artery diameter were observed. These results show that EST and PROG have opposing and regionally distinct effects on CBF and that this relationship is likely not due to interactions with large intracranial arteries. Considering that CBF in healthy women appears tightly linked to their current hormonal state, future studies should consider assessing MC-related hormone fluctuations in the design of functional MRI studies in this population.

Cross-Species Physiological Assessment of Brain Estrogen Receptor Expression Using 18F-FES and 18F-4FMFES PET Imaging.

PURPOSE: A retrospective analysis was performed of preclinical and clinical data acquired during the evaluation of the estrogen receptor (ER) PET tracer 4-fluoro-11ß-methoxy-16α-[18F]-fluoroestradiol (4FMFES) and its comparison with 16α-[18F]-fluoroestradiol (FES) in mice, rats, and humans with a focus on the brain uptake. PROCEDURES: Breast cancer tumor-bearing female BALB/c mice from a previous study and female Sprague-Dawley rats (control and ovariectomized) were imaged by 4FMFES or FES-PET imaging. Immediately after, low-dose CT was performed in the same bed position. Semi-quantitative analysis was conducted to extract %ID/g data. Small cohorts of mice and rats were imaged with 4FMFES in an ultra-high-resolution small animal PET scanner prototype (LabPET II). Rat brains were dissected and imaged separately with both PET and autoradiography. In parallel, 31 breast cancer patients were enrolled in a clinical phase II study to compare 4FMFES with FES for oncological assessment. Since the head was included in the field of view, brain uptake of discernable foci was measured and reported as SUVMax. RESULTS: Regardless of the species studied, 4FMFES and FES uptake were relatively uniform in most regions of the brain, except for bilateral foci at the base of the skull, at the midsection of the brain. Anatomical localization of the PET signal using CT image fusion indicates that the signal origins from the pituitary in all studied species. 4FMFES yielded lower pituitary uptake than FES in patients, but an inverse trend was observed in rodents. 4FMFES pituitary contrast was higher than FES in all assessed groups. High-resolution small animal imaging of the brain of rats and mice revealed a supplemental signal anterior to the pituitary, which is likely to be the medial preoptic area. Dissection data further confirmed those findings and revealed additional signals corresponding to the arcuate and ventromedial nuclei, along with the medial and cortical amygdala. CONCLUSION: 4FMFES allowed visualization of ER expression in the pituitary in humans and two different rodent species with better contrast than FES. Improvement in clinical spatial resolution might allow visualization and analysis of other ER-rich brain areas in humans. Further work is now possible to link 4FMFES pituitary uptake to cognitive functions.

Improved Estrogen Receptor Assessment by PET Using the Novel Radiotracer 18F-4FMFES in Estrogen Receptor-Positive Breast Cancer Patients: An Ongoing Phase II Clinical Trial.

After encouraging preclinical and human dosimetry results for the novel estrogen receptor (ER) PET radiotracer 4-fluoro-11ß-methoxy-16α-18F-fluoroestradiol (18F-4FMFES), a phase II clinical trial was initiated to compare the PET imaging diagnostic potential of 18F-4FMFES with that of 16α-18F-fluoroestradiol (18F-FES) in ER-positive (ER+) breast cancer patients. Methods: Patients diagnosed with ER+ breast cancer (n = 31) were recruited for this study, including 6 who underwent mastectomy or axillary node dissection. For each patient, 18F-FES and 18F-4FMFES PET/CT scans were done sequentially (within a week) and in random order. One hour after injection of either radiotracer, a head-to-thigh static scan with a 2-min acquisition per bed position was obtained. Blood samples were taken at different times after injection to assess each tracer metabolism by reverse-phase thin-layer chromatography. The SUVmean of nonspecific tissues and the SUVmax of the tumor were evaluated for each detected lesion, and tumor-to-nonspecific organ ratios were calculated. Results: Blood metabolite analysis 60 min after injection of the tracer showed a 2.5-fold increase in metabolic stability of 18F-4FMFES over 18F-FES. Although for most foci 18F-4FMFES PET had an SUVmax similar to that of 18F-FES PET, tumor contrast improved substantially in all cases. Lower uptake was consistently observed in nonspecific tissues for 18F-4FMFES, notably a 4-fold decrease in blood-pool activity as compared with 18F-FES. Consequently, image quality was considerably improved using 18F-4FMFES, with lower overall background activity. As a result, 18F-4FMFES successfully identified 9 more lesions than 18F-FES. Conclusion: This phase II study with ER+ breast cancer patients showed that 18F-4FMFES PET achieves a lower nonspecific signal and better tumor contrast than 18F-FES PET, resulting in improved diagnostic confidence and lower false-negative diagnoses.

Clinical Trial with Sodium 99mTc-Pertechnetate Produced by a Medium-Energy Cyclotron: Biodistribution and Safety Assessment in Patients with Abnormal Thyroid Function.

A single-site prospective open-label clinical study with cyclotron-produced sodium 99mTc-pertechnetate (99mTc-NaTcO4) was performed in patients with indications for a thyroid scan to demonstrate the clinical safety and diagnostic efficacy of the drug and to confirm its equivalence with conventional 99mTc-NaTcO4 eluted from a generator. Methods:99mTc-NaTcO4 was produced from enriched 100Mo (99.815%) with a cyclotron (24 MeV; 2 h of irradiation) or supplied by a commercial manufacturer (bulk vial eluted from a generator). Eleven patients received 325 ± 29 (mean ± SD) MBq of the cyclotron-produced 99mTc-NaTcO4, whereas the age- and sex-matched controls received a comparable amount of the generator-derived tracer. Whole-body and thyroid planar images were obtained for each participant. In addition to the standard-energy window (140.5 keV ± 7.5%), data were acquired in lower-energy (117 keV ± 10%) and higher-energy (170 keV ± 10%) windows. Vital signs and hematologic and biochemical parameters were monitored before and after tracer administration. Results: Cyclotron-produced 99mTc-NaTcO4 showed organ and whole-body distributions identical to those of conventional 99mTc-NaTcO4 and was well tolerated. All images led to a clear final diagnosis. The fact that the number of counts in the higher-energy window was significantly higher for cyclotron-produced 99mTc-NaTcO4 did not influence image quality in the standard-energy window. Image definition in the standard-energy window with cyclotron-produced 99mTc was equivalent to that with generator-eluted 99mTc and had no particular features allowing discrimination between the 99mTc production methods. Conclusion: The systemic distribution, clinical safety, and imaging efficacy of cyclotron-produced 99mTc-NaTcO4 in humans provide supporting evidence for the use of this tracer as an equivalent for generator-eluted 99mTc-NaTcO4 in routine clinical practice.

Radioisotopic Purity of Sodium Pertechnetate 99mTc Produced with a Medium-Energy Cyclotron: Implications for Internal Radiation Dose, Image Quality, and Release Specifications.

UNLABELLED: Cyclotron production of 99mTc is a promising route to supply 99mTc radiopharmaceuticals. Higher 99mTc yields can be obtained with medium-energy cyclotrons in comparison to those dedicated to PET isotope production. To take advantage of this capability, evaluation of the radioisotopic purity of 99mTc produced at medium energy (20-24 MeV) and its impact on image quality and dosimetry was required. METHODS: Thick 100Mo (99.03% and 99.815%) targets were irradiated with incident energies of 20, 22, and 24 MeV for 2 or 6 h. The targets were processed to recover an effective thickness corresponding to approximately 5-MeV energy loss, and the resulting sodium pertechnetate 99mTc was assayed for chemical, radiochemical, and radionuclidic purity. Radioisotopic content in final formulation was quantified using γ-ray spectrometry. The internal radiation dose for 99mTc-pertechnetate was calculated on the basis of experimentally measured values and biokinetic data in humans. Planar and SPECT imaging were performed using thin capillary and water-filled Jaszczak phantoms. RESULTS: Extracted sodium pertechnetate 99mTc met all provisional quality standards. The formulated solution for injection had a pH of 5.0-5.5, contained greater than 98% of radioactivity in the form of pertechnetate ion, and was stable for at least 24 h after formulation. Radioisotopic purity of 99mTc produced with 99.03% enriched 100Mo was greater than 99.0% decay corrected to the end of bombardment (EOB). The radioisotopic purity of 99mTc produced with 99.815% enriched 100Mo was 99.98% or greater (decay corrected to the EOB). The estimated dose increase relative to 99mTc without any radionuclidic impurities was below 10% for sodium pertechnetate 99mTc produced from 99.03% 100Mo if injected up to 6 h after the EOB. For 99.815% 100Mo, the increase in effective dose was less than 2% at 6 h after the EOB and less than 4% at 15 h after the EOB when the target was irradiated at an incident energy of 24 MeV. Image spatial resolution and contrast with cyclotron-produced 99mTc were equivalent to those obtained with 99mTc eluted from a conventional generator. CONCLUSION: Clinical-grade sodium pertechnetate 99mTc was produced with a cyclotron at medium energies. Quality control procedures and release specifications were drafted as part of a clinical trial application that received approval from Health Canada. The results of this work are intended to contribute to establishing a regulatory framework for using cyclotron-produced 99mTc in routine clinical practice.

Assessment of inflammation in large arteries with 18F-FDG-PET in elderly.

This paper presents repeated measurements of atherosclerosis using bimodality positron emission tomography and computed tomography (PET/CT) with 18F-fluorodeoxyglucose (18F-FDG) to assess its uptake in aorta, iliac and femoral arteries in three groups of elderly subjects classified as normals (N), hypercholesterolemics (H) and with stable angina (A) in a 12 months follow-up (T0 to T12). The subjects in group H were taking rosuvastatin (20mg/d) for 12 months before the second scan. The calcifications in the arteries were determined by CT imaging and the artery PET images were analyzed slice by slice. The standard uptake values (SUVs) for 18F-FDG uptake were classified in two main groups: calcified and non-calcified arteries and each main group comprises six sub-groups for the three subject groups N, H and A, and for the two measurements 12 months apart. Although the calcifications were present at some portions of the arteries in all subjects (23%, 36% and 44% of calcified sites to total sites analyzed, respectively, in groups N, H and A), the results show the most noticeable SUV changes after 12 months was in group N of non-calcified arteries. In the three groups, the calcified arteries showed no significant differences between T0 and T12 while significant differences were observed for the non-calcified arteries. However, there were no significant changes at T12 between groups N and H following rosuvastatin intake in group H. In conclusion, the quantitative analysis with 18F-FDG-PET/CT could be efficient in the localization of the inflammation and evaluation of its progression in atherosclerosis instead of global evaluations with systemic inflammation biomarkers.

Image-derived input function in dynamic human PET/CT: methodology and validation with 11C-acetate and 18F-fluorothioheptadecanoic acid in muscle and 18F-fluorodeoxyglucose in brain.

PURPOSE: Despite current advances in PET/CT systems, blood sampling still remains the standard method to obtain the radiotracer input function for tracer kinetic modelling. The purpose of this study was to validate the use of image-derived input functions (IDIF) of the carotid and femoral arteries to measure the arterial input function (AIF) in PET imaging. The data were obtained from two different research studies, one using (18)F-FDG for brain imaging and the other using (11)C-acetate and (18)F-fluoro-6-thioheptadecanoic acid ((18)F-FTHA) in femoral muscles. METHODS: The method was validated with two phantom systems. First, a static phantom consisting of syringes of different diameters containing radioactivity was used to determine the recovery coefficient (RC) and spill-in factors. Second, a dynamic phantom built to model bolus injection and clearance of tracers was used to establish the correlation between blood sampling, AIF and IDIF. The RC was then applied to the femoral artery data from PET imaging studies with (11)C-acetate and (18)F-FTHA and to carotid artery data from brain imaging with (18)F-FDG. These IDIF data were then compared to actual AIFs from patients. RESULTS: With (11)C-acetate, the perfusion index in the femoral muscle was 0.34+/-0.18 min(-1) when estimated from the actual time-activity blood curve, 0.29+/-0.15 min(-1) when estimated from the corrected IDIF, and 0.66+/-0.41 min(-1) when the IDIF data were not corrected for RC. A one-way repeated measures (ANOVA) and Tukey's test showed a statistically significant difference for the IDIF not corrected for RC (p<0.0001). With (18)F-FTHA there was a strong correlation between Patlak slopes, the plasma to tissue transfer rate calculated using the true plasma radioactivity content and the corrected IDIF for the femoral muscles (vastus lateralis r=0.86, p=0.027; biceps femoris r=0.90, p=0.017). On the other hand, there was no correlation between the values derived using the AIF and those derived using the uncorrected IDIF. Finally, in the brain imaging study with (18)F-FDG, the cerebral metabolic rate of glucose (CMRglc) measured using the uncorrected IDIF was consistently overestimated. The CMRglc obtained using blood sampling was 13.1+/-3.9 mg/100 g per minute and 14.0+/-5.7 mg/100 g per minute using the corrected IDIF (r ( 2 )=0.90). CONCLUSION: Correctly obtained, carotid and femoral artery IDIFs can be used as a substitute for AIFs to perform tracer kinetic modelling in skeletal femoral muscles and brain analyses.

The impact of charging on low-energy electron beam lithography.

A major issue in low voltage lithography is surface charging, which results in beam deflection presented as uneven exposure between adjacent structures. In this study, charge-induced pattern distortions in low-voltage energy beam lithography (LVEBL) were investigated using a silicide direct-write electron beam lithography process. Two methodologies have been proposed to avert charging effects in LVEBL, namely, pattern randomizing and lithography using the crossover voltage. Experimental results demonstrated that these methods are effective in significantly reducing the problems associated with charging. They indicate that charging on a sample is a function of time interval and proximity between line structures. In addition, the optimum time and distance between exposures for no charge-induced pattern distortion were determined. By using the crossover voltage of the material for lithography, charging effect can be significantly minimized.