The purpose of this study was to document the extent of adhesion of 99mTc-sestamibi to syringes in patient procedures, determine factors that influence the degree of adhesion, and evaluate alternatives to our current practice that would either result in a more reproducible degree of adhesion or, ideally, eliminate adhesion. Methods The extent of adhesion was documented in 216 patient procedures and evaluated in detail in an additional 73 patient procedures. We evaluated the nature of the adhesion and its possible causes, including the location of adhesion in injection sets, the effect of syringe type, and the effect of prerinsing of syringes with various solutions of nonradiolabeled sestamibi and 99mTc-sestamibi. The extent of adhesion was reevaluated in 50 procedures performed using the syringe type that demonstrated the lowest adhesion rate. Results The degree of adhesion of 99mTc-sestamibi to the injection set was found to be 20.1% ± 8.0%, with a range (10th–90th percentiles) of 9%–31%. The primary cause of adhesion appeared to be the lubricant used inside the syringe barrel. Evaluation of 6 different syringe types identified a brand with a lower adhesion rate. Reevaluation in patient procedures using this brand showed a 5.2% ± 2.5% degree of adhesion, with a range (10th–90th percentiles) of 2.5%–7.7%. Conclusion Selection of the appropriate type of syringe can significantly reduce the magnitude and variability of residual 99mTc-sestamibi activity. With more reproducible residual activities, we have been able to achieve an approximately 20% reduction in the dispensed dose of 99mTc-sestamibi used in clinical procedures and a more consistent injected dose with less interpatient variation. The frequent changes in syringe design by manufacturers require that a quality control program for monitoring of residual activity be incorporated into clinical practice. This program has allowed us to maintain image quality and achieve more consistent injected patient doses in clinical procedures that use 99mTc-sestamibi.

The purpose of this study was to evaluate the impact of changes to a patient's prandial status, metabolic status (rest vs. exercise), and peripheral blood flow (via caffeine or warming) on the uptake of 99m Tc-sestamibi in breast tissue. Methods: A total of 154 subjects participated in 1 of 4 study groups that evaluated the effects of 4 types of intervention on the uptake of 99m Tc-sestamibi in breast tissue (effect of fasting, light exercise, caffeine, and peripheral warming). Molecular breast imaging was performed before and after each intervention. Count density was assessed in counts/cm 2 /MBq from the mediolateral oblique view in all studies. Results: Uptake of 99m Tc-sestamibi in breast tissue increased by approximately 25% from 6.6 counts/cm 2 /MBq in the fed state to 8.3 counts/cm 2 /MBq with fasting. Peripheral warming also resulted in an approximately 20% increase in count density from 9.1 to 10.9 counts/cm 2 /MBq. Conversely, exercise caused a 35% drop in count density relative to the resting state. Uptake did not seem to be influenced by caffeine and did not correlate with a patient's height, weight, or breast thickness. There was only a weak correlation between breast activity and body surface area. Conclusion: The combined effects of fasting and warming resulted in an approximately 50% increased uptake of 99m Tc-sestamibi in breast tissue relative to that observed in a reference group to whom no preparatory instructions had been given. Optimal patient preparation before administration of 99m Tc-sestamibi should permit a corresponding reduction in either acquisition time or required dose of 99m Tc-sestamibi.Key Words: 99m Tc-sestamibi; breast; fasting; exercise J Nucl Med Technol 2015; 43:13-20 DOI: 10.2967/jnmt.114.150128 Nucl ear medicine breast imaging techniques, including both single-photon and positron emission technologies, have been evaluated for several diagnostic indications because of their ability to detect mammographically occult disease (1-5). We have reported on the use of molecular breast imaging (MBI), performed with 99m Tc-sestamibi and a dual-head cadmium zinc telluride g camera, for screening of women with mammographically dense breasts (6,7). In the most recent trial (7), supplemental screening with MBI in women with dense breasts improved the breast cancer detection rate from 3.2 per 1,000 with mammography alone to 12 per 1,000 with the combination of MBI and mammography (P , 0.001).A key consideration in the acceptance of MBI for screening use is the need to reduce the associated radiation dose of this procedure. Early studies with nuclear breast imaging technologies, including scintimammography (8) and breast-specific g imaging (1), used administered activities of 99m Tc-sestamibi in the range of 925-1,110 MBq (25-30 mCi), which result in effective doses to the body of 6.8-8.1 mSv (9) and were considered too high for screening (10). By comparison, the effective dose from digital mammography is 0.5 mSv and that from current mammography combined with digital breast tomosy...

BackgroundBackground parenchymal uptake (BPU), which refers to the level of Tc-99m sestamibi uptake within normal fibroglandular tissue on molecular breast imaging (MBI), has been identified as a breast cancer risk factor, independent of mammographic density. Prior analyses have used subjective categories to describe BPU. We evaluate a new quantitative method for assessing BPU by testing its reproducibility, comparing quantitative results with previously established subjective BPU categories, and determining the association of quantitative BPU with breast cancer risk.MethodsTwo nonradiologist operators independently performed region-of-interest analysis on MBI images viewed in conjunction with corresponding digital mammograms. Quantitative BPU was defined as a unitless ratio of the average pixel intensity (counts/pixel) within the fibroglandular tissue versus the average pixel intensity in fat. Operator agreement and the correlation of quantitative BPU measures with subjective BPU categories assessed by expert radiologists were determined. Percent density on mammograms was estimated using Cumulus. The association of quantitative BPU with breast cancer (per one unit BPU) was examined within an established case-control study of 62 incident breast cancer cases and 177 matched controls.ResultsQuantitative BPU ranged from 0.4 to 3.2 across all subjects and was on average higher in cases compared to controls (1.4 versus 1.2, p < 0.007 for both operators). Quantitative BPU was strongly correlated with subjective BPU categories (Spearman’s r = 0.59 to 0.69, p < 0.0001, for each paired combination of two operators and two radiologists). Interoperator and intraoperator agreement in the quantitative BPU measure, assessed by intraclass correlation, was 0.92 and 0.98, respectively. Quantitative BPU measures showed either no correlation or weak negative correlation with mammographic percent density. In a model adjusted for body mass index and percent density, higher quantitative BPU was associated with increased risk of breast cancer for both operators (OR = 4.0, 95% confidence interval (CI) 1.6–10.1, and 2.4, 95% CI 1.2–4.7).ConclusionQuantitative measurement of BPU, defined as the ratio of average counts in fibroglandular tissue relative to that in fat, can be reliably performed by nonradiologist operators with a simple region-of-interest analysis tool. Similar to results obtained with subjective BPU categories, quantitative BPU is a functional imaging biomarker of breast cancer risk, independent of mammographic density and hormonal factors.Electronic supplementary materialThe online version of this article (10.1186/s13058-018-0973-3) contains supplementary material, which is available to authorized users.

Background: Breast lesions closer than 2 cm to the chest wall are difficult to position in the field of view of dedicated breast PET (db-PET) systems. This inability to detect such lesions is a significant limitation of these systems. The primary objective of this study was to determine if modifications to the design of the imaging table and detector used for a db-PET system would enable improved visualization of breast tissue close to the chest wall. All studies were performed on a commercially available db-PET system (Mammi-PET). A central square section of the imaging table, containing the standard 180-mm circular aperture, was modified such that it could be removed and replaced by thinner sections with a larger aperture. Additional changes were made to the cover plate of the detector array and the patient mattress. A total of 60 patients were studied. After administration of F-18 FDG, 30 patients were imaged with a 220-mm-diameter aperture and the standard aperture, and 30 patients with a 200-mm aperture and the standard aperture. On all scans, the length of breast tissue in the field of view was measured as the greatest extent of tissue from the nipple back to the posterior edge of the breast. Image quality and patient comfort were recorded. Results: Averaged over both breasts, relative to the standard aperture, the increase in breast length was 12.5 + 7.7 mm with the 220-mm aperture, and 12.3 + 6.5 mm with the 200-mm aperture (p < 0.05 for both apertures). In~5% of cases, the larger apertures resulted in some degradation in image quality due to closer proximity to cardiac/hepatic activity. In 10-20% of cases, movement of the breast tissue was observed as the detector ring was moved to scan the anterior region of the breast. The patient survey indicated no significant difference in the comfort level between the standard aperture and either of the prototype apertures. Conclusions: Modifications to the image table and system resulted in a significant gain in the volume of breast tissue that could be imaged on the db-PET system and should allow better visualization of lesions close to the chest wall.

No abstract