Related Experiment Video
Updated: Apr 8, 2026
Clinical Imaging of Microwave Mammography
Published on: November 14, 2025
Effect of menstrual cycle phase on background parenchymal uptake at molecular breast imaging
Carrie B Hruska1, Amy Lynn Conners1, Celine M Vachon2
1Department of Radiology, Mayo Clinic, 200 First St SW, Rochester, MN 55905.
Rationale And Objectives:
The level of Tc-99m sestamibi uptake within normal fibroglandular tissue on molecular breast imaging (MBI), termed background parenchymal uptake (BPU), has been anecdotally observed to fluctuate with menstrual cycle. Our objective was to assess the impact of menstrual cycle phase on BPU appearance.
Materials And Methods:
Premenopausal volunteers who reported regular menstrual cycles and no exogenous hormone use were recruited to undergo serial MBI examinations during the follicular and luteal phase. A study radiologist, blinded to cycle phase, categorized BPU as photopenic, minimal mild, moderate, or marked. Change in BPU with cycle phase was determined, as well as correlations of BPU with mammographic density and hormone levels.
Results:
In 42 analyzable participants, high BPU (moderate or marked) was observed more often in luteal phase compared to follicular (P = .016). BPU did not change with phase in 30 of 42 participants (71%) and increased in the luteal phase compared to follicular in 12 (29%). High BPU was more frequent in dense breasts compared to nondense breasts at both the luteal (58% [15 of 26] vs. 13% [2 of 16], P = .004) and follicular phases (35% [9 of 26] vs. 6% [1 of 16], P = .061). Spearman correlation coefficients did not show any correlation of BPU with hormone levels measured at either cycle phase and suggested a weak correlation between change in BPU and changes in estrone and estradiol between phases.
Conclusions:
We observed variable effects of menstrual cycle on BPU among our cohort of premenopausal women; however, when high BPU was observed, it was most frequently seen during the luteal phase compared to follicular phase and in women with dense breasts compared to nondense breasts.
Insights
Background parenchymal uptake (BPU) on molecular breast imaging (MBI) varied with the menstrual cycle in premenopausal women. High BPU was more common in the luteal phase and in women with dense breasts.
Area of Science:
- Radiology and Imaging Science
- Nuclear Medicine
- Breast Imaging Technology
Background:
- Background parenchymal uptake (BPU) on molecular breast imaging (MBI) refers to Tc-99m sestamibi uptake in normal fibroglandular tissue.
- Anecdotal observations suggest BPU may fluctuate with the menstrual cycle in premenopausal women.
Purpose of the Study:
- To investigate the impact of menstrual cycle phase on background parenchymal uptake (BPU) appearance during molecular breast imaging (MBI).
Main Methods:
- Serial MBI examinations were performed on premenopausal volunteers during follicular and luteal phases.
- A radiologist, blinded to cycle phase, categorized BPU (photopenic, minimal, mild, moderate, marked).
- Correlations with mammographic density and hormone levels were assessed.
Main Results:
- High BPU (moderate or marked) was significantly more frequent in the luteal phase compared to the follicular phase (P = .016).
- 71% of participants showed no change in BPU between phases; 29% had increased BPU in the luteal phase.
- High BPU was more frequent in dense breasts than nondense breasts in both luteal and follicular phases.
Conclusions:
- Menstrual cycle phase has variable effects on BPU in premenopausal women.
- When present, high BPU is most frequently observed during the luteal phase.
- Dense breast tissue is associated with higher BPU, irrespective of menstrual cycle phase.
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