Measuring breast volume in hypertrophy: laser scanning or water displacement?

Background: The accurate determination of intact breast volume facilitates preoperative planning for a range of plastic surgical breast procedures. In women with breast hypertrophy, volumetric assessment assists in planning the amount of tissue to be removed during breast reduction surgery to achieve breast symmetry. Further, in jurisdictions where restrictive surgical guidelines exist, measurement of intact breast volume is essential in order to justify breast reduction surgery. Not all practitioners have access to magnetic resonance imaging (MRI) or three dimensional (3D) laser scanning facilities, so the purpose of this study was to determine whether water displacement of the intact breast is an effective substitute method of measurement in women with breast hypertrophy. Methods: A prospective cohort study was undertaken to measure breast volume using water displacement and 3D laser scanning in breast hypertrophy patients. The volume of a total of 322 breasts were determined using both measurement techniques; 194 preoperatively and 128 at 12 months following breast reduction surgery. Pearson correlations, linear regression and Bland-Altman analyses were used to compare the methods of breast volume assessment. Results: The mean breast volume according to 3D laser scan was 1440 millilitres (SD = 588 millilitres) and for water displacement was 1419 millilitres (SD = 811 millilitres). There was a strong linear association between breast volumes as measured using water displacement and 3D laser scanning using a Pearson correlation (r = 0.89, p < 0.001). However, using the Bland-Altman analysis, the two methods were found not to be in agreement, with water displacement values consistently larger than 3D scan values. Br


Introduction
Breast hypertrophy is for some women a cause of considerable physical and psychosocial impairment, and adversely affects quality of life.
Physical symptoms may include: chronic back, neck, shoulder and breast pain; skin rashes; headaches; shoulder grooving from the constant pressure of bra straps; a reduced capacity for carrying out daily activities and exercise; and numbness or tingling in hands/fingers. 1 Psychosocially, women with breast hypertrophy often display low self-esteem and poor body image, reduced psychosexual function, anxiety and depression. 2 Breast reduction surgery is widely known to be the most effective treatment for breast hypertrophy. 3 Surgery provides almost immediate symptomatic relief in most cases, and considerably improves the health-related quality of life and wellbeing in women suffering from the functional symptoms of breast hypertrophy. 4,5 Despite these proven benefits, an increase in the prevalence of breast hypertrophy, and hence in demand for breast reductions, has led to restrictions being placed on surgery by healthcare funders and third-party providers in many jurisdictions. Arbitrary restrictions on either the minimum amount of breast tissue required to be removed at surgery or a body mass index cut-off point have been introduced in many institutions and countries worldwide. 6 Measurement of breast volume plays an important role in breast reduction, reconstruction, developmental asymmetry and augmentation. In women with breast hypertrophy it is important for preoperative planning, in intraoperative decisionmaking regarding the amount of tissue to be taken from each breast to achieve symmetry, and where removal of a minimum amount of breast tissue is required to justify surgery. [7][8][9][10][11] Accurate estimation of breast volume and predicted tissue resection weight also promotes improved counsel to the patient and provides a valuable guide to training surgeons.
A variety of techniques are described in the literature to meet the need for accurate and objective measurement of breast volumes in the clinical setting including magnetic resonance imaging (MRI), mammography, plaster casting, Grossman-Roudner plastic cups, water displacement, anthropometric measurement and 3D surface imaging. [12][13][14][15][16][17][18][19][20][21] In a situation where a woman is undergoing post-mastectomy breast reconstruction, the gold standard for measuring the breast tissue volume for reconstruction is the Archimedes method of water displacement of the mastectomy specimen. 22 When measuring breast tissue volume in the intact state, such as in candidates for breast reduction surgery, MRI is reported as being the most accurate. 23 However, MRI is expensive and not always accessible. Three-dimensional laser scanning has also been demonstrated as a valid method of breast volume measurement, 16,17,22 but some centres lack access to this technology. Water displacement of the intact breast has been used in some centres since 1970, but has not previously been validated against more recent methods. 24 The purpose of this study is to assess the validity of measuring breast tissue volume using water displacement of the intact breast and to compare this measurement technique with 3D laser scan measurement.

Patient selection and measurement
A prospective cohort study was performed at Flinders Medical Centre in Adelaide, Australia.    Linear regression analysis confirmed a degree of proportional bias, meaning that one method gave values that were consistently higher or lower than those of the other method. In this instance, the breast volumes obtained from water displacement tended to be larger than those from the 3D scanner, and the difference between the two methods increased as the mean volume increased. This is evident from the plot where there was a discernable trend for more points to be above the line of mean difference in volume as the mean volume increased (Figure 4).    16 and preoperatively for unilateral reduction or augmentation for asymmetry. 33,34 Three-dimensional scanning technology has also been employed in other areas of plastic surgery including facial symmetrisation 35,36 and for the preoperative planning of nasal surgery. 37 The Cyberware WBX laser scanner and CySlice software used in this study have previously been validated against water displacement in measuring mastectomy specimens with a strong correlation demonstrated. 22 The same 3D laser scanner and protocol were also found to be strongly equivalent to non-contrast MRI for the assessment of breast volume. 16 The most accurate metric of true breast tissue volume is water displacement of mastectomy specimens, however, this is not applicable other than in post-mastectomy reconstruction scenarios. 20,22,38 Additionally, volume measurement of the intact breast has proven to be more variable due to the challenge of correctly differentiating breast tissue from the chest wall. by definition a flat cut plane at the water level.
The manual positioning of landmarks prior to 3D scanning using palpation to accurately identify the margins of the breast base, and relying on these points later in the scan image, helps to control for potential location error.
Key advantages of this study are its large sample size and that the data was collected prospectively. One limitation of this study is that not all participants had breast volume measurements taken at both the preoperative and 12 months postoperative times. It was decided that additional measurement was too onerous for some patients given the commitments associated with voluntarily participating in the study. As a result, both of these techniques were performed on discrete subsets of patients at each time point.
Future extensions to this work would be to incorporate the results of comprehensive anthropometric body shape assessment that was also conducted pre-and postoperatively as part of this study. Analysis of patient-reported outcome measures data collected during the study would also further enhance our understanding of surgery outcomes and of the overall satisfaction in women with reduction in breast volume through surgery.

Conclusion
This study found a strong linear association between the measurement of breast volumes using water displacement and 3D laser scanning techniques in women with breast hypertrophy but the methods have low agreement on actual values. While water displacement may be more convenient and accessible in clinical practice, 3D scanning remains preferable as it has been proven to be a more accurate and reliable technique for the determination of intact breast volume.