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Technical Innovation |
1
Department of Diagnostic Imaging, Bristol Hospital, Brewster Rd., Bristol, CT
06010.
2
86 Windsor Rd., Kensington, CT 06037.
Received July 1, 1999;
accepted after revision September 16, 1999.
Address correspondence to D. G. Russell.
Introduction
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We estimate that approximately 10% of the breasts set up for stereotactic biopsy have compressed to potentially dangerously thin tissue depth. When we encountered this problem, we were often forced to cancel the procedure. If a preliminary examination revealed that a patient had a thin flaccid breast, we hesitated to attempt the procedure because of potential failure, patient distress, and significant unrecoverable costs.
Some methods avoid penetrating the back wall when an apparent negative stroke margin is present. One method is slowly advancing the needle into the target by hand rather than firing it. This technique often pushes the lesion away from the tip of the needle instead of passing the needle through the targeted area. Alternatively, the radiologist can also adjust the tip of the needle so that it is more proximal to the target. This adjustment may add an extra margin of several millimeters to the length of the negative stroke margin. The needle tip will then remain several millimeters away from the breast support after firing [1]. This maneuver can fail to center the lesion in the sample notch and may result in inadequate sampling.
Faced with the loss of approximately 10% of eligible patients and the cancellation of some patients when the compressed breast tissue depth did not support a safe biopsy, we sought a method allowing us to augment breast tissue depth. Ideally, this procedure could be activated during the early phase of the procedure setup, be easily and quickly applied, and result in a realistic increase in tissue depth.
When breast tissue is compressed, no change in tissue volume occurs. The
breast under compression has the configuration of a half cylinder. The formula
for the volume of half of a cylinder is as follows:
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If the radius of this half cylinder is reduced, the height or thickness must necessarily increase to maintain the same volume. Furthermore, because the volume formula specifies that the radius is squared, a small reduction in the radius results in a disproportionate increase in the height. If a breast under compression has a thickness of 4 cm with a radius of 10 cm, reducing the radius by 20% to 8 cm will increase the thickness by 56% to 6.25 cm. This principle is graphically illustrated to scale in Figure 1.
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The breast bolster that we have developed controls the radius, or peripheral dispersion, of a compressed breast. This device is a compressible open-cell elongated plastic sponge (Fig. 2). The lateral margins of the rectangular portion are notched to enhance compressibility and increase flexibility.
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If the patient has a flaccid breast, the initial compression can show a limited tissue depth that may not permit a safe needle throw. An example is shown with a breast model filled with a pliable glazing compound (DAP `33'; DAP, Dayton, OH) and compressed to a thickness of 2.8 cm (Fig. 3). When limited tissue depth is encountered, the operator retracts the compression paddle and leaves an opening of several centimeters. The patient is instructed to roll away from the table opening, and the thin tab at the end of the bolster is placed through the opening in the table. When the patient rolls back, the weight of the patient secures the bolster, which hangs freely and is aligned between the compression plates.
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The operator then positions the breast in contact with the fixed compression plate. The movable compression plate is advanced to the point at which both plates make contact with the slotted lateral margins of the bolster. At this point, the bolster is pressed upward and inward so that it makes contact with and surrounds the entire periphery of the breast. Appropriate additional compression is then applied. The encompassing bolster, held in position by friction with the compression plates, entraps the breast and limits the peripheral dispersion of the breast tissue. This method effectively reduces the radius of the half cylinder and results in an increase in breast tissue thickness. The bolster thus applied is shown with the same breast model in Figure 4. The breast tissue depth has been increased to 4.3 cm.
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The device is entirely outside the imaging field and is applicable to all biopsy tables or platforms. The patient is generally unaware of the bolster. The principle is easy to comprehend, the device is simple, the application takes less than 5 min, and the increase in tissue depth is immediately apparent.
We have used the bolster on 16 patients in whom the breast thickness under initial compression was less than 38 mm, causing a danger of penetration of the back wall of the breast. In these patients, the initial range in breast thickness was 19.0-37.7 mm, averaging 28.27 mm. After application of the bolster, the breast thickness was increased to a range of 31.6 to 50.5 mm, averaging 38.69 mm. The overall increase of breast tissue depth was 36%.
The breast bolster will be most effective in reasonably large breasts that are flaccid and easily compress to a thin tissue depth. The bolster will not be effective when the breasts are small because a limited amount of tissue is available. It is usually not necessary to relocalize the targeted area in the imaging window because the biopsy site is not significantly shifted. An increase in radiographic technique is sometimes needed to compensate for a significant increase in breast thickness.
When the bolster is firmly in place completely surrounding the breast, the absorbent bolster will trap any blood that exudes from the needle opening and runs down between the compression plates. Avoiding contamination of the equipment below the breast is an additional valuable benefit of the bolster.
Acknowledgments
We thank Lori Smarkus, Diane Hare, Ella Scoville, and Eva Albright for
their invaluable help and dedication leading to the development, application,
and use of the breast bolster.
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  R. J. Jackman and F. A. Marzoni Jr. Stereotactic Histologic Biopsy with Patients Prone: Technical Feasibility in 98% of Mammographically Detected Lesions Am. J. Roentgenol., March 1, 2003; 180(3): 785 - 794. [Abstract] [Full Text] [PDF]
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