Purpose

When magnetic resonance imaging (MRI) and computed tomography (CT) are planned, the target organs are included in the scan area. Sometimes, when these studies are performed, not only target lesions but also unexpected lesions are detected. Liver CT was routinely performed before liver MRI at Osaka Red Cross Hospital. We experienced that a mammary lesion was unexpectedly found during liver MRI, rather than during liver CT. This reason could be the different arm positions and respiration styles adopted during MRI and CT. A raised arm position was used during liver CT, because this position enables a decreased exposure dose [1] and increased image quality [2]. In contrast, the patients’ arms were at the sides of the body during liver MRI. This study aimed to evaluate whether the incidental finding of the mammary lesions was influenced by the patient’s arm position and respiration style during liver MRI and CT.

Methods

The study included 473 consecutive female patients who underwent liver MRI with gadolinium contrast medium, and 2759 consecutive female patients who underwent liver CT with iodinated contrast medium, between May 2015 and April 2016. These studies were performed using a 1.5-T MRI unit and a 16- multidetector row CT. All patients who underwent liver MRI underwent liver CT. The detected mammary lesions were retrospectively extracted from diagnostic reports. Furthermore, the proportion of the breast included in the scan, for cases of incidental findings in the scan range, was evaluated using clinical images, with “bottom” defined as the edge of the foot direction of the breast and “top” as the edge of the head direction of the breast. (Fig. 1) We evaluated the proportion of the breast from “bottom” to the upper slice of liver MRI and CT.

Result

No mammary lesions were found during liver CT. Seven mammary lesions were found during liver MRI. On the MRI images, the proportion of the breast within the scan range was as follows: whole breast for four cases, from bottom to between the nipple and the top for two cases, and from the bottom to the nipple for one case

Discussion

The cases in which the mammary lesion was found during liver MRI but not during liver CT were influenced by the arm positon and respiration style. The raised arm position was useful during liver CT [1, 2]. However, the raised arm position was disadvantageous during liver MRI because the patient could become tired during the long examination term. Undue stress could cause the patient to move, leading to a poor study. In liver MRI, the arm position can be freely changed (i.e., the arms are positioned at the sides of the body) as long as there are no artifacts. When the arms were at the sides of the body, the patient could be more relaxed, with reduced mental stress during the examination; therefore, we believed that the arm position at the sides of the body was optimal. We considered that the reason for the detection of mammary lesions during MRI instead of CT was the arm position. When the arms were raised up over the head, the pectoralis muscle moved upward [3], so that the breast was outside of the scanned area. Furthermore, during the scan, the respiration style during liver MRI differed from that during liver CT. The liver position was changed by the movement of the diaphragm because of respiration [4]. When the exhalation style was used during liver MRI, the diaphragm and liver were moved up toward the head; therefore, we considered that the breast was more likely to be moved into the scan area. If the mammary lesion was detected earlier, treatment could be performed earlier and the quality of life would be influenced. Therefore, the finding of mammary lesion during liver studies was useful information. Therefore, with all other things being equal, if the same liver MRI were to be performed, the positioning of the arms at the sides of the body and the exhalation style would be preferable because of the higher probability of detecting an unexpected mammary lesions during liver MRI compared with that using the raised arm position and inhalation style.

Conclusion

The incidental detection of mammary lesions was influenced by the patient’s arm position and breathing style during liver MRI and CT. Unexpected mammary lesions could be detected when the arms were positioned at the sides of the body and the exhalation style was used during liver MRI.

Acknowledgements

No acknowledgement found.

References

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