Staging of breast cancer in the breast and regional lymph nodes using contrast-enhanced photon-counting detector CT: accuracy and potential impact on patient management

Abstract

Objectives: To describe the feasibility and evaluate the performance of multiphasic photon-counting detector (PCD) CT for detecting breast cancer and nodal metastases with correlative dynamic breast MRI and digital mammography as the reference standard.

Methods: Adult females with biopsy-proven breast cancer undergoing staging breast MRI were prospectively recruited to undergo a multiphasic PCD-CT using a 3-phase protocol: a non-contrast ultra-high-resolution (UHR) scan and 2 intravenous contrast-enhanced scans with 50 and 180 s delay. Three breast radiologists compared CT characteristics of the index malignancy, regional lymphadenopathy, and extramammary findings to MRI.

Results: Thirteen patients underwent both an MRI and PCD-CT (mean age: 53 years, range: 36-75 years). Eleven of thirteen cases demonstrated suspicious mass or non-mass enhancement on PCD-CT when compared to MRI. All cases with metastatic lymphadenopathy (3/3 cases) demonstrated early avid enhancement similar to the index malignancy. All cases with multifocal or multicentric disease on MRI were also identified on PCD-CT (3/3 cases), including a 4 mm suspicious satellite lesion. Four of five patients with residual suspicious post-biopsy calcifications on mammograms were detected on the UHR PCD-CT scan. Owing to increased field-of-view at PCD-CT, a 5 mm thoracic vertebral metastasis was identified at PCD-CT and not with the breast MRI.

Conclusions: A 3-phase PCD-CT scan protocol shows initial promising results in characterizing breast cancer and regional lymphadenopathy similar to MRI and detects microcalcifications in 80% of cases.

Advances in knowledge: UHR and spectral capabilities of PCD-CT may allow for comprehensive characterization of breast cancer and may represent an alternative to breast MRI in select cases.

Keywords: breast imaging; multi-energy CT; photon-counting CT; ultrahigh-resolution CT.

Figure 1.

A 35-year-old patient with an index malignancy and a satellite lesion in the right breast detected on PCD-CT and MRI. Contrast enhanced PCD-CT with a 3.2 cm irregular spiculated mass containing biopsy clip in the right upper outer far posterior depth breast (A, white arrow). A tiny 4 mm suspicious focus inferior to the index malignancy is visualized on contrast enhanced PCD-CT (B, yellow arrow). MRI T1 with contrast demonstrates an enhancing spiculated irregular mass in the right upper outer, far posterior depth breast (C, white arrow). MRI T1 with contrast also demonstrating an enhancing 4 mm focus inferior to the breast mass (D, yellow arrow). Abbreviation: PCD = photon-counting detector.

Figure 2.

The patient shown on the previous image with the primary breast mass, small satellite focus and a vertebral metastasis. The 4 mm enhancing focus, located 6 mm inferior to the known index malignancy in the right breast is nicely depicted on contrast enhanced PCD-CT iodine axial and sagittal images inferior to the index malignancy (A and B, yellow arrow). Small subcentimeter lucent lesion in the T10 vertebral body only seen on contrast enhanced PCD-CT (C, open arrow). This thoracic lesion was later biopsied positive for breast metastasis. Comparison MRI post contrast subtraction images again demonstrate this small enhancing right breast focus (D, yellow arrow). MRI MIP sagittal image with small enhancing focus inferior to the right breast mass (E, yellow arrow). Retrospectively the thoracic vertebral lesion is not visualized on MRI scout images and was not included within the field of view on axial MRI images (F). Abbreviation: PCD = photon-counting detector.

Figure 3.

A 55-year-old patient with metastatic lymphadenopathy. Contrast enhanced PCD-CT with iodine axial, sagittal, and coronal images showing an irregular left level 1 axillary node enhancing more avidly when compared to adjacent lymph nodes (A–C, yellow arrow). Contrast-enhanced PCD-CT with iodine map MIP images in axial, sagittal, and coronal planes demonstrating both the known left breast malignancy (D–F, white arrow) and adjacent enhancing biopsy proven left axillary metastasis (yellow arrow) which enhances significantly more than the adjacent normal nodes. Abbreviation: PCD = photon-counting detector.