Gadobutrol

The MRI protocol was optimized following international recommendations and current practice in breast MRI [5 (link),13 (link)]. Images were acquired in axial plane and the patient in a prone position [14 (link)] using either 1.5  T or 3.0 T scanners (Magnetom Avanto/Aera; Verio/Skyra) and dedicated breast array coils (all hardware: Siemens Healthineers, Erlangen, Germany). Protocols included dynamic contrast-enhanced T1-weighted scans, a T2-weighted fat-saturated scan and diffusion-weighted imaging. Protocol parameters are provided in Table 2. The contrast media (0.1  mmol/kg body weight gadobutrol, Bayer Schering Pharma, Berlin, Germany) was injected into an antecubital vein after the first dynamic acquisition [14 (link)] with a flow of 2.0  mL/sec, followed by a 20 mL saline flush. After a 30-second delay, the remaining five dynamic acquisitions were scanned under identical conditions.

All examinations were acquired with a 1.5 T scanner (Siemens Magnetom Sola, Erlangen, Germany) with a multi-array head-coil according to the examination protocol detailed in Table 2. Diffusion-weighted sequence was performed with 13 different b-values (0, 10, 20, 30, 50, 80, 100, 300, 400, 500, 800, 1000, 2000 s/mm²). Dynamic contrast-enhanced sequence was obtained with 36 consecutive scans with a temporal resolution of 6 s after intravenous contrast agent (CA) injection (Gadobutrol; Gadovist, Bayer Schering Pharma, Leverkusen, Germany) at a dose of 0.1 mL/kg body weight and flow rate of 3 mL/s followed by a flush of 20 mL saline solution at the same rate. CA was administered at the start of the first post-contrast scan with the use of an automatic injection system. No adverse reactions were reported.
Informed consent was obtained from all patients involved in the study. The study was conducted according to the guidelines of the Declaration of Helsinki and approved by the Institutional Independent Ethics Committee for Scientific Research (NKBBN/26/2021).

DCE-MR imaging consisted of six fat-suppressed series, one prior to the injection of 0.1 mmol/kg gadolinium-containing contrast agent (Gadobutrol, Bayer Schering Pharma AG, Berlin, Germany), and five series following injection. The protocol consisted of 3D T1-weighted gradient echo sequences for setup 1 (TR/TE 4.3/2.1ms, flip angle 15°, field-of-view (FOV) 350 x 160 x 160 mm³, acquired resolution 1.0 x 1.0 x 1.0 mm³, scan duration 108s) and for setup 2 (TR/TE 5.8/2.5ms, flip angle 15°, FOV 350 x 160 x 160 mm³, acquired resolution 0.7 x 0.7 x 0.7 mm³, scan duration 91s, SENSE acceleration 4 x 2). A radiologist experienced with breast MRI considered all tumors separately using a scoring form based on the standardized American College of Radiology Breast Imaging Reporting and Data System (ACR BI-RADS)-MRI lexicon [27 ]. Tumor size was assessed as the largest tumor extent over three orthogonal directions. For the multivariate model, missing value was denoted as the mean value.

A challenge for scanning polymer vessel casts with MRI is that the solid polymers do not yield an MRI detectable signal. This could be overcome by embedding the cast in a gadolinium-containing gel. The cast (female, 78 years) was placed in a 14% gelatine tap water gel. To increase the attainable signal-to-noise ratio per unit scan time for high resolution imaging, the T₁ of the gel was shortened by using gadolinium-containing contrast-agent (2.8 × 10⁻³ mL contrast-agent/mL water; Gadobutrol, Gadovist 1.0 mmol/mL, Bayer Schering Pharma, Newbury, UK). The complete cast was placed in a custom-made PVC container to which the gadolinium-gelatine solution was added, while avoiding the formation of air bubbles by slowly pouring the gadolinium-gelatine solution. The container was left overnight at 5 degrees Celsius for the gelatine to solidify.