Non-contrast Magnetic Resonance Angiography in Deep Inferior Epigastric Perforator Flap Breast Reconstruction Planning

Rationale. Contrast-free MRA is a new concept for preoperative planning in breast reconstruction that combines the advantages of magnetic resonance imaging (no ionising radiation exposure), requires no potentially harmful contrast agent, and at the same time is highly accurate.

Aim. The aim of the study is to evaluate the efficacy and safety of the contrast-free magnetic resonance angiography (MRA) for perforators mapping in deep inferior epigastric perforator flap planning.

Study design. A retro- and prospective non-randomised non-blinded cohort multicenter study is conducted at the at the Department of Plastic Surgery (Sechenov University, Moscow), and at the Department of Reconstructive and Plastic Surgery (Lancet Clinic, Moscow), with all patients recruited through a single surgical team and all imaging performed at a single institution.

Study population. The investigators plan to conduct a pilot phase of this study using non-contrast MRA in 100 patients and to compare imaging modalities used in deep inferior epigastric perforator flap breast reconstruction (computed tomography angiography with contrast, n=35 and non-contrast magnetic resonance angiography, n=100). Power analysis determine that no less than 35 patients in control group in this study considering 80 % power with 95 % significance. The first group (experimental, MRA "-" group) will be included patients who refused computed tomography angiography (CTA) with contrast due to a number of reasons such as fear of contrast agent administration, history of iodine allergy, fear of radiation exposure, etc was underwent MRA without contrast, and the second group (control, CTA "+" group) will be involved iodine-tolerance patients with healthy kidneys who underwent preoperative planning with a standard technique - CTA with IV iodine-containing contrast injection.

Interventions. Participants in first group (experimental, MRA "-" group) underwent preoperative planning with a contrast-free magnetic resonance angiography (MRA) using an improved contrast-free MRA protocol. MRA was performed on a magnetic resonance machine Philips Ingenia 1.5 T (Royal Philips, Netherlands). High accuracy is achieved by the following actions: certain preprocedural patient's preparation and positioning, special pulse scanning sequence and perforators projection method.

Preprocedural patient's preparation. The investigators added to the MRA protocol a requirement of performing the study on an empty stomach (at least 8 hours of fasting) in order to reduce gastrointestinal activity.

Modified type of patient positioning. The investigators suggest performing MRA scanning in the prone position in order to both limit abdominal wall movement (related to breathing, peristalsis, and aortic pulsation) and to provide the closest location of the target area (vessels) to the coil.

Furthermore, this move allowed to introduce a further trick that facilitated the surgeons' work at the marking stage: the investigators placed the patient on her abdomen on a 3D printed special mesh made of ABS (Acrylonitrile Butadiene Styrene) (the patent for invention № RU 2023118155). The mesh served as a coordinate system, crosshairs of which accommodate capsules with liquid (A), which allows obtaining on the image not only vessels but also all points of capsules to form a basic standardized mesh, coinciding on the image and on the patient's body that is necessary for the most precise and convenient way of marking.

Due to the image directly used for preoperative marking, the protocol of the MRA scans description was not used.

Special pulse sequence and additional series of MRA scans. MRA is performed on a magnetic resonance machine Philips Ingenia 1.5 T in the T2 pulse sequence (to increase the accuracy of muscle localization assessment and the point of vessel immersion into the muscle) at TR and TE using a fat-suppression program with no IV contrast injection, which allows receiving information from moving objects (including blood within the vascular lumen). The investigators have incorporated an additional series of T2 scans without fat suppression with high resolution (thickness of slices from 0.8 to 1.2 mm) and visualization of the muscle fibers, which allows us to determine the site where the vessels pierce the muscle, intramuscular course of the perforating vessels, and the topography of the area of interest with accurate determination of the perforating vessel relative to the anatomical landmarks.

Following scanning, the images were analysed by a plastic surgeon in the OsiriX 10.0 program. The main benefit of the images was extracted by creating multiplanar reconstructions (MPR) in Maximum Intensity Processing (MIP) mode. This mode allows the evaluation of the vessels in length, their lumen diameters and the study of their correlations and distances from each other for the purpose of target vessel selection.The MRA images required simultaneous evaluation in two planes: frontal and sagittal or frontal and axial. This allowed to the investigators to evaluate the localize the point of vessel immersion into the muscle, the extent and direction of the vessel in the muscle thickness and to localize the point of vessel penetration over the muscle with further direction of the vessel course and the point of communications between superficial and deep systems.

The second group participants (control, CTA "+"group) underwent the standard commonly used computed tomography angiography (CTA) IV (intravenous) iodine-containing contrast injection, and in the supine position. CTA was performed on a Toshiba Aquilion 64 CTA scan machine (Toshiba Medical Systems, Tokyo, Japan) according to the Research and Practical Center of Medical Radiology guidelines №12 from March 22, 2017.

Informed consent is obtained from each participant.

Main study parameters. The investigators plan to evaluate the results according to the following criteria: the concordance ratio, the overall operation time, the time of the pedicle cut, the length of the fascia incision, the intraoperative flap perfusion, the presence of early postoperative complications and their nature, the presence of emergent vascular revision surgery. In addition, the investigators plan to evaluate the following parameters: the flap ischemia time, the number of perforators included in the flap, the fact of superficial vein(s) inclusion in the flap, the length of the vascular pedicle.