Imaging: Examination Technique

Fig. 7.1

MR imaging after MtF sex reassignment surgery. The neovagina and the rectum are distended with gel. An inflatable tutor is inserted in the neovagina. (a, b) Sagittal and axial T2-weighted images. (c, d) Sagittal and axial T1-weighted images with fat suppression obtained after gadolinium contrast administration

Perforator arteries are marked with an arrow at the point where they pierce the fascia, i.e., they pass either through or in between the deep tissues (mostly muscle) to reach the skin and subcutaneous tissue. 3D rendering is then obtained to show the complete course of the pedicle from the perforator to the origin of the pedicle from the main vessels (Fig. 7.1b).

3D surface rendering of the flap is then obtained trimming the volume manually including muscles and cutaneous and subcutaneous tissue to show subcutaneous branching of the perforators (Fig. 7.1c). Manual clipping of the overlaying skin is often necessary as density is superior to subcutaneous fat. Arrows are positioned to mark the precise projection of the perforator’s origin on the skin with the use of a Cartesian coordinate system centered on a reference point. In the case of the ALT flap, the system is outlined on the axis of the anterior superior iliac spine and the lateral patella (Fig. 7.1d).

7.3.4 Reporting

Standard report includes description of the technique used and a qualitative judgment of the exam quality. Perforators are indexed with the Cartesian coordinate system centered on the reference point. Providing absolute diameter of perforators can be confounding, as diameter is very close to resolution limit. To visually differentiate the surgically relevant ones, perforators with caliber >1 mm can be marked with a different color. Color Doppler ultrasound is used to investigate the flow characteristics of the perforators. Besides evaluation of the vascularity, MDCT angiography allows a precise measure of the thickness of the subcutaneous fat layer, an information which is crucial to estimate the required dimensions of the flap used to manufacture the neopenis.

Fig. 7.2

MDCT angiography for preoperative planning of anterolateral thigh (ALT) flap for penile reconstruction. Left thigh. (a) Axial 5-mm MIP reconstruction shows a perforator (arrowhead) emerging from the vastus lateralis muscle. (b) 3D volume rendering (VR) reconstruction obtained to show the complete course of the pedicle. (c) 3D surface rendering VR showing subcutaneous branching of the perforators. (d) The flap is outlined on the axis of the anterior superior iliac spine and the lateral patella. The yellow mark shows the precise projection of the perforator’s origin on the skin.

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