Upload Files with Angular 5

Hi, I have a form in angular but I would like to send a file to the api as basically just the sending of that file is done?

<ma-header></ma-header>
<mat-card *ngIf="event">
    <mat-card-title>{{h1Text}}</mat-card-title>
    <mat-card-content>
      <form novalidate (ngSubmit)="submit()" #eventForm="ngForm" enctype="multipart/form-data">

        <p>Estudio del Paciente</p>
        <input type="file" #estudio="ngModel" id="estudio" name="estudio" placeholder="Estudio" [(ngModel)]="event.e_estudio_url">

        <button mat-raised-button color="primary" [disabled]="!eventForm.valid" type="submit">
          <mat-icon>event</mat-icon>
          {{submitText}}
        </button>
      </form>
    </mat-card-content>
  </mat-card>

What would the TS event be like to send it?