[marcoszorrilla]

Por si aporto algo, yo tengo un formulario con 10 fichas en las que se pueden escanear un maximo de 10 historias por paciente y utilizo un único componente Twain y guardo las imágenes así:
(es un resumen).

Código Delphi [-]
procedure TfrClientes.TwainTwainAcquire(Sender: TObject;
  const Index: Integer; Image: TBitmap; var Cancel: Boolean);
begin
  Case nH of
  1bImage1.Picture.Assign(Image);
  2bImage2.Picture.Assign(Image);
  3bImage3.Picture.Assign(Image);
  4bImage4.Picture.Assign(Image);
  5bImage5.Picture.Assign(Image);
  end;

  Cancel := TRUE;  {Only want one image}
end;

procedure TfrClientes.SpeedButton1Click(Sender: TObject);
begin
nh:=1;
  {It is always recommended to load library dynamically, never forcing}
  {final user to have twain installed}
  if Twain.LoadLibrary then
  begin

    {Load source manager}
    Twain.SourceManagerLoaded := TRUE;
    {Allow user to select source}
    SelectedSource := Twain.SelectSource;
    if SelectedSource <> -1 then
    begin
      {Load source, select transference method and enable (display interface)}
      Twain.Source[SelectedSource].Loaded := TRUE;
      Twain.Source[SelectedSource].TransferMode := ttmMemory;
      Twain.Source[SelectedSource].Enabled := TRUE;
    end {if SelectedSource <> -1}

  end
  else
    showmessage('Twain is not installed.');
end;
.....

Un Saludo.