Private Sub AcquirePartOfImage()
        Using deviceManager As New Vintasoft.Twain.DeviceManager()
                Try
                        ' open the device manager
                        deviceManager.Open()

                        deviceManager.ShowDefaultDeviceSelectionDialog()

                        ' get reference to the default device
                        Dim device As Vintasoft.Twain.Device = deviceManager.DefaultDevice

                        device.ShowUI = False
                        device.DisableAfterAcquire = True

                        ' open the device
                        device.Open()

                        ' set image layout (get only the top half of the page)
                        device.UnitOfMeasure = Vintasoft.Twain.UnitOfMeasure.Inches
                        Dim imageLayout As Vintasoft.Primitives.VintasoftRectF = device.ImageLayout.[Get]()
                        device.ImageLayout.[Set](0, 0, imageLayout.Width, imageLayout.Height / 2)

                        Dim tiffFilename As String = System.IO.Path.Combine(System.IO.Directory.GetCurrentDirectory(), "multipage.tif")

                        ' acquire images from device
                        Dim acquireModalState As Vintasoft.Twain.AcquireModalState = Vintasoft.Twain.AcquireModalState.None
                        Do
                                acquireModalState = device.AcquireModal()
                                Select Case acquireModalState
                                        Case Vintasoft.Twain.AcquireModalState.ImageAcquired
                                                ' save acquired image to multipage TIFF file
                                                device.AcquiredImage.Save(tiffFilename)
                                                ' dispose the acquired image
                                                device.AcquiredImage.Dispose()
                                                Exit Select
                                End Select
                        Loop While acquireModalState <> Vintasoft.Twain.AcquireModalState.None

                        ' close the device
                        device.Close()

                        ' close the device manager
                        deviceManager.Close()
                Catch ex As Vintasoft.Twain.TwainException
                        System.Console.WriteLine("Error: " + ex.Message)
                        System.Console.ReadLine()
                End Try
        End Using
End Sub

private void AcquirePartOfImage()
{
    using (Vintasoft.Twain.DeviceManager deviceManager = new Vintasoft.Twain.DeviceManager())
    {
        try
        {
            // open the device manager
            deviceManager.Open();

            deviceManager.ShowDefaultDeviceSelectionDialog();

            // get reference to the default device
            Vintasoft.Twain.Device device = deviceManager.DefaultDevice;

            device.ShowUI = false;
            device.DisableAfterAcquire = true;

            // open the device
            device.Open();

            // set image layout (get only the top half of the page)
            device.UnitOfMeasure = Vintasoft.Twain.UnitOfMeasure.Inches;
            Vintasoft.Primitives.VintasoftRectF imageLayout = device.ImageLayout.Get();
            device.ImageLayout.Set(0, 0, imageLayout.Width, imageLayout.Height / 2);

            string tiffFilename = System.IO.Path.Combine(System.IO.Directory.GetCurrentDirectory(), "multipage.tif");

            // acquire images from device
            Vintasoft.Twain.AcquireModalState acquireModalState = Vintasoft.Twain.AcquireModalState.None;
            do
            {
                acquireModalState = device.AcquireModal();
                switch (acquireModalState)
                {
                    case Vintasoft.Twain.AcquireModalState.ImageAcquired:
                        // save acquired image to multipage TIFF file
                        device.AcquiredImage.Save(tiffFilename);
                        // dispose the acquired image
                        device.AcquiredImage.Dispose();
                        break;
                }
            }
            while (acquireModalState != Vintasoft.Twain.AcquireModalState.None);

            // close the device
            device.Close();

            // close the device manager
            deviceManager.Close();
        }
        catch (Vintasoft.Twain.TwainException ex)
        {
            System.Console.WriteLine("Error: " + ex.Message);
            System.Console.ReadLine();
        }
    }
}