need help with xps to png memory leak

[Legendary_Agent]

hey all ive been reading some tutorials online on how to convert a xps document to image format fiels (i need this because of a problem displaying a3 files) Anyways heres the full code ive came up with for the printing process:

public void SaveXpsDocumentToImage(string xpsFileName, int ResolutionScaling, bool ColorEnabled, int CopyNumber, Form2 Form2)
            {
                PrintDocument pd = new PrintDocument();

                maxPageIndex = 0;
                pd.PrinterSettings.Copies = short.Parse(CopyNumber.ToString());
                pd.PrinterSettings.Collate = true;
                pd.DefaultPageSettings.Color = ColorEnabled;
                pd.DocumentName = xpsFileName;
                pd.PrinterSettings.DefaultPageSettings.Color = ColorEnabled;
                if (Form2.PropertiesSettingsPrinter != "")
                    pd.PrinterSettings.PrinterName = Form2.PropertiesSettingsPrinter;
                pd.DefaultPageSettings.PaperSize = GetPaperSize(pd.PrinterSettings, "A3");

                if (MSList == null)
                    MSList = new List<MemoryStream>();

                XpsDocument xpsDoc = new XpsDocument(Form2.PropertiesSettingsPrintingDirectory + "\\Selected\\" + xpsFileName, System.IO.FileAccess.Read);
                        
                    FixedDocumentSequence docSeq = xpsDoc.GetFixedDocumentSequence();
                    // You can get the total page count from docSeq.PageCount
                    for (int pageNum = 0; pageNum < docSeq.DocumentPaginator.PageCount; ++pageNum)
                    {
                        DocumentPage docPage = docSeq.DocumentPaginator.GetPage(pageNum);
                        RenderTargetBitmap renderTarget = new RenderTargetBitmap((int)docPage.Size.Width * ResolutionScaling, (int)docPage.Size.Height * ResolutionScaling, 96 * ResolutionScaling, // WPF (Avalon) units are 96dpi based
                        96 * ResolutionScaling, System.Windows.Media.PixelFormats.Default);
                        renderTarget.Render(docPage.Visual);
                        PngBitmapEncoder encoder = new PngBitmapEncoder();  // Choose type here ie: JpegBitmapEncoder, etc
                        encoder.Frames.Add(BitmapFrame.Create(renderTarget));
                        MSList.Add(new MemoryStream());
                        encoder.Save(MSList[pageNum]);
                        encoder.Frames.Clear();
                        renderTarget.Clear();
                        docPage.Dispose();
                        maxPageIndex++;
                        renderTarget = null;
                        docPage = null;
                        encoder = null;
                            
                    }
                    pd.PrintPage += new PrintPageEventHandler(PageAdd);
                    currentPageIndex = 0;
                    pd.Print();
                    pd.Dispose();
                    pd = null;
                    docSeq = null;
                    xpsDoc.Close();
                    xpsDoc = null;
                    
                for (int i = 0; i < MSList.Count(); i++)
                {
                    MSList[i].SetLength(0);
                    MSList[i].Close();
                    MSList[i].Dispose();
                }
                MSList.Clear();
                GC.Collect();

            }

            List<MemoryStream> MSList;
            int currentPageIndex = 0, maxPageIndex = 0;

As you can notice ive tried my best to destroy everything so i could get my ram used by this program back, but from 25mb it goes up by around 20mb each time i print that file, it only has 6 pages and ~500kb on disk.
Ive no clue what exactly is the problem, i think its obvious to suspect that this ha something to do with the bmp conversion but i cant exactly put my finger on what exactly is causing this.

This whole function is running on a STA thread
If you require more information tell me and ill try to post it.
Any help is appreciated as usual, thanks in advance!