Top-pest parent column should be as new column

Hi,

i have a table like below 

CREATE TABLE #MyTable (ID Integer,Description varchar(200),ParentID Integer)
insert INTO #MyTable (ID,Description,ParentID) VALUES (1,'1AAA',0)
insert INTO #MyTable (ID,Description,ParentID) VALUES (2,'1BBB',0)
insert INTO #MyTable (ID,Description,ParentID) VALUES (3,'2AAA',1)
insert INTO #MyTable (ID,Description,ParentID) VALUES (4,'2BBB',2)
insert INTO #MyTable (ID,Description,ParentID) VALUES (5,'3AAA',3)
insert INTO #MyTable (ID,Description,ParentID) VALUES (6,'3AAB',3)
insert INTO #MyTable (ID,Description,ParentID) VALUES (7,'3BBB',4)
insert INTO #MyTable (ID,Description,ParentID) VALUES (8,'3BBC',4)
SELECT * from #MyTable

I need a new column which has to display the top-pest parent. like below

Thanks