Christina Aguilera has canceled her 29-date summer tour on the advice of her doctors. The "Dirrty" diva is apparently suffering from strained vocal chords. "I am extremely disappointed to have to cancel this tour," she said in a statement. "I was looking forward to being on the road again and spending time with my fans." Aguilera will now focus on honing her Samantha Jones impersonation for a possible one-woman show.