I have not seen any rules regarding Psychic Hoods. So, here goes: 

Psychic Hood
You have worked for decades if not centuries to shield your mind from the warp. The Adeptus Mechanicus has spent millennium .

This mantle surrounds the Psyker’s head, protecting her from the warp and channeling the psychic energies released by her will.

Prerequisites: Psy Rating 1

Availability: Rare

Cost: 2300 Thrones

The Psychic Hood amplifies the control the Psyker  has over the warp. A Psyker wearing a Psychic Hood may re-roll any 9’s once, but he must keep the new results even if they result in a Psychic Phenomenon or cause the power to fail.

Example: Sharta attempts to use Fearful, with a threshold of 7. She rolls her Psy Rating of 2 and gets 1, 9. She chooses to reroll the 9 and receives a 2. She adds her Willpower bonus and gets a total of 6. She does not activate Fearful but she also does not roll for a Psychic Phenomenon.

Additionally, the Psychic Hood allows for a level of protection against psychic attacks. The Psyker must make a Common Lore roll to determine the power being used. The Psyker may then roll in an attempt to negate a psychic power by rolling a psychic test as if she was the one casting the power. These are an opposing roll.

 
Roll of 9 does not cause a Psychic Phenomenon.

When used defensively the Psyker counts as using the Focus Time of the original power for that round.

 Example: The Farseer attempts to use Precognition, with a threshold of 7. Sharta recognizes the power. Sharta herself has not used a power this round. She rolls her Psy Rating of 2 and gets 6, 8 and adds her Willpower bonus of 3 and gets a total of 17. The Farseer rolls a total of 23. Sharta reduces the Farseer’s threshold test to 6 (23-17). She has blocked the Farseer’s power.

Since Precognition is a Half Action, she can now only activate a power with Focus Time of Half or less this round if she has not already taken her turn.