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Left-to-Right Shunt Study (QP:QS)

Left-to-Right Shunt Study (QP:QS)


  • You have been referred for a Left-to-Right Shunt Study or QP:QS study (ratio of pulmonary blood flow (QP) to the systemic blood flow (QS)).

  • A QP:QS study is sensitive in detecting if there is a hole between the ventricles of your heart (ventricular septal defect) or a hole between the atria of your heart (atrial septal defect).

  • The test involves a small injection of  “tracer” into a vein in your neck using a butterfly needle.

  • The tracer we use is called 99mTc-Pertechnetate (99m-Technetium Pertechnetate).

  • There are rarely any side effects with this injection.

  • You simply lie on a bed and as soon as you have the injection, we image your heart and lungs using a Gamma Camera (1). This takes 5 minutes to do.

  • Sometimes we need to repeat the injection and imaging if we see that the images do not contain the information we require. This is done via the same butterfly needle. Again, this takes 5 minutes to do.

  • You receive a slight radiation dose by having a QP:QS Study ~ up to 2.2 times your yearly background radiation (2).


Patient Preparation:

  • If you are pregnant, trying to fall pregnant or breast feeding, you must inform our staff.

  • There is no preparation for this test i.e. eat and drink as normal.

  • If you are on any medications, please take these as normal.

  • If you have had prior imaging e.g. PET, Nuclear Scan, CT, MRI, X-Ray, Ultrasound, etc... please bring these with you.

  • Please also bring your referral and any blood results that you may have had done.

  • Wear comfortable clothing and minimise the amount of metal jewellery you have on (all metal objects will need to be removed prior to imaging).

  • Important Note: You cannot have this test if you have had a PET or Nuclear Scan within 24 hours prior to this test. If you have had Iodine-131 therapy, allow 4-weeks before having this test. Please ring to discuss booking options.​

Breast-Feeding Mothers: Once you have been given the tracer, you need to stop breast-feeding for 48-hours. During this time, you need to express and discard your breast milk as often as required. You will need to bottle-feed your child during this period.



(1) A Gamma Camera is a device that detects gamma-rays (gamma-rays are very similar to x-rays) and does not emit any radiation.

(2) We all receive a yearly background radiation dose ~ 2.4mSv. QP:QS Study ~ 5.2mSv = 2.2 times yearly background dose.

value. quality care. convenience.

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