Clinical Presentation

Fig. 157.1

Technique

• To block thyroid uptake, potassium perchlorate (400 mg) is administered by mouth 15 minutes before ^99mTc-pertechnetate.

• Indwelling catheters with subcutaneous chambers (such as those of the Port-A-Cath) need to be accessed with sterile technique.

• With the patient lying supine, butterfly needles attached to a three-way stopcock are connected to the accessed central line ports and also placed into a vein in each upper extremity.

• Connected to the stopcocks are 1-mL syringes containing approximately 5 mCi of ^99mTc-pertechne-tate in a volume of 0.1 to 0.3 mL and 10-mL syringes containing 10 mL of normal saline.

• Gamma camera with a large field of view

• Low-energy, parallel-hole, high-resolution collimator

• Energy window 20% centered at 140 keV

• The camera is positioned over the anterior chest and shoulders with the heart in the center of the field of view.

• The tracer is administered as a bolus injection, followed by the infusion of 10-mL flushes of normal saline in rapid sequence: first into the upper extremity ipsilateral to the central line, then the contralateral arm, and finally the central line.