Radiation Safety

DATSCAN emits radiation and must be handled with safety measures to minimize radiation exposure to healthcare providers and patients [see Warnings and Precautions (5.3)]. Radiopharmaceuticals should be used by or under the control of healthcare providers who are qualified by specific training and experienced in the safe use and handling of radionuclides, and whose experience and training have been approved by the appropriate government agency authorized to license the use of radionuclides.

To minimize radiation exposure, encourage hydration prior to and following DATSCAN administration in order to permit frequent voiding. Encourage the patient to void frequently for the first 48 hours following DATSCAN administration [see Dosage and Administration (2.5)].

Thyroid Blockade Before DATSCAN Administration

Administer Potassium Iodide Oral Solution or Strong Iodine Solution (e.g., Lugol's Solution) equivalent to 100 mg iodide to block uptake of iodine-123 by the patient's thyroid at least one hour before the dose of DATSCAN [see Warnings and Precautions (5.2)].

Recommended Dosage

The recommended dose of DATSCAN in adult patients is 111 MBq to 185 MBq (3 mCi to 5 mCi) administered intravenously over at least 20 seconds.

Preparation and Administration

• Assess pregnancy status before administering DATSCAN to a female of reproductive potential [see Use in Specific Populations (8.1)].
• Use aseptic procedures and radiation shielding during preparation and administration.
• Inspect the DATSCAN vial for particulate matter and discoloration prior to administration and do not use it if the vial contains particulate matter or discoloration.
• Measure patient dose using a dose calibrator immediately prior to administration.
• Discard unused portion.

Radiation Dosimetry

The estimated radiation absorbed doses to an adult from intravenous injection of DATSCAN are shown in Table 1. The values are calculated assuming urinary bladder emptying at 4.8-hour intervals and appropriate thyroid blocking (iodine-123 is a known Auger electron emitter).

The Effective Dose resulting from a DATSCAN administration with an administered activity of 185 MBq (5 mCi) is 3.94 mSv in an adult.

Imaging Instructions

Begin SPECT imaging 3 hours to 6 hours following DATSCAN administration.

Use a gamma camera fitted with high-resolution collimators and set to a photopeak of 159 keV with a ± 10% energy window. Angular sampling should be at least 120 views over 360 degrees.

Position the patient supine with the head on an off-the-table headrest, use a flexible head restraint such as a strip of tape across the chin or forehead if necessary to help avoid movement, and set a circular orbit for the detector heads with the radius as small as possible (typically 11 cm to 15 cm).

Obtain images with matrix size and zoom factors selected to give a pixel size of 3.5 mm to 4.5 mm. Collect a minimum of 1.5 million counts for optimal images.

Image Interpretation

Interpret DATSCAN images visually, based upon the appearance of the striata. Reconstructed pixel size should be between 3.5 mm and 4.5 mm with slices 1 pixel thick. Optimum presentation of the reconstructed images for visual interpretation is transaxial slices parallel to the anterior commissure-posterior commissure (AC-PC) line.

Determine whether an image is normal or abnormal by assessing the extent (as indicated by shape) and intensity of the striatal signal. Image interpretation does not involve integration of the striatal image appearance with clinical signs and/or symptoms.

Abnormal: Abnormal DATSCAN images fall into at least one of the following three categories (all are considered abnormal).

• Activity is asymmetric, e.g., activity in the region of the putamen of one hemisphere is absent or greatly reduced with respect to the other. Activity is still visible in the caudate nuclei of both hemispheres resulting in a comma or crescent shape in one and a circular or oval focus in the other. There may be reduced activity between at least one striatum and surrounding tissues (Figure 2).
• Activity is absent in the putamen of both hemispheres and confined to the caudate nuclei. Activity is relatively symmetric and forms two roughly circular or oval foci. Activity of one or both is generally reduced (Figure 3).
• Activity is absent in the putamen of both hemispheres and greatly reduced in one or both caudate nuclei. Activity of the striata with respect to the background is reduced (Figure 4).