Indium DTPA In 111

INDIUM DTPA IN 111- indium in-111 pentetate disodium solution
GE Healthcare, Medi-Physics, Inc.



GE Healthcare (Medi-Physics, Inc.) Indium DTPA In 111 is a diagnostic drug for intrathecal use. It is available as a sterile, pyrogen-free, isotonic, aqueous solution, buffered to pH 7 to 8. At calibration time, each milliliter contains 37 MBq, 1 mCi of Pentetate Indium Disodium In 111 (no-carrier-added), 20 to 50 ยต g of pentetic acid, and sodium bicarbonate for pH adjustment. The drug is to be discarded after single use. Radionuclidic purity at calibration time is at least 99.88% with less than 0.06% Indium In 114m and 0.06% Zinc Zn 65. The concentration of each radionuclidic contaminant changes with time. Graph 1 shows maximum concentration of each radionuclidic impurity as a function of time.

Graph 1 — Radionuclidic Impurities

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The chemical names are 1. Indate(2-)-111 In -[N,N -bis[2-[bis-(carboxymethyl)amino]ethyl]glycinato(5-)]-disodium; and 2. Disodium [N,N -bis[2-(carboxymethyl)amino]glycinato(5-)]-indate (2-)111 In.

Molecular formula: C14 H18 O10 N3 111 In Na2

Molecular weight: 545.29

Structural formula:

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Indium 111 decays by electron capture with a physical half-life of 67.9 hours.* The energies of the photons that are useful for detection and imaging studies are listed in Table 1.

Table 1. Principal Radiation Emission Data *
Radiation Mean %/Disintegration Mean Energy (keV)
Kocher, David C.,”Radioactive Decay Data Tables,”DOE/TIC-11026, 115, (1981).
Gamma-2 90.2 171.3
Gamma-3 94.0 245.4


The specific gamma ray constant for Indium In 111 is 3.3 R/hr-mCi at 1 cm. The half-value thickness of lead (Pb) for Indium In 111 is 0.021 cm. To facilitate control of the radiation exposure from millicurie amounts of this radionuclide, a range of values for the relative attenuation of the radiation emitted by this radionuclide that results from interposition of various thicknesses of Pb is shown in Table 2. For example, the use of a 0.8 cm thickness of Pb will attenuate the radiation emitted by a factor of about 1,000.

Table 2. Radiation Attenuation by Lead Shielding
Shield Thickness
(Pb) cm
Coefficient of Attenuation
To correct for physical decay of this radionuclide, the fractions that remain at selected time intervals after the time of calibration are shown in Table 3.
0.021 0.5
0.19 10-1
0.49 10-2
0.80 10-3
1.1 10-4
Table 3. Physical Decay Chart: Indium In 111, Half-Life 67.9 Hours
Hours Fraction Remaining Hours Fraction Remaining
Calibration Time
0* 1.000 84 0.424
12 0.885 96 0.375
24 0.783 108 0.332
36 0.693 120 0.294
48 0.613 132 0.260
60 0.542 144 0.230
72 0.480 168 0.180


After intrathecal administration, the radiopharmaceutical is absorbed from the subarachnoid space as described below, and the remainder flows superiorly to the basal cisterns within 2 to 4 hours and subsequently will be apparent in the Sylvian cisterns, the interhemispheric cisterns, and over the cerebral convexities. In normal individuals, the radiopharmaceutical will have ascended to the parasagittal region within 24 hours with simultaneous partial or complete clearance of activity from the basal cisterns and Sylvian regions. In contrast to air, the radiopharmaceutical does not normally enter the cerebral ventricles.

Although the primary absorption of cerebrospinal fluid (CSF) into the blood stream occurs at the arachnoid villi, there is some evidence that a significant fraction of CSF is also absorbed across both the cerebral and spinal leptomeninges. Lesser quantities may also be absorbed across the ventricular ependyma. It is also generally held that these alternate routes of CSF absorption may assume primary importance when the major routes of the flow are pathologically obstructed. Approximately 65% of the administered dose is excreted by the kidneys within 24 hours and this increases to 85% in 72 hours.

Indium DTPA In 111 Indications and Usage

Pentetate Indium Disodium In 111 is recommended for use in radionuclide cisternography.


None known.


The contents of the vial are radioactive. Adequate shielding of the preparation must be maintained at all times.

Since the drug is excreted by the kidneys, caution should be exercised in patients with severely impaired renal function.



Pentetate Indium Disodium In 111, as well as other radioactive drugs, must be handled with care and appropriate safety measures should be used to minimize external radiation exposure to clinical personnel, and to minimize radiation exposure to patients consistent with proper patient management.

Radiopharmaceuticals should be used only by physicians who are qualified by training and experience 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.

Do not use after the expiration time and date (7 days after calibration time and date stated on the label).

Discard vial after a single use. Do not use if contents are turbid.

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