Samarium - 153This is a featured page

Photos:
Samarium
Samarium a rare earth metal.[4]		 Quadramet
Quadramet IV [5]
Samarium - 153 - UWL Medical Dosimetry Brachy Class 08-09
Bone Scan [5]





Relevant Historical Data: Samarium-153 lexidronam (chemical name Samarium-153-ethylene diamine tetramethylene phosphonate, abbreviated Samarium-153 EDTMP, trade name Quadramet [1]
Chemical/Radioactive Composition: Samarium-153 lexidronam is a complex of a radioisotope of the lanthanide element samarium with the chelator EDTMP which is used to treat pain when cancer has spread to the bone. It is injected into a vein and distributes throughout the body. It homes in on areas where cancer has invaded the bone. Once there, the radioisotope emits beta particles (electrons) which kill the nearby cancer cells.[1]


Quadramet Chemical Structure [7]
Picture -- LOGO
Energy Characteristics: Samarium-153 is produced in high yield and purity by neutron irradiation of isotopically enriched samarium Sm 152 oxide (152Sm2O3). It emits both medium-energy beta particles and a gamma photon. Samarium-153 has average and maximum beta particle ranges in water of 0.5 mm and 3.0 mm, respectively. [2]


 Radiation Energy (keV)* Abundance
Beta 640 30%
Beta 710 50%
Beta 810 20%
Gamma 103 29%
* Maximum energies are listed for the beta emissions, the average beta particle energy is 233 keV.

Exposure Rate Constant: 0.46 R/mCi-hr at 1cm [3]
Half-life Properties: 46.3 hours (1.93 days)[1]
Forms available for use: IV injectable, Quadramet comes in 1.0 mCi/kg. injected through a catheter over a period on 1 minute, followed by an injection of saline flush. Quadramet injections are supplied frozen in a single-dose vial containing 3 mL with 5550 MBq (150 mCi) of samarium-153 at [3]
HVL in lead: The half-value thickness of lead (Pb) for samarium-153 is approximately 0.10 mm. The use of 1 mm of lead will decrease the external radiation exposure by a factor of approximately 1,000.[3]
Measurement/Calibrations/QA: Measurement/Calibrations:[8]
All radioactivity is calibrated to the reference date and time on the vial.
The dose should be measured by a suitable radioactivity calibration system, such as a radioisotope dose calibrator, immediately before administration. The dose of radioactivity to be administered and the patient should be verified before administering. Patients should not be released until their radioactivity levels and exposure rates comply with federal and local regulations.

Thaw at room temperature before administration and use within 8 hours of thawing.The drug product expires 48 hours after the time of calibration noted on the label, or 8 hours after thawing, whichever is earlier.

Storage: Store frozen at -10° to -20°C in a lead shielded container.
Storage and disposal should be controlled in a manner that complies with the appropriate regulations of the government agency authorized to license the use of this radionuclide.

QA:[9]
  • Time-minimize the time spent working with radioactive materials without compromising the quality of care.
  • Distance-maximize the distance between the source and the workers.
  • Shielding-proper shielding should be used to limit exposure. The half value layer (HVL) is the amount of shielding required to limit the exposure by half of its magnitude. It could take several HVLs to reduce radiation exposure to personnel within limits.

Used in formula/calculation: For Quadramet injections it is supplied frozen in a single-dose glass vial containing 3 mL with 5550 MBq (150 mCi) of samarium-153 at calibration Samarium-153 has average and maximum beta particle ranges in water of 0.5mm and 3.0mm, respectively.[3] The specific gamma-ray constant for samarium-153 is 0.46 R/mCi-hr at 1 cm (1.24x10-5 mSv/MBq-hr at 1 meter).[3] All Radioactivity is calibrated to the reference date and time on the vial. Physical Decay Chart Half Life 46.3 hrs.[3]
Time (hour) Factor Time ( hour) Factor
-48 2.05 +1 .99
-36 1.71 +2 .97
-24 1.43 +3 .96
-20 1.35 +4 .94
-16 1.27 +6 .91
-12 1.20 +8 .89
-8 1.13 +12 .84
-6 1.09 +16 .80
-4 1.06 +20 .74
-3 1.05 +24 .70
-2 1.03 +36 .58
-1 1.02 +48 .49
Uses in Radiation Oncology: A radioactive isotope used in the treatment of bone cancer and bone metastases. Samarium 153 is a radioactive form of the element samarium. It collects in bone, where it releases radiation that may kill cancer cells.[2]
Treatment Planning: The recommended dose of Quadramet is 1.0 mCi/kg, administered intravenously. Dose adjustment in patients at the extremes of weight have not been studied. Caution should be exercised when determining the dose in very thin or very obese patients.
Patients should not be released until their radioactivity levels and exposure rates comply with federal and local regulation.[3]
One other interesting fact: Samarium-153 is a compound that will accumulate particularly in osteoblastic or mixed metastatic lesions, with greater uptake in diseased bone than in normal bone. Sixty-five percent of the dose injected will be taken up by the skeleton, and most of that radioactivity will be cleared from the blood in about 30 minutes. Thirty-five percent of the dose is excreted in the urine, and most of that urinary excretion will be completed within 6 hours. [6]

The estimated absorbed radiation doses to an average 70 kg adult patient from an i.v. injection are shown in Table 7.[8] Radiation exposure is based on a urinary voiding interval of 4.8 hours.[8]

ABLE 7: RADIATION ABSORBED DOSES

70 kg ADULT
Target Organ Rad/mCi mGy/MBq
Bone Surfaces 25.0 6.76
Red Marrow 5.70 1.54
Urinary Bladder Wall 3.60 0.097
Kidneys 0.065 0.018
Whole Body 0.040 0.011
Lower large intestine 0.037 0.010
Ovaries 0.032 0.0086
Muscle 0.028 0.0076
Small Intestine 0.023 0.0062
Upper Large Intestine 0.020 0.0054
Testes 0.020 0.0054
Liver 0.019 0.0051
Spleen 0.018 0.0049
Stomach 0.015 0.0041



Links:
http://www.cytogen.com/professional/quadramet/pi.php
http://www.rxlist.com/quadramet-drug.htm
http://www.medicinenet.com/samarium_sm-153lexidronam-injection/article.htm
http://www.pslgroup.com/dg/68bb6.htm
http://www.hps.org/publicinformation/ate/q2052.html

References
1.Samarium-153,wikipedia. Available at: wikipedia.org/wiki/Samarium-153 lexidronam. Accessed on March 10,2009.
2.National Cancer Institute. Samarium-153. Available at: www.cancer.gov. Accessed on March7,2009.
3. Cytogen. Health Care Professional Information Center. Quadramet-prescribing information. Available at: http://www.cytogen.com/professional/quadramet/pi.php. Accessed on March 21, 2009.
4. Web elements website. Available at: http://www.webelements.com/samarium/pictures.html. Accessed March 23, 2009.
5. Quadramet website. Available at: http://www.ansto.gov.au/commercial_services/health/ari/products/radiopharmaceuticals/quadramet/quadramet. Accessed March 23, 2009.
6. Perez, CA. Other Options Available for the Palliation of Pain Secondary to Bone Metastases. Medscape. 2007. Available at: http://www.medscape.com/viewarticle/551143. Accessed on March 30, 2009.
7. Goeckeler, WF. Quadramet Overview. Cytogen. 2005. Available at: http://www.secinfo.com/d14D5a.z5kHq.d.htm. Accesed on March 31, 2009.
8. RxList. Quadramet- Samarium 153 Injection. Available at: http://www.rxlist.com/quadramet-drug.htm. Accessed on March 31, 2009.
9. University of Wisconsin-LaCrosse Dosimetry Program. Brachytherapy QA D2L notes. Available at: www.uwlax.edu. Accessed on April 3, 2009.

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