Electron Microscopy and Computed Microtomography Studies of in Vivo Implanted Mini-Tl Dosimeters

Strand, Sven‐Erik; Strandh, Margareta; Spanne, P.

doi:10.3109/02841869309096137

Cited by 3 publications

(1 citation statement)

References 7 publications

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“…Since 1986, many studies have been performed concerning miniature thermoluminescent CaSO 4 :Dy dosimeters. Whereas Wessels observed no sensitivity loss for these dosimeters when used in a liquid environment, other researchers have detected the dissolution of CaSO 4 :Dy crystals (Strand et al 1993, Strand and Strandh 1994, Demidecki et al 1993. However, CaSO 4 :Dy mini-TLDs have been used in vivo with imprecise dosimetric results (Griffith et al 1988, Chiou et al 1991, Langmuir et al 1992, Ugur et al 1995.…”

Section: Introductionmentioning

confidence: 98%

Production of new thermoluminescent mini-dosimeters

Martin¹,

Lisbona²,

Richard³

et al. 2000

Phys. Med. Biol.

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A method of producing CaSO4:Dy thermoluminescent mini-dosimeters was reported in 1986 by B W Wessels for determination of the in vivo absorbed dose in radioimmunotherapy, a field in which absorbed dose gradients are important. These dosimeters, which undergo dissolution when used in a liquid environment, showed a sensitivity loss of up to 30% after 4 days of immersion in our tests. Moreover, several studies have shown that biocompatibility problems can occur during in vivo studies in animals. This paper describes the production and testing of a new type of thermoluminescent mini-dosimeter obtained by microextrusion of a mixture of LiF:Mg,Cu,P polypropylene and plastic adjuvants. These dosimeters, in the form of long 400 microm diameter filaments, can be cut to the desired length. The production process allows an LiF:Mg,Cu,P load of up to 50%. Results obtained in external irradiation indicate that these new miniature LiF:Mg,Cu,P dosimeters have good sensitivity (about 1.6 times that of CaSO4:Dy mini-TLDs), homogeneous response within a production batch (mean +/-4%), response stability in water (0.7% of variation in sensitivity after 2 weeks of immersion) and stability in aqueous solutions at different pH. LiF:Mg,Cu,P mini-dosimeters appear to be highly promising for internal dosimetry, and evaluation is in progress in animals.

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Section: Introductionmentioning

confidence: 98%

Production of new thermoluminescent mini-dosimeters

Martin¹,

Lisbona²,

Richard³

et al. 2000

Phys. Med. Biol.

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New thermoluminescent dosimeters (TLD): optimization and characterization of TLD threads sterilizable by autoclave

Jarnet¹,

Denizot²,

Hindré³

et al. 2004

Phys. Med. Biol.

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To improve the performance of mono-extruded TLD threads as a dosimetric thermoluminescent tool (French Patent 9903729), a new process was developed by co-extrusion methodology leading to threads of 600 microm diameter with a 50 microm homogeneous polypropylene sheath. In this optimization work, study of parameters such as LiF:Mg,Cu,P powder granulometry, load rate and proportion of components led to an increased sensitivity of around 40%. Moreover, the co-extrusion technique allowed the threads to be sterilized by humid steam (134 degrees C/18 min) without significant variation of the linearity response between 0 and 30 Gy after gamma irradiation (60Co).

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In Vivo Absorbed Dose Measurements with Mini-TLDs Parameters affecting the reliability

Strandh

Strand

1996

Acta Oncologica

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Mini-TLDs have been proposed and widely used for in vivo measurements of absorbed doses in radionuclide therapies. The present investigation reports in detail on the signal dependence on different parameters and the accuracy of this method. Rodshaped Teflon-imbedded CaSO4:Dy or LiF thermoluminescent dosimeters (TLDs) with dimensions 0.2 x 0.4 x 5 mm3 were prepared from TLD-discs. To remove paraffin from the mini-TLDs after cutting in a microtome the TLDs were Xylene-treated, which does not affect the sensitivity. Irradiated mini-TLDs are sensitive to illumination. Fading effects in darkness were examined after 60Co-irradiation at temperatures 4, 22 and 37 degrees C. For CaSO4:Dy mini-TLDs fading in air is small. The observed signal loss after implanting CaSO4:Dy mini-TLDs in gel and muscle tissue is the same at constant temperature and is increasing with the temperature. For LiF mini-TLDs the effect of signal loss in gel was smaller than for CaSO4:Dy dosimeters. For 60Co external irradiation supralinearity already starts between 0.5 and 1 Gy for both kinds of dosimeter material. There is a strong pH dependence of the signals from the mini-TLDs. For CaSO4:Dy dosimeters the loss of sensitivity in gel is smaller at higher pHs. For LiF dosimeters the loss of sensitivity is smallest for neutral pH. We conclude that using mini-TLDs for in vivo dosimetry requires careful handling and proper calibration for accuracy in the measurements. Without such calibration errors exceeding 65% for CaSO4:Dy and 40% for LiF may easily occur.

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Electron Microscopy and Computed Microtomography Studies of in Vivo Implanted Mini-Tl Dosimeters

Cited by 3 publications

References 7 publications

Production of new thermoluminescent mini-dosimeters

Production of new thermoluminescent mini-dosimeters

New thermoluminescent dosimeters (TLD): optimization and characterization of TLD threads sterilizable by autoclave

In Vivo Absorbed Dose Measurements with Mini-TLDs Parameters affecting the reliability

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