The response of the thermoluminescent dosimeter CaF2:Tm to protons in the energy range 15–30 MeV

This study describes the response of the thermoluminescent dosimeter CaF₂:Tm to protons from a compact cyclotron with energies between 15 and 30 MeV. Glow curve analysis indicates that the response of CaF₂:Tm to protons depends on proton energy and proton current.     

Measurements and nuclear model calculations on proton-induced reactions on Rh up to 40 MeV: evaluation of the excitation function of the Rh(p,n)Pd reaction relevant to the production of the therapeutic radionuclide Pd

Excitation functions were measured by the stacked-foil technique for the reactions ¹⁰³Rh(p,n)¹⁰³Pd, ¹⁰³Rh(p,3n)¹⁰¹Pd and ¹⁰³Rh(p,4n)¹⁰⁰Pd from their respective thresholds up to 39.6 MeV. The radioactivity of the activation products was determined by high-resolution X-ray and γ-ray spectrometry. Statistical model calculations taking into account the precompound effects were performed for all reactions, and good agreement was found with our data. A critical evaluation of the existing and present data for the ¹⁰³Rh(p,n)¹⁰³Pd reaction was carried out. Recommended cross sections and integral yields for this reaction of key importance in the production of the widely used therapeutic radionuclide ¹⁰³Pd are given.     

Nuclear data relevant to the production of I via the Te(p,n)-Process at aSmall-Sized Cyclotron

Excitation functions of the nuclear reactions ¹²⁰Te(p,xn)^119,120m,gI were measured for the first time from their respective thresholds up to 35 MeV. Use was made of the stacked-foil technique. Thin samples were prepared by electrolytic deposition of highly enriched ¹²⁰Te (99.0%) on Ti-backing. Integralyields of ^119,120m,gI were calculated from the measured cross section data. For the production of the medically interesting β⁺-emitting radioisotope ^120gI (T_1/2=1.35 h) the energy range E_p=16→9 MeV appears to be optimum, the thick target yield of ^120gI amounting to 2.3 GBq (62 mCi)/μAh and the ^120mI and ¹¹⁹I impurity levels to 4.8 and 4.4%, respectively. A comparison of the ¹²²Te(p,3n)- and ¹²⁰Te(p,n)-processes for the production of ^120gI is given. Despite the higher cost of the target material, the ¹²⁰Te(p,n)-process is superior since a small-sized cyclotron is adequate and the radionuclidic quality of the product is better.     

Excitation functions of 125Te(p, xn)-reactions from their respective thresholds up to 100 MeV with special reference to the production of 124I.

Excitation functions of the nuclear reactions 125Te(p, xn) (119,120m, 120g, 121,122,123,124,125)I were measured for the first time from their respective thresholds up to 100 MeV using the stacked-foil technique. Thin samples were prepared by electrolytic deposition of 98.3% enriched 125Te on Ti-backing. In addition to experimental studies, excitation functions were calculated by the modified hybrid model code ALICE-IPPE. The experimental and theoretical data generally showed good agreement. From the measured cross section data, integral yields of (123,124,125)I were calculated. The energy range Ep 21 --> 15 MeV appears to be very suitable for the production of the medically interesting radionuclide 124I (T(1/2) = 4.18 d; I(beta)+ = 25%). The thick target yield of 124I amounts to 81 MBq/microA h and the level of 125I-impurity to 0.9%. The 125Te(p,2n)124I reaction gives 124I yield about four times higher than the commonly used 124Te(p,n)124I and 124Te(d,2n)124I reactions. The proposed production energy range is too high for small cyclotrons but large quantities of 124I can be produced with medium-sized commercial machines.     

Development of a computer code using the EGS4 Monte Carlo simulation system to evaluate the response of a NaI(Tl) detector to photons with energies below 300 keV.

In this paper, the EGS4 Monte Carlo simulation system was used to develop a computer code for a study of the response of a NaI(Tl) detector exposed to gamma-rays with energies below 300 keV. This study comprised registration of the spectra of the incident rays and determination of the photo peaks. In addition, the probability of the K X-ray escape from a NaI(Tl) crystal and its dependence on the detector shape and volume were considered. The results of the Monte Carlo simulation are in good agreement with the experimental data (the estimated discrepancy is below 5%). This demonstrates a high efficiency of the used simulation code in quantifying the physical parameters that are difficult to evaluate by experimental methods.     

The Br(p,x)Se nuclear processes: a convenient route for the production of radioselenium tracers relevant to amino acid labelling

A possible route for the production of no-carrier-added (n.c.a.) ⁷³Se (T_1/2=7.1 h) and ⁷⁵Se (120 d) is introduced. -2-Amino-4-([⁷³Se]methyl-seleno) butanoic acid ( -[⁷³Se]selenomethionine) with an overall radiochemical yield of >40% could be prepared via a 3-step polymer-supported synthesis after successful separation of ⁷³Se from KBr targets. Excitation functions for the ^natBr(p,x) ^72,73,75Se processes were measured from threshold up to 100 MeV utilizing pellets of pressed KBr. Targets were irradiated at the NAC cyclotron with proton beams having primary energies of 40.4, 66.8 and 100.9 MeV. The calculated ⁷³Se yield (EOB) for 1 h irradiation in 1 μA of beam at the optimum proton energy range of 62→42 MeV is 81.4 MBq (2.2 mCi), and the calculated ⁷⁵Se yield (EOB) for the overall range 62 MeV→threshold for the same irradiation conditions is 0.97 MBq (0.026 mCi).     

Treatment of lung tumor colonies with 90Y targeted to blood vessels: comparison with the alpha-particle emitter 213Bi

An in vivo lung tumor model system for radioimmunotherapy of lung metastases was used to test the relative effectiveness of the vascular- targeted beta-particle emitter 90Y, and alpha-particle emitter, 213Bi. Yttrium-90 was shown to be stably bound by CHXa" DTPA-MAb 201B conjugates and delivered efficiently to lung tumor blood vessels. Dosimetry calculations indicated that the lung received 16.2 Gy/MBq from treatment with 90Y MAb 201B, which was a sevenfold greater absorbed dose than any other organ examined. Therapy was optimal for 90Y with 3 MBq injected. Bismuth-213 MAb 201B also delivered a similar absorbed dose (15Gy/MBq) to the lung. Yttrium-90 was found to be slightly more effective against larger tumors than 213Bi, consistent with the larger range of 2 MeV beta particles from 90Y than the 8 MeV alpha particles from 213Bi. Treatment of EMT-6 tumors growing in immunodeficient SCID mice with 90Y or 213Bi MAb 201 resulted in significant destruction of tumor colonies; however, 90Y MAb 201B was toxic for the SCID mice, inflicting acute lung damage. In another tumor model, IC-12 rat tracheal carcinoma growing in SCID mouse lungs, 90Y therapy was more effective than 213Bi at destroying lung tumors. However, 90Y MAb 201B toxicity for the lung limited any therapeutic effect. We conclude that, although vascular-targeted 90Y MAb can be an effective therapeutic agent, particularly for larger tumors, in this model system, acute damage to the lung may limit its application.     

The natBr(p,x)73,75Se nuclear processes: a convenient route for the production of radioselenium tracers relevant to amino acid labelling

A possible route for the production of no-carrier-added (n.c.a.) ⁷³Se (T_1/2=7.1 h) and ⁷⁵Se (120 d) is introduced. d,l-2-Amino-4-([⁷³Se]methyl-seleno) butanoic acid (d,l-[⁷³Se]selenomethionine) with an overall radiochemical yield of >40% could be prepared via a 3-step polymer-supported synthesis after successful separation of ⁷³Se from KBr targets. Excitation functions for the ^natBr(p,x) ^72,73,75Se processes were measured from threshold up to 100 MeV utilizing pellets of pressed KBr. Targets were irradiated at the NAC cyclotron with proton beams having primary energies of 40.4, 66.8 and 100.9 MeV. The calculated ⁷³Se yield (EOB) for 1 h irradiation in 1 μA of beam at the optimum proton energy range of 62→42 MeV is 81.4 MBq (2.2 mCi), and the calculated ⁷⁵Se yield (EOB) for the overall range 62 MeV→threshold for the same irradiation conditions is 0.97 MBq (0.026 mCi).     

Excitation functions of 120Te(d,xn)121,120m,gI reactions from threshold up to 13.5 MeV: comparative studies on the production of 120gI.

Excitation functions of the nuclear reactions 120Te(d,xn)121,120m,gI were measured for the first time from their respective thresholds up to 13.5 MeV. Thin samples prepared by electrolytic deposition of 99.0% enriched 120Te on Ti-backing were used. Integral yields of 121,120m,gI were calculated from the measured cross section data. A comparison of the 122Te(p,3n)-, 120Te(p,n)- and 120Te(d,2n)-processes for the production of 120gI is given. The 120Te(d,2n)-process is unsuitable for production purposes since the yield of 120gI is very low and the level of 121I impurity very high. The choice lies either on the 122Te(p,3n)- or the 120Te(p,n)-reaction and is governed by the available proton energy and the financial resources for procuring the enriched target material.     

Excitation functions of 124Te(d,xn)124,125I reactions from threshold up to 14 MeV: comparative evaluation of nuclear routes for the production of 124I.

Excitation functions of the nuclear reactions 124Te(d,xn)124-125I were measured from their respective thresholds up to 14.0 MeV via the stacked-foil technique. Thin samples were prepared by electrolytic deposition of 99.8% enriched 124Te on Ti-backing. The excitation function of the 124Te(d,n)125I reaction was measured for the first time. The present data for the 124Te(d,2n)124I reaction are by an order of magnitude higher than the literature experimental data but are in good agreement with the results of a hybrid model calculation. From the measured cross sections, integral yields of 124,125I were calculated. The energy range Ed = 14 --> 10 MeV appears to be the best compromise between 124I-yield and 1251-impurity. The calculated 124I-yield amounts to 17.5 MBq/microA h and the 125I-impurity to 1.7%. A critical evaluation of the three nuclear routes for the production of 124I, viz. 124Te(d,2n)-, 124Te(p,n)- and 125Te(p,2n)-processes, is given. The reaction studied in this work proved to be least suitable. The 124Te(p,n)-reaction gives 124I of the highest radionuclidic purity, and a small-sized cyclotron is adequate for production purposes. The 125Te(p,2n)-reaction is more suitable at a medium-sized cyclotron: the yield of 124I is four times higher than in the other two reactions but the level of 0.9% 125I-impurity is relatively high.     

Excitation functions of natGe(p,xn)71,72,73,74 As reactions up to 100 MeV with a focus on the production of 72 As for medical and 73 As for environmental studies.

Excitation functions for the formation of the arsenic radionuclides (71)As, (72)As, (73)As and (74)As in the interaction of protons with (nat)Ge were measured from the respective threshold energy up to 100 MeV. The conventional stacked-foil technique was used and the needed thin samples were prepared by sedimentation. Irradiations were done at three cyclotrons: CV 28 and injector of COSY at Forschungszentrum Jülich, and Separate Sector Cyclotron at iThemba LABS, Somerset West. The radioactivity was measured via high-resolution gamma-ray spectrometry. The measured cross section data were compared with the literature data as well as with the nuclear model calculations. In both cases, the results generally agree but there are discrepancies in some areas, the results of nuclear model calculation and some of the literature data being somewhat higher than our data. The integral yields of the four radionuclides were calculated from the measured excitation functions. The beta(+) emitting nuclide (72)As (T(1/2)=26.01 h) can be produced with reasonable radionuclidic purity ((71)As impurity: <10%) over the energy range E(p) = 18-->8 MeV; the yield of 93 MBq/microAh is, however, low. The radionuclide (73)As (T(1/2)=80.30 d), a potentially useful indicator in environmental studies, could be produced with good radionuclidic purity ((74)As impurity: <11%) over the energy range E(p) = 30 --> 18 MeV, provided, a decay time of about 60 days is allowed. Its yield would then correspond to 2.4 MBq/microAh, and GBq amounts could be produced when using a high current target.     

Investigation of the natZn(p,x)62Zn nuclear process up to 70 MeV: a new 62Zn/62Cu generator

The excitation function of the ^natZn(p,x)⁶²Zn nuclear process was measured by the stacked-foil technique up to a proton energy of 70 MeV to obtain accurate data for production of the ‘mother nuclide’ (⁶²Zn) of the PET related β⁺ emitting radioisotope ⁶²Cu. Investigations were also made on the ⁶⁶Zn(p,x)⁶²Zn and ^natZn(p,xn)⁶⁶Ga processes and on the ⁶⁶Zn(p,n)⁶⁶Ga reaction using ^natZn and highly enriched ⁶⁶Zn. The excitation functions were compared with the published data. Thick target yields for the ^natZn(p,x)⁶²Zn and ^natCu(p,xn)⁶²Zn processes were also calculated up to 70 MeV. On the basis of these calculations the ^natZn+p process results in higher yield for ⁶²Zn above 50 MeV than the ^natCu+p process. The latter process is presently used for practical production of ⁶²Zn. In an energy window from 70 to 30 MeV the available EOB yield of the ^natZn+p reactions is around 19 mCi/μA h (0.7 GBq/μAh) that makes the ^natZn(p,x)⁶²Zn process a good candidate for routine generator production.     

Well-differentiated adenocarcinoma of the gallbladder with intratumoral cystic components due to abundant mucin production: a mimicker of adenomyomatosis

The prevalence and etiology of the cystic components within gallbladder carcinomas as seen on MR images were evaluated. A retrospective review of MR images was performed for 35 proven gallbladder carcinomas in search of radiologically detectable intratumoral cystic components. The pathologic specimens were meticulously reviewed to determine the etiology. MR images of 31 adenomyomatoses were also reviewed for comparison to clarify the difference in MR features between these two entities. Three cases out of 35 proven gallbladder carcinomas were found to have intratumoral cystic components. They were all well-differentiated adenocarcinomas, and the cystic components consisted of dilated neoplastic glands filled with abundant mucin pool. Adenomyomatosis tended to have more and rounded cystic components (Rokitansky-Aschoff sinuses) lined in a linear fashion and were flat-elevated in shape, smaller in size and had a regular surface, as compared to the three carcinomas. Although rare, radiologists need to be aware that well-differentiated gallbladder carcinoma with mucin production can have cystic components, which may mimic adenomyomatosis. Careful interpretation of MR images may provide useful information in the differentiation of these two entities.     

The effect of 90Sr given to pregnant mice on spermatogenesis in the male offspring: a comparison with the effect on the ovaries in the female offspring

In previous studies in which the effect of intra-uterine exposure to 90Sr on the mouse was ascertained, the foetal ovary was found to be very sensitive. This paper reports the effects of the administration of 90Sr on spermatogenesis in the male littermates of these female mice. Doses of 370 and 740 kBq 90Sr administered to the dam at day 19 of gestation were found to cause a transient retardation in the appearance of more advanced types of germ cells in the testis. In comparison with the control testes, in the 90Sr treated mice less tubular cross-sections showed spermatocytes or round spermatids at days 14 and 2i p.p., respectively. After 56 days, spermatogenesis in the 90Sr treated mice was similar to that in control mice. Doses of 92.5 and 185 kBq 90Sr had no visible effect. It is concluded that the foetal testis is much less vulnerable to the damaging effects of 90Sr administration than the ovary, in which a dose of 92.5 kBq permanently decreased germ cell numbers to 40 per cent of the control numbers. Nevertheless, presumably also in the foetal testis, many germ cell will be killed by the radiation from the 90Sr. However, in the testis the surviving stem cells apparently quickly restore their numbers at the cost of a delay in the production of differentiating cells.     

Fractal analysis of the trabecular bone pattern in the presence/absence of metal artifact–producing objects: Comparison of cone-beam computed tomography with panoramic and periapical radiography

Objectives:The effect of metallic objects on the fractal dimension (FD), bone area fraction (BAF) and gray scale values (GSVs) of cone-beam CT (CBCT) images was assessed. Also, FD, BAF and GSV were compared among CBCT, digital periapical and panoramic radiographies.Methods:Digital periapical and panoramic radiographs were acquired from six blocks of bovine rib. Additionally, different arrangements of titanium implants and intracanal metallic posts were created in the bone blocks and CBCT scans were taken from the different implant-root arrangements. The three radiographical modalities were compared by analysis of variance. Pairwise comparisons between the modalities were performed by the Tukey test (significance level set at 0.05).Results:Different root-implant arrangements in the CBCT images revealed no significant differences in the FD (p = 0.920), BAF and GSV values (p = 0.623). FD differed significantly among the three modalities (p < 0.001). Significant differences were found between CBCT and each of the periapical and panoramic techniques (p < 0.001), while no remarkable differences were observed in the FD of the periapical and panoramic images (p = 0.294). BAF and GSV showed significantly different results among the three radiographical techniques (p < 0.001). The difference was remarkable between CBCT and periapical (p < 0.001), CBCT and panoramic (p < 0.001) and periapical and panoramic (p = 0.008).Conclusion:Presence of titanium implants and intracanal posts does not produce different results in the fractal analysis (FA) of the CBCT images. The trabecular bone pattern is best assessed by FA of the periapical radiographs followed by the panoramic and CBCT techniques, respectively.     

Effectiveness of quantitative MAA SPECT/CT for the definition of vascularized hepatic volume and dosimetric approach: phantom validation and clinical preliminary results in patients with complex hepatic vascularization treated with yttrium-90-labeled microspheres

The goal of this study was to assess the use of quantitative single-photon emission computed tomography/computed tomography (SPECT/CT) analysis for vascularized volume measurements in the use of the yttrium-90-radiolabeled microspheres (TheraSphere). A phantom study was conducted for the validation of SPECT/CT volume measurement. SPECT/CT quantitative analysis was used for the measurement of the volume of distribution of the albumin macroaggregates (MAA; i.e., the vascularized volume) in the liver and the tumor, and the total activity contained in the liver and the tumor in four consecutive patients presenting with a complex liver vascularization referred for a treatment with TheraSphere. SPECT/CT volume measurement proved to be accurate (mean error <7%) and reproducible (interobserver concordance 0.99). For eight treatments, in cases of complex hepatic vascularization, the hepatic volumes based on angiography and CT led to a relative overestimation or underestimation of the vascularized hepatic volume by 43.2 ± 32.7% (5-87%) compared with SPECT/CT analyses. The vascularized liver volume taken into account calculated from SPECT/CT data, instead of angiography and CT data, results in modifying the activity injected for three treatments of eight. Moreover, quantitative analysis of SPECT/CT allows us to calculate the absorbed dose in the tumor and in the healthy liver, leading to doubling of the injected activity for one treatment of eight. MAA SPECT/CT is accurate for volume measurements. It provides a valuable contribution to the therapeutic planning of patients presenting with complex hepatic vascularization, in particular for calculating the vascularized liver volume, the activity to be injected and the absorbed doses. Studies should be conducted to assess the role of quantitative MAA/SPECT CT in therapeutic planning.