Thrombin-soaked embolization coils: the effect on whole blood clotting time.

Embolization coils are well established as embolic agents for the treatment of various conditions. Several authors have commented on the increased 'thrombogenicity' of coils following soaking in thrombin solutions. We have carried out an in vitro study, carefully measuring the effect on whole blood clotting time (WBCT), of soaking coils in thrombin solutions of different concentrations (100, 200, 400, 1000 U/ml). Untreated steel coils are shown to have clot promoting activity (CPA) in vitro, reducing WBCT from 14.85 min to 5.53 min. Passing the coils down a saline-filled catheter slightly reduces their CPA, but not significantly (p = 0.21). With thrombin concentrations above 100 U/ml, a significant reduction in WBCT is recorded, but although there is a trend of increasing CPA with increasing thrombin concentration from 200-1000 U/ml, a plateau in WBCT is seen, and the difference is not significant. It therefore appears that the clot promoting activity of embolic coils is significantly increased by soaking them in a relatively weak thrombin solution. The use of such a solution (e.g. 200 U/ml) in vivo would have obvious value in limiting the potential systemic effects of thrombin.     

Steel occlusion coils: pretreatment with thrombin

Stainless steel vascular occlusion coils provide a convenient and effective means for occluding large vessels. Occasionally, coagulopathies or extremely high-flow states delay or preclude the formation of an effective thrombus around this device. A technique is described for pretreating these coils with a thrombin solution. This pretreatment assures a prompt and effective occlusion of the target vessel.     

Embolization of a subclavian artery aneurysm with steel coils and thrombin

Subclavian artery aneurysms are rare lesions usually treated by surgical excision or ligation. Steel coils were used successfully to treat a rapidly enlarging subclavian aneurysm in a patient deemed unsuitable for surgery. Because of a profound, uncorrectable coagulopath, thrombin was required to obtain effective thrombosis.     

Combination of signals from array coils using image-based estimation of coil sensitivity profiles.

It is well established that the optimal unbiased way to combine image data from array coils is a pixel-by-pixel sum of coil signals, with each signal weighted by the individual coil sensitivity at the location of the pixel. A pragmatic alternative combines the images from the coils as the square root of the sum of squares (SOS), which can reduce the signal-to-noise ratio (SNR) and introduce bias. This work describes how to replace coil sensitivity by an image-derived quantity that enables close to optimal signal combination up to a global intensity scaling. Typical scaling is by an individual coil sensitivity or a linear or SOS combination of the sensitivities of some or all of the coils in the array. The method decreases signal bias, improves SNR when coils have unequal noise levels, and can reduce image artifacts. It can produce phase-corrected data, which eliminates bias completely. In addition, the method allows images from arrays that include highly localized coils, such as a prostate coil and external pelvic array, to be combined with near-optimal SNR and an intensity modulation that makes them easier to view.     

166Ho-DOTMP radiation-absorbed dose estimation for skeletal targeted radiotherapy.

166Ho-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetramethylene-phosphonate (DOTMP) is a tetraphosphonate molecule radiolabeled with 166Ho that localizes to bone surfaces. This study evaluated pharmacokinetics and radiation-absorbed dose to all organs from this beta-emitting radiopharmaceutical. METHODS: After two 1.1-GBq administrations of 166Ho-DOTMP, data from whole-body counting using a gamma-camera or uptake probe were assessed for reproducibility of whole-body retention in 12 patients with multiple myeloma. The radiation-absorbed dose to normal organs was estimated using MIRD methodology, applying residence times and S values for 166Ho. Marrow dose was estimated from measured activity retained after 18 h. The activity to deliver a therapeutic dose of 25 Gy to the marrow was determined. Methods based on region-of-interest (ROI) and whole-body clearance were evaluated to estimate kidney activity, because the radiotracer is rapidly excreted in the urine. The dose to the surface of the bladder wall was estimated using a dynamic bladder model. RESULTS: In clinical practice, gamma-camera methods were more reliable than uptake probe-based methods for whole-body counting. The intrapatient variability of dose calculations was less than 10% between the 2 tracer studies. Skeletal uptake of 166Ho-DOTMP varied from 19% to 39% (mean, 28%). The activity of 166Ho prescribed for therapy ranged from 38 to 67 GBq (1,030-1,810 mCi). After high-dose therapy, the estimates of absorbed dose to the kidney varied from 1.6 to 4 Gy using the whole-body clearance-based method and from 8.3 to 17.3 Gy using the ROI-based method. Bladder dose ranged from 10 to 20 Gy, bone surface dose ranged from 39 to 57 Gy, and doses to other organs were less than 2 Gy for all patients. Repetitive administration had no impact on tracer biodistribution, pharmacokinetics, or organ dose. CONCLUSION: Pharmacokinetics analysis validated gamma-camera whole-body counting of 166Ho as an appropriate approach to assess clearance and to estimate radiation-absorbed dose to normal organs except the kidneys. Quantitative gamma-camera imaging is difficult and requires scatter subtraction because of the multiple energy emissions of 166Ho. Kidney dose estimates were approximately 5-fold higher when the ROI-based method was used rather than the clearance-based model, and neither appeared reliable. In future clinical trials with 166Ho-DOTMP, we recommend that dose estimation based on the methods described here be used for all organs except the kidneys. Assumptions for the kidney dose require further evaluation.     

A radionuclide therapy treatment planning and dose estimation system.

An object-oriented software system is described for estimating internal emitter absorbed doses using a set of computer modules operating within a personal computer environment. The system is called the Radionuclide Treatment Planning and Absorbed Dose Estimation System (RTDS). It is intended for radioimmunotherapy applications, although other forms of internal emitter therapy may also be considered. METHODS: Four software modules interact through a database backend. Clinical, demographic and image data are directly entered into the database. Modules include those devoted to clinical imaging (nuclear, CT and MR), activity determination, organ compartmental modeling and absorbed dose estimation. RESULTS: Both standard phantom (Medical Internal Radiation Dose [MIRD]) and patient-specific absorbed doses are estimated. All modules interact with the database backend so that changes in one process do not influence other operations. Results of the modular operations are written to the database as computations are completed. Dose-volume histograms are an intrinsic part of the output for patient-specific absorbed dose estimates. A sample dose estimate for a potential 90Y monoclonal antibody is described. CONCLUSION: A four-module software system has been implemented to estimate MIRD phantom and patient-specific absorbed doses. Computations of the doses and their statistical distribution for a pure beta emitter such as 90Y take approximately 1 min on a 300 MHz personal computer.     

Solenoidal array coils.

New concepts are presented for inherent decoupling of multi-element solenoidal arrays. First, an uneven counter-rotational (UCR) coil is reported in which two counter-rotational sections are wound unevenly, resulting in a quasi-one-peak sensitivity profile with a null-B1 point. Adding a second solenoid element near the null-B1 point forms an inherently-decoupled solenoidal array. Unlike a sandwiched solenoidal array, an UCR solenoidal array allows for signal contribution at the center from both solenoid elements. Second, a double counter-rotational (DCR) coil is presented in which two null-B1 points are formed by having one counter-rotational winding on each side of the coil. Two solenoidal elements can be added to form a solenoidal array. Finally, more solenoid elements can be added to the array provided that the added coil elements are DCR elements. These DCR coil elements can be used as building blocks for more complex solenoidal arrays. These concepts are illustrated using numerical simulations and tested using prototype coils.     

Retrospective dosimetry: estimation of the dose to quartz using the single-aliquot regenerative-dose protocol.

We report on the application of the single-aliquot regenerative-dose protocol to retrospective dosimetry, using the optically stimulated luminescence (OSL) from quartz extracted from fired bricks. These bricks had previously been exposed to enhanced levels of ionising radiation while part of inhabited structures in the Chernobyl area. The time dependence of the OSL signals is considered first and we conclude that it is most appropriate to use the initial part of the OSL signal for dose estimation, after subtraction of a slowly varying background component. It is then shown that this signal meets the fundamental requirement of the single-aliquot regenerative-dose protocol, in that any change in the luminescence recombination probability can be corrected for by using the OSL response to a fixed test dose. The response of a particular aliquot is examined after three different treatments (untreated, reset by exposure to light and reset by heating to 500 degrees C) and it is shown that, after sensitivity correction, the dose-response curves are indistinguishable up to 10 Gy. The routine application of the protocol is then described and dose estimates are shown to be insensitive to preheat temperature and test-dose size. Finally, dose-depth profiles are presented for two bricks. These profiles demonstrate that the high precisions (approximately 1%) obtained using the regenerative-dose protocol are reflected in smooth dose-depth dependencies.     

Projection-based estimation and nonuniformity correction of sensitivity profiles in phased-array surface coils

PURPOSE: To develop a novel approach for calculating the accurate sensitivity profiles of phased-array coils, resulting in correction of nonuniform intensity in parallel MRI. MATERIALS AND METHODS: The proposed intensity-correction method estimates the accurate sensitivity profile of each channel of the phased-array coil. The sensitivity profile is estimated by fitting a nonlinear curve to every projection view through the imaged object. The nonlinear curve-fitting efficiently obtains the low-frequency sensitivity profile by eliminating the high-frequency image contents. Filtered back-projection (FBP) is then used to compute the estimates of the sensitivity profile of each channel. The method was applied to both phantom and brain images acquired from the phased-array coil. RESULTS: Intensity-corrected images from the proposed method had more uniform intensity than those obtained by the commonly used sum-of-squares (SOS) approach. With the use of the proposed correction method, the intensity variation was reduced to 6.1% from 13.1% of the SOS. When the proposed approach was applied to the computation of the sensitivity maps during sensitivity encoding (SENSE) reconstruction, it outperformed the SOS approach in terms of the reconstructed image uniformity. CONCLUSION: The proposed method is more effective at correcting the intensity nonuniformity of phased-array surface-coil images than the conventional SOS method. In addition, the method was shown to be resilient to noise and was successfully applied for image reconstruction in parallel imaging.     

Radiation signature on exposed cells: Relevance in dose estimation

The radiation is considered as a double edged sword, as its beneficial and detrimental effects have been demonstrated. The potential benefits are being exploited to its maximum by adopting safe handling of radionuclide stipulated by the regulatory agencies. While the occupational workers are monitored by personnel monitoring devices, for general publics, it is not a regular practice. However, it can be achieved by using biomarkers with a potential for the radiation triage and medical management. An ideal biomarker to adopt in those situations should be rapid, specific, sensitive, reproducible, and able to categorize the nature of exposure and could provide a reliable dose estimation irrespective of the time of the exposures. Since cytogenetic markers shown to have many advantages relatively than other markers, the origins of various chromosomal abnormalities induced by ionizing radiations along with dose-response curves generated in the laboratory are presented. Current status of the gold standard dicentric chromosome assay, micronucleus assay, translocation measurement by fluorescence in-situ hybridization and an emerging protein marker the γ-H2AX assay are discussed with our laboratory data. With the wide choice of methods, an appropriate assay can be employed based on the net.     

全国生物剂量估算能力考核结果分析

目的 分析2015—2017年全国放射卫生技术机构生物剂量估算能力考核结果,研判近年来此类机构检测能力发展情况。方法 对2015—2017年参加考核的资料进行分析整理,对合格率、优秀率、参加单位情况及剂量估算偏差分布情况进行统计学分析。结果 合格率逐年升高,2017年同2015年比较,合格率明显提高,差异具有统计学意义（χ²=3.978,P<0.05）。3年共53家单位参与了生物剂量考核,其中连续3年均参加的单位有30家,占57%。3年连续参加考核单位的剂量估算相对偏差分布情况中,估算偏差在5%~10%内的所占比例升高,15%~20%和>20%所占比例下降。结论 2015—2017年全国各单位生物剂量估算能力基本保持稳定,检测水平和合格率逐步提升,优秀率保持平稳。     

Retrospective dose estimation using the dicentric distribution in human peripheral lymphocytes.

The paper presents the results of retrospective dose estimations for a number of Chernobyl victims by different approaches to the analysis of dicentric distributions in peripheral lymphocytes in blood samples taken a long time after the accident. Retrospective dose estimations are compared with dose estimates in the same individuals made immediately after the accident by dicentric frequencies.     

Absorbed dose estimation of some 99mTc-hepatobiliary agents

The absorbed dose estimates of several organs after administration in humans of six new hepatobiliary agents (five ^99mTc-Pyridoxal amino acid complexes and the ^99mTc-HIDA) are presented in comparison with ¹³¹I-Rose-Bengal. The results indicated that the radiation doses absorbed by the total body and gonads as well as by the critical organ (upper part of the large intestine) are significantly lower than those of Rose Bengal. Therefore, the new ^99mTc-agents can be safely applied to humans.     

Absorbed dose estimation of some 99mTc-hepatobiliary agents

The absorbed dose estimates of several organs after administration in humans of six new hepatobiliary agents (five 99mTc-Pyridoxal amino acid complexes and the 99mTc-HIDA) are presented in comparison with 131I-Rose-Bengal. The results indicated that the radiation doses absorbed by the total body and gonads as well as by the critical organ (upper part of the large intestine) are significantly lower than those of Rose Bengal. Therefore, the new 99mTc-agents can be safely applied to humans.     

Measurement and estimation of organ Bremsstrahlung radiation dose

Bremsstrahlung radiation doses were measured in an anthropomorphic phantom using thermoluminescent dosimeters. A single source of 90Y (beta-ray range less than or equal to 1.0 cm) was inserted in the bladder region and dosimeters were placed at distances greater than or equal to 3 cm to preclude detection of decay betas. Doses were corrected so as to represent the case of no biologic clearance. By comparing dosimeter location with the standard MIRD human geometry, sample organ doses could be determined. Representative results were 432 +/- 76 mrad/mCi at 3 cm (bladder), 260 +/- 60 mrad/mCi (uterus), 71 +/- 4 mrad/mCi (lower large intestine), and 1.4 +/- 0.7 mrad/mCi (liver). An estimation method, based on absorbed fraction tables, gave organ doses that were within the errors of measurement for all tissues with the exception of the bladder site. We conclude that organ bremsstrahlung radiation doses are not negligible and that they can be estimated using an integration over both the brake and beta-ray spectra.     

Radiosensitive functional dye: clinical application for estimation of patient skin dose

Institutional review board approval and informed patient consent were obtained. The purpose of the study was to prospectively evaluate the use of radiosensitive indicators to estimate patient entrance skin dose (ESD). Forty-six patients wore a jacket with 48 or 52 indicators adhered to the back during percutaneous coronary interventions; they had eight additional indicators on their upper arms. The patients' ESDs were calculated according to the change in color of the indicators. There were good correlations between the ESDs estimated by using color measurements performed with an optical instrument and those estimated at visual observation (P < .001) and between the ESDs estimated by using a thermoluminescent dosimeter and those estimated by using color measurements (P < .001). The radiosensitive indicator method seems to be useful for estimating ESDs and their distribution during percutaneous coronary intervention; however, visual observation is reliable for estimating doses of up to 5 Gy only. (c) RSNA, 2006.     

基于体型特异性剂量估算值推算冠状动脉CT血管成像中患者器官剂量和个体有效剂量的可行性研究

目的 探讨将体型特异性剂量估算值（SSDE）用于估算冠状动脉CT血管成像（CTA）中患者器官剂量和个体有效剂量的可行性。方法 回顾性连续纳入冠状动脉CTA患者421例,均于第3代双源Force型CT采用前瞻性心电门控触发轴扫协议检查。通过Radimetrics计算患者水当量直径以计算每位患者的SSDE;使用Monte Carlo模拟估算患者扫描范围内器官的吸收剂量包括心脏、肺、肝和乳腺。使用国际放射防护委员会（ICRP）103报告的器官敏感加权系数,将患者主要敏感器官的剂量加权求和计算个体有效剂量。使用线性相关分析验证SSDE与器官剂量及个体有效剂量的相关性,并推导基于SSDE估算器官剂量和个体有效剂量的转换系数。使用平均差值比评价该估算方法的准确性。结果 容积CT剂量指数（CTDI_vol）为（16.8±8.7） mGy,SSDE为（20.8±8.8） mGy,个体有效剂量为（4.4±2.9） mSv。基于SSDE估算器官剂量的线性拟合公式为：心脏Y=1.2X-6.4（R²=0.91,P<0.05,平均误差0.1%）;乳腺Y=1.4X-7.4（R²=0.91,P<0.05,平均误差7.9%）;肺脏Y=0.89X-4.6（R²=0.86,P<0.05,平均误差8.3%）;肝脏Y=0.36X-1.8（R²=0.64,P<0.05,平均误差-17.9%）。基于SSDE估算个体有效剂量的线性拟合公式为：男Y=0.21X-1.2（R²=0.92,P<0.05,平均误差0.2%）;女Y=0.39X-2.2（R²=0.93,P<0.05,平均误差1.7%）。结论 在冠状动脉CTA检查中通过SSDE和相应的转换系数可估算被照射器官吸收剂量和个体有效剂量,将有助于在临床工作中实现患者辐射剂量及风险的个性化评估和精准管理。