Diagnostic reference levels and complexity indices in interventional radiology: a national programme.

OBJECTIVES: To propose national diagnostic reference levels (DRLs) for interventional radiology and to evaluate the impact of the procedural complexity on patient doses. METHODS: Eight interventional radiology units from Spanish hospitals were involved in this project. The participants agreed to undergo common quality control procedures for X-ray systems. Kerma area product (KAP) was collected from a sample of 1,649 procedures. A consensus document established the criteria to evaluate the complexity of seven types of procedures. DRLs were set as the 3rd quartile of KAP values. RESULTS: The KAP (3rd quartile) in Gy cm2 for the procedures included in the survey were: lower extremity arteriography (n = 784) 78; renal arteriography (n = 37) 107; transjugular hepatic biopsies (THB) (n = 30) 45; biliary drainage (BD) (n = 314) 30; uterine fibroid embolization (UFE) (n = 56) 214; colon endoprostheses (CE) (n = 31) 169; hepatic chemoembolization (HC) (n = 269) 303; femoropopliteal revascularization (FR) (n = 62) 119; and iliac stent (n = 66) 170. The complexity involved the increases in the following KAP factors from simple to complex procedures: THB x4; BD x13; UFE x3; CE x3; HC x5; FR x5 and IS x4. CONCLUSIONS: The evaluation of the procedure complexity in patient doses will allow the proper use of DRLs for the optimization of interventional radiology. KEY POINTS: • National DRLs for interventional procedures have been proposed given level of complexity • For clinical audits, the level of complexity should be taken into account. • An evaluation of the complexity levels of the procedure should be made.

Influence of source batch S dispersion on dosimetry for prostate cancer treatment with permanent implants.

PURPOSE: In clinical practice, specific air kerma strength (SK) value is used in treatment planning system (TPS) permanent brachytherapy implant calculations with (125)I and (103)Pd sources; in fact, commercial TPS provide only one SK input value for all implanted sources and the certified shipment average is typically used. However, the value for SK is dispersed: this dispersion is not only due to the manufacturing process and variation between different source batches but also due to the classification of sources into different classes according to their SK values. The purpose of this work is to examine the impact of SK dispersion on typical implant parameters that are used to evaluate the dose volume histogram (DVH) for both planning target volume (PTV) and organs at risk (OARs). METHODS: The authors have developed a new algorithm to compute dose distributions with different SK values for each source. Three different prostate volumes (20, 30, and 40 cm(3)) were considered and two typical commercial sources of different radionuclides were used. Using a conventional TPS, clinically accepted calculations were made for (125)I sources; for the palladium, typical implants were simulated. To assess the many different possible SK values for each source belonging to a class, the authors assigned an SK value to each source in a randomized process 1000 times for each source and volume. All the dose distributions generated for each set of simulations were assessed through the DVH distributions comparing with dose distributions obtained using a uniform SK value for all the implanted sources. The authors analyzed several dose coverage (V100 and D90) and overdosage parameters for prostate and PTV and also the limiting and overdosage parameters for OARs, urethra and rectum. RESULTS: The parameters analyzed followed a Gaussian distribution for the entire set of computed dosimetries. PTV and prostate V100 and D90 variations ranged between 0.2% and 1.78% for both sources. Variations for the overdosage parameters V150 and V200 compared to dose coverage parameters were observed and, in general, variations were larger for parameters related to (125)I sources than (103)Pd sources. For OAR dosimetry, variations with respect to the reference D0.1cm(3) were observed for rectum values, ranging from 2% to 3%, compared with urethra values, which ranged from 1% to 2%. CONCLUSIONS: Dose coverage for prostate and PTV was practically unaffected by SK dispersion, as was the maximum dose deposited in the urethra due to the implant technique geometry. However, the authors observed larger variations for the PTV V150, rectum V100, and rectum D0.1cm(3) values. The variations in rectum parameters were caused by the specific location of sources with SK value that differed from the average in the vicinity. Finally, on comparing the two sources, variations were larger for (125)I than for (103)Pd. This is because for (103)Pd, a greater number of sources were used to obtain a valid dose distribution than for (125)I, resulting in a lower variation for each SK value for each source (because the variations become averaged out statistically speaking).

Arrival of radionuclides released by the Fukushima accident to Tenerife (Canary Islands).

Two weeks after the accident at the Fukushima-Daichi nuclear power plant, 131I, 137Cs and 134Cs activities were measured in two different stations located in Tenerife (Canary Islands), situated at 300 (FIMERALL) and 2400 (IZAÑA) m.a.s.l, respectively. Peak measured activity concentrations were: 1.851 mBq/m3 (131I); 0.408 mBq/m3 (137Cs) and 0.382 mBq/m3 (134Cs). The activities measured at the FIMERALL station were always higher than at IZAÑA station, suggesting that the radioactive plume arrived to the island associated with low altitude air masses. Simulations of potential dispersion of the radioactive cloud (137Cs) after the nuclear accident in reactor Fukushima I show that radioactive pollution reached remote regions such as the Canary Islands in the Eastern subtropical North Atlantic. The corresponding effective dose to the local population was 1.17 nSv, a value less than one millionth of the annual limit for the general public. Therefore, there was no risk to public health.

Radiometric analysis of farmed fish (sea bass, gilthead bream, and rainbow trout) from Tenerife Island, Spain.

This study analyzed the content of gamma-emitting radionuclides in fish farmed on the island of Tenerife (Canary Islands, Spain). The fish species included in this study were sea bass, gilthead bream, and rainbow trout. The first two species are produced in offshore enclosures, while the third is produced in a freshwater fish farm. All measurements were performed using two high-purity germanium gamma-ray detectors. The content of gamma-emitting radionuclides in the fodder used to feed the different species of farmed fish studied was also determined. The following nuclides were often detected in the analyzed samples: 137Cs, 40K, 235U, 228Ac, 214Bi, 208Tl, 212Pb, and 214Pb. As a complement to this analysis, 210Po concentrations in two fish samples were determined by alpha spectrometry. The nuclide presenting the highest concentration was, as expected, the naturally occurring 40K, with an average concentration of 0.13 +/- 0.01 Bq/g (wet weight) (Bq/gww) in gilthead bream and sea bass and 0.12 +/- 0.01 Bq/gww in rainbow trout. The 235U concentrations determined in the same fish species were 0.6 +/- 0.5, 0.8 +/- 0.7, and 1.6 +/- 1.0 mBq/gww, respectively. This nuclide is seldom reported in fish samples. The concentrations of 137Cs (the only artificial nuclide determined in this study) in gilthead bream and sea bass were 0.026 +/- 0.006 and 0.044 +/- 0.01 mBq/gww, respectively. In addition to the radiometric analysis, the contribution of the analyzed nuclides to the effective dose from the mean daily intake of the fish was calculated. The calculated contribution, in terms of dose per person, produced by intake of the analyzed fish was 0.8 microSv/year. This value does not represent a significant risk to the local population.

Activity concentrations and mean annual effective dose of foodstuffs on the island of Tenerife, Spain.

A total of 26 different food types and 12 elaborated diets were analysed by low-level gamma spectrometry to measure their content of 238U(234Th), 228Ra(228Ac), 226Ra(214Pb), 210Pb, 137Cs and 40K. The concentrations of these radionuclides measured in some imported foodstuffs were compared with those measured in some locally produced ones. Moreover, the concentrations found in the analysed foodstuffs and composite diets were compared with the data available in literature from other locations, such as Egypt, Brazil, Poland and Hong Kong. 40K contributed highest to the daily dose produced by the intake of comestibles. The largest 40K concentrations were measured in the chickpeas and beans with 380 +/- 30 and 380 +/- 20 Bq kg(-1) fresh weights, respectively. The artificial radionuclide 137Cs was measured only above detection limits in the potatoes and sweet potatoes. A mean annual effective dose of 362 microSv with a standard deviation of 110 microSv was calculated from the composite diets.

Estimation of effective dose in some digital angiographic and interventional procedures.

In general, effective dose values for similar interventional vascular radiology (IVR) procedures are different. This is due to problems with the classification of radiological procedures, which make comparisons difficult. Patient size, examination technique and clinical condition as well as the skill of the medical radiologists also affect effective dose. Currently, there is a broad agreement on the classification of similar procedures so that effective dose estimates can be made from measurements of the dose area product (DAP). Thus, reference dose values may be established and comparative studies between different services and hospitals can be made. The objective of this study is to provide dose data for some digital angiographic and interventional procedures. Values of measured DAP for 143 patients for five types of procedures are presented. Procedures investigated were abdominal angiography, arteriography of lower limbs, biliary drainage, embolization of spermatic vein and nephrostomy. All the procedures were performed using digital equipment. Values of DAP and effective dose were 30 Gy cm2 and 6.2 mSv for arteriography of lower limbs and 150 Gy cm2 and 38.2 mSv for biliary drainage. In each one of these procedures, effective dose values per minute of fluoroscopy and per radiography film have been calculated. It is possible to use this information for the rapid estimation of effective dose.