National survey to update the diagnostic reference levels in interventional radiology procedures in Italy: working methodology

Interventional Radiology (IR) deals with the diagnosis and treatment of various diseases through medically guided imaging. It provides unquestionable benefits to patients, but requires, in many cases, the use of high doses of ionizing radiation with a high impact on radiation risks to patients and to overall dose to the population. The International Commission on Radiological Protection introduced Diagnostic reference levels (DRLs) as an effective tool to facilitate dose verification and optimize protection for patients undergoing radiological procedures. In addition, EURATOM Council Directive 2013/59 and its Italian transposition (Legislative Decree 101/2020) have reiterated that DRLs must be established for many common radiological diagnostic procedures to compare the radiation dose delivered for the same diagnostic examination. Within this framework, Istituto Superiore di Sanità-Italian National Institute of Health (ISS)-, in collaboration with relevant Italian Scientific Societies, has provided documents on DRLs in radiological practices such as diagnostic and IR and diagnostic nuclear medicine. These reference documents enable National Hospitals to comply national regulation. The implementation of DRLs in IR is a difficult task because of the wide distribution of doses to patients even within the same procedure. Some studies have revealed that the amount of radiation in IR procedures is influenced more by the complexity of the procedure than by the weight of the patient, so complexity should be included in the definition of DRLs. For this reason, ISS promoted a survey among a sample of Italian Centers update national DRL in IR procedures with related complexity factors than can be useful for other radiological centers and to standardize the DRLs values. In the present paper the procedural methodology developed by ISS and used for the survey will be illustrated.

DNA damage in lens epithelial cells exposed to occupationally-relevant X-ray doses and role in cataract formation

The current framework of radiological protection of occupational exposed medical workers reduced the eye-lens equivalent dose limit from 150 to 20 mSv per year requiring an accurate dosimetric evaluation and an increase understanding of radiation induced effects on Lens cells considering the typical scenario of occupational exposed medical operators. Indeed, it is widely accepted that genomic damage of Lens epithelial cells (LEC) is a key mechanism of cataractogenesis. However, the relationship between apoptosis and cataractogenesis is still controversial. In this study biological and physical data are combined to improve the understanding of radiation induced effects on LEC. To characterize the occupational exposure of medical workers during angiographic procedures an INNOVA 4100 (General Electric Healthcare) equipment was used (scenario A). Additional experiments were conducted using a research tube (scenario B). For both scenarios, the frequencies of binucleated cells, micronuclei, p21-positive cells were assessed with different doses and dose rates. A Monte-Carlo study was conducted using a model for the photon generation with the X-ray tubes and with the Petri dishes considering the two different scenarios (A and B) to reproduce the experimental conditions and validate the irradiation setups to the cells. The simulation results have been tallied using the Monte Carlo code MCNP6. The spectral characteristics of the different X-ray beams have been estimated. All irradiated samples showed frequencies of micronuclei and p21-positive cells higher than the unirradiated controls. Differences in frequencies increased with the delivered dose measured with Gafchromic films XR-RV3. The spectrum incident on eye lens and Petri, as estimated with MCNP6, was in good agreement in the scenario A (confirming the experimental setup), while the mean energy spectrum was higher in the scenario B. Nevertheless, the response of LEC seemed mainly related to the measured absorbed dose. No effects on viability were detected. Our results support the hypothesis that apoptosis is not responsible for cataract induced by low doses of X-ray (i.e. 25 mGy) while the induction of transient p21 may interfere with the disassembly of the nuclear envelop in differentiating LEC, leading to cataract formation. Further studies are needed to better clarify the relationship we suggested between DNA damage, transient p21 induction and the inability of LEC enucleation.

Provision of Italian diagnostic reference levels for diagnostic and interventional radiology

OBJECTIVES

The diagnostic reference level (DRL) is a useful tool for the optimisation of medical exposures. Thus, a Working Party coordinated by the Italian National Institute of Health and the National Workers Compensation Authority has been formed to provide Italian DRLs, for both diagnostic and interventional procedures, to be used as appropriate for the implementation of the 2013/59 European Directive into the national regulation.

MATERIALS AND METHODS

The multidisciplinary Working Party was formed by professionals involved in diagnostic and interventional radiology medical exposures and started from a critical revision of both the literature and the results of previous Italian surveys. The procedures were divided into five sections for adult (projection radiography, mammography, diagnostic fluoroscopy, CT and interventional radiology) and two sections for paediatric patients (projection radiography and CT). The provided DRL values have been identified for "normal" adult patients and for age-classes of paediatric patients.

RESULTS

Some of the DRL values provided by the Working Party are reported in this study as an example, divided by adult/paediatric patients, radiological technique and examination: specifically, DRLs for new radiological practices and new dose quantities as DRLs metric were introduced. The median value (rather than the mean) for each procedure, derived from a sample of patients, has to be compared with the corresponding DRL value, and dosimetric data related to a minimum number of patients should be collected for each examination.

CONCLUSIONS

The approach to the definition and use of DRLs through guidelines of national Authorities in collaboration with scientific Associations should simplify the periodical updating and could be useful for keeping the optimisation of medical exposures faithful to the development of radiological practice.

HPV DNA Associates With Breast Cancer Malignancy and It Is Transferred to Breast Cancer Stromal Cells by Extracellular Vesicles

A causal link between Human Papillomavirus (HPV) and breast cancer (BC) remains controversial. In spite of this, the observation that HPV DNA is over-represented in the Triple Negative (TN) BC has been reported. Here we remark the high prevalence of HPV DNA (44.4%) in aggressive BC subtypes (TN and HER2+) in a population of 273 Italian women and we convey the presence of HPV DNA in the epithelial and stromal compartments by in situ hybridization. As previously reported, we also found that serum derived-extracellular vesicles (EVs) from BC affected patients contain HPV DNA. Interestingly, in one TNBC patient, the same HPV DNA type was detected in the serum-derived EVs, cervical and BC tissue samples. Then, we report that HPV DNA can be transferred by EVs to recipient BC stromal cells that show an activated phenotype (e.g., CD44, IL6 expression) and an enhanced capability to sustain mammospheres (MS) formation. These data suggest that HPV DNA vehiculated by EVs is a potential trigger for BC niche aggressiveness.

Conversion factors of effective and equivalent organ doses with the air kerma area product in patients undergoing coronary angiography and percutaneous coronary interventions

To derive effective dose (E), organ dose (H_T) and conversion factors with the air kerma area product (KAP) in coronary angiography (CA) and percutaneous coronary intervention (PCI) by the radial route, using the ICRP 103 tissue weighting factors. The study included 34 patients referred for CA and 31 for PCI. E and H_T were derived from in-the-field KAP measurements using Montecarlo methods. Median KAP of 23.2 and 56.8Gycm² and E of 6.9 and 20.0mSv were found for CA and PCI, respectively. Mean KAP and E were significantly higher in males than in females (52.4±40.0 vs 32.3±16.6Gycm²; p=0.02) and (16.8±13.6 vs 10.7±5.8mSv; p=0.04). KAP (r=0.39; p=0.001) and E (r=0.34; p=0.005) showed a significant correlation with the patient's weight. Conversion factors between KAP and E (E/KAP) were 0.30±0.04mSvGy^-1cm^-2 for CA and 0.33±0.05mSvGy^-1cm^-2 for PCI. No significant differences in the E/KAP between males and females were found (0.31±0.05 vs 0.33±0.05; p=0.08). Again, no significant correlation was found between E/KAP and patient's weight (r=0.23; p=0.07). The correlation between E and KAP was excellent for CA (r=0.99) and PCI (r=0.96). The correlation between H_T and KAP ranged from r=0.87 to r=1 and from r=0.71 to r=0.98 for CA and PCI, respectively. A single factor, the total KAP, could be used for a specific acquisition protocol to reliably estimate E and H_T without the need of a patient's specific analysis. Conversion factors might be installation, X-ray beam quality or protocol dependent.

Intensity Modulated Radiation Therapy With Simultaneous Integrated Boost in Patients With Brain Oligometastases: A Phase 1 Study (ISIDE-BM-1)

PURPOSE

To investigate the maximum tolerated dose of intensity modulated radiation therapy simultaneous integrated boost whole-brain radiation therapy for palliative treatment of patients with <5 brain metastases using a standard linear accelerator.

MATERIALS AND METHODS

The whole brain plus 3-mm margin was defined as the planning target volume (PTV_wb), whereas each brain metastasis, defined as the contrast-enhancing tumor on MRI T1 scans, plus a 3-mm isotropic margin, was defined as metastases PTV (PTV_m). Radiation therapy was delivered in 10 daily fractions (2 weeks). Only the dose to PTV_m was progressively increased in the patient cohorts (35 Gy, 40 Gy, 45 Gy, 50 Gy), whereas the PTV_wb was always treated with 30 Gy (3 Gy per fraction) in all patients. The dose-limiting toxicity was evaluated providing that 3 months of follow-up had occurred after the treatment of a 6-patient cohort.

RESULTS

Thirty patients were enrolled in the study (dose PTV_m: 35 Gy, 8 patients; 40 Gy, 6 patients; 45 Gy, 6 patients; 50 Gy, 10 patients). The number of treated brain metastases was 1 in 18 patients, 2 in 5 patients, 3 in 6 patients, and 4 in 1 patient. Three patients experienced dose-limiting toxicity: 1 patient at dose level 2 presented grade 3 (G3) skin toxicity; 1 patient at dose level 4 presented G3 neurologic toxicity; and 1 patient at the same level showed brain hemorrhage. Most patients showed G1 to 2 acute toxicity, in most cases skin (n=19) or neurologic (n=10). Twenty-seven were evaluable for response: 6 (22%) stable disease, 18 (67%) partial response, and 3 (11%) complete response. Median survival and 1-year overall survival were 12 months and 53%, respectively. No patient showed late toxicity.

CONCLUSIONS

In this first prospective trial on the use of intensity modulated radiation therapy simultaneous integrated boost delivered with a standard linear accelerator in patients with brain oligometastases, a boost dose up to 50 Gy in 10 fractions was tolerable according to the study design.

Radiation-induced mesothelioma among long-term solid cancer survivors: a longitudinal analysis of SEER database

We investigated the association between external beam radiotherapy (EBRT) and pleural and peritoneal mesothelioma among long‐term (>5 years) solid cancer survivors. We analyzed data from the US Surveillance, Epidemiology, and End Results (SEER) program (1973–2012). We fitted survival models adjusted by age, gender, race, year, surgery, and relative risk of primary mesothelioma in the county of residence (proxy for individual asbestos exposure). We estimated hazard ratios [HR] with reference to nonirradiated patients. We distinguished between scattered and direct irradiation to study the dose–response. We observed 301 mesotheliomas (265 pleural; 32 peritoneal; 4 others) among 935,637 patients. EBRT increased the risk of mesothelioma (any site; HR 1.34, 95% CI 1.04–1.77). We observed an increased risk of pleural mesothelioma (HR for EBRT 1.34, 95% CI 1.01–1.77), but we did not find signs of a dose–response relationship (HR for scattered irradiation 1.38; HR for direct irradiation 1.23). On the opposite, only direct peritoneal irradiation was associated with peritoneal mesothelioma (HR 2.20, 95% CI 0.99–4.88), particularly for latencies ≥10 years (HR 3.28, 95% CI 1.14–9.43). A competing risks analysis revealed that the clinical impact of radiation‐induced mesothelioma was limited by the high frequency of competing events. The cumulative incidence function of mesothelioma after 40 years of observation was very low (nonirradiated patients 0.00032, irradiated patients 0.00055).EBRT might be a determinant of mesothelioma. Longer latency periods are associated with higher risks, while the dose–response seems nonlinear. The clinical impact of mesothelioma after EBRT for primary solid cancers is limited.

X-ray population exposure from projection radiology and computed tomography in Emilia-Romagna from 2001 to 2010: comparison of ICRP 60 and ICRP 103 weighting factors

PURPOSE

This paper shows the trends from 2001 to 2010 of per caput and collective effective dose (S) to the Emilia-Romagna population due to radiation exposure from projection radiology (PR) and computed tomography (CT), calculated according to both ICRP60 and ICRP103 tissue weighting factors.

MATERIALS AND METHODS

The frequency of examinations and dose calculations were based on data provided directly by Emilia-Romagna Health Trusts. In particular, effective doses were evaluated using the tissue weighting (w T) factors reported both in ICRP60 (w T,60) and in ICRP103 (w T,103).

RESULTS

A decrease in the frequency of PR skull examinations and an increase in the frequency of mammography, CT of the abdomen, chest, and head-neck were found during the decade. In 2010, the PR/CT procedures contributed 75.4 %/24.6 % to examination frequency and approximately 10 %/90 % to dose; S was 6,169.2 man Sv when w T,60 was used and 5,855.1-6,665.5 man Sv when w T,103 in two different mathematical models was utilised.

CONCLUSIONS

Dose estimates pre- and post-ICRP103 must be compared carefully, because changes due to different radiological practices could be confused with changes due to the use of different w T's. In general, dose evaluations with the use of w T,60 until 2007 and w T,103 from 2008 seem to be consistent and coherent.

Optimisation of radiological protocols for chest imaging using computed radiography and flat-panel X-ray detectors

PURPOSE

Digital radiography technology has replaced conventional screen-film systems in many hospitals. Despite the different characteristics of new detector materials, frequently, the same radiological protocols previously optimised for screen film are still used with digital equipment without any critical review. This study addressed optimisation of exposure settings for chest examinations with digital systems, considering both image quality and patient dose.

MATERIALS AND METHODS

Images acquired with direct digital radiography equipment and a computed radiography system were analysed with specially developed commercial software with a four-alternative forced-choice method: the most promising protocols were then scored by two senior radiologists.

RESULTS

Digital technology offers a wide dynamic range and the ability to postprocess images, allowing use of lower tube potentials in chest examinations. The computed radiography system showed both better image quality and lower dose at lower energies (85 kVp and 95 kVp) than those currently used (125 kVp). Direct digital radiography equipment confirmed both its superior image quality and lower dose requirements compared with the storage phosphor plate system.

CONCLUSIONS

Generally, lowering tube potentials in chest examinations seems to allow better image quality/effective dose ratio when using digital equipment.

Survey of the interventional cardiology procedures in Italy

Interventional cardiology procedures are increasing because they offer many advantages to patients compared with other techniques: therefore the Italian National Institution for Insurance against Accidents at Work decided to start a survey for monitoring the state-of-the-art regarding the professionals involved in those procedures. The survey covered six cardiology and medical physics Italian departments. Each centre was asked to record 10 examinations for five types of procedures: coronary angiography (CA), electrophysiology studies (ES), pacemaker implantation (PI), percutaneous transluminal coronary angioplasty (PTCA) and radiofrequency catheter ablation (RA). For each examination all the centres were requested to fill in a questionnaire containing information regarding the operator performing the examination, the patient and the procedure. A total of 290 examinations were recorded: 103 CA, 14 ES, 68 PI, 79 PTCA and 26 RA. As occupational doses are strongly related to patient doses, both patients and operators radiation dose data are reported. Ratios of maximum to minimum mean patient doses across the hospitals surveyed were 2.0, 3.9, 7.0, 1.8 and 1.4 for CA, ES, PI, PTCA and RA, respectively. The calculated rounded mean dose-area product values across all participating hospitals were comparable with other values reported in the literature. In general, specific radiation protection tools were used by all operators performing different procedures in all hospitals. A major issue in this survey was the absence of information about correlation between staff and patient doses in a single procedure: future studies could be more aimed to prospective goals where occupational exposures per procedure are monitored specifically.

Early predictive value of 18F-FDG-PET assessment in advanced esophagogastric junction and gastric cancer patients treated with cetuximab-containing therapy

e15601

Background: 18F-FDG-PET/CT (PET) was reported to predict the pathological response during preoperative chemotherapy in esophagogastric junction (GEJ) or gastric (G) cancer pts. The aim of this study is to evaluate the usefulness of an early change in PET at several time-points in predicting response to cetuximab-containing therapy in pts with advanced GEJ or G cancer. Methods: We evaluated 51 pts with locally advanced/metastatic GEJ or G adenocarcinoma who underwent a first line cetuximab- treatment in two Italian phase II studies. Twenty nine pts (GEJ/G = 5/24; locally advanced/metastatic = 2/27) received cetuximab in combination with cisplatin/docetaxel (DOCETUX study) and 22 pts (GEJ/G = 2/20; locally advanced/metastatic = 3/19) received cetuximab in combination with FOLFIRI (FOLCETUX Study). PET scans were performed at baseline, and in FDG-avid pts, again on day 21 in the DOCETUX study and on day 42 in the FOLCETUX study. Metabolic response was defined as a decrease in maximum standard uptake value (SUV) ≥35% on the basis of our previous study (Di Fabio et al., Gastric Cancer 10:221–227, 2007).Objective response, according to RECIST criteria, was assessed by CT scan at baseline and every 6 weeks. Results: Five pts (10.2%) had FDG non- avid tumor (all pts with signet cell carcinoma). In the 46 FDG-avid tumor pts, the median SUV at baseline was 10.3 (range 5.0 - 36.4). The response rate (RR) was significantly higher in pts with a drop ≥35% in SUV from baseline to day 42: 83% (10/12 pts) in metabolic responders vs. 25% (2/8 pts) in non-metabolic responders (p= 0.019). In contrast, the SUV change at day 21 did not correlate with objective response: RR 57.1% (8/14 pts) in metabolic responders vs. 41.7% (5/12 pts) in non-metabolic responders (p= 0.695). The RR in non-avid tumor pts was 20% (1/5 pts). Conclusions.Our study suggests that in advanced gastric cancer pts with FDG-avid tumor the PET predicts objective response at day 42, but not at day 21. A PET response assessment can provide an opportunity to change the treatment in non-responder pts. Prospective trials defining the role of PET in gastric cancer are warranted.

No significant financial relationships to disclose.

Transjugular intrahepatic portosystemic shunt: a case report of rescue management of unrestrainable variceal bleeding in a pregnant woman

Liver cirrhosis complications in pregnant women are frequent and death rate secondary to variceal bleeding is relevant. Both sclerotherapy and banding ligation seem to be safe procedures in pregnancy; when bleeding is not arrested endoscopically an emergency transjugular intrahepatic portosystemic shunt should be considered, but data regarding pregnant cirrhotic women are scarce. We describe the case of a pregnant woman at 14 weeks of gestation who underwent management of acute variceal bleeding by transjugular intrahepatic portosystemic shunt. Transjugular intrahepatic portosystemic shunt may represent a rescue treatment for failed attempts of band ligation or sclerotherapy.

Patient dose in digital projection radiography

In projection radiography, two types of digital imaging systems are currently available, computed radiography (CR) and direct radiography (DR): a difference between them can be stated in terms of dose and image quality. In the Radiology Emergency Department of our hospital, a flat-panel DR equipment (Siemens Axiom Aristos FX) and two CR systems (Kodak CR-850) are employed. In 2006, five standard radiographic examinations (abdomen, chest, lumbar spine, pelvis, skull) were considered: doses delivered to patients in terms of both entrance skin dose (ESD) and effective dose (E) were calculated and compared in order to study the dosimetric discrepancies between CR and DR. Assessment of image quality is undertaken by Consultant Radiologists to ensure that the quality criteria for diagnostic radiographic images of the European guidelines were met. Results showed that both ESD and E in DR are lower than that in CR; all images met the criteria in the European Guidelines for both modalities and were used for reporting by the radiologists. Since the operators are the same and the image quality is comparable in both modalities, this study shows that in the considered examinations, DR can perform better than CR from a dosimetric point of view.

Comparison of radiation doses to patients undergoing standard radiographic examinations with conventional screen–film radiography, computed radiography and direct digital radiography

New flat-panel direct digital radiography equipment has recently been installed in our Accident and Emergency Department; its characteristics and versatility are well suited to the work undertaken in this environment. The aim of this study was to compare radiation doses to patients undergoing standard radiographic examinations using conventional screen-film radiography, computed radiography and direct digital radiography; entrance surface dose and effective dose were calculated for six standard examinations (a total of 10 projections) using standard patient exposure parameters for the three imaging modalities. It was found that doses for computed radiography (all examinations) were higher than the doses for the other two modalities; effective doses for direct digital radiography were approximately 29% and approximately 43% lower than those for screen-film radiography and computed radiography, respectively. The image quality met the criteria in the European guidelines for all modalities.

Monitoring of the medical radiological exposures of the population of the Emilia–Romagna Region

PURPOSE

The Italian Decree of Law 187/2000 provides for many fulfilments relevant to justification and optimisation of medical exposures that can complicate the daily work of radiology departments if considered as mere legal requirements. On the contrary, this law should be regarded as a good opportunity to analyse and optimise working practices. To this end, the Emilia- Romagna Region carried out an initial assessment of medical exposures to its population in 2001 followed by a second survey taking into account new dosimetric evaluations. This paper illustrates the results of this second survey and analyses the most significant parameters in comparison with similar studies reported in the literature.

MATERIALS AND METHODS

We first determined the examinations to be considered: 12 easily identifiable examinations divided into macroaggregates were selected for conventional radiography and computed tomography (CT). Hospitals of the Emilia-Romagna Region were directly asked to provide the number of examinations performed subdivided by type and grouped by nomenclature code, some technical parameters related to both examination protocol and equipment and the value of dose quantities as measured by local medical physicists.

RESULTS

Study of distribution of the entrance skin dose for different examinations in single hospitals showed no systematic differences in kilovoltage settings versus dose whereas the number of examinations tended to be inversely proportional to dose. These trends could be explained by the fact that in hospitals where many examinations of the same type are performed, operators, equipment and procedures are well integrated, leading to a level of specialisation that allows efficient interaction in order to deliver an "optimal dose". Analysis of the "entrance skin dosemax"/"entrance skin dosemin" ratios for various projections and comparison with literature data seem to show that a "scale factor" has a fundamental role in the variability of entrance skin dose values amongst hospitals and that "chest" examinations are the most critical, with the greatest differences in entrance skin doses.

CONCLUSIONS

The evaluations performed in this study show that this type of analysis heavily relies not only on the cooperation of all professionals responsible for patient radiation protection but also on the experience gained during previous surveys because data collection is a very critical process that can invalidate, if not carefully performed, all subsequent processing.

Usefulness of the (F/T)/PSA Density Ratio to Detect Prostate Cancer

INTRODUCTION

Prostate-specific antigen (PSA) is the most important marker in the detection of prostate cancer, but its reliability is limited by a low specificity. To improve the specificity of PSA, a new parameter, based on the combination of free/total PSA (F/T) with PSA density, is proposed.

MATERIALS AND METHODS

From April 1999 to June 2003, a series of 647 men with high serum PSA levels were submitted to ultrasound-guided multiple prostate biopsies. Total PSA and free PSA were measured by immunoassay (DASIT, Italy). Receiver operating characteristic (ROC) curves of PSA density, F/T and (F/T)/PSA density (F/T divided by PSA/prostate volume) were constructed, and relative specificity and sensitivity were calculated.

RESULTS

Prostate cancer was present in 284 cases (137 of them with PSA values between 4 and 10 ng/ml), 31 patientshad intraepithelial neoplasia and the remaining cases showed benign prostatic hyperplasia. Analysis of ROC curves in all examined patients showed that the area under the curve (AUC) for (F/T)/PSA density (0.849) was significantly higher than the AUC for F/T (0.681) (p = 0.012). Similar results were observed in the cases with PSA levels between 4 and 10 ng/ml, where the AUC for (F/T)/PSA density (0.768) was significantly higher than the AUC for F/T (0.610) (p = 0.041). In our study, the prostate cancer risk became very high when (F/T)/PSA density values decreased to <1.5.

CONCLUSION

The use of the (F/T)/PSA density ratio may be useful in the detection of prostate cancer, reducing unnecessary prostate biopsies. A cutoff of 1.5 for the (F/T)/PSA density value is recommended for patients with PSA levels between 4 and 10 ng/ml.

Comparison of six phantoms for entrance skin dose evaluation in 11 standard X-ray examinations

Entrance skin dose (ESD) is an important parameter for assessing the dose received by a patient in a single radiographic exposure. The most useful way to evaluate ESD is either by direct measurement on phantoms using an ionization chamber or using calculations based on a mathematical model. We compared six phantoms (three anthropomorphic, two physical, and one mathematical) in 11 standard clinical examinations (anterior‐posterior (AP) abdomen, posterior‐anterior (PA) chest, AP chest, lateral (LAT) chest, AP lumbar spine, LAT lumbar spine, LAT lumbo‐sacral joint, AP pelvis, PA skull, LAT skull, and AP urinary tract) for two reasons: to determine the conversion factors to use for ESDs measured on different phantoms and to validate the mathematical model used. First, a comparison was done between the three anthropomorphic phantoms (Alderson Rando, chest RSD‐77SPL, and 3M skull) and the two physical phantoms (Uniform and AAPM 31); for each examination we obtained “relative entrance skin dose factors.” Second, we compared these five phantoms with the mathematical phantom: the overall accuracy of the model was better than 14%. Total mathematical model and total ionization chamber uncertainties, calculated by quadratic propagation of errors of the single components, were estimated to be on the order of ±12% and ±3%, respectively. To reduce the most significant source of uncertainty, the overall accuracy of the model was recalculated using new backscatter factors. The overall accuracy of the model improved: better than 12%. For each examination an anthropomorphic phantom was considered as the gold standard relative to the physical phantoms. In this way, it was possible to analyze the variations in phantom design and characteristics. Finally, the mathematical model was validated by more than 400 measurements taken on different phantoms and using a variety of radiological equipment. We conclude that the mathematical model can be used satisfactorily in ESD evaluations because it optimizes available resources, it is based on direct measurements, and it is an easy dynamic tool.

PACS number(s): 87.66.Xa

Effective dose calculations in conventional diagnostic X-ray examinations for adult and paediatric patients in a large Italian hospital

The effective dose E is an efficient and powerful parameter to study the radioprotection of the patient. In our hospital, eight radiological departments and more than 100 radiological X-ray tubes are present. The effective doses were calculated for adults and paediatric patients in 10 standard projections. To calculate E, first the entrance skin dose (ESD) was evaluated by a mathematical model that was validated by >400 direct measurements taken with an ionisation chamber on four different phantoms: the overall accuracy of the model was better than 12%. Second, to relate ESD to E, conversion coefficients calculated by Monte Carlo techniques were used. The E-values obtained were of the same order as those presented in the literature. Finally, we analysed how the study of E distributions among the various radiological departments can help to optimise the procedures, by identifying the most critical examinations or sub-optimal clinical protocols.

Local diagnostic reference levels in standard X-ray examinations

The national diagnostic reference levels (NDRLs) form an efficient, concise and powerful standard for optimising radiation protection of a patient. However, in a large hospital, where many radiological departments are present, it is also possible to calculate and define lower dose values as local diagnostic reference levels (LDRLs). In our hospital there are eight radiological departments; in each of these, the entrance skin dose (ESD) distributions were determined for 10 standard projections (AP Abdomen, PA and LAT Chest, AP and LAT Lumbar Spine, LAT Lumbo-Sacral Joint, AP Pelvis, PA and LAT Skull and AP Urinary tract) and then the ESDs were compared with data previously published and with Italian NDRLs. All ESD values were below the corresponding NDRLs. The maximum/minimum ratio of ESDs ranged from 3.9 (LAT Skull) to 34.3 (AP Abdomen) for individual adult patients and from 2.1 (PA Skull) to 6.5 (Urinary tract) across the mean values of the radiological departments. Finally, it is shown how LDRLs can be proposed to obtain a more fully optimised radiation protection of patients.

Quality control of 99Mo/99Tcm generators: results of a survey of the Radiopharmacy Working Group of the Italian Association of Nuclear Medicine (AIMN)

A multicentre survey of the quality control of 99Tcm generators has been completed: 245 generators from seven different commercial sources were tested over a period of 2 years. The results indicate that the mean pH of the eluates was 5.8 +/- 0.6; the aluminium contents were typically < 10 ppm; the radiochemical purity was 99.8 +/- 0.4% and the median 99Mo content was 3.8 x 10(-4) percent. The elution profiles gave a volume of 1.9 ml to obtain 50% of the total eluted activity and of 4.9 ml to obtain 95%. Other radionuclide impurities and heavy metal breakthrough were evaluated by graphite furnace absorption spectrometry and inductively coupled plasma mass spectrometry. National guidelines for the standardization of radiopharmacy procedures are currently being compiled.

[Performance assessment of mammographic diagnostic systems: evolution of methods and their application to a digital image study]

INTRODUCTION

"Receiver Operating Characteristic" (ROC) curves are one of the most efficient analysis tools for the complete evaluation of a diagnostic system performance. However this method is limited in visualizing and locating abnormal structures, such as clusters of microcalcifications on mammographic images. Other more refined and complex techniques have also been suggested, where particular statistical hypotheses are assumed, namely the "Free-response ROC" (FROC), the "Alternative FROC" (AFROC) and the "Free-response Forced Error" (FFE) analyses. We studied the theoretical bases of these different methods and their experimental applications to assess the correctness of the hypothetical statistical distributions.

MATERIAL AND METHODS

We considered two statistical hypotheses: first, that the false-positive response distribution follows the Poissonian statistics; second, that "signal" and "noise" distributions have a Gaussian trend with different means and variances. Thus, we applied the different methods to the responses given by 8 observers (5 radiologists and 3 medical physicists) who independently evaluated 3 digital mammographic samples. Every sample consisted of 39 images, with 1-15 clusters each (total: 100 clusters). The samples were obtained from 39 images available in an Internet database (sample 1); 2 different digital filters were applied to each image (samples 2 and 3). To collects responses, we provided for two phases: first, every observer visualized and located the clusters at a given confidence level; second, when a false-positive response was given, spontaneously or after forcing, the responses were ordered by decreasing conspicuity. Finally, data were analyzed with a "home-made" software by applying the FROC and AFROC analyses to the data collected in phase 1 and the FFE analysis to those collected in phase 2.

RESULTS

We considered the area under the AFROC curve as the most important parameter: the values obtained with the 3 types of analysis are well in agreement within their uncertainties. In particular, the FROC-AFROC agreement did not exceed 5.9% (10 of 14 cases within 2.5%), while the FFE analysis had higher standard deviations associated with the area value (about 10%). The interpolated curves from both FROC and AFROC data were very similar. The three methods had various advantages: the FFE is very simple to calculate and makes the most of the information given by the observer; FROC and AFROC can provide true-positive and false-positive responses on the same image, which permits to optimize the evaluation of a diagnostic system performance. The statistical tools used in the simplest methods are usually integrated with the completeness characteristics of the location of multiple signals on mammograms.

CONCLUSIONS

In theory, every method is necessary because it provides additional information to validate the statistical hypotheses under investigation. In fact, when the methods are used to evaluate and compare several diagnostic systems, the results of the three techniques are equivalent. Therefore, choosing a specific technique depends on both available resources and response type all the hypothetical statistical distributions in our study proved correct.

Evaluation of lung clearance of inhaled pertechnegas

Pertechnegas is a new ventilation agent produced by modifying the atmosphere of combustion of Technegas. Due to its rapid disappearance from the lungs, Pertechnegas has been suggested as useful in measuring pulmonary epithelial permeability. This study aimed to assess the reliability of ventilation scans with Pertechnegas to evaluate alveolar-capillary permeability. Six non-smokers with no evidence of pulmonary disease were investigated. Scintigraphic data were used to evaluate the site of Pertechnegas deposition (by assessing the Penetration Index [PI] of the gas), its clearance rate (by calculating the time to half-clearance [T1/2]) and its lung distribution (by means of a pixel-by-pixel analysis. PI measurements produced a mean value of 88.8 +/- 13.3% (range 69-117%). Time activity curves showed a fast clearance in all cases (mean T1/2 = 10.7 +/- 2.1 min, range 8.1-14.3 min). Comparison of statistical indices of uniform deposition (skewness and kurtosis) indicated satisfactory homogeneity of Pertechnegas distribution throughout the lungs. These data show that after inhalation Pertechnegas has a peripheral deposition and a homogeneous distribution in the lungs and is rapidly cleared through the alveolar-capillary barrier. In conclusion Pertechnegas can be recommended as a potential radiopharmaceutical for studying the pulmonary epithelial barrier.

Early pulmonary involvement in systemic sclerosis assessed by technetium-99m-DTPA clearance rate

Systemic sclerosis (SS) is frequently associated with interstitial lung disease, but clinical symptoms and radiologic abnormalities may occur late in the course of the disease. This study investigated early pulmonary involvement by assessing the clearance rate of inhaled 99mTc-diethylenetriaminepentaacetic acid (DTPA).

METHODS

Sixteen patients with proved SS, no clinical pulmonary symptoms and normal chest radiogram were prospectively studied. The 99mTc-DTPA clearance rate was calculated as the time to half clearance (T1/2) and compared with values obtained in healthy nonsmokers.

RESULTS

Six patients showed abnormally increased clearance (T1/2 < 53 min). Rapid clearance was not correlated to SS disease duration or to abnormal pulmonary function tests. Five of six patients with abnormally increased clearance underwent high-resolution CT, which in all five demonstrated pathologic findings that were suggestive of early interstitial disease.

CONCLUSION

These findings indicate that in SS asymptomatic patients may frequently present with abnormal 99mTc-DTPA clearance; 99mTc-DTPA lung scintigraphy may allow early detection of subclinical pulmonary involvement in SS.

[En-bloc treatment of tumors of the hypopharyngeal-laryngeal-tracheal tract with a new isocentric multipendular technic]

The authors propose a new technique for the treatment of hypopharyngeal-laryngeal-tracheal tract tumors using cobalt-60 irradiation. This technique allows the simultaneous irradiation of both primary tumor and cervical lymph nodes. Therapeutically effective doses can be administered without affecting the spinal cord. The above-mentioned technique consists of 3 isocentric rotations, the widest one carried out by interposing a small lead bar shielding in the middle of the field. Dose distributions obtained in an Alderson-Rando phantom and in a patient are reported.