Occupational skin dose from radionuclide contamination: one country's approach at standardising skin dose estimates using Varskin.

The manipulation of unsealed radiopharmaceuticals by healthcare workers can cause accidental personal contamination leading to occupational radiation skin dose. The UK Ionising Radiations Regulations 2017 require that potential skin doses arising from reasonably foreseeable accident scenarios are included in risk assessments. Workers must be designated as classified if these dose estimates exceed 150 mSv equivalent dose averaged over 1 cm2. Updates from the UK Health and Safety Executive recently prompted many in the UK to review the classification of workers in Nuclear Medicine. Skin dose from contamination cannot be measured, it must be estimated. Varskin+ is a code that is widely recommended for estimating skin dose. The subjective choices made by users when defining modelled scenarios in Varskin+ lead to significant variation in the calculated skin doses. At the time of writing there is no definitive calculation method and all calculations rely on theoretical models. NHS Health Boards in Scotland have adopted a standardised framework for performing skin dose estimates for risk assessments. The parametric sensitivity of Varskin+ inputs were examined and the available evidence was reviewed. Generic, reasonably forseeable, worst-case accident scenarios were decided upon for: direct skin contamination, glove contamination and needlestick injury. Standardised inputs and assumptions for each scenario were compiled in a protocol that has been adopted by the Scottish Health Boards. The protocol allows for differences in practice between departments, but standardises most inputs. While significant uncertainty remains in the estimated skin doses, this approach reduces variation and enables the comparison of estimated skin doses between departments. The framework facilitates continuous improvement as more evidence is gathered to refine the standardised assumptions. Task by task skin dose estimates were made for workers in Nuclear Medicine in Scotland and many workers were designated classified as a result.

Improvement to visualization of nodes in breast cancer patients following audit: are we seeing the problem?

Successful localization of nodes in breast cancer patients depends upon the effectiveness of the lymphoscintigraphy technique employed. A benefit of performing imaging as part of this procedure is that it allows sites to audit their technique. An audit of breast cancer patients at the Glasgow Royal Infirmary (GRI) hospital showed nodes to be visualized in only 81% of patients. Current guidelines state that nodes should be seen in more than 95% of patients. A period of investigation and review led to changes being made to the injection and imaging technique employed at the GRI site. Following these changes a re-audit was performed that showed that the node visualization rate has successfully been increased to 97%, thereby meeting the standards set in the guidelines. This technical note details the results of the initial audit and re-audit, and explains the investigation and changes made to clinical procedures at the GRI site to improve the node visualization rate. The challenges that can occur when performing breast sentinel node procedures are also discussed.

White cell and marrow imaging: subtracting uncertainty.

A subtraction method for assessments of dual-isotope indium-111 (In)-labelled white cell and Tc-nanocoll was proposed, and following a pilot study was introduced in routine service to improve the confidence of reporters. This technical note describes a simple technique to produce subtraction images from routinely acquired images to investigate and exclude post joint replacement infection. Labelled leucocytes (with In) show areas of increased white cell accumulation, whereas Tc-nanocoll images show bone marrow distribution. Images resulting from the subtraction protocol highlight any areas of white cell activity which is not concurrent with the marrow distribution indicative of infection. Fusion images produced from these images sets also assists in localization of white cell accumulation(s). Key to the success of this technique is the use of simultaneous acquisition of both white cell and marrow images; thus removing any issues with patient movement and/or repositioning. Reporting clinicians convey a clear preference for the inclusion of the subtracted and fused images at clinical review.

The clinical safety, biodistribution and internal radiation dosimetry of flutemetamol (¹8F) injection in healthy Japanese adult volunteers.

OBJECTIVES: The Phase I safety, biodistribution and internal radiation dosimetry study in adult healthy Japanese males of flutemetamol ((18)F) injection, an in vivo ß-amyloid imaging agent, is reported and compared with previously obtained Caucasian data. METHODS: Whole-body PET scans of 6 healthy volunteers (age 51.8-61.7 years) were acquired approximately 4 h post-injection (administered activity 102-160 MBq). Venous blood sampling determined (18)F activity concentrations in whole blood and plasma and high-performance liquid chromatography (HPLC) established the percentages of parent [(18)F]flutemetamol and its metabolites. Voided urine activity was recorded. The decay-corrected and normalised (18)F activity of 14 source organ regions as a function of time was entered into the OLINDA/EXM software to calculate the internal radiation dosimetry and effective dose of each subject following the MIRD schema. The pharmacokinetics, biodistribution and dosimetry profiles were compared to data obtained from a cohort of healthy Caucasian adult volunteers from a previous Phase I study of [(18)F]flutemetamol. RESULTS: Flutemetamol ((18)F) injection was well tolerated. The highest mean initial uptakes were measured in the liver (15.2%), lungs (10.2%) and brain (6.6%). The highest mean radiation absorbed doses were received by the gallbladder wall (366 µGy/MBq), upper large intestine (138 µGy/MBq) and small intestine (121 µGy/MBq). The mean effective dose was 34.9 µSv/MBq. HPLC analysis demonstrated that at 5-min post-injection about 75% of plasma (18)F radioactivity was in the form of parent [(18)F]flutemetamol, reducing to 8 and 2% at 25 and 90 min, respectively, giving rise to less lipophilic (18)F-labelled metabolites. Comparisons with the Caucasian cohort showed no differences that could be regarded as clinically significant. CONCLUSION: The clinical safety of [(18)F]flutemetamol demonstrated no differences of clinical significance in the pharmacokinetics, biodistribution and internal radiation dosimetry profiles between Caucasian and Japanese adults.

Impacts of golf courses on macroinvertebrate community structure in Precambrian shield streams.

The influence of golf course operation on benthic macroinvertebrate communities in Precambrian Shield streams was evaluated using rapid bioassessment and the reference condition approach. Streams were sampled for water chemistry and invertebrates in 1999 and 2000, six on operational golf courses, and seven in forested reference locations. Correspondence analysis (CA) was used to determine the major patterns in the macroinvertebrate taxa, and canonical correspondence analysis (CCA) was used to evaluate relationships with environmental variables. The reference streams were used to define the normal range of variation for a variety of summary indices to evaluate the golf course streams. In all cases, golf course streams were higher in nutrients and dissolved ions and more alkaline than the forested reference streams. There was considerable variability in the macroinvertebrate fauna from the golf course streams, which was related to differences in golf course land management practices and to the potential influence of highway runoff. Of the management practices evaluated, fertilizer application rates in particular were important, as was the presence of ponds upstream on the course. Invertebrate taxa with higher abundances in golf course streams included Turbellaria, Isopoda, Amphipoda, Zygoptera, and Trombidiformes. Taxa more common in the reference streams included Ephemeroptera, Megaloptera, Culicidae, and Plecoptera. There were marked differences in the overall benthic macroinvertebrate community in three of the six golf course streams studied relative to the forested reference streams, suggesting that golf course land management on the Precambrian Shield can be associated with significant differences in macroinvertebrate community structure.

Mapping of nuclear import signal and importin α3 binding regions of 52K protein of bovine adenovirus-3.

The L1 region of bovine adenovirus (BAdV)-3 encodes a non-structural protein designated 52K. Anti-52K serum detected a protein of 40kDa, which localized to the nucleus but not to the nucleolus in BAdV-3-infected or transfected cells. Analysis of mutant 52K proteins suggested that three basic residues ((105)RKR(107)) of the identified domain (amino acids (102)GMPRKRVLT(110)) are essential for nuclear localization of 52K. The nuclear import of a GST-52K fusion protein utilizes the classical importin α/ß-dependent nuclear transport pathway. The 52K protein is preferentially bound to the cellular nuclear import receptor importin α3. Although deletion of amino acid 102-110 is sufficient to abrogate the nuclear localization of 52K, amino acid 90-133 are required for interaction with importin-α3 and localizing a cytoplasmic protein to the nucleus. These results suggest that 52K contains a bipartite NLS, which preferentially utilize an importin α3 nuclear import receptor-mediated pathway to transport 52K to the nucleus.

Quantitative analysis shows that contrast medium in positron emission tomography/computed tomography may cause significant artefacts.

OBJECTIVES: Attenuation correction algorithms are required for accurate quantification of PET data and for mapping of radioactive tracers. Modern PET systems incorporate computed tomography (CT) systems to perform attenuation correction. However, high-density media, such as contrast agents, may introduce potentially clinically significant artefacts in PET images when CT-based attenuation correction algorithms are used. Although various groups have investigated this issue, no study has quantitatively assessed the clinical significance of these artefacts by comparing artefact and lesion standardized uptake values (SUVs) in controlled phantom experiments. Furthermore, previous studies have focussed on the effects of increasing the concentration of contrast medium, without investigating the effects of increasing its transaxial area. This study quantifies the clinical significance of increasing the concentration and transaxial area of contrast agents and evaluates a commercially available contrast agent correction algorithm. METHODS: Images of a phantom containing background activity, a volume of contrast agent and varying sizes of hot lesions were acquired using clinical acquisition protocols. Quantitative analysis was performed on transaxial image slices of PET data. RESULTS: The densest medium caused a 125% SUV(mean) increase in the area containing, and immediately adjacent to, contrast medium when compared with a reference water phantom. As the transaxial area of the contrast medium increased, artefacts appeared as a ring of activity around the periphery of the contrast medium. The contrast correction algorithm reduced these artefacts to within ± 39% of the reference results. CONCLUSION: Oral and IV contrast agents can cause clinically significant artefacts in CT-based attenuation-corrected PET images and should be used with caution.