Use of Lean Six Sigma methodology shows reduction of inpatient waiting time for peripherally inserted central catheter placement.

AIM: The aim of this study was to assess the use of Lean Six Sigma methodology to improve the turnaround time (TAT) for inpatient peripherally inserted central catheter (PICC) placement. MATERIALS AND METHODS: Value stream mapping was used to analyse the workflow process for inpatient PICC placement and to divide it into its component parts. Unnecessary steps were eliminated and variation minimised in the remaining processes. The TAT for PICC line placement was recorded for the 6 months prior to implementation of changes, and subsequently, at the 6-month and 2-year follow-up points. RESULTS: Prior to implementing the changes, the mean TAT for PICC line placement was 3.74±3.28 days (95% confidence interval [CI]=3.3-4.17). Six months after implementation, the mean TAT was 1.89±1.82 days (95% CI=1.72-2.06, p<0.0001). The reduction was sustained such that at 2 years post-implementation the mean TAT was 1.88±1.87 days (95% CI=1.78-1.99, p<0.0001). This was achieved despite a 13.8% increase in overall interventional radiological activity. CONCLUSION: By applying Lean Six Sigma methodology to the complex multifactorial processes involved from ordering a PICC to its final insertion, it was possible to identify areas for improvement and to introduce simple, effective measures that resulted in a significant sustained decrease in the TAT without additional resources.

Ice-volume-forced erosion of the Chinese Loess Plateau global Quaternary stratotype site.

The International Commission on Stratigraphy (ICS) utilises benchmark chronostratigraphies to divide geologic time. The reliability of these records is fundamental to understand past global change. Here we use the most detailed luminescence dating age model yet published to show that the ICS chronology for the Quaternary terrestrial type section at Jingbian, desert marginal Chinese Loess Plateau, is inaccurate. There are large hiatuses and depositional changes expressed across a dynamic gully landform at the site, which demonstrates rapid environmental shifts at the East Asian desert margin. We propose a new independent age model and reconstruct monsoon climate and desert expansion/contraction for the last ~250 ka. Our record demonstrates the dominant influence of ice volume on desert expansion, dust dynamics and sediment preservation, and further shows that East Asian Summer Monsoon (EASM) variation closely matches that of ice volume, but lags insolation by ~5 ka. These observations show that the EASM at the monsoon margin does not respond directly to precessional forcing.

An assessment of cumulative external doses from Chernobyl fallout for a forested area in Russia using the optically stimulated luminescence from quartz inclusions in bricks.

Optically stimulated luminescence (OSL) has been used for estimation of the accumulated doses in quartz inclusions obtained from two fired bricks, extracted in July 2004 from a building located in the forested surroundings of the recreational area Novie Bobovichi, the Bryansk Region, Russia. The area was significantly contaminated by Chernobyl fallout with initial (137)Cs ground deposition level of approximately 1.1 MBq m(-2). The accumulated OSL doses in sections of the bricks varied from 141 to 207 mGy, of which between 76 and 146 mGy are attributable to Chernobyl fallout. Using the OSL depth-dose profiles obtained from the exposed bricks and the results from a gamma-ray-survey of the area, the Chernobyl-related cumulative gamma-ray dose for a point detector located in free air at a height of 1m above the ground in the study area was estimated to be ca. 240 mGy for the time period starting on 27 April 1986 and ending on 31 July 2004. This result is in good agreement with the result of deterministic modelling of the cumulative gamma-ray dose in free air above undisturbed ground from the Chernobyl source in the Bryansk Region. Over the same time period, the external Chernobyl-related dose via forest pathway for the most exposed individuals (e.g., forest workers) is estimated to be approximately 39 mSv. Prognosis for the external exposure from 1986 to 2056 is presented and compared with the predictions given by other investigators of the region.

Thermal pre-treatment in the OSL dating of quartz: is it necessary?

Thermal treatment before optically stimulated luminescence (OSL) measurement is an important step in all widely accepted OSL dating procedures used with quartz. This is a major constraint on the design of a portable luminescence instrument for estimating ages in the field. Preliminary experiments show that using a standard dating protocol without heating caused a 30-50% underestimation of equivalent dose. This underestimate arises mainly from OSL derived from the 110 degrees C thermoluminescence (TL) trap; because of the thermal instability of this trap, this OSL contribution is only present in unheated laboratory-regenerated signals, but not in the natural signal. An alternative to thermal pre-treatment is investigated, based on the mathematical separation of the stable dosimetry OSL signal from the total OSL; the latter is the sum of signals from several traps, including the 110 degrees C TL trap. Our results show consistency with dose estimates obtained using a standard measurement protocol including pre-heating.

A comparison of quartz OSL and isothermal TL measurements on Chinese loess.

The reliability of equivalent doses (De) from Chinese loess, measured using isothermal thermoluminescence (ITL) is tested. Dose calculations use the single-aliquot regenerative-dose (SAR) procedure. Despite good reproducibility of laboratory-induced signals and negligible response at zero dose, a significant overestimation of De is observed, compared with OSL measurements. Measurement of a known laboratory dose administered after optical bleaching, but before any heating, demonstrates that the first heating during measurement of the natural signal causes a significant sensitivity change, undetected by SAR. Using the single-aliquot regeneration and added (SARA) dose procedure, which allows for initial sensitivity change, good agreement with OSL is obtained after allowance is made for initial incomplete bleaching. It is concluded that SAR-ITL, in its present form, is not a suitable method for dating Chinese loess; it is very important to undertake a dose recovery test before any TL procedure is used to date sediments.

Luminescence dating of the barrier spit at Chilika Lake, Orissa, India.

Optically stimulated luminescence dating has been used to investigate the chronological development of the outer barrier spit forming Chilika Lake (Orissa, India), the largest brackish-water lagoon in Asia. Sixteen samples were examined, and these yielded equivalent doses of between 153 +/- 3 mGy and 2.23 +/- 0.07 Gy, corresponding to ages from approximately 40 y at the top of the spit to approximately 300 y at the bottom. The youngest ages are consistent with the age of the overlying vegetation, and modern material taken from the sub-tidal beach gave a dose of 4 +/- 2 mGy (corresponding to an age of 0.7 +/- 0.4 y), confirming that any previous potential luminescence signal in the source sediment is completely set to zero before incorporation into the spit. A clearly defined period of >2.5 m of barrier construction approximately 40 y ago is identified; prior to that the deposition rate was relatively constant for approximately 300 y.

Enhancements in luminescence measurement techniques.

New developments in the Risø TL/OSL system includes a software controlled heater fitted underneath the beta source to enable irradiation of samples at an elevated temperature. This allows investigations of competition effects from thermally shallow traps and centres. Significant additional software developments include the facility to vary linearly the stimulation power during stimulation (linearly modulated OSL). The elevated temperature irradiator facility has been further expanded to allow the measurement of radioluminescence (RL) during beta irradiation. This additional facility allows the measurement of TL, OSL and RL in the same software controlled automatic sequence. This paper provides a description of the capabilities of the new combined automatic TL/OSL/RL reader, and illustrates the application of the elevated temperature irradiator facility, and the RL unit. The new measurement facilities have provided preliminary information about possible trap competition during storage, and changes in recombination processes.

Retrospective dose assessment: the measurement of the dose in quartz in dating and accident dosimetry.

In retrospective dosimetry using luminescence it is never possible to obtain a sample of the unaltered phosphor as it was at somc time in the past and before radiation exposure. This prevents direct calibration using conventional personnel dosimetry techniques, and so measurement protocols must be devised which allow accurate estimation of the dose using only the exposed phosphor. This has led to the use of complex protocols, requiring many tens of notionally identical subsamples, to obtain one estimate of the unknown dose. More recently, considerable effort has gone into devising protocols which provide an estimate of the unknown dose from only one subsample. These avoid the need to assume homogeneity in the sample. These protocols also allow faster measurement, which for the first time makes it practical to obtain multiple estimates of the unknown dose and thus externally calculated random errors. This paper discusses the development of single-aliquot protocols, with particular reference to those devised for use with quartz, and finally reviews some of their applications in the retrospective assessment of dose.

Optically stimulated luminescence in retrospective dosimetry.

Since the beginning of the 1990s the exploration of optically stimulated luminescence (OSL) in retrospective accident dosimetry has driven an intensive investigation and development programme at Risø into measurement facilities and techniques. This paper reviews some of the outcomes of this programme, including the evaluation of the single-aliquot regenerative-dose (SAR) measurement protocol with brick quartz and the determination of dose-depth profiles in building materials as a guide to determining the mean energy of the incident radiation. Investigations into heated materials are most advanced, and a lower detection limit for quartz extracted from Chernobyl bricks was determined to be <10 mGy. The first results from the measurement of doses in unheated building materials such as mortar and concrete are also discussed. Both small-aliquot and single-grain techniques have been used to assess accident doses in these cement based building materials more commonly found in workplaces. Finally some results of a preliminary investigation of the OSL properties of household chemicals are discussed with reference to their potential as accident dosemeters.

Electron-trapping probability in natural dosemeters as a function of irradiation temperature.

The electron-trapping probability in OSL traps as a function of irradiation temperature is investigated for sedimentary quartz and feldspar. A dependency was found for both minerals; this phenomenon could give rise to errors in dose estimation when the irradiation temperature used in laboratory procedures is different from that in the natural environment. No evidence was found for the existence of shallow trap saturation effects that could give rise to a dose-rate dependency of electron trapping.

Retrospective dosimetry using unheated quartz: a feasibility study.

Most attempts to apply retrospective dosimetry to building materials have made use of heated (sensitised) items such as brick or tile ceramic. Unfired materials, such as concrete, are far more widespread in the industrial environment, but unfortunately these cannot be assumed to contain a negligible dose at the time of construction. This paper reports on preliminary attempts to measure, using optically stimulated luminescence (OSL), a dose-depth profile in a new concrete brick which had been given a known dose in the laboratory. The dose distribution in individual samples was measured before and after irradiation using small aliquots each of 65 quartz grains, and also using single grains, extracted from the concrete. Despite the material being very poorly zeroed prior to irradiation, both approaches gave satisfactory results and it is concluded that measurement of individual grains from poorly zeroed building materials can provide useful information on accident doses.

Measurement of the dose in quartz in the presence of feldspar contamination.

To allow the determination of the dose in quartz in the presence of feldspar contamination, the quartz-to-feldspar optically stimulated luminescence (OSL) ratio needs to be maximised. Experiments were carried out to find the optimum procedure to bleach the feldspar by exposure to infrared light, without seriously affecting the quartz OSL signal. A single-aliquot regenerative-dose protocol is proposed which, in our samples, allows accurate measurement of the dose in quartz in the presence of feldspar contamination. The protocol also has potential use for quartz dose determination in mixed-mineral samples.

Dose estimation using quartz OSL in the non-linear region of the growth curve.

The reliability of equivalent-dose determinations on quartz made with the single-aliquot regenerative-dose (SAR) protocol is examined using a suite of sedimentary samples for which the equivalent dose is expected to be >200 Gy. Experiments on one sample were used to evaluate the precision obtained using the standard measurement procedure with (a) a range of pre-heat temperatures, and (b) a single pre-heat temperature. The precision is compared with that achieved using SAR for a repeated dose point after an initial pre-heat, and for a known dose given before the initial pre-heat. It is concluded that, at least for this sample, the scatter in OSL measurements dominates the spread in the estimates of De.

Household and workplace chemicals as retrospective luminescence dosemeters.

In the development of techniques for the retrospective assessment of the dose absorbed by communities living and working adjacent to the site of a nuclear accident, attention has concentrated on the use of natural minerals such as quartz and feldspar as dosemeters. These minerals are widely found in household earthenware and almost all types of bricks and concrete. Their main disadvantages are variable and often low sensitivity, and the possibility of a comparatively large natural dose prior to the accident, depending on the age of the building and the type or building material. However, there are other potential unheated crystalline materials found in the domestic and industrial environment which may also act as retrospective dosemeters, and may be considerably more sensitive. We have surveyed the thermoluminescent and optically stimulated luminescent (OSL) characteristics of several such chemicals and this paper reports on the OSL sensitivity, the size of the residual dose immediately after manufacture, stability and derived minimum detection limits.

Retrospective dosimetry: dose evaluation using unheated and heated quartz from a radioactive waste storage building.

In the assessment of dose received from a nuclear accident, considerable attention has been paid to retrospective dosimetry using heated materials such as household ceramics and bricks. However, unheated materials such as mortar and concrete are more commonly found in industrial sites and particularly in nuclear installations. These materials contain natural dosemeters such as quartz, which usually is less sensitive than its heated counterpart. The potential of quartz extracted from mortar in a wall of a low-level radioactive-waste storage facility containing distributed sources of 60Co and 137Cs has been investigated. Dose-depth proliles based on small aliquots and single grains from the quartz extracted from the mortar samples are reported here. These are compared with results from heated quartz and polymineral fine grains extracted from an adjacent brick, and the integrated dose recorded by environmental TLDs.

Leishmania mexicana: identification of genes that are preferentially expressed in amastigotes.

The protozoan parasite Leishmania has a digenetic life cycle, alternating between the promastigote and the amastigote stages. Amastigotes infect macrophage cells and reside in the hydrolytic environment of the phagolysosome. Leishmania show distinct morphological and biochemical changes during differentiation into amastigotes. These alterations are believed to be regulated by stage-specific expression of a discrete number of genes. Selective-suppression PCR, a PCR-based subtractive hybridization technique, identified two genes preferentially expressed in L. mexicana lesion amastigotes: a novel gene family, A600, and a differentially expressed beta-tubulin gene. Northern blot analysis confirmed amastigote-specific expression of these genes and quantitation showed a sixfold higher abundance of A600 and beta-tubulin transcripts in lesion amastigotes. The A600 gene was predicted to contain a 293-bp open reading frame (ORF) that was tandemly repeated in the L. mexicana genome. Sequence analysis predicted that the A600 ORF encodes either a membrane-bound or a secreted protein that may have a functional role in amastigote differentiation or intraphagolysosomal parasite survival.

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.