Overexposure In Patients Research Articles

The implementation of diagnostic reference levels to Australian radiology practice

At the present time, there is no national surveillance of the increasing ionising radiation dose to the population from diagnostic imaging procedures. As the number of procedures undertaken is increasing, it is expected that the population dose will also increase. A substantial component of that contribution is from multi-detector computed tomography (MDCT) systems. The Australian Radiation Protection & Nuclear Safety Agency (ARPANSA) estimates that the growth in MDCT scans, based on Medicare Benefits Schedule data, is increasing at approximately 9% per annum, with over 2 million MDCT scans being performed in 2009. The caput effective dose (mSv) from this modality is expected to be approaching 1.2 mSv per annum. If current dose-detriment models are accurate, the risk of induction of carcinogenic detriment from current MDCT scanning patterns is a significant public health issue that requires a concerted and ongoing response. For the application of ionising radiation in medicine, the International Commission on Radiological Protection recommends the conservative philosophy of Justification and Optimisation via the measurement of 'Diagnostic Reference Levels' to limit the potential overexposure of patients and decrease the overall population burden. The Australian government has commissioned ARPANSA to survey, calculate and construct representative national diagnostic reference levels for diagnostic imaging modalities that use ionising radiation. This will be achieved in close consultation with the professional organisations who represent the professionals responsible for the use of ionising radiation in diagnostic imaging.

Sécurisation de l’activité de radiothérapie bi-site dans le cadre de la reprise des traitements au centre hospitalier d’Épinal par l’équipe du centre Alexis-Vautrin de Nancy

In February 2007, the radiation therapy department of the Jean Monnet Hospital in Épinal (France) has stopped the radiotherapy treatments after the discovery of a radiotherapy accident and bad practices leading to overexposure of patients between 1987 and 2006. The Regional Cancer Center “Centre Alexis Vautrin” in Nancy (France) was given the task of the new start of treatment activity. From February 2007 to January 2008, actions of training, updates of equipments and practices have been performed in the Épinal Hospital, guided by the quality approach, allowing the treatment of new patients in February 2008, with the radiation oncologists and the medical physicists of the Centre Alexis Vautrin, with the highest conditions of security and confidence.

Explaining Variability in Tacrolimus Pharmacokinetics to Optimize Early Exposure in Adult Kidney Transplant Recipients

To prevent acute rejection episodes, it is important to reach adequate tacrolimus (TRL) exposure early after kidney transplantation. With a better understanding of the high variability in the pharmacokinetics of TRL, the starting dose can be individualized, resulting in a reduction in dose adjustments to obtain the target exposure. A population pharmacokinetic analysis was performed to estimate the effects of demographic factors, hematocrit, serum albumin concentration, prednisolone dose, TRL dose interval, polymorphisms in genes coding for ABCB1, CYP3A5, CYP3A4, and the pregnane X receptor on TRL pharmacokinetics. Pharmacokinetic data were prospectively obtained in 31 de novo kidney transplant patients randomized to receive TRL once or twice daily, and subsequently, the data were analyzed by means of nonlinear mixed-effects modeling. TRL clearance was 1.5-fold higher for patients with the CYP3A5*1/*3 genotype compared with the CYP3A5*3/*3 genotype (5.5 +/- 0.5 L/h versus 3.7 +/- 0.3 L/h, respectively). This factor explained 30% of the interindividual variability in apparent clearance (exposure). Also, a relationship between the pregnane X receptor A+7635G genotype and TRL clearance was identified with a clearance of 3.9 +/- 0.3 L/h in the A allele carriers versus 5.4 +/- 0.6 L/h in the GG genotype. Finally, a concomitant prednisolone dose of more than 10 mg/d increased the TRL apparent clearance by 15%. In contrast, body weight was not related to TRL clearance in this population. Because patients are typically dosed per kilogram body weight, this might result in underexposure and overexposure in patients, with a low and high body weight, respectively. This integrated analysis shows that adult renal transplant recipients with the CYP3A5*1/*3 genotype require a 1.5 times higher, fixed, starting dose compared with CYP3A5*3/*3 to reach the predefined target exposure early after transplantation.

A well‐tolerated 5‐FU‐based treatment subsequent to severe capecitabine‐induced toxicity in a DPD‐deficient patient

5-Fluorouracil (5-FU) is widely administered as a continuous infusion to treat gastrointestinal tract or head and neck cancers, and as bolus injections in breast cancer chemotherapy regimens. Grade 3–4 toxicity occurs in about 30% of patients receiving 5-FU as a continuous infusion, and proves lethal in 0.5% of these patients [1]. 5-FU-related toxicity has mostly been reported with intravenous administration [1–3]. However, some cases of severe toxicity, including deaths, have been described after oral administration of 5-FU derivatives, such as capecitabine (Xeloda®) [4, 5]. A polymorphism of the dihydropyrimidine dehydrogenase (DPD) gene has been identified as a frequent cause of such toxicity [6, 7]. DPD catalyses the rate-limiting step of fluoropyrimidine catabolism. Partial or total DPD deficiency therefore leads to substantial overexposure in patients treated with the standard dose, exacerbating drug toxicity. This raises questions about possible screening for DPD deficiency before the administration of fluoropyrimidine drugs, including their oral forms. Patients found to have a deficiency on screening before treatment or following signs of toxicity during a previous course are usually given alternative treatments based on nonfluoropyrimidine compounds. However, 5-FU is highly active and its use may be essential in patients who fail to respond to other treatments. We report the case of a patient with DPD deficiency detected due to severe toxicity during capecitabine treatment, who has since received a continuous infusion of 5-FU at almost the standard dose with no significant signs of toxicity.

A survey of incidents in radiology and nuclear medicine in the West of Scotland

Data on 606 incidents in radiology and nuclear medicine departments reported to a central health physics service have been analysed and causes reviewed. 85% of incidents in radiology departments and 37% in nuclear medicine were overexposures of patients. 80% of these resulted from human error or procedural failure, and of these 32% were mistakes by the referrer. Other incidents in nuclear medicine were contamination events (49%) and failure in management of radioactive materials (10%). Effective doses for patient overexposures covered a broad range with those for CT being 1 mSv and above, while those for other radiology examinations were mostly less than 2 mSv. Reporting of patient overexposure incidents in radiology has increased by four-fold in recent years. The average numbers reported during the last 3 years were 91 per year in radiology and 12 per year in nuclear medicine, for hospitals with a population base of 2.8 million. Incident investigations demonstrated the importance of robust procedures and defences to identify mistakes that could lead to incidents. The central incident reporting and investigation system has raised the awareness of staff about the type of mistakes which could lead to incidents and promoted the introduction of recommended actions to reduce these risks.

PET/CT

Clinical studies demonstrate a gain in diagnostic accuracy by employing combined PET/CT instead of separate CT and PET imaging. However, whole-body PET/CT examinations result in a comparatively high radiation burden to patients and thus require a proper justification and optimization to avoid repeated exposure or over-exposure of patients. This review article summarizes relevant data concerning radiation exposure of patients resulting from the different components of a combined PET/CT examination and presents different imaging strategies that can help to balance the diagnostic needs and the radiation protection requirements. In addition various dose reduction measures are discussed, some of which can be adopted from CT practice, while others mandate modifications to the existing hard- and software of PET/CT systems.

A device for minimizing the risk of overexposure of patients undergoing phototherapy.

Phototherapy irradiation cabinets normally rely on one timer or dose meter in order to control the ultraviolet (UV) exposure of patients. Faults may occur in the electronic control, or the operator may set the prescribed dose incorrectly. If this happens, a patient will receive an exposure different from that intended, which in the case of overexposure may result in severe burning resulting in hospitalization. Some phototherapy equipment has secondary devices (e.g. mechanical timer) for controlling the dose in case the primary system fails. We have designed and built a secondary dose meter that sounds an alarm if an overdose is about to occur. The unique feature of our device is that it measures the irradiance level within the cabinet and uses this value in combination with the dose set by the operator, to calculate the alarm time. Using the measured irradiance value in this manner ensures that the calculated exposure time compensates for variations in UV output as the lamps age.

Half-side comparison of erythemogenic versus suberythemogenic UVA doses in oral photochemotherapy of psoriasis

Background: Early American and European multicenter trials on the efficacy of photochemotherapy (PUVA) for psoriasis have clearly shown that the treatment protocol has a crucial impact on the cumulative UVA dose required for clearing patients. Most, if not all, treatment protocols rely on the PUVA-induced erythema as a guideline for UVA dosimetry. Objective: Our aim was to investigate whether phototoxic erythema is integral to an optimized PUVA protocol or reflects an unnecessary overexposure of patients. Methods: A standard high-dose UVA regimen using minimal phototoxic doses (MPD) was compared against two different low-dose regimens. To this purpose a bilateral comparison study was performed on 31 patients and divided in two parts. In the first trial on 14 patients, half of each patient’s body was irradiated at each visit with 1 MPD, whereas the other half received only two thirds of the MPD. In the second trial on 17 patients treatment with 1 MPD was compared against treatment with one half of the MPD. Results: A total of 27 patients (12 patients in the first trial, 15 patients in the second trial) completed the study. In both trials the suberythemogenic doses were therapeutically as effective as the minimal phototoxic doses. Conclusion: We conclude that PUVA-induced erythema is not a prerequisite for effective psoriasis treatment and that a low-dose UVA regimen is a promising approach to increase the short- and long-term safety of photochemotherapy. (J Am Acad Dermatol 1999;41:408-13.)

Overexposure of Patients Due to Malfunctions or Defects in Radiation Equipment

Overexposure of Patients Due to Malfunctions or Defects in Radiation Equipment

Overexposure of Patients Due to Malfunctions or Defects in Radiation Equipment

Some 38 incidents involving patient overexposure due to malfunctions or defects in radiation equipment were notified to HSE between 1986 and 1990. Of these cases, 30 involved diagnostic X ray equipment, while the remainder involved nuclear medicine or radiotherapy equipment. Those cases involving diagnostic X ray equipment are examined in detail and grouped into six categories. The numbers of patients affected varied. In one case an estimated 350 patients were affected; in another, 240; while 13 cases affected only a single patient. A very rough estimate of the collective effective dose equivalent in the 30 cases comes to 5 man sieverts. It is concluded that improvements are needed in fault finding procedures, and guidance is needed on consistent methods of dose estimation and reporting. Improvements for the longer term include the selection of reliable components during manufacture; application of HSE guidance in software design for programmable electronic systems; and equipment design to incorporate fault detection and inhibition of operation to prevent excessive exposures.