7 research outputs found
Richtlijn ‘Beeldvorming met ioniserende straling’
No full textThe guideline 'imaging with ionizing radiation' provides information about the risks when using ionizing radiation and the communication thereabout. Because most radiological investigations are performed at one time, the chance of adverse effects, is small, even in children and pregnant women. In case of complex or multiple investigations, the medical physicist can be consulted to estimate the risks. The working group recommends using population diagrams when discussing possible risks. The working group recommends giving patients/caregivers room to express their concerns and questions. The working group advices using supporting material. The working group advocates the development of nationally uniform information material. If the patient/caregiver still has concerns, the working group recommends calling in experts such as radiologists, medical physicists, and radiographers
Guideline 'Imaging with ionizing radiation':risks, communication and shielding
No full textThe guideline 'imaging with ionizing radiation' provides information about the risks when using ionizing radiation and the communication thereabout. Because most radiological investigations are performed at one time, the chance of adverse effects, is small, even in children and pregnant women. In case of complex or multiple investigations, the medical physicist can be consulted to estimate the risks. The working group recommends using population diagrams when discussing possible risks. The working group recommends giving patients/caregivers room to express their concerns and questions. The working group advices using supporting material. The working group advocates the development of nationally uniform information material. If the patient/caregiver still has concerns, the working group recommends calling in experts such as radiologists, medical physicists, and radiographers.</p
Guideline 'Imaging with ionizing radiation':risks, communication and shielding
No full textThe guideline 'imaging with ionizing radiation' provides information about the risks when using ionizing radiation and the communication thereabout. Because most radiological investigations are performed at one time, the chance of adverse effects, is small, even in children and pregnant women. In case of complex or multiple investigations, the medical physicist can be consulted to estimate the risks. The working group recommends using population diagrams when discussing possible risks. The working group recommends giving patients/caregivers room to express their concerns and questions. The working group advices using supporting material. The working group advocates the development of nationally uniform information material. If the patient/caregiver still has concerns, the working group recommends calling in experts such as radiologists, medical physicists, and radiographers.</p
I-124 PET/CT to Predict the Outcome of Blind I-131 Treatment in Patients with Biochemical Recurrence of Differentiated Thyroid Cancer: Results of a Multicenter Diagnostic Cohort Study (THYROPET)
No full textPatients with suspected recurrence from differentiated thyroid carcinoma, based on an increased thyroglobulin (Tg) level and negative neck ultrasound (US), pose a clinical dilemma. Because standard imaging has a low yield identifying potential recurrence, blind I-131 treatment is often applied. However, a tumor-negative I-131 whole-body scintigraphy (WBS) prevails in 38%-50% of patients. We performed a prospective multicenter observational cohort study to test the hypothesis that I-124 PET/CT can identify the patients with a tumor-negative posttherapy I-131 WBS. Methods: Our study was designed to include 100 patients with detectable Tg and a negative neck US, who were planned for blind I-131 therapy. All patients underwent I-124 PET/CT after administration of recombinant human thyroid stimulating hormone. Subsequently, after 4-6 wk of thyroid hormone withdrawal patients were treated with 5.5-7.4 GBq of I-131, followed by WBS a week later. The primary endpoint was the number of I-131 therapies that could have been omitted using the predicted outcome of the I-124 PET/CT, operationalized as the concordance of tumor detection by I-124 PET/CT, using post-I-131 therapy WBS as the reference test. The study would be terminated if 3 patients had a negative I-124 PET/CT and a positive posttherapy I-131 scan. Results: After inclusion of 17 patients, we terminated the study preliminarily because the stopping rule had been met. Median Tg level at I-131 therapy was 28 mu g/L (interquartile range, 129). Eight posttherapy WBS were negative (47%), all of which were correctly predicted by negative I-124 PET/CT. Nine posttherapy WBS showed iodine-avid tumor, of which 4 also had positive I-124 PET/CT findings. Sensitivity, specificity, negative predictive value, and positive predictive value of I-124 PET/CT were 44% (confidence interval [CI], 14%-79%), 100% (CI, 63%-100%), 62% (CI, 32%-86%), and 100% (CI, 40%-100%), respectively. Implementation of I-124 PET in this setting would have led to 47% (8/17) less futile I-131 treatments, but 29% of patients (5/17) would have been denied potentially effective therapy. Conclusion: In patients with biochemical evidence of recurrent differentiated thyroid carcinoma and a tumor-negative neck US, the high false-negative rate of I-124 PET/CT after recombinant human thyroid stimulating hormone I-124 PET/CT as implemented in this study precludes its use as a scouting procedure to prevent futile blind I-131 therapy
Calibration of PET/CT scanners for multicenter studies on differentiated thyroid cancer with 124I
No full textBackground: Studies on imaging of differentiated thyroid cancer (DTC) using 124I often require a multicenter approach, as the prevalence of DTC is low. Calibration of participating scanners is required to obtain comparable quantification. As determination of a well-defined range of recovery coefficients is complicated for various reasons, a simpler approach based on the assumption that the iodine uptake is highly focal with a background that significantly lacks radioactivity might be more efficient. For each scanner, a linear conversion between known and observed activity can be derived, allowing quantification that can be traced to a common source for all scanners within one study-protocol. The aim of this paper is to outline a procedure using this approach in order to set up a multicenter calibration of PET/CT scanners for 124I. Methods: A cylindrical polyethylene phantom contained six 2-ml vials with reference activities of ~2, 10, 20, 100, 400, and 2000 kBq, produced by dilution from a known activity. The phantom was scanned twice on PET/CT scanners of participating centers within 1 week. For each scanner, the best proportional and linear fit between measured and known activities were derived and based on statistical analyses of the results of all scanners; it was determined which fit should be applied. In addition, a Bland-Altman analysis was done on calibrated activities with respect to reference activities to asses the relative precision of the scanners. Results: Nine Philips (vendor A) and nine Siemens (vendor B) PET/CT scanners were calibrated in a time period of 3 days before and after the reference time. No significant differences were detected between the two subsequent scans on any scanner. Six fitted intercepts of vendor A were significantly different from zero, so the linear model was used. Intercepts ranged from −8 to 26 kBq and slopes ranged from 0.80 to 0.98. Bland-Altman analysis of calibrated and reference activities showed that the relative error of calibrated activities was smaller than that of uncalibrated activities. Conclusions: A simplified multicenter calibration procedure for PET/CT scans that show highly focal uptake and negligible background is feasible and results in more precise quantification. Our procedure can be used in multicenter 124I PET scans focusing on (recurrent) DTC
Recurrent differentiated thyroid cancer: Towards personalized treatment based on evaluation of tumor characteristics with PET (THYROPET Study): Study protocol of a multicenter observational cohort study
No full textBackground: After initial treatment of differentiated thyroid carcinoma (DTC) patients are followed with thyroglobulin (Tg) measurements to detect recurrences. In case of elevated levels of Tg and negative neck ultrasonography, patients are treated 'blindly' with Iodine-131 (131I). However, in up to 50% of patients, the post-therapy scan reveals no 131I-targeting of tumor lesions. Such patients derive no benefit from the blind therapy but are exposed to its toxicity. Alternatively, iodine-124 (124I) Positron Emission Tomography/Computed Tomography (PET/CT) has become available to visualize DTC lesions and without toxicity. In addition to this, 18F-fluorodeoxyglucose (18F-FDG) PET/CT detects the recurrent DTC phenotype, which lost the capacity to accumulate iodine. Taken together, the combination of 124I and 18F-FDG PET/CT has potential to stratify patients for treatment with 131I.Methods/Design: In a multicenter prospective observational cohort study the hypothesis that the combination of 124I and 18F-FDG PET/CT can avoid futile 131I treatments in patients planned for 'blind' therapy with 131I, is tested.One hundred patients planned for 131I undergo both 124I and 18F-FDG PET/CT after rhTSH stimulation. Independent of the outcome of the scans, all patients will subsequently receive, after thyroid hormone withdrawal, the 131I therapy. The post 131I therapeutic scintigraphy is compared with the outcome of the 124I and 18F-FDG PET/CT in order to evaluate the diagnostic value of the combined PET modalities.This study primary aims to reduce the number of futile 131I therapies. Secondary aims are the nationwide introduction of 124I PET/CT by a quality assurance and quality control (QA/QC) program, to correlate imaging outcome with histopathological features, to compare 124I PET/CT after rhTSH and after withdrawal of thyroid hormone, and to compare 124I and 131I dosimetry.Discussion: This study aims to evaluate the potential value of the combination of 124I and 18F-FDG PET/CT in the prevention of futile 131I therapies in patients with biochemically suspected recurrence of DTC. To our best knowledge no studies addressed this in a prospective cohort of patients. This is of great clinical importance as a futile 131I is a costly treatment associated with morbidity and therefore should be restricted to those likely to benefit from this treatment.Trial registration: Clinicaltrials.gov identifier: NCT01641679
Recommended from our members
History in the literary imagination: the telling of Nongqawuse and the Xhosa Cattle-Killing in South African literature and culture (1891-1937)
No full textThis thesis takes as its subject the millenarian movement of 1856–7, commonly known as the Xhosa Cattle-Killing. My project examines a range of literary representations of this seminal moment in South African history: novels, plays, and short stories in English or English translation. The period under consideration encompasses the earliest literary responses to the Cattle-Killing and includes critical historical-political moments such as: the incorporation of the last independent black territory into the Cape Colony, the creation of the Union of South Africa, the passing of the Land Act, the enfranchisement of white women and the enactment of Hertzog’s ‘native bills’. The project consists of close, contextual readings, and the approach is cross-cultural and interdisciplinary.
In this dissertation I examine the meaning that has accrued to the Cattle-Killing, and the role that literary accounts have played in interpreting and defining this pivotal event in the historical consciousness of their sometimes considerable audiences. In some cases, these creative works have anticipated trends in formal historiography and suggested new ways to interrogate the evidence. But the accounts do more than creatively reconstruct the past. They are also implicated in their respective presents and use the Cattle-Killing to ‘write out’ contemporaneous concerns: be it female emancipation, ‘native education’ or Black Nationalism. The various manifestations of the Cattle-Killing story chart not only the shifting ‘truth’ of the event but also the ways in which it has been made relevant and useable for different communities at various points in South Africa’s history. To read these accounts of the Cattle-Killing, I argue, is to ‘read’ the history of this period.
While taking as its subject an event from 150 years ago, and literary responses from shortly after, my project contributes to wider, on-going conversations relating to history as a field of argument and literature as a social and historical force. A related aim is to contribute to the revaluation of early South African literature, which has been neglected or homogenized in recent years. My dissertation seeks to recuperate and complicate by representing a variety of subject positions and resuscitating voices discarded or forgotten
