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J Van Dam

Publications and source records attributed to J Van Dam.

At least 19 recordsLinked to original sources
PubMed2006

Characteristics of dosemeter types for skin dose measurements in practice.

A growing number of papers report deterministic effects in the skin of patients who have undergone interventional radiological procedures. Dose measurements, and especially skin dose measurements, are therefore increasingly important. Methods and acceptable dosemeters are, however, not clearly defined. This paper is the result of a literature overview with regard to assessing the entrance skin dose during radiological examinations by putting a dosemeter on the patient's skin. The relevant intrinsic characteristics, as well as some examples of clinical use of the different detector types, are presented. In this respect, thermoluminescence, scintillation, semiconductor and film dosemeters are discussed and compared with respect to their practical use.

Film Dosimetry↗
PubMed2004

Radiation doses of indirect and direct digital cephalometric radiography.

AIM: The aim of this study was to measure organ doses and calculate the effective dose for indirect and direct digital cephalometric exposures. MATERIAL AND METHODS: Indirect digital cephalometric exposures were made of a Rando phantom head using a Cranex Tome multipurpose unit with storage phosphor plates from Agfa and the direct digital (Charge Coupled Device, CCD) exposures were made with a Proline Ceph CM unit. Exposure settings were 70 kV and 4 mAs for indirect digital exposures. Direct digital exposures were made with 70 kV, 10 mA and a total scanning time of 23 s. TLD700 dosemeters were used to measure organ doses, and the effective doses were calculated with (effective dose(sal)) and without inclusion of the salivary glands. A pilot study was carried out to compare diagnostic image quality of both imaging modalities. RESULTS: Effective doses were 1.7 microSv for direct digital and 1.6 microSv for indirect digital cephalometric imaging. When salivary glands were included in the calculation, effective doses(sal) were 3.4 microSv and 2.2 microSv respectively. Organ doses were higher for direct digital imaging, except for the thyroid gland, where the organ doses were comparable. Diagnostic image quality of indirect and direct digital cephalometric images seemed comparable. CONCLUSION: Effective dose and effective dose(sal) were higher for direct digital cephalometric exposure compared with indirect digital exposure. Organ doses were higher for direct digital cephalography. From preliminary data, it may be presumed that diagnostic image quality of indirect and direct digital cephalometric images are comparable.

Cephalometry↗
PubMed2004

[The EQUAL-ESTRO external quality control laboratory in France].

PURPOSE: The EQUAL-ESTRO laboratory was set up in 1998 to perform external audits of radiotherapy beams for all the European centres. Until the end of the year 2003, it was funded by EC projects. The external quality control is based on measurements performed with thermoluminescent dosimeters (TLD) sent by postal mail to the participating centre in order to be irradiated on axis in reference conditions and in conditions close to clinical conditions for photon and electron beams. The EQUAL-ESTRO laboratory also started in 2002, a new TLD control allowed to check the dosimetry of complex clinical fields for photon beams with multileaf collimator (MLC). New geometric and dosimetric checks have also been developed for brachytherapy. MATERIAL AND METHODS: The participating centre irradiates TLDs (7LiF: Na, mg, Ti, TLD 937 [Philitec]) in water at a dose of 2 Gy, calculated with the TPS used clinically, following the EQUAL-ESTRO protocol. RESULTS: Since the beginning of the activities, 46% of the French radiotherapy centres and 55% of the European radiotherapy centres applied to participate to the EQUAL quality control programme. In France, the EQUAL-ESTRO laboratory checked, from 1998 and June 2004, 283 photon beams, 180 electron beams and 61 photon beams with MLC. For all the French beams checks, the following results have been observed: for the photon beams, the results show that about 1% of the measured doses in the reference conditions on axis have been detected outside the tolerance level (deviation between the measured dose and the stated dose > +/- 5%) after a first or a second check. For points checked in photon beams with wedge filter, 2.5% of the beams checked show a deviation > +/- 5% after a first or a second check. For the electron beams, the check has been set up in January 1999. For the 180 electron beams checked, 5% of the measured doses in the reference conditions have been found outside the tolerance level (> +/- 5%). CONCLUSION: These results show clearly the importance of the quality control in radiotherapy in the frame of an external audit. This audit should now be a part of a quality assurance programme in the radiotherapy centres in addition to the internal quality control as planned in the French law (02/03/2004) concerning the external quality control conditions of the radiotherapy treatment units.

Europe↗
PubMed2003

A prospective randomized trial comparing a virtual reality simulator to bedside teaching for training in sigmoidoscopy.

BACKGROUND AND STUDY AIMS: Clinical investigation using endoscopy simulators is now possible due to recent advances in virtual reality technology. A prospective randomized trial was conducted to compare the exclusive use of a virtual reality endoscopy simulator with bedside teaching for training in sigmoidoscopy. MATERIALS AND METHODS: Internal medicine residents were randomly assigned to training exclusively using a virtual reality simulator (group 1) or via bedside teaching (group 2). Residents were then observed performing five sigmoidoscopic procedures in asymptomatic patients referred for colorectal cancer screening. Endoscopic examinations were evaluated for procedure duration, completion, ability to perform retroflexion, and level of patient comfort/discomfort. Each examination was scored from 1 (inability to insert the endoscope beyond the rectum) to 5 (able to complete the entire examination independently in less than 20 min). RESULTS: Sixty-six sigmoidoscopic examinations were completed by nine residents in group 1 (simulator-trained group) and seven residents in group 2 (traditional teaching group). Participants in group 1 had more difficulty with initial endoscope insertion and negotiation of the rectosigmoid junction (mean score +/- SEM 2.9 +/- 0.2) than those in group 2 (3.8 +/- 0.2) ( P < 0.001). The splenic flexure was reached independently in 10 of 34 examinations (29 %) in group 1, compared with 23 of 32 examinations (72 %) in group 2 ( P = 0.001). Retroflexion was successfully performed by 19 of 34 (56 %) in group 1 compared to 27 of 32 (84 %) in group 2 ( P = 0.02). The average procedure time, patient satisfaction, and discomfort associated with the procedure did not differ statistically between the two groups. CONCLUSIONS: The use of a state-of-the-art virtual reality-based endoscopy simulator is inferior to traditional bedside teaching techniques when used exclusively for training medical residents to perform sigmoidoscopy.

Adult↗
PubMed2003

Safety of ERCP during pregnancy.

OBJECTIVES: There are few data in the literature regarding the indications, therapy, and safety of endoscopic management of pancreatico-biliary disorders during pregnancy. We report the largest single center experience with ERCP in pregnancy. METHODS: We reviewed 15 patients that underwent ERCP during pregnancy. In all patients, the pelvis was lead-shielded and the fetus was monitored by an obstetrician. Fluoroscopy was minimized and hard copy radiographs taken only when essential. RESULTS: The mean patient age was 28.9 yr (15-36 yr). The mean duration of gestation was 25 wk (12-33 wk); one patient was in the first, five in the second, and nine in the third trimester. The indications were gallstone pancreatitis (n = 6), choledocholithiasis on ultrasound (n = 5), elevated liver enzymes and a dilated bile duct on ultrasound (n = 2), abdominal pain and gallstones (n = 1), and chronic pancreatitis (n = 1). ERCP findings were bile duct stones (n = 6), patulous papilla (n = 1), bile duct debris (n = 1), normal bile duct and gallstones or gallbladder sludge (n = 3), dilated bile duct and gallstones (n = 1), normal bile duct and no gallstones (n = 2), and chronic pancreatitis (n = 1). Six patients underwent sphincterotomies and one a biliary stent insertion. One sphincterotomy was complicated by mild pancreatitis. All infants delivered to date have had Apgar-scores >8, and continuing pregnancies are uneventful. Mean fluorosocopy time was 3.2 min (SD +/- 1.8). An estimated fetal radiation exposure was 310 mrad (SD +/- 164) which is substantially below the accepted teratogenic dose. CONCLUSIONS: ERCP in pregnancy seems to be safe for both mother and fetus; however, it should be restricted to therapeutic indications with additional intraprocedure safety measures.

Adult↗
PubMed2003

Novel methods of enhanced endoscopic imaging.

Endoscopy has become an essential part of the practice of gastroenterology. Techniques exploiting previously unused properties of light have demonstrated the potential to enhance the ability to make clinical diagnoses without removing tissue as has been standard practice for decades. The term used for many of these techniques is "optical biopsy" and, although not yet widely available, enthusiasm for such techniques has grown as has research in their potential clinical utility.

Barrett Esophagus↗
PubMed2003

Radiation doses of collimated vs non-collimated cephalometric exposures.

OBJECTIVES: The aim of the study was to compare organ and effective radiation doses for collimated and non-collimated cephalometric radiographs made by a multipurpose extraoral radiation unit. METHODS: Cephalometric exposures were made from a Rando head phantom representing an average man with the Cranex Tome multipurpose radiation unit. A collimator was fabricated from a 3-mm thick piece of lead. The collimator was designed so that structures relevant for orthodontic diagnosis were not shielded, whereas the thyroid gland and the major part of the skull were shielded. Absorbed organ doses were measured using thermoluminescent dosimeters. The effective dose was calculated both with (E(sal)) and without (E) inclusion of the salivary glands. RESULTS: Use of a wedge-shaped lead collimator yielded a reduction in field size of 55% and a reduction in E from 3.0 micro Sv to 1.6 micro Sv (47%) and in E(sal) from 3.7 micro Sv to 2.2 micro Sv (41%). CONCLUSIONS: Use of a wedge-shaped collimator should be advocated in all cases where depiction of the thyroid gland and the neurocranium is not required. The resulting reduction in effective dose using our collimator was 47% (41% when the salivary glands are included), which is of clinical importance, especially in children.

Bone Marrow↗
PubMed2002

A comparison of the effective dose from scanography with periapical radiography.

OBJECTIVES: To compare organ and effective doses from analogue scanographic and periapical radiography. METHODS: Thermoluminescent dosimeters (TLD-700) were inserted in the parotid glands (bilateral), submandibular glands (bilateral) and bone marrow (left ascending ramus) of three human cadavers. Dosimeters were also attached to the skin, thyroid gland and lens of both eyes. Central, left lateral and left posterior scanograms were obtained with a Cranex Tome (Soredex, Helsinki, Finland) multimodal imaging system. A similar procedure was applied for periapical radiographs of the midline, left lateral and left molar regions using E-speed film both with and without rectangular collimation. Organ and effective doses were calculated for scanograms and periapical radiographs. RESULTS: The effective doses for the scanograms were 0.001 mSv (central), 0.011 mSv (lateral) and 0.015 mSv (posterior). The effective doses for periapical radiographs were 0.001 mSv (anterior), 0.001 mSv (lateral) and 0.003 mSv (posterior) for rectangular collimation and 0.001 mSv (anterior), 0.002 mSv (lateral) and 0.005 mSv (posterior) for round collimation. CONCLUSIONS: When a larger area of the upper or lower jaw needs to be visualised, scanograms might be considered as an alternative to periapical radiography since the effective dose is lower.

Bone Marrow↗
PubMed2001

HIV infection among youth in a South African mining town is associated with herpes simplex virus-2 seropositivity and sexual behaviour.

OBJECTIVES: To determine the seroprevalence of HIV and herpes simplex virus-2 (HSV-2) by age and gender among young people aged 14--24 years in a South African town and to identify risk factors for HIV infection. DESIGN: A community-based, cross-sectional study was conducted on a random sample of men (n = 723) and women (n = 784) living in a township in the Carletonville district of South Africa. METHODS: Potential demographic and behavioural risk factors associated with HIV were recorded by questionnaire and biological tests were performed on serum and urine. Data analysis was performed using multivariate logistic regression. RESULTS: Among men and women the prevalence of HIV infection was 9.4 and 34.4%, respectively, and of positive HSV-2 serology was 17.0 and 53.3%, respectively. Among 24-year-old women the prevalence of HIV was 66.7% [95% confidence interval (CI), 54.6--77.3%]. HSV-2 seropositivity was a strong independent risk factor for HIV infection with odds ratios of 5.3 (95% CI, 2.7--10.3) for men and 8.4 (95% CI, 4.9--14.2) for women. There was no independent effect of age at first sex or serological markers of other sexually transmitted infections on HIV infection. CONCLUSIONS: HIV infection among young women increases rapidly after the onset of sexual activity and reaches extremely high levels by 24 years of age. These findings suggest that rates of HIV transmission from men to women are high and that HSV-2 plays a major role in the spread of HIV in this population.

Adolescent↗
PubMed2001

Clinical outcome of the use of enteral stents for palliation of patients with malignant upper GI obstruction.

BACKGROUND: The endoscopically placed enteral stent has emerged as a reasonable alternative to palliative surgery for malignant intestinal obstruction. This is a report of our experience with the use of enteral stents for nonesophageal malignant upper GI obstruction. METHODS: Data on all patients who had undergone enteral stent placement were reviewed. Those with a diagnosis of pancreatic cancer were compared with another similar cohort of patients who underwent palliative gastrojejunostomy. RESULTS: Thirty-one procedures were performed on 29 patients (mean age 67.7 years). Thirteen (45%) were men and 16 (55%) women. The diagnoses were gastric (13.8%), duodenal (10.3%), pancreatic (41.4%), metastatic (27.6%), and other malignancies (6.9%). Malignant obstruction occurred at the pylorus (20.7%), first part of duodenum (37.9%), second part of duodenum (27.6%), third part of duodenum (3.5%), and anastomotic sites (10.3%). Twenty-nine (93.5%) procedures were successful and good clinical outcome was achieved in 25 (80.6%). Re-obstruction by tumor ingrowth occurred in 2 patients after a mean of 183 days. The median survival time for patients with pancreatic cancer who underwent enteral stent placement compared with those who underwent surgical gastrojejunostomy was 94 and 92 days, charges were $9921 and $28,173, and duration of hospitalization was 4 and 14 days, respectively (latter 2 differences with p value < 0.005). CONCLUSION: Endoscopic enteral stent placement of nonesophageal malignant upper GI obstruction is a safe, efficacious, and cost-effective procedure with good clinical outcome, lower charges, and shorter hospitalization period than the surgical alternative.

Adult↗
PubMed2001

Current status of diagnostic and therapeutic endoscopic ultrasonography.

Endoscopic ultrasonography is firmly established as an imaging modality that can be used for diagnosing and staging both malignant and nonmalignant disorders of the pancreas, gastrointestinal tract, biliary tree, and mediastinum. In the future, as more physicians are trained and as technologic developments continue to advance, endosonography will likely assume a greater role in therapeutic management.

Endosonography↗
PubMed2001

External audits of electron beams using mailed TLD dosimetry: preliminary results.

AIM: A feasibility study has been performed to investigate the possibility of using mailed thermoluminescence dosimetry (TLD) for external audits of clinical electron beams in Europe. METHODS: In the frame of the EC Network Project for Quality Assurance in Radiotherapy, instruction sheets and mailing procedures have been defined for mailed TLD dosimetry using the dedicated holder developed by a panel of experts of the International Atomic Energy Agency (IAEA). Three hundred and thirty electron beam set-ups have been checked in the reference centres and some local centres of the EC Network Project and in addition through the centres participating to the EORTC Radiotherapy Group trial 22922. RESULTS: The mean ratio of measured dose to stated dose is 0.2% and the standard deviation of measured dose to stated dose is 3.2%. In seven beam set-ups, deviations greater than 10% were observed (max. 66%), showing the usefulness of these checks. CONCLUSION: The results of this feasibility study (instruction sheets, mailing procedures, holder) are presently endorsed by the EQUAL-ESTRO structure in order to offer in the future to all ESTRO members the possibility to request external audits of clinical electron beams.

Cobalt Radioisotopes↗
PubMed2001

Fluorescence, reflectance, and light-scattering spectroscopy for evaluating dysplasia in patients with Barrett's esophagus.

BACKGROUND & AIMS: The aim of this study was to assess the potential of 3 spectroscopic techniques (fluorescence, reflectance, and light-scattering spectroscopy) individually and in combination, for evaluating low- and high-grade dysplasia in patients with Barrett's esophagus (BE). METHODS: Fluorescence spectra at 11 excitation wavelengths and a reflectance spectrum were acquired in approximately 1 second from each site before biopsy using an optical fiber probe. The measured fluorescence spectra were combined with the reflectance spectra to extract the intrinsic tissue fluorescence. The reflectance spectra provided morphologic information about the bulk tissue, whereas light-scattering spectroscopy was used to determine cell nuclear crowding and enlargement in Barrett's epithelium. RESULTS: Significant differences were observed between dysplastic and nondysplastic BE in terms of intrinsic fluorescence, bulk scattering properties, and levels of epithelial cell nuclear crowding and enlargement. The combination of all 3 techniques resulted in superior sensitivity and specificity for separating high-grade from non-high-grade and dysplastic from nondysplastic epithelium. CONCLUSIONS: Intrinsic fluorescence, reflectance, and light-scattering spectroscopies provide complementary information about biochemical and morphologic changes that occur during the development of dysplasia. The combination of these techniques (Tri-Modal Spectroscopy) can serve as an excellent tool for the evaluation of dysplasia in BE.

Barrett Esophagus↗