Ernest Osei

Ernest Osei
Grand River Hospital | GRH

PhD

About

93
Publications
12,620
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1,095
Citations
Citations since 2017
31 Research Items
617 Citations
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2017201820192020202120222023020406080100120140
2017201820192020202120222023020406080100120140
2017201820192020202120222023020406080100120140

Publications

Publications (93)
Article
Background In recent years, there has been a growing interest to enhance patients’ symptom management during routine cancer care using patient-reported outcome measures. The goal of this study is to analyse patients’ responses to the Edmonton Symptom Assessment System (ESAS) to determine whether patient-reported outcomes could help characterise tho...
Article
Full-text available
Background and purpose This paper reports on results from the foremost national survey on external beam radiation therapy (EBRT) treatment practice at the three radiotherapy (RT) facilities in Ghana. It is to survey the current EBRT treatment protocols and its resources available in the country for breast cancer treatment. Results are intended to f...
Article
Intensity-modulated radiation therapy (IMRT) with sliding windows is a form of radiation therapy that delivers precise radiation dose to a tumor/target region. It uses a multi-leaf collimator (MLC) to move pairs of unidirectional tungsten leaves across a radiation emitting region to conform the shape of the radiation beam to the target regions. Thi...
Article
Background The complexity associated with the treatment planning and delivery of stereotactic radiosurgery (SRS) or stereotactic radiotherapy (SRT) volumetric modulated arc therapy (VMAT) plans which employs continuous dynamic modulation of dose rate, field aperture and gantry speed necessitates diligent pre-treatment patient-specific quality assur...
Article
The COVID-19 (SARS-CoV-2) pandemic has profoundly impacted almost every aspect of healthcare systems worldwide, placing the health and safety of frontline healthcare workers at risk and still continues to remain an important public health challenge. Several hospitals have put in place strategies to manage space, staff, and supplies in order to cont...
Article
Background Pancreatic cancer is the 12th most commonly diagnosed cancer and the 3rd leading cause of cancer mortality and accounts for approximately 2·7% of all newly diagnosed cancer cases and 6·4% of all cancer mortalities in Canada. It has a very poor survival rate mainly due to the difficulty of detecting the disease at an early stage. Conseque...
Article
Background Prostate cancer is the most commonly diagnosed cancer in men and it is responsible for about 10% of all cancer mortality in Canadian men. The current ‘gold standard’ for the diagnosis of prostate cancer is a prostate biopsy and the decision on when to biopsy a patient with non-suspicious Digital Rectal Examination (DRE) result and total...
Article
Objectives Lung cancer is the most commonly diagnosed cancer in Canada and the leading cause of cancer-related mortality in both men and women in North America. Surgery is usually the primary treatment option for early-stage non-small cell lung cancer (NSCLC). However, for patients who may not be suitable candidates for surgery, stereotactic body r...
Article
Background Breast cancer is the most commonly diagnosed cancer among women and the second leading cause of cancer-related death in Canadian women. Surgery is often the first line of treatment for low-risk early stage patients, followed by adjuvant radiation therapy to reduce the risk of local recurrence and prevent metastasis after lumpectomy or ma...
Article
Background The standard treatment modalities for prostate cancer include surgery, chemotherapy, hormonal therapy and radiation therapy or any combination depending on the stage of the tumour. Radiation therapy is a common and effective treatment modality for low-intermediate-risk patients with localised prostate cancer, to treat the intact prostate...
Article
Background Neuroblastoma is the most common extracranial solid tumour of infancy and accounts for about 6–10% of paediatric cancers. It has a biologically and clinically heterogeneous behaviour that ranges from spontaneous regression to cases of highly aggressive metastatic disease that could be unresponsive to standard therapy. In recent years, th...
Article
Background The purpose of this study is to evaluate the effectiveness and sensitivity of the Varian portal dosimetry (PD) system as a quality assurance (QA) tool for breast intensity-modulated radiation therapy (IMRT) treatment plans. Materials and methods Four hundred portal dose images from 200 breast cancer patient IMRT treatment plans were ana...
Article
Background Brain tumours are relatively rare disease but present a large medical challenge as there is currently no method for early detection of the tumour and are typically not diagnosed until patients have progressed to symptomatic stage which significantly decreases chances of survival and also minimises treatment efficacy. However, if brain ca...
Article
Introduction Lung cancer has a high mortality rate mainly due to the lack of early detection or outward signs and symptoms, thereby often progressing to advanced stages (e.g., stage IV) before it is diagnosed. However, if lung cancers can be diagnosed at an early stage and also if clinicians can prospectively identify patients likely to respond to...
Article
Background and purpose: This study investigated the variations of rectal motion and wall thickness in prostate intensity-modulated radiotherapy using a novel 2D probability density function. To evaluate the impact of the position, thickness, and deformation of the rectum on the dose distribution in prostate intensity-modulated radiotherapy plans,...
Article
Background The unique behaviour of microbubbles under ultrasound acoustic pressure makes them useful agents for drug and gene delivery. Several studies have demonstrated the potential application of microbubbles as a non-invasive, safe and effective technique for targeted delivery of drugs and genes. The drugs can be incorporated into the microbubb...
Article
Background Tobacco is a known addictive consumer product and its use has been reported to be associated with several health problems as well as the leading cause of premature, preventable mortality worldwide. For patients undergoing cancer treatment, tobacco smoking can potentially compromise treatment effectiveness; however, there is sufficient ev...
Article
Background The adverse health effects associated with smoking tobacco have been well investigated, and its detrimental effects on cancer treatment outcomes, efficacy and quality of life (QOL) for cancer patients have also been well documented. Tobacco smoke contains many thousands of chemicals, including a plethora of carcinogens, and the exposure...
Article
Objective: Cardiac catheterization procedures provide tremendous benefits to modern healthcare and the benefit derived by the patient should far outweigh the radiation risk associated with a properly optimized procedure. With increasing utilization of such procedures, there is growing concern regarding the magnitude and variations of dose to patie...
Article
Background Research in the applications of the principles of quantum physics in oncology has progressed significantly over the past decades; and several research groups with professionals from diverse scientific background, including electrical engineers, mathematicians, biologists, atomic physicists, computer programmers, and biochemists, are work...
Article
Background An increasing number of external beam treatment modalities including intensity modulated radiation therapy, volumetric modulated arc therapy (VMAT) and stereotactic radiosurgery uses very small fields for treatment planning and delivery. However, there are major challenges in small photon field dosimetry, due to the partial occlusion of...
Article
Full-text available
Gold nanoparticles (AuNPs) are a focus of growing medical research applications due to their unique chemical, electrical and optical properties. Because of uncertain toxicity, “green” synthesis methods are emerging, using plant extracts to improve biological and environmental compatibility. Here we explore the biodistribution of green AuNPs in mice...
Article
Full-text available
A novel polymer-based nanocomposite was fabricated to investigate its shielding properties against high-energy electron radiation for potential applications in space industry. Bismuth oxide (Bi2O3) nanoparticles and multi-walled carbon nanotubes (MWCNT) were added to poly (methyl methacrylate) (PMMA) to fabricate the nanocomposite. Radiation shield...
Article
Background Radiation therapy (RT) remains a common and effective treatment modality for patients with locally advanced prostate cancer. Technological advancements over the past decade have resulted in the introduction of intensity-modulated radiation therapy (IMRT) planning and delivery techniques that maximise the dose of radiation delivered to th...
Article
Background The success of radiation therapy for cancer patients is dependent on the ability to deliver a total tumouricidal radiation dose capable of eradicating all cancer cells within the clinical target volume, however, the radiation dose tolerance of the surrounding healthy tissues becomes the main dose-limiting factor. The normal tissue advers...
Article
Aim The purpose of the study was to investigate the detailed angularly dependent attenuation characteristics of three different commercial couch-tops: Varian IGRT, Qfix kVue Standard and Qfix kVue Dose Max couch-tops used in radiation therapy. Materials and methods The attenuation of photon beams by the treatment couch-tops was measured using a fa...
Article
Gold nanoparticles synthesized using plant extracts with medicinal properties have gained traction in recent years, especially for their use in various biomedical applications. Colloidal stability of these nanoparticles in different environments is critical to retain the expected therapeutic/diagnostic efficacy and toxicological outcome. Any change...
Article
Background Volumetric-modulated arc therapy (VMAT) has emerged as one of the most favourable techniques for radiotherapy treatment in recent years because of its conformal dose distribution to the planning target volume (PTV), lower doses to adjacent normal organs at risk (OARs) and faster and easier dose delivery. A typical conventional VMAT proto...
Article
Background Electronic portal imaging device (EPID) offers high-resolution digital image that can be compared with a predicted portal dose image. A very common method to quantitatively compare a measured and calculated dose distribution that is routinely used for quality assurance (QA) of volumetric-modulated arc therapy (VMAT) and intensity-modulat...
Article
Background Due to the increased degree of modulation and complexity of volumetric-modulated arc therapy (VMAT) plans, it is necessary to have a pre-treatment patient-specific quality assurance (QA) programme. The gamma index is commonly used to quantitatively compare two dose distributions. In this study we investigated the sensitivity of single- a...
Article
Purpose:A recent retrospective study found 53 patients previously treated to 78Gy/39 using flattened filtered (FF) 6X-VMAT at GRRCC had rectal DVH more than one standard deviation higher than the average. This study was to investigate if using 6FFFor10FFF beams could reduce these DVHs without compromising target coverage. Methods:Twenty patients’ p...
Article
An addendum/revision to AAPM TG-51 electron reference dosimetry is highly expected to meet the clinical requirement with the increasing usage of new ion chambers not covered in TG-51. A recent study, Med. Phys. 41, 111701, proposed a new fitting equation for the beam quality conversion factor k’Q to a wide spectrum of chambers. In the study, an opt...
Article
Introduction:The purpose of this study is to investigate the effects of daily setup variations on prone breast forward field-in-field (FinF) and inverse IMRT treatment planning. Methods:Rando Phantom (Left breast) and Pixy phantom (Right breast) were built and CT scanned in prone position. The treatment planning (TP) is performed in Eclipse TP syst...
Article
Purpose:The purpose of this study is to retrospectively analyze the portal dosimetry based quality assurance of prostate VMAT plans. Methods:Our standard quality assurance of VMAT treatment plans are performed using EPID installed on Varian TrueBeam Linac. In our current study we analyzed 84 prostate pretreatment VMAT plans. All plans consisted of...
Article
Purpose:Prone breast treatment is used to reduce acute and late toxicities for large or pendulous breast patients. This study developed and implemented the clinical workflow of prone breast radiotherapy treatment. Methods:Varian kVue Access360™ Prone Breast Couchtop was used as prone breast board. The treatment planning (TP)is performed in Eclipse...
Article
Purpose:To evaluate the effectiveness of using the Portal Dosimetry (PD) method for patient specific quality assurance of prostate VMAT plans. Methods:As per institutional protocol all VMAT plans were measured using the Varian Portal Dosimetry (PD) method. A gamma evaluation criterion of 3%-3mm with a minimum area gamma pass rate (gamma <1) of 95%...
Article
Radiation therapy of the intact breast is the standard therapy for preventing local recurrence of early-stage breast cancer following breast conservation surgery. To improve patient standard of care, there is a need to define a consistent and transparent treatment path for all patients that reduces significance variations in the acceptability of tr...
Article
Dose distributions of RapidArc Plan can be quite different from standard 3D conformal radiation therapy. SBRT plans can be optimized with high conformity or mimic the 3D conformal treatment planning with very high dose in the center of the tumor. This study quantifies the dosimetric differences among 3D conformal plan; flattened beam and FFF beam R...
Article
A method is established to improve the accuracy of the IMRT dose delivery for the treatment of breast and chest wall tumors when the higher dose gradient is delivered at the end of the leaf sequence. Dynamic MLC deliveries on Varian Linacs are achieved through the motion of the leaves from X1 to X2 direction. If the higher dose gradient is at the e...
Article
Full-text available
The increased use of diagnostic x-rays, especially in the field of medical radiology, has necessitated a significant demand for high resolution, real-time radiation detectors. In this regard, the photoresponse of bismuth sulfide (Bi2S3), an n-type semiconducting metal chalcogenide, to low energy x-rays has been investigated in this study. In recent...
Article
Full-text available
The aim of this study is to provide guidelines for the selection of external-beam radiation therapy target margins to compensate for target motion in the lung during treatment planning. A convolution model was employed to predict the effect of target motion on the delivered dose distribution. The accuracy of the model was confirmed with radiochromi...
Article
Background: In order to improve the evaluation of possible rectal toxicity based on the rectal normal tissue complication probability (NTCP), we consider the fractional dependence of the NTCP on the wall thickness (t(W)) and rectal displacement (R-M). Materials and Methods: The two-dimensional NTCP model (NTCP2D) was developed using radiotherapy pl...
Article
The in-water output ratio (Scp), in-air output ratio (Sc), and phantom scattering factor (Sp) are important parameters for radiotherapy dose calculation. Experimentally, Scp is obtained by measuring the dose rate ratio in water phantom, and Sc the water Kerma rate ratio in air. There is no method that allows direct measurement of Sp. Monte Carlo (M...
Article
Flattening filter free (FFF) beams have been adopted by many clinics and used for patient treatment. However, compared to the traditional flattened beams, we have limited knowledge of FFF beams. In this study, we successfully modeled the 6 MV FFF beam for Varian TrueBeam accelerator with the Monte Carlo (MC) method. Both the percentage depth dose a...
Article
Volumetric modulated arc therapy (VMAT) allows fast delivery of stereotactic radiotherapy. However, the discrepancies between the calculated and delivered dose distributions due to respiratory motion and dynamic multileaf collimators (MLCs) interplay are not avoidable. The purpose of this study is to investigate RapidArc lung SBRT treatment deliver...
Article
The major advantages of the VMAT SBRT plans compared to the conventional 3D conformai plan include faster delivery and improved target dose conformity. This study quantifies the dosimetric differences among 3D conformai plan; flattened beam and flattening filter-free (FFF) beam RapidArc Plans for lung SBRT. Five early stage lung cancer patients wit...
Article
This study investigated the dependence of the probability density function (pdf) describing rectal wall geometry on the rectum position (Rm) and the rectal wall thickness (tw). Probability density functions describing the organ motion uncertainties of the rectum (pdf M) have been reported by many authors. In this study, we further proposed a pdf de...
Article
Frequently, in radiation therapy one must treat superficial lesions on cancer patients; these are at or adjacent to the skin. Megavoltage photon radiotherapy penetrates through the skin to irradiate deep-seated tumors, with skin-sparing property. Hence, to treat superficial lesions, one must use a layer of scattering material to feign as the skin s...
Article
Lead is commonly used in medical radiology departments as a shielding material. Lead‐based protective materials are also used by clinical personnel during X‐ray image‐guided interventional radiology (IVR) procedures. However, lead is extremely toxic and prolonged exposure to it can result in serious health concerns. Polymer composites, on the other...
Article
Full-text available
In diagnostic radiology examinations there is a benefit that the patient derives from the resulting diagnosis. Given that so many examinations are performed each year, it is inevitable that there will be occasions when an examination(s) may be inadvertently performed on pregnant patients or occasionally it may become clinically necessary to perform...
Article
Full-text available
The quantification of radiation risks associated with radiological examinations has been a subject of interest with the increased use of X-rays. Effective dose, which is a risk-weighted measure of radiation to organs in the body associated with radiological examination, is considered a good indicator of radiological risk. We have therefore investig...
Article
Digital imaging and communications in medicine (DICOM) format is the de facto standard for communications between therapeutic and diagnostic modalities. A plan generated by a treatment planning system (TPS) is often exported in DICOM format. BEAMnrc/DOSXYZnrc is a widely used Monte Carlo (MC) package for modelling the Linac head and simulating dose...
Article
Volumetric modulated arc therapy (VMAT) has recently been used to improve the dose distribution and efficiency of treatment delivery over the standard intensity-modulated radiotherapy (IMRT) technique. This study compares the dosimetry between RapidArc plan and standard IMRT plan for head and neck cancer. Three head and neck patients treated clinic...
Article
Adjuvant radiotherapy for left breast cancers increases local tumor control, but also increases the risk of radiation-induced cardiac disease. Deep Inspiration Breath Hold (DIBH) can minimize dose to the heart for left breast patients where the heart is within the tangential field. In this study, we evaluated the dosimetric benefit of DIBH techniqu...
Article
Bacteriorhodopsin is a proton-pump protein in the cell membrane of Halobacterium salinarium. Unlike many other biomaterials, bacteriorhodopsin keeps most of its physical, chemical and electrical properties in the dry thin film form. This makes bacteriorhodopsin an excellent candidate for fabrication of electro-mechanical devices in the scale of mic...
Article
Purpose: This study presents the development and implementation of the clinical workflow of Deep Inspiration Breath Hold (DIBH) radiation therapytreatment for left breast cancer patients, which includes patient simulation, treatment planning (TP) and treatmentdelivery. Materials: DIBH is used for left chest‐wall or left breast cancer patients where...
Article
Purpose: Superficial low energy X‐ray treatments are widely available in many cancer centers for skintumours. In comparison with the low energy electron treatmentsdelivered by modern Linacs, it has the advantage of easy setup, less resource intensive, and cost effective, but still achieves the same purpose of tumour control or cure. For some tumour...
Article
Purpose: To develop lead‐free polymercomposites for shielding diagnostic x‐rays employed in interventional radiological (IVR) procedures. Methods: Polydimethylsiloxane(PDMS)composites of different weight percentages (wt%) were developed from the following high atomic‐number (Z) materials: (i) bismuthtungsten oxide (BTO), (ii) bismuth oxide (BO). X‐...
Article
The respiratory related dosimetric uncertainties in the 4DCT based lung stereotactic body radiotherapy(SBRT)treatment planning and treatment delivery are evaluated by performing density assignment correction (DAC) in the ITV. Siemens 40‐slice CT scanner was used to acquire 8 phases of 4DCT images and a free breathing CT scan using a CIRS Dynamic Th...
Article
The purpose of this study was to determine the impact of internal target volume (ITV) density on the 4DCT based lung stereotactic body radiotherapy(SBRT)treatment planning (TP) using the ITV density assignment correction (DAC). Siemens 40?slice CT scanner was used to acquire 8 phases of 4DCT images and a free breathing CT scan of CIRS Dynamic Thora...
Article
Diagnostic radiological imaging such as conventional radiography, fluoroscopy and computed tomography (CT) examinations will continue to provide tremendous benefits in modern healthcare. The benefit derived by the patient should far outweigh the risk associated with a properly conducted imaging examination. Nonetheless, it is very important to be a...
Article
The purpose of this study was to evaluate the difference between planned and delivered doses within the ITV generated by the co?alignment of the standard and slow CT scan. A QUASAR? phantom with a cedar insert (to simulate the lung) and an ionization chamber with buildup cap was scanned twice using modified slow CT scan technique. The respiratory c...
Article
Diagnostic radiological imaging such as conventional radiography,fluoroscopy and computed tomography(CT) examinations will continue to provide tremendous benefits in modern healthcare. The benefit derived by the patient should far outweigh the risk associated with a properly conducted imaging examination. Nonetheless, it is very important to be abl...
Article
The purpose of this study was to investigate the volume of the ITV generated by a modified slow CT scan and CBCT using a QUASAR? phantom. The standard CT scan(CTstandard) was acquired with pitch 1.7 and scan time 1 second followed by the slow CT scan(CTslow) limited to the tumor region with pitch 1 and scan time 3 seconds. The two image sets were c...
Article
Diagnostic radiology imaging techniques including conventional radiography,fluoroscopy and computed tomography will continue to provide tremendous benefits to modern healthcare. The quantification of radiation risks associated with radiological examinations has been the subject of interest for some time now with the increased used of x?rays in the...
Article
We have investigated the dosimetric properties of a commercial kilovoltage cone beam computerised tomography (kV-CBCT) system. The kV-CBCT doses were measured in 16 and 32 cm diameter standard cylindrical Perspex computerised tomography (CT) and Rando anthropomorphic phantoms using 125 kVp and 1.0-2.0 mA s per projection. We also measured skin dose...
Article
Full-text available
We have studied and analysed the magnitude of interfraction set-up errors and gold seed marker and prostate displacement in 118 patients using three gold seeds implanted within the prostate. Set-up errors and gold seed marker displacements were determined from bony anatomy and gold seed marker mismatch between the electronic portal image and the si...
Article
Linac‐mounted cone beam computed tomography (CBCT) using Varian's On Board Imager (OBI) currently delivers significant imaging dose and lacks automatic methods for clinical target volume (CTV) registration. In this work, we address these two issues to enable frequent treatment corrections during a course of prostate intensity modulated radiation th...
Article
Internal organ motion was studied for 20 prostate patients who were treated with IGRT using MV EPI with three gold seeds implanted in the prostate. Prostate motion was determined from the gold seed displacement relative to bony anatomy between the EPI and the DRR fraction?to?fraction before any correction was applied. The patients were planned with...
Article
Purpose: Daily MV EPI for localization of prostate implanted with gold seeds provided data for analysis of setup error and organ motion for 118 patients. Simultaneous time?course trends of prostate motion and setup error were analyzed fraction?to?fraction for 20 patients. The correlations of setup error and organ motion, setup error and body size,...
Article
Full-text available
There can be several reasons why a pregnant patient may receive a radiological examination. It could have been a planned exposure, or the exposure might have resulted from an emergency when a thorough evaluation of pregnancy was impractical. Sometimes the pregnancy was unsuspected at the time of the examination and, with younger women being diagnos...
Article
An image‐guided localization system has been developed for daily localization of the prostate using electronic portal images, digitally reconstructedradiographs(DRR) and implanted radio‐opaque fiducial markers or anatomic landmarks. This paper describes the computer program (ProLoc) and its potentials with particular application to the daily locali...
Article
Early stage lungcancer, presenting as a small solitary pulmonary mass, is treated with radiation when concurrent disease precludes a surgical option. These small lesions are usually surrounded by less dense normal lung, which affects the ability to deliver a homogenous dose to the target volume. In low‐density tissue, such as lung, there is increas...
Article
There can be several reasons why a pregnant patient may receive a radiological examination. It could have been a planned exposure or may have resulted from an emergency when a thorough evaluation of pregnancy was impractical or the pregnancy was unsuspected during the examination. With younger women being diagnosed with breast cancer, the likelihoo...
Article
There can be several reasons why a pregnant patient may receive a radiological examination. It could have been a planned exposure or the exposure may have resulted from an emergency when a thorough evaluation of pregnancy was impractical. Sometimes the pregnancy was unsuspected at the time of the examination and with younger women being diagnosed w...
Article
Background: The ability to deliver a homogenous dose distribution to small lung lesions is usually affected by the surrounding less dense normal lung. In low‐density tissue, there is increased transmission of photons relative to that in tissue. The lateral scatter of electrons out of the beam can lead to loss of field flatness and increased penumbr...
Article
The dose distribution in small lung tumors (coin lesions) is affected by the combined effects of reduced attenuation of photons and extended range of electrons in lung. The increased range of electrons in low-density tissues can lead to loss of field flatness and increased penumbra width, especially at high energies. The EGSNRC Monte Carlo code, to...
Article
Occasionally, it is clinically necessary to perform a radiological examination(s) on a woman who is known to be pregnant or an examination is performed on a woman who subsequently discovers that she was pregnant at the time. In radiological examinations, especially of the lower abdomen and pelvis area, the foetus is directly irradiated. It is there...
Article
Full-text available
Ocular melanoma is frequently treated using brachytherapy implants (such as 125 I and 60 Co plaques or 184 Ta wire), surgery, or external beam radiotherapy using small 60 Co beams, high energy x-rays, or proton therapy. The last technique, though very expensive, provides improved dose distributions and dose localizations in the treatment of tumours...
Article
Full-text available
Ocular melanoma is frequently treated using brachytherapy implants (such as 125I and 60Co plaques or 184Ta wire), surgery, or external beam radiotherapy using small 60Co beams, high energy x-rays, or proton therapy. The last technique, though very expensive, provides improved dose distributions and dose localizations in the treatment of tumours adj...
Article
Full-text available
The protection of the unborn children of pregnant women from ionizing radiations is very important because the fetus is particularly vulnerable to the effects of ionizing radiation. From the radiation protection perspective, the International Commission on Radiological Protection regards the unborn child as a member of the public when considering t...
Article
Exposure to relatively high dose ionising radiation during pregnancy may induce some effects that are seen at birth and others that are not manifested until later in life. A review of the published literature indicates that the very early and later stages of fetal development are at lower risk than the period in between. The evidence relating in ut...
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Full-text available
There has been growing concern about radiation exposures in the case of pregnant women who undergo radiological examinations of the lower abdomen and pelvis, when the embryo/fetus is near or included in the X-ray field. This paper describes a retrospective study of 50 pregnant women accrued over a period of 10 years. Most of these women were not aw...