Papers by Christopher Njeh
Critical Reviews in Oncology Hematology, 2012
Lumpectomy followed by whole breast radiation therapy (i.e. breast conservation therapy (BCT)) is... more Lumpectomy followed by whole breast radiation therapy (i.e. breast conservation therapy (BCT)) is the standard of care for management of early stage breast cancer. However, its utilization has not been maximized because of a number of reasons including the logistic issues associated with the 5-6 weeks of radiation treatment. Also, pathological and clinical data suggest that most ipsilateral breast cancer recurrences are in the vicinity of the lumpectomy. Accelerated partial breast irradiation (APBI) is an approach that treats only the lumpectomy bed plus a 1-2 cm margin, rather than the whole breast with higher doses of radiation in a shorter period of time. There has been growing interest for APBI and various approaches have been developed and are under phase I-III clinical studies. This paper reviews external beam conformal radiation therapy (EBCRT) as a possible technique to APBI. The various EBCRT approaches such as 3D conformal radiation therapy, IMRT, proton therapy, tomotherapy, and volumetric arc therapy are discussed. Issues with the implementation of these techniques such as target volume delineation and organ motion are also presented. It is evident that EBCRT has potential for APBI of a selected group of early breast cancer patient. However, issues with setup errors and breathing motions need to be adequately addressed.
Faculty of Science and Technology; Institute of Health and Biomedical Innovation, Oct 4, 2010
Breast conservation therapy (BCT) is the procedure of choice for the management of the early stag... more Breast conservation therapy (BCT) is the procedure of choice for the management of the early stage breast cancer. However, its utilization has not been maximized because of logistics issues associated with the protracted treatment involved with the radiation treatment. Accelerated Partial Breast Irradiation (APBI) is an approach that treats only the lumpectomy bed plus a 1-2 cm margin, rather than the whole breast. Hence because of the small volume of irradiation a higher dose can be delivered in a shorter period of time. There has been growing interest for APBI and various approaches have been developed under phase I-III clinical studies; these include multicatheter interstitial brachytherapy, balloon catheter brachytherapy, conformal external beam radiation therapy and intraoperative radiation therapy (IORT). Balloon-based brachytherapy approaches include Mammosite, Axxent electronic brachytherapy and Contura, Hybrid brachytherapy devices include SAVI and ClearPath. This paper reviews the different techniques, identifying the weaknesses and strength of each approach and proposes a direction for future research and development. It is evident that APBI will play a role in the management of a selected group of early breast cancer. However, the relative role of the different techniques is yet to be clearly identified.
IOP Publishing Ltd eBooks, Nov 26, 2004
The Physical Measurement of Bone
IOP Publishing Ltd eBooks, Nov 26, 2004
The Physical Measurement of Bone, 2016
Medical Physics, Jun 1, 2015
Purpose:Prostate cancer is the most frequently diagnosed malignancy in American males. To date, n... more Purpose:Prostate cancer is the most frequently diagnosed malignancy in American males. To date, no single study has examined the effect of obesity on the outcomes of all three treatment modalities in a single population. We examined the relationship between obesity and prostate cancer treatment decisions as well as outcomes.Methods:We conducted a retrospective observational cohort study of the patients treated for prostate cancer with curative intent between January 1998 and December 2010. Wilcoxon ranksum and Chi‐Square tests were used to analyze the association between treatment mode and body mass index (BMI). Cox proportional Hazards models adjusted for risk category, age, and androgen deprivation therapy (ADT) were performed to evaluate the effects of BMI on overall, disease‐free, biochemical recurrence‐free, incontinence‐free, and impotence‐free survival.Results:A total of 1681 patients were included in the analysis, including 338 that received BT, 439 that received EBRT, and 904 that received RP. When BMI was assessed as a continuous variable, median BMI was higher in patients treated with BT (29.4) than in those treated with EBRT (28.8) or RP (28.9) (P = 0.0677, Wilcoxon rank‐sum test). After stratifying BMI into two groups (BMI < 29.4 or ≥ 29.4), Chi‐Square test showed that the treatment mode was significantly related to BMI where the proportion of high BMI individuals undergoing was 50.9% for BT, 42.4% for EBRT, and 43.2% for RP (P = 0.0309). Cox proportional hazards modeling was used to assess the relationship between BMI and survival outcomes. For patients receiving EBRT, BMI was a significant risk factor for incontinence‐free survival where HR for incontinence in the lower BMI group was 0.515 (95% CI 0.307–0.865, P = 0.0121).Conclusion:BMI appears to be related to prostate cancer treatment decisions, High BMI (≥ 29.4) is associated with poorer incontinence‐free survival for EBRT.This study was supported by a grant from the Marshfield Clinic Research Foundation
Brachytherapy, May 1, 2015
Medical Dosimetry, 2020
Applying dual, or mixed photon energies during radiation therapy is a common practice in 3-dimens... more Applying dual, or mixed photon energies during radiation therapy is a common practice in 3-dimensional conformal radiation therapy (3D-CRT). Mixed photon energies are used to provide uniform dose coverage to a planning target volume (PTV) that ranges in depth from the skin surface. Though the application of mixed photon energies in 3D-CRT was once the convention for treating anal cancers with lymph node involvement (AC-LNI), the advantages offered by volumetric modulated arc therapy (VMAT) prove to be the optimal form of therapy for AC-LNI. Recently, multiple researchers have uncovered benefits in employing multiple photon energies in VMAT planning for prostate cancer. A retrospective study was completed to assess the impact of implementing mixed energy VMAT planning in comparison to conventional single energy VMAT planning for AC-LNI. Data from 20 patients with AC-LNI was collected to analyze the dosimetric effects of mixed energy VMAT treatments in terms of PT V conformity index, PT V homogeneity index, monitor unit usage, and organs at risk sparing. For each patient 3 treatment plans were created: a single energy 6 MV plan, a single energy 10 MV plan, and a mixed 6 MV and 10 MV energy plan. Analysis of the resulting dosimetric outcomes showed statistical significance. The current study concluded that mixed energy VMAT plans have some effect on treating AC-LNI when compared to single energy VMAT plans.
Journal of Applied Clinical Medical Physics, 2022
A simple quality assurance test tool for the visual verification of light and radiation field con... more A simple quality assurance test tool for the visual verification of light and radiation field congruent using electronic portal images device and computed radiography Njeh et al.
Quantitative Ultrasound: Assessment of Osteoporosis and Bone Status, ed. Njeh CF, Hans D, Fuerst T, Gluer CC. Genant, HK, 1999
Journal of Applied Clinical Medical Physics, 2015
Dose inhomogeneity in treatment planning can be compensated using physical wedges. Enhanced dynam... more Dose inhomogeneity in treatment planning can be compensated using physical wedges. Enhanced dynamic wedges (EDW) were introduced by Varian to overcome some of the shortcomings of physical wedges. The objectives of this study were to measure EDW output factors for 6 MV and 20 MV photon energies for a Varian 2300CD. Secondly, to review the literature in terms of published enhanced dynamic wedge output factors (EDWOF) for different Varian models and thereby add credence to the case of the validity of reference databases. The enhanced dynamic wedge output factors were measured for the Varian 2300CD for both 6 MV and 20 MV photon energies. Twelve papers with published EDWOF for different Varian linac models were found in the literature. Comparing our results with the published mean, we found an excellent agreement for 6 MV EDWOF, with the percentage differences ranging from 0.01% to 0.57%, with a mean of 0.03%. The coefficient of variation of published EDWOF ranged from 0.17% to 0.85% and 0.1% to 0.9% for the for 6 MV and 18 MV photon energies, respectively. This paper provides the first published EDWOF for 20 MV photon energy. In addition, we have provided the first compendium of EDWOFs for different Varian linac models. The consistency of value across models and institution provide further support that a standard dataset of basic photon and electron dosimetry could be established as a guide for future commissioning, beam modeling, and quality assurance purposes.
Calcified Tissue International, 2003
The aim of this study was to evaluate the association among phalangeal morphometric parameters, a... more The aim of this study was to evaluate the association among phalangeal morphometric parameters, amplitude-dependent speed of sound (AD-SOS), ultrasound bone profile index (UBPI), and spinal bone mineral density (BMD) and fracture status. One hundred women (controls, mean age 53 +/- 12 years) and 40 osteoporotic women (mean age 59 +/- 7 years) with atraumatic fractures, diagnosed by spinal radiographs, were investigated. Quantitative ultrasound (QUS) assessment was performed using the DBM Sonic 1200. Morphological properties of the phalanges were measured from a digitized X-ray image of the hand acquired using industrial film. Spinal BMD was assessed by dual X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). An increase in medullary canal width and a decrease in cortical thickness with aging were observed from the morphometric analysis of the hand radiographs. This phenomenon can be attributed mainly to endosteal resorption. QUS measurements at the phalanges were not significantly related to finger thickness (r <0.20, n.s.). They were significantly correlated to medullary canal ratio (r = -0.57, P <0.0001, for AD-SOS and r = -0.64, P <0.0001, for UBPI) and to cortical thickness (r = +0.52, P <0.0001 for AD-SOS and r = +0.59, P <0.0001 for UBPI). In the discrimination analysis between nonfractured and atraumatic vertebral fracture subjects we found that cortical thickness at the level of the phalanges were similar to lumbar spine BMD. The age and BMI-adjusted odds ratio ranged from 2.0 to 3.1 for QUS, 4.28 for BMD by QCT, 4.1 for BMD by DXA, and 4.1 for cortical thickness. We conclude from these data that phalangeal QUS is related to cortical thickness, which in turn is influenced by endosteal bone resorption occurring in association with spinal osteoporosis.
Series in Medical Physics and Biomedical Engineering, 2003
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Papers by Christopher Njeh