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At least 469 records · Page 26Linked to original sources
PubMed1993

The effects of therapeutic doses of irradiation on experimental bone graft incorporation over a porous-coated segmental defect endoprosthesis.

The incorporation of autogeneic bone graft into a porous coated segmental endoprosthesis after high-dose irradiation was studied in dogs. A mid-diaphyseal defect was surgically created and then reconstructed with a porous-coated segmental endoprosthesis in 16 dogs. Autogeneic bone grafts were placed over the porous-coated regions of the endoprosthesis and at the endoprosthesis-bone junctions to achieve extracortical fixation. In eight dogs, the reconstructed femora were treated with a time-equivalent dose of 5500 cGy, delivered over a five-week period, beginning three weeks after surgery. In eight dogs, which served as the control group, the reconstructed femora were not irradiated. Dogs were killed 12 weeks after surgery, and the reconstructed femora were evaluated clinically, roentgenographically, mechanically, and histologically. Extracortical bone formation and bone ingrowth into the porous-coated segmental endoprosthesis were significantly inhibited by high-dose irradiation. Nonirradiated reconstructed femora had higher maximum torque at the implant-bone junction than irradiated femora. Nonirradiated femora had significantly greater bone ingrowth within the porous space than irradiated femora. Intracortically, irradiated femora had greater unlabeled bone and less porosity as well as more new bone than nonirradiated femora at 12 weeks postsurgery. Extracortically, irradiated femora had greater original cortical bone and less porosity as well as more new bone than nonirradiated femora at 12 weeks postsurgery. Mineral apposition was less in the irradiated femora from the initiation of radiotherapy to the time of killing five weeks after cessation of irradiation.

Analysis of Variance↗
PubMed1983

High dose rate afterloading treatment in carcinoma of the uterine cervix using an individual planning and reconstruction system.

The results of intracavitary radiation treatment of 100 cases of cervical carcinoma stage I B and II A with a high dose rate afterloading system are reported. To increase treatment precision an individual method was used with definition of the target and with a detailed three-dimensional computer planning system. A Wertheim operation followed intracavitary treatment and postoperative external irradiation was only given to cases with positive nodes. Residual tumor was found to the same extent as with the former manual radium treatment. Besides having achieved full radiation protection of the staff, radiation reactions among patients were almost eliminated.

Adenocarcinoma↗
PubMed2002

Three-dimensional surface rendering reconstruction of scoliotic vertebrae using a non stereo-corresponding points technique.

The medical imaging techniques that allow a three-dimensional (3D) surface rendering reconstruction, which is usually required by the clinician when dealing with scoliotic patients, are computed tomography (CT) and stereoradiography. However, CT cannot provide a 3D rendering of the whole spine because of the high irradiating dose, while the stereoradiographic 3D reconstruction techniques, which use an algorithm derived from the direct linear transformation (DLT), are usually limited in accuracy because of the small number of corresponding anatomical landmarks identifiable on both radiographs. The purpose of the present study is to validate a recent biplanar 3D surface rendering reconstruction technique on scoliotic vertebrae. This technique, called "non stereo-corresponding points" (NSCP), has already been tested on non-pathologic dry cervical vertebrae and frozen lumbar specimens, and the results have proved very encouraging. Since scoliosis is a 3D deformity of the vertebrae and of the global spine, such a technique could be a very useful clinical tool for the diagnostic, follow-up and surgical planning when dealing with scoliotic patients. The validation of the NSCP technique on scoliotic patients was performed on 58 scoliotic vertebrae in 14 patients, by comparison with the CT scan 3D rendering technique. The results of this study show mean errors of 1.5 mm. On the basis of this study, we can conclude that the NSCP 3D reconstruction technique is a definite improvement over existing techniques, and can serve as a useful diagnosis tool in scoliosis. However, the results of the technique still need to be optimized for use in geometrical modeling.

Adolescent↗
PubMed2001

Cone-beam computed tomography with a flat-panel imager: magnitude and effects of x-ray scatter.

A system for cone-beam computed tomography (CBCT) based on a flat-panel imager (FPI) is used to examine the magnitude and effects of x-ray scatter in FPI-CBCT volume reconstructions. The system is being developed for application in image-guided therapies and has previously demonstrated spatial resolution and soft-tissue visibility comparable or superior to a conventional CT scanner under conditions of low x-ray scatter. For larger objects consistent with imaging of human anatomy (e.g., the pelvis) and for increased cone angle (i.e., larger volumetric reconstructions), however, the effects of x-ray scatter become significant. The magnitude of x-ray scatter with which the FPI-CBCT system must contend is quantified in terms of the scatter-to-primary energy fluence ratio (SPR) and scatter intensity profiles in the detector plane, each measured as a function of object size and cone angle. For large objects and cone angles (e.g., a pelvis imaged with a cone angle of 6 degrees), SPR in excess of 100% is observed. Associated with such levels of x-ray scatter are cup and streak artifacts as well as reduced accuracy in reconstruction values, quantified herein across a range of SPR consistent with the clinical setting. The effect of x-ray scatter on the contrast, noise, and contrast-to-noise ratio (CNR) in FPI-CBCT reconstructions was measured as a function of SPR and compared to predictions of a simple analytical model. The results quantify the degree to which elevated SPR degrades the CNR. For example, FPI-CBCT images of a breast-equivalent insert in water were degraded in CNR by nearly a factor of 2 for SPR ranging from approximately 2% to 120%. The analytical model for CNR provides a quantitative understanding of the relationship between CNR, dose, and spatial resolution and allows knowledgeable selection of the acquisition and reconstruction parameters that, for a given SPR, are required to restore the CNR to values achieved under conditions of low x-ray scatter. For example, for SPR = 100%, the CNR in FPI-CBCT images can be fully restored by: (1) increasing the dose by a factor of 4 (at full spatial resolution); (2) increasing dose and slice thickness by a factor of 2; or (3) increasing slice thickness by a factor of 4 (with no increase in dose). Other reconstruction parameters, such as transaxial resolution length and reconstruction filter, can be similarly adjusted to achieve CNR equal to that obtained in the scatter-free case.

Biophysical Phenomena↗
PubMed1994

Retrospective reconstruction of three-dimensional radiotherapy treatment plans of the thorax from two dimensional planning data.

PURPOSE: A method for the retrospective reconstruction of three-dimensional (3-D) radiotherapy treatment plans from two-dimensional (2-D) planning data is detailed in this paper. METHODS AND MATERIALS: With these techniques the user can register an arbitrarily shaped portal on a simulation film with a diagnostic computed tomography study of the patient and then generate the resultant 3-D dose distribution or dose-volume histogram. Seven treatment plans were reconstructed of patients who had previously undergone 3-D treatment planning for fields involving the thorax and who had had a diagnostic computed tomography (CT) scan. The dose-volume histograms and the spatial positions of the beams on the reconstructed plans were then compared to those of the original 3-D plan, which until then, were not made available to the investigators. RESULTS: The dose-volume histograms of the reconstructed plans did not differ from those of the original plans by more than 3% except in the low dose region. The error in positioning the beam in the reconstructed plan was determined to be approximately 5 mm. CONCLUSION: The technique of 3-D treatment plan reconstruction can be used, through retrospective studies, to obtain better assessments of normal tissue complication probabilities and tumor control probabilities.

Humans↗
PubMed1987

The current approach to breast reconstruction.

Over the last 30 years, breast reconstruction has become a standard part of the care of the breast cancer patient. While it may take another 30 years for many of the traditional oncologic concerns about reconstruction to be answered, indications are that reconstruction does not alter the patient's prognosis in any way. The increased understanding of breast cancer as a disease which is systemic from early in its course has removed many of the former objections to reconstruction. Reconstruction can be performed after almost any type of mastectomy. Chemotherapy does not interfere with reconstruction, as long as the timing of doses is considered. However, therapeutic radiation does present problems which may preclude reconstruction. Conversely, having had reconstruction does not interfere with later chemo or radiation therapy. The author describes reconstructive options and their relationship to oncological decisions and concerns.

Breast↗
PubMed1998

[Management and delivery of radiation dose distribution images using the Internet].

Dose distribution images play important roles in the management of cancer patients. To date hard copies of these images have been stored and referred to by radiation oncologists as needed. In most cases, these images were not available to medical personnel outside the radiation oncology department. We have developed a mechanism in the hospital to access these dose distribution images via WWW (World Wide Web). A screen snapshot of a dose distribution image on the CRT of a treatment planning machine is copied to the WWW server and converted to a GIF image. Similarly, we can register dose volume histograms and digitally reconstructed radiographs on the WWW. Medical personnel throughout the hospital can access the images through the WWW browser. As a result, radiation oncologists are given detailed information on target definition in treatment planning by expert physicians. The system also helps co-medical staff in understanding dose distributions and predicting radiation injuries. At the same time, it actualizes an electronic archive of dose distribution images, which is a database for quick and reliable review, evaluation and comparison of treatment plans. This technique also furthers a close relationship among radiation oncologists, physicians, and co-medical personnel.

Computer Communication Networks↗
PubMed2003

Genetic effects of radiotherapy for childhood cancer.

Radiation-induced heritable diseases have not been demonstrated in humans and estimates of genetic risks for protection purposes are based on mouse experiments. The most comprehensive epidemiologic study is of the Japanese atomic bomb survivors and their children, which found little evidence for inherited defects attributable to parental radiation. Studies of workers exposed to occupational radiation or of populations exposed to environmental radiation appear too small and exposures too low to convincingly detect inherited genetic damage. In contrast, survivors of childhood cancer form the largest group of people exposed to high doses of ionizing radiation before reproduction and offer unique advantages for studying trans-generation effects. A wide range of gonadal doses are possible, several comparison groups are readily available (including siblings), and there is a strong willingness among cancer survivors to participate in health studies. Cancer patients also have detailed medical records that facilitate both the accurate estimation of gonadal doses and the assessment of potentially confounding factors, such as intercurrent illness, personal and family medical histories, lifestyle characteristics such as tobacco use, and circumstances at delivery. An international study is nearing completion of over 25,000 survivors of childhood cancer in the United States and Denmark who gave birth to or fathered over 6,000 children. Doses to gonads are being reconstructed from radiotherapy records with 46% over 100 mSv and 16% over 1,000 mSv. Adverse pregnancy outcomes being evaluated include major congenital malformations, cytogenetic abnormalities, stillbirths, miscarriages, neonatal deaths, total deaths, leukemia and childhood cancers, altered sex ratio, and birth weight. The main analyses are based on dose-response evaluations. Blood studies of trios (cancer survivor, spouse or partner and offspring) have been initiated to evaluate mechanistic evidence for the transmission of any radiation-induced genetic damage such as minisatellite mutations. Markers of cancer susceptibility such as chromosomal radiosensitivity and genotype profile will also be examined. In the United States series to date, 4,214 children were born to cancer survivors among whom 157 (3.7%) genetic diseases were reported in contrast to 95 (4.1%) reported conditions among 2,339 children born to sibling controls. In the Denmark series the comparable figures were 82 (6.1%) birth defects among 1,345 children of cancer survivors and 211 (5.0%) among 4,225 children of sibling controls. Coupled with prior studies, these preliminary findings, if sustained by ongoing dose-response analyses, provide reassurance that cancer treatments including radiotherapy do not carry much if any risk for inherited genetic disease in offspring conceived after exposure.

Abnormalities, Radiation-Induced↗
PubMedDate not supplied

Clinical usefulness of the management and delivery of radiation dose-distribution images using the Internet.

Dose distribution images in radiation therapy play important roles in the management of cancer patients. To date, hard copies of these images have been stored for referral by radiation oncologists as needed. In most cases, these images are not available to medical personnel outside the radiation oncology department. We have developed a means to access these dose distribution images from the hospital via the World-Wide Web (WWW). A screen snapshot of a dose distribution image on the CRT of a treatment planning unit is copied to the WWW server and converted to a GIF (graphic interchange format) image. Similarly, we can register dose volume histograms and digitally reconstructed radiographs (DRR) on the WWW. Medical personnel can view these images through the WWW browser from anywhere in the hospital. As a result, radiation oncologists are given detailed information on target definition in treatment planning by expert physicians. The system also helps co-medical personnel in understanding dose distribution and predicting radiation injury. At the same time, it actualizes an electronic archive of dose distribution images, which is a database for quick and reliable review, evaluation, and comparison of treatment plans. This technique also fosters closer relationships among radiation oncologists, physicians, and co-medical personnel.

Humans↗
PubMed1998

[Norwood procedure to hypoplastic left heart syndrome].

Since March 1992, 25 neonates and small infants with HLHS have undergone a modified Norwood procedure. The mean age and weight at operation were 17 days (2 days-2 months) and 2.7 kg (1.6-3.3 kg). Isolated cerebral and/or myocardial perfusion (ICMP) with direct anastomosis of aorta and pulmonary artery was utilized since January 1995 to 16 patients. Under median sternotomy, PTFE graft (usually 3.0-3.5 mm) was anastomosed to the brachiocephalic artery and the arterial cannula was inserted to this PTFE graft. The left carotid and the left subclavian arteries were snared and a clamp was placed on the aortic arch just distal to the brachiocephalic artery. This allowed blood to enter the brain and the coronary arteries, keeping the brain perfused and the heart-beating. After reconstruction of distal aortic arch, a single dose of crystalloid cardioplesia was infused and the rest of the arch was reconstructed. There were 14 early deaths (56%) and 4 late deaths (16%). Bidirectional Glenn procedure was performed to 5 patients with 1 death. Three patients underwent modified Fontan procedure without mortality. Mean aortic cross clamp time was 24 min. and mean ICMP time was 32 min. There was no neurologic complications. In conclusion, isolated cerebral and/or myocardial perfusion may offer an advantage of protecting the brain and myocardium during arch in Norwood procedure.

Aorta↗
PubMed1994

Electron arc therapy of the postmastectomy prosthetic breast.

PURPOSE: Reconstructive surgery of the postmastectomy breast presents new challenges to postoperative radiation therapy. This paper evaluates the dosimetric significance of oblique incidence of the electron field on the reconstructed mound during arc therapy. METHODS AND MATERIALS: Using film densitometry, the relative dose distributions resulting from electron arc therapy incident on phantoms simulating the breast and chest wall dimensions of an actual patient are evaluated. RESULTS: Irradiation of the breast phantom in normal supine position results in constriction of the dose distribution at the junction of the reconstructed mound with the chest wall. Angulation of the phantom to provide a more normal incidence of the electron beam during arc reduces the constriction by minimizing obliquity of the incident electrons. CONCLUSION: These measurements suggest that, with proper positioning of the patient relative to the incident electron beam, electron arc therapy may be used as an alternative treatment technique for treatment of the postmastectomy reconstructed breast and chest wall.

Breast Neoplasms↗
PubMed1987

Three-dimensional reconstruction from a single-exposure, random conical tilt series applied to the 50S ribosomal subunit of Escherichia coli.

We present a new reconstruction method that takes advantage of the fact that many biological macromolecular assemblies show a preferred orientation with respect to the plane of the specimen grid in the electron microscopic preparation. From one micrograph taken of such a specimen tilted by a large angle, a conical tilt series with random azimuthal angles can be extracted and used for a three-dimensional reconstruction. Our technique allows the determination of the molecular structure under low-dose conditions, which are not achievable with reconstruction methods that use conventional tilt series. The reconstruction method combines a number of existing image processing techniques with a newly developed weighted back-projection algorithm designed for three-dimensional reconstruction from projections taken with arbitrary projecting directions. The method is described as it was applied to the three-dimensional reconstruction of the structure of the 50S ribosomal subunit of Escherichia coli (E. coli).

Escherichia coli↗
PubMed2005

Dosimetric effects of seed anisotropy and interseed attenuation for 103Pd and 125I prostate implants.

A Monte Carlo study is carried out to quantify the effects of seed anisotropy and interseed attenuation for 103Pd and 125I prostate implants. Two idealized and two real prostate implants are considered. Full Monte Carlo simulation (FMCS) of implants (seeds are physically and simultaneously simulated) is compared with isotropic point-source dose-kernel superposition (PSKS) and line-source dose-kernel superposition (LSKS) methods. For clinical pre- and post-procedure implants, the dose to the different structures (prostate, rectum wall, and urethra) is calculated. The discretized volumes of these structures are reconstructed using transrectal ultrasound contours. Local dose differences (PSKS versus FMCS and LSKS versus FMCS) are investigated. The dose contributions from primary versus scattered photons are calculated separately. For 103Pd, the average absolute total dose difference between FMCS and PSKS can be as high as 7.4% for the idealized model and 6.1% for the clinical preprocedure implant. Similarly, the total dose difference is lower for the case of 125I: 4.4% for the idealized model and 4.6% for a clinical post-procedure implant. Average absolute dose differences between LSKS and FMCS are less significant for both seed models: 3 to 3.6% for the idealized models and 2.9 to 3.2% for the clinical plans. Dose differences between PSKS and FMCS are due to the absence of both seed anisotropy and interseed attenuation modeling in the PSKS approach. LSKS accounts for seed anisotropy but not for the interseed effect, leading to systematically overestimated dose values in comparison with the more accurate FMCS method. For both idealized and clinical implants the dose from scattered photons represent less than 1/3 of the total dose. For all studied cases, LSKS prostate DVHs overestimate D90 by 2 to 5% because of the missing interseed attenuation effect. PSKS and LSKS predictions of V150 and V200 are overestimated by up to 9% in comparison with the FMCS results. Finally, effects of seed anisotropy and interseed attenuation must be viewed in the context of other significant sources of dose uncertainty, namely seed orientation, source misplacement, prostate morphological changes and tissue heterogeneity.

Anisotropy↗
PubMed1993

Optimizing antimicrobial prophylaxis in reconstructive vascular surgery.

The combinations of cefuroxime and metronidazole, and amoxycillin/clavulanate (Augmentin) are useful as prophylactic drugs during vascular surgery. In this study the pharmacokinetic profiles of different dosing regimens utilizing these drugs during reconstructive vascular procedures are presented. Three groups of patients, undergoing aortobifemoral or femoropopliteal prosthetic surgery, received one of the following regimens: Group I: 1500 mg metronidazole plus 1500 mg cefuroxime at premedication, Group II: 1500 mg metronidazole at premedication plus 1500 mg cefuroxime at the time of induction anaesthesia, followed by 750 mg of cefuroxime 2 h later, Group III: 2000 mg amoxycillin/200 mg clavulanate at time of induction anaesthesia, followed by 1000 mg amoxycillin/200 mg clavulanate, 3 h later. For determination of the antibiotic concentrations, arterial blood samples were obtained at 30-minute intervals during the entire procedure. An additional sample was collected at the time of inguinal graft site anastomosis. Cefuroxime concentrations in these additional samples were 29.3 +/- 11.2 mg/l in group I and 44.7 +/- 15.9 mg/l in group II. Metronidazole concentrations were satisfactorily high in all patients (38.4 +/- 4.5 mg/l). Amoxycillin/clavulanate concentrations were 35.1 +/- 21.5 mg/l and 4.4 +/- 3.7 mg/l respectively. We recommend a multiple dose administration scheme for prophylaxis in high-risk prosthetic vascular surgery, if the procedure takes more than 2-3 h and antimicrobial agents with a rapid elimination time are used. A multiple dosing scheme ensures sufficiently high antibiotic concentrations, exceeding the MIC of staphylococci and enterobacteria approximately twice, at the time of inguinal graft site anastomosis.

Aged↗
PubMed1990

Technical aspects of myocardial SPECT imaging with technetium-99m sestamibi.

Most reports to date using single photon emission computed tomography (SPECT) with technetium-99m (Tc-99m) sestamibi have used acquisition parameters that were optimized for thallium-201. To fully utilize the superior imaging characteristics of Tc-99m sestamibi, there is a need to optimize the technical aspects of SPECT imaging for this agent. Performance can be enhanced through the careful selection of optimal radiopharmaceutical doses, imaging sequences, acquisition parameters, reconstruction filters, perfusion quantification methods and multidimensional methods for visualizing perfusion distribution. The current report describes theoretical considerations, phantom studies and preliminary patient results that have led to optimized protocols, developed at Emory University and Cedars-Sinai Medical Center, for same-day rest-stress studies, given existing instrumentation and recommended dose limits. The optimizations were designed to fit a low-dose-high-dose rest-stress same-day imaging protocol. A principal change in the acquisition parameters compared with previous Tc-99m sestamibi protocols is the use of a high-resolution collimator. The approach is being developed in both prone and supine positions. A new method for extracting a 3-dimensional myocardial count distribution has been developed that uses spherical coordinates to sample the apical region and cylindrical coordinates to sample the rest of the myocardium. New methods for visualizing the myocardial distribution in multiple dimensions are also described, with improved 2-dimensional, as well as 3- and 4-dimensional (3 dimensions plus time) displays. In the improved 2-dimensional display, distance-weighted and volume-weighted polar maps are used that appear to significantly improve the representation of defect location and defect extent, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Computer Graphics↗
PubMed2005

Noise correlation in PET, CT, SPECT and PET/CT data evaluated using autocorrelation function: a phantom study on data, reconstructed using FBP and OSEM.

BACKGROUND: Positron Emission Tomography (PET), Computed Tomography (CT), PET/CT and Single Photon Emission Tomography (SPECT) are non-invasive imaging tools used for creating two dimensional (2D) cross section images of three dimensional (3D) objects. PET and SPECT have the potential of providing functional or biochemical information by measuring distribution and kinetics of radiolabelled molecules, whereas CT visualizes X-ray density in tissues in the body. PET/CT provides fused images representing both functional and anatomical information with better precision in localization than PET alone. Images generated by these types of techniques are generally noisy, thereby impairing the imaging potential and affecting the precision in quantitative values derived from the images. It is crucial to explore and understand the properties of noise in these imaging techniques. Here we used autocorrelation function (ACF) specifically to describe noise correlation and its non-isotropic behaviour in experimentally generated images of PET, CT, PET/CT and SPECT. METHODS: Experiments were performed using phantoms with different shapes. In PET and PET/CT studies, data were acquired in 2D acquisition mode and reconstructed by both analytical filter back projection (FBP) and iterative, ordered subsets expectation maximisation (OSEM) methods. In the PET/CT studies, different magnitudes of X-ray dose in the transmission were employed by using different mA settings for the X-ray tube. In the CT studies, data were acquired using different slice thickness with and without applied dose reduction function and the images were reconstructed by FBP. SPECT studies were performed in 2D, reconstructed using FBP and OSEM, using post 3D filtering. ACF images were generated from the primary images, and profiles across the ACF images were used to describe the noise correlation in different directions. The variance of noise across the images was visualised as images and with profiles across these images. RESULTS: The most important finding was that the pattern of noise correlation is rotation symmetric or isotropic, independent of object shape in PET and PET/CT images reconstructed using the iterative method. This is, however, not the case in FBP images when the shape of phantom is not circular. Also CT images reconstructed using FBP show the same non-isotropic pattern independent of slice thickness and utilization of care dose function. SPECT images show an isotropic correlation of the noise independent of object shape or applied reconstruction algorithm. Noise in PET/CT images was identical independent of the applied X-ray dose in the transmission part (CT), indicating that the noise from transmission with the applied doses does not propagate into the PET images showing that the noise from the emission part is dominant. The results indicate that in human studies it is possible to utilize a low dose in transmission part while maintaining the noise behaviour and the quality of the images. CONCLUSION: The combined effect of noise correlation for asymmetric objects and a varying noise variance across the image field significantly complicates the interpretation of the images when statistical methods are used, such as with statistical estimates of precision in average values, use of statistical parametric mapping methods and principal component analysis. Hence it is recommended that iterative reconstruction methods are used for such applications. However, it is possible to calculate the noise analytically in images reconstructed by FBP, while it is not possible to do the same calculation in images reconstructed by iterative methods. Therefore for performing statistical methods of analysis which depend on knowing the noise, FBP would be preferred.

Journal Article↗
PubMed1998

CT-simulator based brachytherapy planner: seed localization and incorporation of biological considerations.

Radiation dose prescription, interpretation, and planning can be problematic for brachytherapy due to high spatial heterogeneity, varying and various dose rates, absence of superimposed calculated isodose distributions onto affected tissues, and lack of dose volume histograms. A new treatment planner has been developed to reduce these limitations in brachytherapy planning. The PC-based planning system uses a CT-simulator to sequentially scan the patient to generate orthogonal images (to localize seed positions) and subsequently axially scan the patient. This sequential scanning procedure avoids using multiple independent patient scans, templates, external frames, or fiducial markers to register the reconstructed seed positions with patient contours. Dose is computed after assigning activity to (low dose rate) Ir192, linear Cs137, or I125 seeds or dwell times (high dose rate) to the Ir192 source. The planar isodose distribution is superimposed onto axial, coronal, or sagittal views of the tissues following image reconstruction. The treatment plan computes (1) direct and cumulative volume dose histograms for individual tissues, (2) the average, standard deviation, and coefficient of skewness of the dose distribution within individual tissues, (3) an average (over all tissue pixels) survival probability (S) and average survival dose DASD for a given radiation treatment, (4) normal tissue complication probability (NTCP) delivered to a given tissue. All four computed quantities account for dose heterogeneity. These estimates of the biological response to radiation from laboratory-based studies may help guide the evaluation of the prescribed low- or high-dose rate therapy in retrospective and prospective clinical studies at a number of treatment sites.

Brachytherapy↗
PubMed2002

[Radiotherapy of lung cancer: the inspiration breath hold with spirometric monitoring].

A CT acquisition during a free breathing examination generates images of poor quality. It creates an uncertainty on the reconstructed gross tumour volume and dose distribution. The aim of this study is to test the feasibility of a breath hold method applied in all preparation and treatment days. Five patients received a thoracic radiotherapy with the benefit of this procedure. The breathing of the patient was measured with a spirometer. The patient was coached to reproduce a constant level of breath-hold in a deep inspiration. Video glasses helped the patients to fix the breath-hold at the reference level. The patients followed the coaching during preparation and treatment, without any difficulty. The better quality of the CT reconstructed images resulted in an easier contouring. No movements of the gross tumour volume lead to a better coverage. The deep breath hold decreased the volume of irradiated lung. This method improves the reproducibility of the thoracic irradiation. The decrease of irradiated lung volume offers prospects in dose escalation and intensity modulation radiotherapy.

Aged↗