Biomedical subjects

J Damilakis

Publications and source records attributed to J Damilakis.

At least 37 records · Page 2Linked to original sources

PubMed2001

Imaging ultrasonometry of the calcaneus: optimum T-score thresholds for the identification of osteoporotic subjects.

The purpose of the present study was to (1) examine the age dependence of T-score results for calcaneal imaging ultrasonometry and dual X-ray absorptiometry of the axial skeleton and (2) determine the optimum T-score thresholds appropriate for broadband ultrasound attenuation (BUA) and speed of sound (SOS) measurements. A total of 453 healthy women aged 20-9 years were included in the study. All study participants underwent bone mineral density (BMD) measurements of the lumbar spine, femoral neck, total hip and calcaneal measurements of the BUA and SOS. An imaging ultrasound device (UBIS, DMS, France) was used for the ultrasound measurements. T-scores were calculated using a subgroup of 71 healthy women aged 20-35 years to estimate the mean value of young normals and SD for BUA, SOS, and BMD. The age-related decline in both BUA and SOS T-scores was slower than that in the equivalent figures obtained by BMD measurements. The optimum T-score thresholds estimated by receiver operating characteristic (ROC) analysis were 1.3 for BUA and 1.5 for SOS. Using the optimum threshold, the sensitivity and specificity for BUA was 68% and 83%, respectively. Corresponding values for SOS were 63% and 79%. Utilizing calculated optimum T score thresholds for BUA and SOS, the agreement among BUA, SOS, and BMD at the femoral neck was improved compared with that found using the T-score of < or = -2.5 criterion. In conclusion, the definition of osteoporosis by a T-score of , or = -2.5 was not applicable to imaging ultrasonometry of the calcaneus. Optimum T-score thresholds were determined for both BUA and SOS suitable to Ubis QUS device.

Absorptiometry, Photon↗

PubMed2001

Broadband ultrasound attenuation imaging: influence of location of region of measurement.

The aim of the study was to investigate the effect of three different regions of interest (ROIs) varying in size and shape on broadband ultrasound attenuation (BUA) measurements of the calcaneus. Two hundred and sixty-five postmenopausal Caucasian women participated in this study. In 43 women osteoporotic fractures were documented on spinal radiographs. Bone mineral density (BMD) measurements of the lumbar spine and the femur were made using dual-energy X-ray absorptiometry. BUA measurements were obtained at a circular ROI automatically determined by the imaging system (ROIc), at a manually traced irregular ROI encompassing the posterior part of the calcaneus (ROIi), and at an anatomical square ROI located in the posterior part of the calcaneus (ROIs). Reproducibility was better in ROIc than in ROIi and ROIs. High correlations were found between BUA measurements with ROIc and ROIs (r = 0.981, P < 0.0001) as well as between those with ROIc and ROIi (r = 0.965, P < 0.0001). There were no significant differences between the correlations of BUA with axial BMD at ROIc compared with ROIi and ROIs. No significant difference was found between the areas under the ROC curve at ROIi, ROIc, and ROIs for women with fractures. The results show that superior reproducibility makes ROIc the most appropriate region of BUA measurement in a comparison with ROIi and ROIs.

Algorithms↗

PubMed2001

An individualized approach for the implantation of a humeral prosthesis with the proper retroversion in fractures.

We applied a new methodology in 7 patients with a fracture of the upper humeral head that required hemiarthroplasty, to implant a humeral prosthesis with an individualized posterior version. Our goal was to determine preoperatively the distance from the posterior edge of the bicipital groove where the lateral fin of the humeral prosthesis should sit, in order to reproduce the individual retroversion during surgery. Using three computed tomography scan sections of the upper humerus and image processing software, we estimated the above-mentioned distance in the sound humerus and implanted the prosthesis in each patient accordingly. The differences in retroversion between the left and right humeral heads permit a better approximation to normal applying this methodology than inserting the prosthesis in a standard retroversion.

Humans↗

PubMed2001

Patient dose reduction in CT examinations by optimising scanogram acquisition.

The objective was to determine the optimum settings of the scanogram performed in computed tomography (CT) examinations for scan localisation. Head, abdomen and thorax scanograms were performed on a Rando anthropomorphic phantom using various selectable combinations of tube voltage and tube current values. Thermoluminescence dosemeters were used to obtain entrance skin dose data. Effective dose was estimated using normalised organ dose data provided by the National Radiological Protection Board. One hundred and twelve head, 114 thoracic and 111 abdominal patient scanograms were obtained with lower settings than those recommended by the operator's manual. Scanogram sufficiency was assessed by four observers. Head and thoracic scanograms obtained with 80 kV/50 mA and abdominal scanograms obtained with 80 kV/75 mA were found to be acceptable, even though the operator's manual recommendation was 120 kV/100 mA. Thus, the scanogram effective dose was reduced by 72%, 84% and 88% for head, thorax and abdomen examination respectively. Effective dose from a complete CT examination may be reduced by up to 3.5% without any subsequent image quality degradation of the diagnostically important sectional images.

Abdomen↗

PubMed2001

Film-screen magnification versus electronic magnification and enhancement of digitized contact mammograms in the assessment of subtle microcalcifications.

RATIONALE AND OBJECTIVES: To compare information drawn from magnification mammography with that extracted from electronic magnification, processing, and display of the digitized contact images. METHODS: Contact and magnification images of a mammographic statistical phantom were obtained. The magnification films versus the computer-enhanced, digitized images of the corresponding contact mammograms were separately presented to three observers. Receiver operating characteristic analysis was used to compare lesion detectability. The contact and magnification mammograms of 86 patients with subtle microcalcifications were also studied. The breast imaging reporting and data system (BI-RADS) scheme was used to compare the magnification patient films versus the corresponding digitized contact images. Differences in mammographic assessment were evaluated by using the kappa statistic. The dose to breast tissue from contact and magnification mammography was measured to evaluate dose reduction in instances where magnification mammography was to be avoided. RESULTS: Lesion detectability was found to be similar when either the digitized film image or the magnification hard-copy film was inspected. Interpretation of patient images by inspection of the contact and magnification screen-film mammograms on a view-box was in excellent agreement with that yielded by inspection of the contact image on a view-box and the computer-enhanced, digitized contact image on a display monitor. CONCLUSIONS: Electronic magnification and processing of the digitized contact image may provide valuable information concerning subtle microcalcifications, rendering magnification mammography unnecessary for many patients with such lesions.

Breast Diseases↗

PubMed2001

Image segmentation in treatment planning for prostate cancer using the region growing technique.

The purpose of this study was to evaluate the performance of a region growing technique for segmenting prostate, bladder and rectum in CT images of prostate cancer patients. Prostate, bladder and rectum were segmented in all CT images of 10 patients using the region growing technique and manual tracing. Volumes of the above organs computed with the region growing technique were compared with those from manually traced images on a slice-by-slice basis. Measurement reproducibility of both segmentation techniques was evaluated using the data obtained from four independent observers. The region growing technique was 1.5 times faster than manual tracing. There was no statistical difference between the slice volumes of prostate, bladder and rectum obtained by the two segmentation techniques (p > 0.05, paired Student's t-test). Correlation between slice volumes of all organs of interest provided both by region growing and by manual tracing was very good (prostate r2 = 0.84; bladder r2 = 0.93; rectum r2 = 0.85). An overall reasonable agreement was found between the two segmentation techniques. The intraobserver and interobserver variations for prostate, bladder and rectum volume segmentation were found to be lower with the region growing technique than with manual tracing. The suggested semi-automatic technique allows the possibility of generating accurate and reproducible segmentation of prostate, bladder and rectum from CT data with great saving in labour.

Humans↗

PubMed2000

Imaging ultrasonometry of the calcaneus: dependence on calcaneal area.

The purpose of this study was (1) to investigate the dependence of broadband ultrasound attenuation (BUA) and speed of sound (SOS) measured in a circular region of interest (ROI) having a fixed size on calcaneal area and (2) to examine whether the normalization of ultrasonic variables for the area of the calcaneus provides better differentiation of diseased subjects from healthy individuals. Ultrasound variables were estimated in 169 healthy postmenopausal women (mean age 66.5 years, range 42-87 years) and 39 women with vertebral fractures (mean age 72.9 years, range 51-86 years). A minimum attenuation ROI, 15 mm in diameter, with a commercial imaging ultrasonometer was used. Significant relationships were found between both ultrasonic variables and calcaneal area (r2 = 0.06, P < 0.001 for BUA, r2 = 0.12, P < 0.0001 for SOS). Normalization of ultrasound variables (BUAn and SOSn) was based on the regression equations of the relationships among BUA, SOS, and calcaneal area. In a precision study, nine women were examined five times each to determine the errors arising from both the repositioning of the foot and selection of the calcaneal area. The reproducibility errors of BUA, SOS, BUAn, SOSn, and area were 0.87%, 0.20%, 1.07%, 0.27%, and 3.72%, respectively. Significant differences were found between the areas under the ROC curve for BUAn and BUA (area under the curve = 0.93 for BUAn versus 0.90 for BUA, P = 0.003) as well as for SOSn and SOS (area under the curve = 0.85 for SOSn versus 0.79 for SOS, P = 0.003). Normalization of ultrasound variables for calcaneal area improves the discrimination of clinical studies.

Adult↗

PubMed2000

Estimation of spleen volume using MR imaging and a random marking technique.

The aim of this study was to apply a random marking volumetric technique in MR images for estimation of spleen volume. The MR imaging was performed in phantoms and 16 patients with indications unrelated to splenic disease. Images were transferred to a workstation to perform volumetric measurements using the random marking technique and the conventional technique of manual planimetry. Two observers independently measured splenic volume in order to evaluate reproducibility of both volumetric techniques. Phantom experiments revealed that the accuracy of the random marking technique and manual planimetry was approximately the same. In vivo splenic volume measurements derived from both volumetric techniques were highly correlated (r = 0.99, p < 0.0001). For both observers intraobserver variation was found to be lower with the random marking technique than with manual planimetry. Interobserver coefficient of variation using the manual planimetry was 4.6% and was reduced to 2.9% by adopting the random marking technique. The random marking technique was almost two times faster than the manual planimetry. The combination of the random marking technique with MR imaging might provide accurate, reproducible, quick splenic volume estimations.

Female↗

PubMed2000

Estimation of fetal radiation dose from computed tomography scanning in late pregnancy: depth-dose data from routine examinations.

RATIONALE AND OBJECTIVES: To provide depth-dose data for estimating fetal radiation dose from routine computed tomography (CT) examinations of the trunk. METHODS: Doses were measured during CT examinations of the thorax, upper abdomen, abdomen, and pelvis in two anthropomorphic phantoms simulating pregnant women in the second and third trimesters. Thermoluminescent dose meters were used for dose measurements. RESULTS: In CT examinations of the abdomen, doses of 30.0 to 43.6 mGy and of 29.1 to 42.0 mGy were measured at the measuring points in the phantom simulating pregnancy in the second and third trimesters, respectively. In CT examinations of the upper abdomen, pelvis, and thorax, both phantoms received lower doses of radiation. Knowledge of the normalized weighted dose index of the CT scanner and of the kVp and mAs settings of the protocol used for examination of the pregnant woman is needed to adjust the dose data found in the present study to modified protocols and different CT equipment. CONCLUSIONS: These dosimetric data may be used to guide the management of pregnant patients undergoing CT examinations of the trunk.

Female↗

PubMed1999

A method of estimating fetal dose during brain radiation therapy.

PURPOSE: To develop a simple method of estimating fetal dose during brain radiation therapy. METHODS AND MATERIALS: An anthropomorphic phantom was modified to simulate pregnancy at 12 and 24 weeks of gestation. Fetal dose measurements were carried out using thermoluminescent dosimeters. Brain radiation therapy was performed with two lateral and opposed fields using 6 MV photons. Three sheets of lead, 5.1-cm-thick, were positioned over the phantom's abdomen to reduce fetal exposure. Linear and nonlinear regression analysis was used to investigate the dependence of radiation dose to an unshielded and/or shielded fetus upon field size and distance from field isocenter. RESULTS: Formulas describing the exponential decrease of radiation dose to an unshielded and/or shielded fetus with distance from the field isocenter are presented. All fitted parameters of the above formulas can be easily derived using a set of graphs showing their correlation with field size. CONCLUSION: This study describes a method of estimating fetal dose during brain radiotherapy, accounting for the effects of gestational age, field size and distance from field isocenter. Accurate knowledge of absorbed dose to the fetus before treatment course allows for the selection of the proper irradiation technique in order to achieve the maximum patient benefit with the least risk to the fetus.

Adolescent↗

PubMed1999

Effect of lifetime occupational physical activity on indices of bone mineral status in healthy postmenopausal women.

The purpose of this study was to examine the effect of lifetime physical activity of farmers on skeletal status. Seventy-one healthy, postmenopausal women (mean age 52.3 +/- 5.9 years, range 42-61 years) who worked professionally on farms were compared with 78 matched controls (mean age 51.8 +/- 5.5 years, range 42-61 years). Broadband ultrasound attenuation (BUA) and speed of sound (SOS) at the os calcis were measured using an ultrasound transmission imaging system. Bone mineral density (BMD) of the lumbar spine and femoral neck were measured by dual-energy X-ray absorptiometry (DXA). Differences in BUA, SOS, and BMD between farmers and controls were expressed relative to standard deviation (SD) of the farmers. Farmers had significantly higher density values than controls (difference = 1.3 SD in the spine and 1.5 SD in the femoral neck, P < 0.0001 for both comparisons). Ultrasound values were significantly higher in the farmers compared with the controls in calcaneus (difference = 1.1 SD for BUA and 0.7 SD for SOS, P < 0.0001 for both comparisons). The difference of spine BMD, femoral neck BMD, BUA, and SOS between farmers and controls, as judged by comparison of the slopes of the regression lines, was unchanged with age and years since menopause. These results suggest that lifetime physical activity has a positive effect on bone status of postmenopausal farmers.

Adult↗

PubMed1999

Embryo depth during the first trimester. Data required for embryo dosimetry.

RATIONALE AND OBJECTIVES: To provide data regarding embryo depth during the extremely radiosensitive gestational stages of organogenesis and early fetal period for use in embryo dosimetry. METHODS: Ultrasound examination was performed in 73 pregnant women at gestational age 5 to 13 weeks and in a control group of 75 nonpregnant women. Embryo skull and abdominal depth from the maternal skin surface were determined in the anteroposterior direction. Uterus depth was measured in the control group. Measurements were taken before and after voiding. Gestational age and maternal age, height, and weight were noted. Body mass index (BMI) was estimated for every woman from the formula BMI = W/H2. RESULTS: The mean embryo pre- and postvoid skull depth was 8.3 and 5.7 cm and the mean abdominal depth was 8.4 and 5.8 cm, respectively. The mean pre- and postvoid uterus depth was 9.5 and 4.7 cm. Mean abdominal depth and mean skull depth values were significantly different than mean uterus depth for full as well as for empty bladder. Embryo skull depth and abdominal depth were found to be significantly correlated with maternal BMI. Skull and abdominal dimensions were found to be significantly correlated with gestational age. CONCLUSIONS: During the first trimester, embryo depth ranges from 4 to 10 cm, depending on the individual, the status of the bladder, and the maternal BMI. For an accurate determination of embryo depth, ultrasound measurement should be performed.

Abdomen↗

PubMed1999

Brain radiotherapy during pregnancy: an analysis of conceptus dose using anthropomorphic phantoms.

The aims of this study were: (a) to determine conceptus dose resulting from brain radiotherapy; (b) to investigate the necessity of using shielding devices over patient's abdomen during treatment; and (c) to estimate the components of conceptus dose. Radiation doses received by conceptus were measured using anthropomorphic phantoms simulating pregnancy at 4, 12 and 24 weeks gestation and thermoluminescent dosemeters. All irradiations were performed with two lateral and opposed fields approximating the minimum, medium and maximum field size used during treatment of brain malignancies. For a treatment course delivering 65 Gy to tumour without using shielding equipment, conceptus dose never exceeded 100 mGy. Appropriate positioning of 5.1 cm of lead over the phantom's abdomen provided reduction of conceptus dose from 26% to 71%, depending upon gestational age, field size and distance from the field isocentre. The contribution of scatter arising from within the phantom to the conceptus dose was small compared with that from head leakage and collimator scatter. Our dosimetric results indicate that the construction of special shielding equipment is not a prerequisite for treating brain malignancies during pregnancy. However, based on the concept that exposures in women of childbearing age should be kept as low as reasonably achievable, we suggest that shielding devices should be used whenever possible.

Anthropometry↗

PubMed1999

The position of the axillary nerve in the deltoid muscle. A cadaveric study.

In 134 deltoid preparations taken from 67 fresh cadavers we examined the position of the axillary nerve in relation to the upper border of the muscle. The vertical distances from the upper deltoid border to the nerve in 17 of 67 cadavers was less than 4 cm in both shoulders. The minimal distance, measured from the mid-middle portion of the deltoid to the axillary nerve, was 2 cm. There was a significant negative correlation between the deltoid ratio (width/length) and the vertical distance, measured in all examined sites. The shorter the deltoid length the greater the danger of damaging the nerve in the short distance during surgical splitting of the muscle.

Adolescent↗

PubMed1998

Effect of region of interest location on ultrasound measurements of the calcaneus.

Ultrasound (US) measurements of the calcaneus are usually carried out in a region of interest (ROI) at a fixed site relative to a footplate. Recently, US transmission systems have been developed with imaging capability that enable selection of the position of ROI; the region of measurement is always the area of minimum attenuation in the posterior part of the calcaneus. This study compares measurements of broadband ultrasound attenuation (BUA) and speed of sound (SOS) at the variable ROI of minimum attenuation (ROIv) and at fixed coordinates (ROIf). Ultrasound variables were estimated at ROIv and ROIf in 212 female subjects, including 26 patients with osteoporotic fractures. Among the 186 women without fractures, 63 were classified as having osteoporosis on the basis of their vertebral bone density. Precision of BUA and SOS were better at ROIv than at ROIf. BUA was more highly correlated with bone mineral density (BMD) at the lumbar spine and femoral neck at ROIv than ROIf (r = 0.64 for lumbar spine and 0.68 for femoral neck at ROIv versus 0.50 for lumbar spine and 0.54 for femoral neck at ROIf, P < 0.05 for both comparisons). There were no significant differences between the correlations of SOS with axial BMD at ROIv compared with ROIf. Significant difference was found between the areas under the ROC curve for each ultrasound variable at ROIv and ROIf for both groups of patients, subjects with osteoporosis (area under curve = 0.87 for BUA at ROIv versus 0.82 at ROIf, P < 0.05; area under curve = 0.85 for SOS at ROIv versus 0.81 at ROIf, P < 0. 05), and women with fractures (area under curve = 0.93 for BUA at ROIv versus 0.86 at ROIf, P < 0.05; area under curve = 0.91 for SOS at ROIv versus 0.82 at ROIf, P < 0.05). Ultrasound variables measured at ROIv enable improved reproducibility and significantly better differentiation of diseased subjects from healthy individuals as compared with measurements at ROIf.

Aged↗

PubMed1998

Effect of dual and triple energy window scatter correction methods on image quality in liver scintigraphy.

AIM: To investigate the effect of two scatter correction methods on lesion detectability for both planar and tomographic hepatic imaging. METHODS: All planar and tomographic acquisitions involved simultaneous collection of photons in the main photopeak window (126-154 keV) and three additional windows (92-116, 116-126 and 154-164 keV). Uncorrected and corrected for scatter images were obtained from the same acquisition data. The dual energy window (DEW) and the triple energy window (TEW) scatter compensation methods were used to obtain two sets of corrected images. The DEW method was implemented with main photopeak window 126-154 keV, Compton scatter window 92-126 keV and scatter multiplier k = 0.5. A modified TEW method was also applied with main photopeak window 126-154 keV and scatter subwindows 116-126 keV and 154-164 keV. Phantoms were used to study the effect of scatter correction on contrast and signal-to-noise ratio. The observer's ability to identify lesions was studied on uncorrected and corrected for scatter patient images. RESULTS: In planar imaging, both scatter compensation methods yielded contrast enhancement. However signal to noise ratio (SNR) was degraded to 0.63 and 0.67 when DEW and TEW were applied respectively. In SPECT images, contrast was increased by a factor of 2.4 and 1.7, while SNR was degraded to 0.60 and 0.64 when DEW and TEW methods were used respectively. CONCLUSIONS: Scatter correction using DEW and TEW methods may improve observer's ability to distinguish lesions in planar (p < 0.05 for both methods) and SPECT (p < 0.05 for both methods) liver studies.

Adult↗

PubMed1997

CT of the sacroiliac joints. Dosimetry and optimal settings for a high-resolution technique.

PURPOSE: The aim was to select an optimal technique for low-dose high-resolution CT of the sacroiliac joints (SJ). MATERIAL AND METHODS: Dose measurements were performed on a Rando anthropomorphic phantom using thermoluminescence dosimeters for 4 CT protocols and 2 conventional radiography protocols used for SJ evaluation. Six available reconstruction algorithms were tested on CT protocols using 285-665 mAs and 120 or 130 kVp settings and noncontiguous 1.5-mm-thin sections with 3.5-mm intervals. Settings with optimum performance on phantom tests were also applied in a series of 10 patients with SJ arthropathies. RESULTS: A CT protocol using 120 kVp/175 mA/2.9 s/1.5-mm slice thickness/5-mm table increment implied the lower radiation dose among all examination protocols tested and provided high image quality of the SJ. A reconstruction algorithm yielding images of improved spatial resolution with acceptable noise was selected. CONCLUSION: A high spatial frequency reconstruction algorithm, and 120 kVp and 508 mAs were considered optimal for a low-dose CT examination of the SJ that employed narrow (1.5 mm) slice images with interspacing.

Algorithms↗

PubMed1997

Effectiveness of Tc-99m sestamibi compared to Ga-67 in patients with pulmonary sarcoidosis.

The authors evaluated the suitability of Tc-99m MIBI to be used as an alternative to Ga-67 in pulmonary sarcoidosis imaging. Studies were performed on 21 patients. Eleven patients (group I) had been on corticosteroid treatment before the study, while 10 patients (group II) had received no treatment. Activity of sarcoidosis was assessed from clinical manifestations of the disease, pulmonary function tests, bronchoalveolar lavage, high-resolution computed tomography, and serum biochemistry. Ga-67 imaging results were abnormal in 73% of patients of group I (n = 8) and 90% of patients of group II (n = 9). Tc-99m MIBI imaging results were abnormal in 0% of patients of group I (n = 0) and 40% of patients of group II (n = 4). The lymph nodes were better demonstrated with Ga-67. Abnormal results of Ga-67 imaging were 100% sensitive to clinically active sarcoidosis, but had a relatively low specificity (33%). In contrast, abnormal MIBI imaging had very low sensitivity (11%). The authors conclude that planar Tc-99m MIBI scintigraphic images are not sensitive for the diagnosis of pulmonary sarcoidosis.

Adult↗