Dosimetric accuracy of a deterministic radiation transport based (192)Ir brachytherapy treatment planning system. Part III. Comparison to Monte Carlo simulation in voxelized anatomical computational models

PURPOSE

To compare TG43-based and Acuros deterministic radiation transport-based calculations of the BrachyVision treatment planning system (TPS) with corresponding Monte Carlo (MC) simulation results in heterogeneous patient geometries, in order to validate Acuros and quantify the accuracy improvement it marks relative to TG43.

METHODS

Dosimetric comparisons in the form of isodose lines, percentage dose difference maps, and dose volume histogram results were performed for two voxelized mathematical models resembling an esophageal and a breast brachytherapy patient, as well as an actual breast brachytherapy patient model. The mathematical models were converted to digital imaging and communications in medicine (DICOM) image series for input to the TPS. The MCNP5 v.1.40 general-purpose simulation code input files for each model were prepared using information derived from the corresponding DICOM RT exports from the TPS.

RESULTS

Comparisons of MC and TG43 results in all models showed significant differences, as reported previously in the literature and expected from the inability of the TG43 based algorithm to account for heterogeneities and model specific scatter conditions. A close agreement was observed between MC and Acuros results in all models except for a limited number of points that lay in the penumbra of perfectly shaped structures in the esophageal model, or at distances very close to the catheters in all models.

CONCLUSIONS

Acuros marks a significant dosimetry improvement relative to TG43. The assessment of the clinical significance of this accuracy improvement requires further work. Mathematical patient equivalent models and models prepared from actual patient CT series are useful complementary tools in the methodology outlined in this series of works for the benchmarking of any advanced dose calculation algorithm beyond TG43.

Quantifying the bystander-effect of 2.5G mobile telephones on the speech perception of digital hearing aid users

OBJECTIVE

To quantify the bystander-effect of 2.5G mobile telephones (2.5G-MTs) on the speech perception of digital hearing-aid (dHA) users. Differences in the susceptibility of behind-the-ear (BTE) compared to in-to-the-ear (ITE) dHAs were also assessed.

MATERIALS/METHODS

Prospective-comparative study conducted at a tertiary referral centre (ENT Department) and a HA-fitting laboratory. Key-word recognition scores from open-sentence lists were calculated. Power-analysis determined that a minimum of 60 subjects with SNHL (30 in each group), using either BTE or ITE dHAs, were required for reliable study outcomes. Sixty-four adults were tested with a functioning 2.5G-MT at almost physical contact with their ear; thirty subjects used BTE and 34 ITE dHAs.

MAIN OUTCOME MEASURES

Aided word recognition score differences between studied groups and within each group, while a 2.5G-MT was activated. Cut-off inclusion criterion regarding baseline aided word recognition score was 75%.

RESULTS

Baseline aided word recognition scores for ITE dHAs were better compared to BTE ones (p < 0.01). Following the 2.5G-MT activation, this difference disappeared. No statistically significant difference in word recognition was observed between the examined groups, or within the BTE group, from the bystander-effect of the 2.5G-MT. ITE dHAs proved more susceptible to electromagnetic interference (p < 0.05).

CONCLUSION

The bystander-effect of 2.5G-MTs on the speech perception of dHA users is either minimal, or not significant. The observed compatibility has a positive impact on the lives of millions of people worldwide. The long-standing theory of more interference in BTE compared to ITE HAs is not confirmed by the results of the present study. EBM level of evidence: 2c.

Height, Whole Body Surface Area, Gender, Working Outdoors, and Sunbathing in Previous Summer are Important Determinants of Serum 25-hydroxyvitamin D Levels

To investigate if serum 25-hydroxyvitamin D (25(OH)D) is related to the whole Body Surface Area (BSA), and to several other anthropometric and environmental factors.

Serum 25(OH)D was determined in 489 apparently healthy subjects (346 women and 143 men, mean age 43.9 years) in April and May. From all subjects the following data were available: height, body weight, waist to hip ratio, BSA, BMI, environment of work (indoors vs. outdoors), habit of regularly sunbathing during previous summer(s), fear of sun, dwelling in city or village, and skin color.

Approximately 43% of the participants had serum 25(OH)D levels between 10 and 20 ng/ml, 44% had values between 20.1 and 30 ng/ml, whereas about 5% had values below 10 ng/ml and only 9% had values above 30 ng/ml. There was a significant positive relationship between 25(OH)D, height and BSA, which was more pronounced for BSA in obese subjects even after adjustment for work outdoors and sunbathing during previous summer(s). Outdoor workers and sunbathers had higher 25(OH)D compared to indoor workers and non-sunbathers respectively. Men when compared to women had higher 25(OH)D regardless of BMI and this difference was apparently due to the fact that men were taller, had greater BSA, and worked more often outdoors.

Height, whole BSA, gender, working outdoors and sunbathing in previous summer(s) proved to be significant determinants of serum 25(OH)D. Vitamin D status is higher in taller individuals with greater BSA, and in men when compared to women.

Epigenetically-targeted therapies for the treatment of hematological malignancies

Epigenetic modifications, which are heritable changes in gene expression not involving DNA sequence alterations, are important early events in the multi -step process of tumorigenesis. Among them, DNA methylation and histone acetylation are the most extensively studied. Although they are, by definition, somatically heritable, epigenetic modifications of DNA and histones are also reversible. This characteristic difference from genetic alterations makes them interesting targets for therapeutic intervention. The huge amount of knowledge gathered in the field of epigenetics the last decade, was followed by the development of novel therapies: old drugs finding new identity and new targets and an increasing list of novel compounds for the treatment of malignant diseases. Hematological malignancies offer a broad spectrum of diseases where epigenetic therapies are shown to be active, providing encouraging results. Some of the more recent reports on this field of therapeutic interventions are reviewed below.

Dosimetry using Gafchromic XR-RV2 radiochromic films in interventional radiology

Patient dose measurements of local entrance dose to the skin have been carried out using radiochromic film (Gafchromic XR-RV2) in a sample of interventional procedures. The major aim of the work was to measure patient entrance dose from such examinations using Gafchromic XR-RV2. Forty-five various interventional procedures (including nefrostomies and urinary stenting, biliary stenting and percutaneous transhepatic biliary drainage (PTBD) and aorta stent grafting) were evaluated. Maximum entrance doses were 537 ± 119 mGy in nephrostomies, 943 ± 631 mGy in biliary stenting and PTBD and 2425 ± 569 mGy in aorta stent grafting. Results indicate that all patients undergoing aorta stent grafting received skin dose above 1500 mGy, which means that there is an increasing potential to suffer radiation-induced skin injuries. The film provides dose mapping, the position of the skin area with highest dose and can be used for immediate qualitative and as well as for quantitative assessment of patient skin dose.

Contribution of (99m)Tc-depreotide (Neospect) scintigraphy in lung cancer staging

PURPOSE

The aim of this study was to evaluate the usefulness of scintigraphy with (99m)Tc-depreotide in the staging of lung cancer, especially in cases where CT findings are doubtful.

METHODS

53 patients with suspected lung cancer were investigated with whole body planar acquisition and single photon emission computed tomography (SPECT) of the thorax after i.v. injection of 740 MBq (99m)Tc-depreotide (Neospect). The results were compared with CT and correlated with histological findings.

RESULTS

In 50 of 53 patients the biopsy was positive for bronchogenic carcinoma (31 patients with non small cell lung cancer [NSCLC], 18 with small cell lung cancer (SCLC), and 1 patient with neuroendocrine cancer). In the remaining 3, biopsy revealed no bronchogenic carcinoma (3 patients with inflammation). In 2/31 patients with NSCLC and doubtful CT findings, uptake of (99m)Tc-depreotide was the only non invasive reliable staging method.

CONCLUSION

It seems that scintigraphy with (99m)Tc-depreotide in patients with SCLC does not change the tumor stage, whereas in NSCLC the contribution of Neospect in lung cancer staging may be a helpful tool, especially in cases where CT alone is unable to distinguish between IIIA and IIIB stages (operable from non operable status).

Effective dose variation in pediatric computed tomography: dose reference levels in Greece

Computed tomography provides high-resolution imaging of the human body. However, it contributes mainly to the doses on the population. Additionally, the fact that children are two to three times more sensitive to the x rays compared to the adults results in the increased need of taking action for the reduction of the dose regarding the computed tomography examinations. The first part of this paper presents the results of an investigation on the variation of doses to children while the second part compares those results with the European standards. This project took place in twelve hospitals distributed throughout the country. The weighted computed dose-index and the dose length product were calculated for four different age-categories (namely 0, 1, 5 and 10-year-old) and for the three most often examinations (brain, thorax and abdomen). Effective dose values were estimated using coefficients and patients' data. The measurements showed that only a few hospitals are taking into account the protocols regarding the age of the children. As a result, many patients receive high doses without this being necessary. Thus, reducing dose methods should be adapted in order to improve the optimization of this high dose modality.

Early postexercise thallium-201 reinjection after sublingual nitroglycerin augmentation: effects on detection of myocardial ischemia and/or viability

BACKGROUND

Thallium-201 (201Tl) reinjection after conventional redistribution imaging is a standard procedure, resulting in enhanced 201Tl redistribution which is compatible with viable myocardium. Although this method significantly improves identification of viable myocardium, it increases the investigation time by approximately 1 h. Thus, this technique is suboptimal from the standpoint of patient convenience, since its routine performance may be impractical in a high-volume nuclear medicine laboratory.

HYPOTHESIS

This study was undertaken to evaluate the efficacy of an early 201Tl reinjection and imaging protocol in combination with sublingual nitroglycerin, to detect myocardial ischemia and/or viability, and to reduce the need for conventional (4 h) redistribution imaging.

MATERIALS AND METHODS

In this study, 62 consecutive coronary patients, referred for the detection of possible myocardial ischemia and/or viability, were involved (mean age 55 years, range 41-70). Of those, 50 had previous angina attacks, with 42 having a history of previous myocardial infarction; 10 patients had coronary artery bypass grafting; and the remaining 2 had atypical chest pain. Immediately after the completion of the initial postexer-cise imaging, 0.3 mg sublingual nitroglycerin followed by the reinjection of 1 m Ci of 201Tl were administered, and two further sets of images were acquired 1 h and 4 h later.

RESULTS

In each set of images, a total of 496 segments were analyzed. On postexercise imaging, 305 (61%) segments demonstrated defects of which 198 (65%) showed enhanced thallium uptake, 97 (32%) did not change, and 10 (3%) showed reverse redistribution on 1 h reinjection imaging (IRI). Of the 97 persistent defects, only 17 (6%) showed fill-in of 201Tl on 4 h redistribution imaging (CRI), while 12 (4%) segments showed reverse redistribution. On the other hand, after analyzing the 62 patients of the 1 h IRI, 17 (27%) remained unchanged while in only 1 patient (6%) of 17 the diagnosis changed from myocardial necrosis to ischemia after analysis of the 4 h CRI.

CONCLUSION

These results indicate that early postexercise reinjection of 201Tl in combination with sublingual nitroglycerin followed by 1 h image acquisition may prove useful for a comprehensive and convenient assessment of myocardial ischemia and/or viability.

Dosimetric characterization of CyberKnife radiosurgical photon beams using polymer gels

Dose distributions registered in water equivalent, polymer gel dosimeters were used to measure the output factors and off-axis profiles of the radiosurgical photon beams employed for CyberKnife radiosurgery. Corresponding measurements were also performed using a shielded silicon diode commonly employed for CyberKnife commissioning, the PinPoint ion chamber, and Gafchromic EBT films, for reasons of comparison. Polymer gel results of this work for the output factors of the 5, 7.5, and 10 mm diameter beams are (0.702 +/- 0.029), (0.872 +/- 0.039), and (0.929 +/- 0.041), respectively. Comparison of polymer gel and diode measurements shows that the latter overestimate output factors of the two small beams (5% for the 5 mm beam and 3% for the 7.5 mm beams). This is attributed to the nonwater equivalence of the high atomic number silicon material of the diode detector. On the other hand, the PinPoint chamber is found to underestimate output factors up to 10% for the 5 mm beam due to volume averaging effects. Polymer gel and EBT film output factor results are found in close agreement for all beam sizes, emphasizing the importance of water equivalence and fine detector sensitive volume for small field dosimetry. Relative off-axis profile results are in good agreement for all dosimeters used in this work, with noticeable differences observed only in the PinPoint estimate of the 80%-20% penumbra width, which is relatively overestimated.

Dosimetric evaluation of a new collimator insert system for stereotactic radiotherapy

The prototype of a stereotactic collimator set developed in our department is evaluated for clinical use. This set consists of three cylindrical blocks mounted on a tray which slides in the wedge insert of a Siemens Primus accelerator. Each block has a collimating hole along its long axis to produce radiation fields of circular cross-section at the isocentre plane with diameters of 15 mm, 20 mm and 25 mm. Different geometric and dosimetric quality assurance tests were performed and results are found within the limits set for stereotactic radiotherapy. Dosimetry results measured using Kodak EDR-2 radiographic film and a pinpoint ion chamber also show good agreement with corresponding results calculated by Monte Carlo simulation of the linear accelerator head and the collimators. Measured dosimetry data were used to adapt a conventional PLATO treatment planning system for stereotactic radiotherapy using the prototype collimator set. Treatment planning system calculations and film measurements for treatment of an intracranial lesion in an anthropomorphic head phantom using coplanar 180 degrees arcs are compared and found to agree within 2 mm. This supports the accuracy of dose delivery using the prototype stereotactic collimators. Despite their increased penumbra (2.5-3.5 mm relative to 2-2.5 mm for commercially available collimators) the ease of construction makes the proposed stereotactic collimators an interesting alternative for accomplishing cost effective stereotactic treatments.

A dosimetric comparison of Yb169 and Ir192 for HDR brachytherapy of the breast, accounting for the effect of finite patient dimensions and tissue inhomogeneities

Monte Carlo simulation dosimetry is used to compare 169Yb to 192Ir for breast high dose rate (HDR) brachytherapy applications using multiple catheter implants. Results for bare point sources show that while 169Yb delivers a greater dose rate per unit air kerma strength at the radial distance range of interest to brachytherapy in homogeneous water phantoms, it suffers a greater dose rate deficit in missing scatter conditions relative to 192Ir. As a result of these two opposing factors, in the scatter conditions defined by the presence of the lung and the finite patient dimensions in breast brachytherapy the dose distributions calculated in a patient equivalent mathematical phantom by Monte Carlo simulations for the same implant of either 169Yb or 1921r commercially available sources are found comparable. Dose volume histogram results support that 169Yb could be at least as effective as 192Ir delivering the same dose to the lung and slightly reduced dose to the breast skin. The current treatment planning systems' approach of employing dosimetry data precalculated in a homogeneous water phantom of given shape and dimensions, however, is shown to notably overestimate the delivered dose distribution for 169Yb. Especially at the skin and the lung, the treatment planning system dose overestimation is on the order of 15%-30%. These findings do not undermine the potential of 169Yb HDR sources for breast brachytherapy relative to the most commonly used 192Ir HDR sources. They imply, however, that there could be a need for the amendment of dose calculation algorithms employed in clinical treatment planning of particular brachytherapy applications, especially for intermediate photon energy sources such as 169Yb.

Radiation risk assessment in neonatal radiographic examinations of the chest and abdomen: a clinical and Monte Carlo dosimetry study

Seeking to assess the radiation risk associated with radiological examinations in neonatal intensive care units, thermo-luminescence dosimetry was used for the measurement of entrance surface dose (ESD) in 44 AP chest and 28 AP combined chest-abdominal exposures of a sample of 60 neonates. The mean values of ESD were found to be equal to 44 +/- 16 microGy and 43 +/- 19 microGy, respectively. The MCNP-4C2 code with a mathematical phantom simulating a neonate and appropriate x-ray energy spectra were employed for the simulation of the AP chest and AP combined chest-abdominal exposures. Equivalent organ dose per unit ESD and energy imparted per unit ESD calculations are presented in tabular form. Combined with ESD measurements, these calculations yield an effective dose of 10.2 +/- 3.7 microSv, regardless of sex, and an imparted energy of 18.5 +/- 6.7 microJ for the chest radiograph. The corresponding results for the combined chest-abdominal examination are 14.7 +/- 7.6 microSv (males)/17.2 +/- 7.6 microSv (females) and 29.7 +/- 13.2 microJ. The calculated total risk per radiograph was low, ranging between 1.7 and 2.9 per million neonates, per film, and being slightly higher for females. Results of this study are in good agreement with previous studies, especially in view of the diversity met in the calculation methods.

Comparison of radiation shielding requirements for HDR brachytherapy using Yb169 and Ir192 sources

169Yb has received a renewed focus lately as an alternative to 192Ir sources for high dose rate (HDR) brachytherapy. Following the results of a recent work by our group which proved 169Yb to be a good candidate for HDR prostate brachytherapy, this work seeks to quantify the radiation shielding requirements for 169Yb HDR brachytherapy applications in comparison to the corresponding requirements for the current 192Ir HDR brachytherapy standard. Monte Carlo simulation (MC) is used to obtain 169Yb and 192Ir broad beam transmission data through lead and concrete. Results are fitted to an analytical equation which can be used to readily calculate the barrier thickness required to achieve a given dose rate reduction. Shielding requirements for a HDR brachytherapy treatment room facility are presented as a function of distance, occupancy, dose limit, and facility workload, using analytical calculations for both 169Yb and 192Ir HDR sources. The barrier thickness required for 169Yb is lower than that for 192Ir by a factor of 4-5 for lead and 1.5-2 for concrete. Regarding 169Yb HDR brachytherapy applications, the lead shielding requirements do not exceed 15 mm, even in highly conservative case scenarios. This allows for the construction of a lead door in most cases, thus avoiding the construction of a space consuming, specially designed maze. The effects of source structure, attenuation by the patient, and scatter conditions within an actual treatment room on the above-noted findings are also discussed using corresponding MC simulation results.

Effects of thyroxine withdrawal in biochemical parameters and cardiac function and structure in patients with differentiated thyroid cancer

AIM

Patients with differentiated thyroid carcinoma (DTC) are closely monitored during the first decade after diagnosis. At intervals of 1-2 years withdrawal of suppressive doses of T(4) is recommended in order to check thyroglobulin (Tg) levels under increased TSH. T(4) therapy is usually withdrawn for 5 weeks (during the first 3 weeks patients receive treatment with T(3) instead of T(4), and the last 2 weeks stop all medication). There are a few reported studies looking into the effects of T(4) withdrawal in athyreotic patients in terms of biochemical parameters and ultrasound indices. We studied patients with DTC at two time points: during suppressive T(4) treatment and at the end of the T(4) withdrawal protocol in order to identify acute changes that become apparent after 5 weeks of treatment modification.

METHODS

Hormonal and biochemical parameters were measured as well as ultrasound indices of cardiac function and structure.

RESULTS

Statistically significant increases were found in total cholesterol, low density lipoprotein (LDL) and high density lipoprotein (HDL) cholesterol and triglycerides with T(4) withdrawal. Creatine phosphokinase showed a striking increase with treatment withdrawal. In addition, liver enzymes, total protein and albumin concentrations increased. Creatinine levels increased significantly and sodium decreased on stopping T(4) treatment. The ultrasound indices of cardiac function and structure did not show significant changes.

CONCLUSIONS

Acute hypothyroidism following T(4) withdrawal in DTC patients leads to important biochemical changes without significant alterations in cardiac function and structure. These changes may adversely affect patients, especially older patients or those with other chronic diseases.

Polymer gel dosimetry for the TG-43 dosimetric characterization of a new 125I interstitial brachytherapy seed

In this work, a polymer gel-magnetic resonance (MR) imaging method is employed for the dosimetric characterization of a new 125I low dose rate seed (IsoSeed model I25.S17). Two vials filled with PABIG gel were prepared in-house and one new seed as well as one commercially available 125I seed of similar dose rate and well-known dosimetric parameters (IsoSeed model I25.S06) were positioned in each vial. Both seeds in each vial were MR scanned simultaneously on days 11 and 26 after implantation. The data obtained from the known seed in each vial are used to calibrate the gel dose response which, for the prolonged irradiation duration necessitated by the investigated dose rates, depends on the overall irradiation time. Data for this study are presented according to the AAPM TG-43 dosimetric formalism. Polymer gel results concerning the new seed are compared to corresponding, published dosimetric results obtained, for the purpose of the new seed clinical implementation, by our group using the established methods of Monte Carlo (MC) simulation and thermo-luminescence dosimetry (TLD). Polymer gel dosimetry yields an average dose rate constant value of lambda = (0.921 +/- 0.031) cGy h(-1) U(-1) relative to (MC)lambda = (0.929 +/- 0.014) cGy h(-1) U(-1), (TLD)lambda = (0.951 +/- 0.044) cGy h(-1) U(-1) and the average value of Lambda = (0.940 +/- 0.051) cGy h(-1) U(-1) proposed for the clinical implementation of the new seed. Results for radial dose function, g(L)(r), and anisotropy function, F(r, theta), also agree with corresponding MC calculations within experimental uncertainties which are smaller for the polymer gel method compared to TLD. It is concluded that the proposed polymer gel-magnetic resonance imaging methodology could be used at least as a supplement to the established techniques for the dosimetric characterization of new low energy and low dose rate interstitial brachytherapy seeds.

An evaluation of the TSE MR sequence for time efficient data acquisition in polymer gel dosimetry of applications involving high doses and steep dose gradients

The use of magnetic resonance imaging as a readout method for polymer gel dosimetry commonly involves long imaging sessions, particularly when high spatial resolution is required in all three dimensions, for the investigation of dose distributions with steep dose gradients and stringent dose delivery specifications. In this work, a volume selective turbo spin echo (TSE) pulse sequence is compared to the established Carr-Purcell-Meiboom-Gill (CPMG) multiecho acquisition with regard to providing accurate dosimetric results in significantly reduced imaging times. Polyethylene glycol diacrylate based (PABIG) gels were irradiated and subsequently scanned to obtain R2 relaxation rate measurements, using a CPMG multiecho sequence and a dual echo TSE utilizing an acceleration (turbo) factor of 64. R2 values, plotted against corresponding Monte Carlo dose calculations, provided calibration data of PABIG gels dose response over a wide dose range. A linear R2 versus dose relationship was demonstrated for both sequences with TSE results presenting reduced dose sensitivity. Although TSE data were found to deviate from linearity at lower doses compared to CPMG data, a relatively wide dynamic dose range of response extending up to approximately 100 Gy was observed for both sequences. The TSE and CPMG sequences were evaluated with a brachytherapy irradiation using a high dose rate 192Ir source and a gamma knife stereotactic radiosurgery irradiation with a single 4 mm collimator helmet shot. Dosimetric results obtained with the TSE and CPMG are shown to compare equally well with the expected dose distributions for these irradiations. The 60-fold scan time reduction achieved with TSE implies that this sequence could prove to be a useful tool for the introduction of polymer gel dosimetry in clinical radiation therapy applications involving high doses and steep dose gradients.

Radiation doses to patients from digital subtraction angiography

This investigation determined patient doses during digital subtraction angiography (DSA). Fluoroscopy time, dose-area product (DAP) and entrance surface air kerma (ESAK) were analysed from 263 DSA examinations, classified into seven categories: (1) abdominal aorta, iliac, femoral, popliteal and leg arteries; (2) abdominal aorta and superselective DSA of renal arteries; (3) combination of (1) and (2); (4) superselective DSA of common carotid and vertebral arteries, intracranial branches in face and profile projections; (5) superselective DSA of hepatic, splenic, superior and inferior mesenteric arteries; (6) combination of (1) and (4); and (7) celiac trunk and branches. Median DAP values were 67.7, 92.9, 76.6, 53.6, 105.7, 76.1 and 2.6 Gy cm2, respectively. With the exception of one examination, ESAK values were below 2 Gy: the limit for erythema. Compared with published data, DAP values were within the range reported for (1) and (4), slightly larger for (2) and (5), whereas no references were identified for the remaining three categories.

The effect of various regimens of hormone replacement therapy on mammographic breast density

OBJECTIVES

To evaluate the effect of three distinct hormone replacement therapy regimens on mammography.

METHODS

121 postmenopausal women who had never received or were past users of hormone replacement therapy were studied prospectively. Women with an intact uterus were randomly allocated either to conjugated equine estrogens 0.625 mg plus medroxyprogesterone acetate 5 mg (CEE/MPA, n=34) or to 17beta-estradiol 2 mg plus norethisterone acetate 1 mg (E(2)/NETA, n=35). Hysterectomized women received CEE 0.625 mg (CEE, n=25). Women who either declined or did not qualify for treatment served as controls (n=27). Treatment was continuous and the study period lasted 12 months. Main outcome measures were the changes according to Wolfe classification between baseline and 12-month-mammograms.

RESULTS

No increase in breast density was identified in any of the women in the control group. Two women (8%) in the CEE group showed an increase in breast density. Four women (11.8%) in the CEE/MPA and 11 women (31.4%) in the E(2)/NETA group revealed an increase in breast density. No woman in the therapy groups showed an involution of fibroglandular tissue while seven women (25.9%) in the control group exhibited involution of breast parenchyma.

CONCLUSIONS

Our study suggests that hormone replacement therapy may suspend breast involution but does not increase breast density in the majority of patients. In the minority of patients who show a density increase, the magnitude of this increase varies according to the regimen employed.

Thermally induced irreversible conformational changes in collagen probed by optical second harmonic generation and laser-induced fluorescence

Irreversible thermal conformational changes induced to collagen have been studied by optical methods. More specifically, second harmonic generation (SHG) from incident nanosecond Ng:YAG 1064 nm radiation and laser-induced fluorescence by 337 nm, pulsed nanosecond nitrogen laser excitation, at 405, 410 and 415 nm emission wavelengths were registered at eight temperatures (40 degrees, 50 degrees, 55 degrees, 60 degrees, 65 degrees, 70 degrees, 75 degrees and 80 degrees C) and normalised with respect to the corresponding values at the ambient temperature of 30 degrees C. The heating protocol used in this work, was selected to monitor only permanent changes reflecting in the optical properties of the samples under investigation. In this context, the SHG, directly related to the collagen fibril population in triple helix conformation, indicated on irreversible phase transition around 64 degrees C. On the other hand fluorescence related to the destruction of cross-linked chromophores in collagen, some of which are related to the triple helix tertiary structure, also indicated a permanent phase transition around 63 degrees C. These results are in agreement with previous results from studies with differential scanning calorimetry. However SHG and fluorescence, being non-invasive optical methods are expected to have a significant impact in the fields of laser ablative surgery and laser tissue welding.

Body composition changes in protease inhibitor-naive HIV-infected patients treated with two nucleoside reverse transcriptase inhibitors

OBJECTIVES

In the era of highly active antiretroviral treatment (HAART), there are insufficient data regarding lipodystrophy syndromes in HIV-1-infected patients treated with regimens that do not include protease inhibitors (PIs). We studied changes in body composition in HIV-1-infected patients before and 2 years after starting a non-PI-containing antiretroviral treatment regimen.

METHODS

We studied retrospectively the whole body dual energy X-ray absorptiometry (DEXA) scans of 23 PI-naive HIV-1-infected patients (17 males, six females), aged 37.4 +/- 9.3 years with mean CD4 count 401 +/- 130 cells/microL. Thirteen patients were on zidovudine (ZDV) + lamivudine (3TC) and 10 on ZDV + didanosine (ddI). Subjects were evaluated before the beginning of antiretroviral treatment and approximately 24 months later. For each patient body weight, CD4 T-cell counts, bone mineral content (BMC), bone mineral density (BMD) and whole body as well as regional fat and lean body mass were evaluated.

RESULTS

A significant decrease in BMC was observed, although the T scores remained within the normal limits. Our patients also exhibited a significant decrease in body weight due almost exclusively to fat loss, while lean mass was minimally affected. Fat loss was statistically significant in the arms and legs, but not in the trunk. The above changes were most prominent in the ZDV + 3TC treatment group; in this group of patients, fat loss was also evident in the trunk. Patients on ZDV + ddI, on the other hand, only showed a significant increase in their legs' lean mass; they preserved their total fat mass and exhibited no other significant changes between the two assessments.

CONCLUSIONS

Dual NRTI therapy contributes to fat loss and reduction of bone mineral content in otherwise healthy, clinically stable, PI-naive HIV-infected adults. Compared with patients on ZDV + ddI, patients on ZDV + 3TC had a more prominent fat loss in all body regions.

Cytotoxic therapy of gastroenteropancreatic (GEP) tumors

Neuroendocrine gut and pancreatic tumors have provided a diagnostic and therapeutic challenge over the years. Although they are considered slow growing, when disseminated their prognosis is poor. Currently, the various therapeutic options available for patients with inoperable GEP tumors aim either to control symptoms engendered by bioactive mediators, released by tumor cells, or to achieve control of tumor proliferation. The interpretation of the efficacy of the cytotoxic therapy on GEP tumors is hampered by the small size of the studies performed and the inconsistence in tumor type, origin and degree of differentiation. Nevertheless, it is widely recognized that chemotherapy has some role in the management of Neuroendocrine Pancreatic Tumors (NPTs); while in Metastatic Carcinoid Tumors (MCTs) it has only a minimal effect.

Visual observation of infrared laser speckle patterns at half their fundamental wavelength

In the course of work aimed to examine second harmonic generation in biological macromolecules, it was discovered that 1064 nm pulsed nanosecond infrared laser radiation, after scattering on the optically rough sample surface, was perceived as double the fundamental frequency green speckle pattern by the unaided eye. The threshold of this arresting phenomenon was found to be around 60 mJ/cm2 on hyaluronic acid potassium salt in dark ambient conditions. This effect is of a second order non-linear nature. After experiments with nearsighted, farsighted and normal vision observers in combination with second harmonic generation experiments on various lamb eye tissues, the effect was mainly attributed to second harmonic generation in the cornea arising from phase interference of the incident infrared radiation. The current work could possibly have implications in the fields of speckle interferometry and biomedicine.

Dimensions of the lumbar spinal canal: variations and correlations with somatometric parameters using CT

The aim of this study was to investigate the correlation of vertebral dimensions with somatometric parameters in patients without clinical symptoms and radiological signs of central lumbar spinal stenosis. One hundred patients presenting with low back pain or sciatica were studied with CT. In each of the L3, L4 and L5 vertebra three slices were taken with the following measurements: 1. Slice through the intervertebral disc: (a) spinal canal area; (b) interarticular diameter; (c) interligamentous diameter. 2. Slice below the vertebral arcus: (a) dural sac area; (b) vertebral body area. 3. Pediculolaminar level: (a) anteroposterior diameter and interpedicular diameter of the spinal canal; (b) spinal canal area; (c) width of the lateral recesses. The Jones-Thomson index was also estimated. The results of the present study showed that there is a statistically significant correlation of height, weight and age with various vertebral indices. The conventional, widely accepted, anteroposterior diameter of 11.5 mm of the lumbar spinal canal is independent of somatometric parameters, and it is the only constant measurement for the estimation of lumbar spinal stenosis with a single value. The present study suggests that there are variations of the dimensions of the lumbar spinal canal and correlations with height, weight and age of the patient.

Body composition assessment by dual-energy x-ray absorptiometry: comparison of prone and supine measurements

The aim of the study was to assess whether changes in the interposition of body compartments affect the results of body composition measurements by dual-energy x-ray absorptiometry (DEXA) in the fan-beam mode. Thirty healthy subjects underwent two sequential measurements: the first was performed in the supine position as described by the manufacturer, and the second in the prone position. Estimates of body composition were compared between the two measurements. Mean body weight did not differ between measurements ([mean+/-SD] supine vprone, 68.561+/-12.461 v 68.589+/-12.469 kg). Mean bone mineral content (BMC) was lower in the prone position versus the supine position. When the head was excluded, this difference reached statistical significance (supine v prone, 1,738+/-361 v 1,688+/-360 g, P=.0001). The mean fat tissue mass (FTM) was lower and lean tissue mass (LTM) higher in the prone measurements. When the head was excluded, the mean FTM difference between the two measurements became greater (FTM supine v prone, 25.129+/-10.445 v 24.030+/-10.388 kg, P=.0001; LTM supine v prone, 37.309+/-9.357 v 38.246+/-9.150 kg, P=.0001). It is concluded that the positioning of the patient on the examination table affects DEXA body composition measurements by the fan-beam mode. This could imply a lack of accuracy of the method, which may be due to subtle changes in regional tissue depth and fat distribution caused by patient repositioning.

Thallium-201 for detection of myocardial viability: comparison of early postexercise reinjection and imaging with 4 and 18-24 hours redistribution imaging

To evaluate the efficacy of an early 201Tl reinjection and imaging protocol for reducing the need for conventional 4-hour or optimal 24-hour redistribution imaging (RI) and detecting of myocardial viability, we compared the results of early postexercise Tl reinjection and imaging with those of 4- and 24-hour RI in 74 consecutive patients aged 55 +/- 9 years (mean +/- SD) who were assessed for myocardial ischemia. One millicurie of Tl was injected promptly after completion of the initial postexercise imaging (PEX) and three additional sets of images were acquired 1, 4 and 18-24 h later. A total of 2,368 segments were evaluated. On PEX, 390 (17%) segments showed defects, of which 287 (74%) showed enhanced Tl uptake at 1-hour RI; 89 (23%) did not change and 14 (4%) showed reverse redistribution. Of the 103 persistent defects, only 27 (7%) showed further fill-in of Tl; 62 (16%) segments showed reverse redistribution at 4-hour RI while at 18- to 24-hour RI 17 (4%) and 47 (12%) segments showed further fill-in of Tl and reverse redistribution, respectively. Finally, after analysis of 4- and 18- to 24-hour RI, the diagnosis changed from myocardial necrosis to ischemia in only 2 (3%) patients. In conclusion, these results suggest that by eliminating the need for an additional delayed set of images for detection of myocardial viability, this protocol reduces the total investigation procedure, is more convenient for the patient, increases patient turnover and expedites the decision-making process.

Coronary artery disease: changes of blood lymphocyte subsets induced by physical exercise

To examine the changes in the absolute numbers of blood lymphocyte subsets in patients with coronary artery disease, we studied 26 patients with documented coronary artery disease (group I) and 15 other subjects (group II) with atypical complaints and negative exercise test who served as controls. Blood lymphocyte subsets were determined at rest, immediately and 24 h after a bicycle exercise test. In both groups the absolute number of leukocytes/mm3 and lymphocytes/mm3 was significantly greater immediately after exercise than at rest and returned to baseline values by 24 h post-exercise. The absolute number of B-lymphocytes and CD8+ T-lymphocytes did not change significantly in both groups, while CD3+ and CD4+ T-lymphocytes as well as CD25+ activated T-lymphocytes declined insignificantly immediately after exercise but increased significantly 24 h after exercise in both groups, with a higher increase (P<0.01) in all three variables under study (CD3+, CD4+ and CD25+ T-lymphocytes) in group I in comparison to group II (P<0.05). Our findings showed that changes in lymphocyte subsets induced by physical exercise differ between patients with and without documented coronary artery disease, suggesting that an alteration in immune function may account for these differences.

Body composition changes in chronic hemodialysis patients before and after hemodialysis as assessed by dual-energy x-ray absorptiometry

The aim of this study was to investigate the effect of hemodialysis on body composition assessment by dual-energy x-ray absorptiometry (DEXA). Seventeen patients with chronic renal failure who were on a regular hemodialysis schedule were studied. Body weight and body composition were assessed immediately before and approximately 1 hour after a typical hemodialysis session. Body weight was assessed by means of an electronic balance. Body composition measurements were made by DEXA. Whole-body and subtotal (head and neck excluded) analysis assessed the following parameters: body weight, bone mineral density (BMD), bone mineral content (BMC), and fat (FTM) and lean (LTM) tissue mass. BMC, FTM, and LTM were estimated separately for the trunk, arms, and legs. The mean body weight reduction after hemodialysis was 2.8 +/- 1.1 kg (mean +/- SD). Concerning whole-body analysis, no change was observed in mean BMC and FTM after hemodialysis. On the contrary, a significant reduction was observed in mean body weight as assessed by DEXA (before hemodialysis, 65.0 +/- 11.4 kg; after, 62.2 +/- 10.9 kg, P = .0003), as well as in mean LTM (before hemodialysis, 42.7 +/- 9.4 kg; after, 39.7 +/- 9.0 kg, P = .0003). Similar results were obtained from subtotal and regional analysis. Body weight changes as measured by the electronic balance exhibited a strong positive correlation with the changes in both body weight and LTM as assessed by DEXA (r = .989, standard error of the estimate [SEE] = 0.167 kg and r = .941, SEE = 0.382 kg, respectively, P < .0001). It is concluded that gravimetric changes induced by hemodialysis are highly correlated with LTM changes and are not associated with changes in BMC or FTM estimated by DEXA.

Estimation of body composition in competitive swimmers by means of three different techniques

Up to now controversial reports have been published in regard to the beneficial effects of swimming, a non-weight-bearing activity, on bone mass (BM). Therefore, the aim of this study was to investigate the effects of competitive swimming practice on the bone mineral density (BMD) and bone mineral content (BMC) as well as on the different factors of body composition. For this purpose, competitive swimmers (16 males and 16 females) were selected as subjects in order to investigate the influence of swimming on the three main factors of body composition (BMC, lean body mass [LBM] and body fat [BF]) of the human body. The latter were estimated using three different approaches: the skinfold, the dual energy x-ray absorptiometry (DEXA) and the whole body potassium (K-40) methods. Since BM and LBM are also related, the possible correlations between shoulder strength (extensions and flexion movements) and performance with BMD, BMC, LBM and BF were also investigated. Our results showed that BMD was not affected by swimming exercise since z (%) values were similar between swimmers and their respective age-matched controls. Swimmers also showed lower BF and increased LBM in the region of upper extremities (arms and trunk) as compared to their lower extremities (legs), a finding which is typical for the sport they are trained for. Also, comparison between sexes showed that males had a more central distribution of fat when compared to females, in which BF was built up in the region of legs. Furthermore, shoulder strength and performance were significantly related (p < 0.05) to age, BMC, and LBM while performance was also significantly related (p < 0.05) to all the other BM indices. So, mineralization of the bone is important for shoulder muscular strength which is subsequently related to performance. We used the DEXA because it enabled the direct estimation of the three factors of body composition (BM, BF and LBM).

Energy intake and monounsaturated fat in relation to bone mineral density among women and men in Greece

BACKGROUND

Several variables have been established as risk factors for osteoporosis: it is more common among women and the gender difference increases with age and with years since menopause. Estrogens, androgens, physical activity, and body mass index have been previously shown to be positively associated with bone mineral density and inversely with risk for fractures.

METHODS

To assess the effect on bone mineral content of energy-generating nutrients, healthy men (n = 36) and women (n = 118) ages 25-69 years were interviewed among visitors and staff of the University of Athens Department of Medical Physics. Bone mineral density (BMD) was measured by single photon absorptiometry.

RESULTS

Demographic and lifestyle variables were not significantly related to BMD in this study, although the patterns were consistent with those previously reported by other investigators. Total energy intake, which also reflects energy expenditure through physical activity, was positively associated with BMD among both men (P = 0.003) and women (P = 0.04). After adjustment for nonnutritional variables and energy intake, monounsaturated fat, which in the Greek population is mostly derived from olive oil, was associated with BMD. The association was positive among both men (P = 0.01) and women (P = 0.03). There was evidence for an inverse association between carbohydrate intake and BMD, but the association was significant only with respect to mono- and disaccharides.

CONCLUSIONS

In this population, consumption of monounsaturated fat and physical activity were predictive of bone mineral density, but larger studies are needed.

Sex hormones in postmenopausal women with breast cancer on tamoxifen

In 42 postmenopausal women with breast cancer aged 48-85 (mean age 62.4) years, the blood sex hormone levels were measured before and after 6 months of tamoxifen administration (20 mg daily). Follicle-stimulating hormone and luteinizing hormone levels decreased after tamoxifen administration (p < 0.001), but remained in the postmenopausal range, oestradiol levels increased (p < 0.05), sex hormone binding globulin levels increased (p < 0.001), testosterone levels remained stable (p > 0.1), free testosterone levels decreased (p < 0.001), delta4-androstenedione, 17-hydroxyprogesterone, and dehydroepiandrosterone sulfate levels remained unchanged (p > 0.1), and basal prolactin levels and their response to thyrotrophin-releasing hormone injection decreased significantly (p < 0.001) after tamoxifen therapy. It is concluded that tamoxifen has many and diverse effects on sex hormone levels, and its adverse effects do not affect the biological status of the patient, except perhaps for oestradiol, that increases in some cases, whose possible effect must be studied.

Captopril adjuvant therapy to beta-blockers and nitrates improves post-myocardial infarction left ventricular performance

A growing body of data support the beneficial effects of angiotensin-converting enzyme inhibitors in the prevention of cardiac enlargement and improvement of left ventricular function in patients with acute myocardial infarction. However, very little information exists about the direct effect of increased afterload on cardiac performance in these patients and the possible favourable effects of angiotensin-converting enzyme inhibitors as adjunctive treatment to thrombolysis, beta-blockers and nitrates. We have, therefore, studied the effects of captopril as adjuvant therapy to thrombolysis, beta-blockers and nitrates (standard therapy) on left ventricular performance in 77 consecutive patients with uncomplicated Q-wave acute myocardial infarction, by the measurement of the pre-ejection period/left ventricular ejection time ratio before and after (0.25-0.50 mg) phenylephrine administration on the 4th and 30th post-infarction days. Patients were randomized on day 4 either to continue standard therapy alone (group 1, 35 patients) or to receive oral captopril therapy (12.5 mg t.i.d.) in addition to standard therapy (group 2, 42 patients) in a double-blind parallel study. Among the patients of group 1 there was a significant deterioration of left ventricular function after phenylephrine administration. This was shown by an increase of pre-ejection period/left ventricular ejection time ratio only in the subset of patients with ejection fraction < 40%, as measured by contrast ventriculography, on both the 4th and 30th post-infarction days changing from 0.435 +/- 0.070 to 0.528 +/- 0.101, P < 0.01 and from 0.404 +/- 0.098 to 0.515 +/- 0.092, P < 0.02, respectively. In contrast there were no significant changes in patients with ejection fraction > or = 40%. Among patients of group 2, phenylephrine administration induced a significant increase, only on the 4th day, in pre-ejection period/left ventricular ejection time ratio only in the subset of patients with ejection fraction < 40% changing from 0.410 +/- 0.107 to 0.535 +/- 0.102, P < 0.01. In the remaining patients with ejection fraction > or = 40% there were no significant changes on either the 4th or 30th post-infarction days. Furthermore, a significant improvement was observed after phenylephrine administration in the pre-ejection period/left ventricular ejection time ratio between the 4th and 30th post-infarction days, which changed from 0.535 +/- 0.102 on day 4 to 0.368 +/- 0.052 on day 30 (P < 0.004). Also, a four-way ANOVA detected a significant reduction of heart rate in patients with ejection fraction < 40% from day 4 to day 30. The results indicate that: (1) the response of pre-ejection period/left ventricular ejection time ratio after increasing afterload may be a useful non-invasive method for the detection of left ventricular dysfunction in myocardial infarction patients; and (2) captopril adjuvant therapy as compared to thrombolysis, beta-blockers and nitrates alone, after phenylephrine administration, improves the left ventricular performance response in asymptomatic Q-wave post-infarction patients and beneficially affects heart rate. This effect is most pronounced in patients with ejection fraction < 40% whereas those with ejection fraction > or = 40% do not obtain clear benefit.

Paratesticular tumours in a patient with Nelson's syndrome

An extremely rare case of a 39-year-old man with Nelson's syndrome and paratesticular tumours is presented. The patient had undergone bilateral adrenalectomy at the age 23 years for Cushing's syndrome. Later he developed skin and mucosal hyperpigmentation. Nelson's syndrome was diagnosed, and he underwent transfrontal hypophysectomy. At age 29, the presence of paratesticular tumours was noted which were excised together with the left testis. The preoperative levels of testosterone, produced by the paratesticular tumours, were extremely high; they fell after surgery.