Visible blue light inhibits infection and replication of SARS-CoV-2 at doses that are well-tolerated by human respiratory tissue

The delivery of safe, visible wavelengths of light can be an effective, pathogen-agnostic, countermeasure that would expand the current portfolio of SARS-CoV-2 intervention strategies beyond the conventional approaches of vaccine, antibody, and antiviral therapeutics. Employing custom biological light units, that incorporate optically engineered light-emitting diode (LED) arrays, we harnessed monochromatic wavelengths of light for uniform delivery across biological surfaces. We demonstrated that primary 3D human tracheal/bronchial-derived epithelial tissues tolerated high doses of a narrow spectral band of visible light centered at a peak wavelength of 425 nm. We extended these studies to Vero E6 cells to understand how light may influence the viability of a mammalian cell line conventionally used for assaying SARS-CoV-2. The exposure of single-cell monolayers of Vero E6 cells to similar doses of 425 nm blue light resulted in viabilities that were dependent on dose and cell density. Doses of 425 nm blue light that are well-tolerated by Vero E6 cells also inhibited infection and replication of cell-associated SARS-CoV-2 by > 99% 24 h post-infection after a single five-minute light exposure. Moreover, the 425 nm blue light inactivated cell-free betacoronaviruses including SARS-CoV-1, MERS-CoV, and SARS-CoV-2 up to 99.99% in a dose-dependent manner. Importantly, clinically applicable doses of 425 nm blue light dramatically inhibited SARS-CoV-2 infection and replication in primary human 3D tracheal/bronchial tissue. Safe doses of visible light should be considered part of the strategic portfolio for the development of SARS-CoV-2 therapeutic countermeasures to mitigate coronavirus disease 2019 (COVID-19).

Light-Emitting Diode treatment ameliorates allergic lung inflammation in experimental model of asthma induced by ovalbumin

Since asthma is a multifactorial disease where treatment sometimes is not effective, new therapies that improve the respiratory discomfort of patients are of great importance. Phototherapy as Light-emitting diode (LED) has emerged as a treatment that presents good results for diseases that are characterized by inflammation. Thus, our objective was to investigate the effects of LED on lung inflammation, by an evaluation of lung cell infiltration, mucus secretion, oedema, and the production of cytokines. Male Balb/c mice were or not sensitized and challenged with ovalbumin (OVA) and treated or not with LED therapy (1 h and 4 h after each OVA challenge). Twenty-four hours after the last OVA challenge, analyzes were performed. Our results showed that LED treatment in asthmatic mice reduced the lung cell infiltration, the mucus production, the oedema, and the tracheal's contractile response. It also increased the IL-10 and the IFN-gamma levels. The effects of LED treatment on lung inflammation may be modulated by IL-10, IFN-gamma, and by mast cells. This study may provide important information about the effects of LED, and in addition, it may open the possibility of a new approach for the treatment of asthma.

Intermediate Megavoltage Photon Beams for Improved Lung Cancer Treatments

The goal of this study is to evaluate the effects of intermediate megavoltage (3-MV) photon beams on SBRT lung cancer treatments. To start with, a 3-MV virtual beam was commissioned on a commercial treatment planning system based on Monte Carlo simulations. Three optimized plans (6-MV, 3-MV and dual energy of 3- and 6-MV) were generated for 31 lung cancer patients with identical beam configuration and optimization constraints for each patient. Dosimetric metrics were evaluated and compared among the three plans. Overall, planned dose conformity was comparable among three plans for all 31 patients. For 21 thin patients with average short effective path length (< 10 cm), the 3-MV plans showed better target coverage and homogeneity with dose spillage index R_50% = 4.68±0.83 and homogeneity index = 1.26±0.06, as compared to 4.95±1.01 and 1.31±0.08 in the 6-MV plans (p < 0.001). Correspondingly, the average/maximum reductions of lung volumes receiving 20 Gy (V_20Gy), 5 Gy (V_5Gy), and mean lung dose (MLD) were 7%/20%, 9%/30% and 5%/10%, respectively in the 3-MV plans (p < 0.05). The doses to 5% volumes of the cord, esophagus, trachea and heart were reduced by 9.0%, 10.6%, 11.4% and 7.4%, respectively (p < 0.05). For 10 thick patients, dual energy plans can bring dosimetric benefits with comparable target coverage, integral dose and reduced dose to the critical structures, as compared to the 6-MV plans. In conclusion, our study indicated that 3-MV photon beams have potential dosimetric benefits in treating lung tumors in terms of improved tumor coverage and reduced doses to the adjacent critical structures, in comparison to 6-MV photon beams. Intermediate megavoltage photon beams (< 6-MV) may be considered and added into current treatment approaches to reduce the adjacent normal tissue doses while maintaining sufficient tumor dose coverage in lung cancer radiotherapy.

[Radiation injury of interstitial implantation 125I seeds on normal trachea tissue of rabbits]

OBJECTIVE

To study the radition injury of tracheal mucous membrane tissue after interstitial implanted radioactive 125I in normal rabbit,improve the safety of clinical application.

METHOD

Sixty New Zealand rabbits, weighing 2.15-2.30 kg, were randomly divided into 1 w, 1 m, 2 m, 4 m and the control group, the control group was further divided into four subgroups. The 0.8mCi 125I seeds were implanted into the tissue by the first tracheal ring in the treatment groups and nonradioactive seeds were implanted in the control group. Taking the tracheal mucous membrane tissue for pathological examination by HE staining to observe the mucosal injury and VEGF, Pan-Cadherin immunohistochemical staining to observe the expression in differernt time.

RESULT

Immunohistochemical staining: VEGF and Pan-Cadherin have statistically significant differences in the expression on different time, the expression is dynamic.

CONCLUSION

The expression of VEGF and Pan-Cadherin reflect the radioactive 125I seed has little influence on normal trachea tissue and the damage can be repaired by the regeneration of the basal cell.

[Morphologic changes in mice trachea, bronchi and lungs after prolonged combined radiation and inhaled chemical exposure]

Investigations of morphology and morphometry of the breathing organs (trachea, bronchi and lungs) and immunogenesis of mice subject to a combined sequential exposure to fractionated external γ-irradiation by the total dose of 350 cGy and a mix of acetone, ethanol and acetaldehyde in MPCs for piloted spacecrafts simulating the estimated levels in crewed exploration missions were conducted. Morphologic changes in the breathing organs of animals after space missions point to immunogenesis activation and appearance of a "structural trace" as a chronic inflammation with the growth of fibrous connective tissue in tracheal, bronchial and lung walls, increase in volume fractions of glands and vessels and reduction in loose fibrous connective tissue. Formation of the fibrous connective tissue was particularly noticeable in respiratory parts of the breathing organs suggesting a high risk of long-term adverse effects.

Prediction of lung cancer risk for radon exposures based on cellular alpha particle hits

To explore the role of the multiplicity of cellular hits by radon progeny alpha particles for lung cancer incidence, the number of single and multiple alpha particle hits were computed for basal and secretory cells in the bronchial epithelium of human airway bifurcations. Hot spots of alpha particle hits were observed at the branching points of bronchial airway bifurcations. The effect of single and multiple alpha particle intersections of bronchial cells during a given exposure period, selected from a Poisson distribution, on lung cancer risk were simulated by a transformation frequency--tissue response model, based on experimentally observed cellular transformation and survival functions. Calculations of lung cancer risk at low radon exposure levels suggest that single hits produce a linear-dose response relationship, while the superposition of single and increasing multiple hits at higher exposure levels may also be approximated by a quasi-linear dose-effect curve. The simulations predict a carcinogenic enhancement effect for radon progeny accumulations at bifurcation branching sites, which may increase current risk estimates.

Probability of bystander effect induced by alpha-particles emitted by radon progeny using the analytical model of tracheobronchial tree

Radiation-induced biological bystander effects have become a phenomenon associated with the interaction of radiation with cells. There is a need to include the influence of biological effects in the dosimetry of the human lung. With this aim, the purpose of this work is to calculate the probability of bystander effect induced by alpha-particle radiation on sensitive cells of the human lung. Probability was calculated by applying the analytical model cylinder bifurcation, which was created to simulate the geometry of the human lung with the geometric distribution of cell nuclei in the airway wall of the tracheobronchial tree. This analytical model of the human tracheobronchial tree represents the extension of the ICRP 66 model, and follows it as much as possible. Reported probabilities are calculated for various targets and alpha-particle energies. Probability of bystander effect has been calculated for alpha particles with 6 and 7.69 MeV energies, which are emitted in the (222)Rn chain. The application of these results may enhance current dose risk estimation approaches in the sense of the inclusion of the influence of the biological effects.

Screening of differential expressive genes in murine cells following radon exposure

This study was designed to construct and identify the subtracted cDNA library in peripheral blood cells of BALB/c mice and tracheal-bronchial epithelial cells of Wistar rats following exposure to radon inhalation. Two groups of the animals were exposed in a radon chamber at an accumulative dose of 100 WLM, while control animals were housed in a room at a background dose of 1 WLM. To construct a subtracted cDNA library enriched with differentially expressed genes, the SMART technique and suppression subtractive hybridization (SSH) assay were performed. The obtained forward and reverse cDNA fragments were directly inserted into a pMD-18 vector and transformed into Escherichia coli JM109. In total, 593 white bacterial clones were selected from both forward- and reverse-subtracted libraries. Among them, 81 clones were chosen for their differential expressions based on reverse Northern blot. Portions of these cDNA clones were also verified by a quantitative real-time polymerase chain reaction (PCR). The screening resulted in 14 upregulative and 8 downregulative known function/annotation genes, which were revealed to be functionally related to cell proliferation, cell oxidative and DNA damage, apoptosis, and tumor promotion. Access numbers were obtained from the GenBank for 11 unknown expressed sequence tags (EST). Analysis of biological roles of these cDNA fragments may provide further insight into mechanisms underlying adverse molecular events induced by high-dose radon exposure.

Low level laser therapy (LLLT) decreases pulmonary microvascular leakage, neutrophil influx and IL-1beta levels in airway and lung from rat subjected to LPS-induced inflammation

BACKGROUND AND OBJECTIVE

Low level laser therapy (LLLT) is a known anti-inflammatory therapy. Herein we studied the effect of LLLT on lung permeability and the IL-1beta level in LPS-induced pulmonary inflammation. STUDY DESIGN/METHODOLOGY: Rats were divided into 12 groups (n = 7 for each group). Lung permeability was measured by quantifying extravasated albumin concentration in lung homogenate, inflammatory cells influx was determined by myeloperoxidase activity, IL-1beta in BAL was determined by ELISA and IL-1beta mRNA expression in trachea was evaluated by RT-PCR. The rats were irradiated on the skin over the upper bronchus at the site of tracheotomy after LPS.

RESULTS

LLLT attenuated lung permeability. In addition, there was reduced neutrophil influx, myeloperoxidase activity and both IL-1beta in BAL and IL-1beta mRNA expression in trachea obtained from animals subjected to LPS-induced inflammation.

CONCLUSION

LLLT reduced the lung permeability by a mechanism in which the IL-1beta seems to have an important role.

[Dosimetric analysis of radiotherapy with middle shielding blocks of different widths at the lower cervical supraclavicular field for stage N2-3 nasopharyngeal carcinoma]

BACKGROUND & OBJECTIVE

Anterior tangential field irradiation with middle shielding block at the lower cervical and supraclavicular region is needed in the conventional radiotherapy for stage N2-3 nasopharyngeal carcinoma (NPC), but there are still some disagreements on block width. This study was to explore a reasonable block width by dosimetric analysis of anterior tangential field irradiation with middle shielding blocks of different widths designed by the 3-dimensional treatment planning system (3D-TPS) at the lower cervical supraclavicular region for stage N2-3 NPC.

METHODS

Ten untreated patients with stage N2-3 NPC received 3D-TPS-designed irradiation plan. For every patient, a gradual shrinking field technique was adopted. Single anterior tangential fields were set at the lower cervical and supraclavicular region and irradiated with middle shielding blocks of different widths: 0 cm (Plan A), 2.1 cm (Plan B), 2.5 cm (Plan C), and 3 cm (Plan D) for the first 40 Gy, then 3 cm for residual dose for all 4 plans. The prescribed doses were the same for 4 plans for every patient. The irradiated volumes and doses of target volumes and organs at risk among the 4 plans were compared.

RESULTS

The high dose coverage (V95 and V90) of plan target volume (PTV) for the subclinical lesion region at the lower cervical supraclavicular region (PTV50a) was significantly higher in Plan A than in Plans B, C, and D (82.44% vs. 78.21%, 77.10% and 73.80% for V95, 87.89% vs. 84.03%, 82.68% and 77.50% for V90, P<0.05), and significantly higher in Plans B and C than in Plan D (P<0.05), but there was no difference between Plans B and C (P>0.05). There was no significant difference in high dose coverage (V95 and V90) of PTV for the primary gross tumor region (PTVnx), PTV for the cervical metastatic nodes (PTVnd), PTV for the high risk region around primary gross tumor (PTVnx60), PTV for the high risk region around metastatic nodes (PTVnd60), and subclinical lesion region above cricoid cartilage (PTV50b) among the 4 plans. There was no difference in the doses for the spinal cord and larynx among the 4 plans. The maximal doses for 50% volumes of target organs (D50) were significantly higher in Plan A than in Plans B, C, and D (49.47 Gy vs. 41.95 Gy, 38.73 Gy, and 26.82 Gy for the thyroid gland, 44.52 Gy vs. 8.41 Gy, 7.03 Gy, and 5.63 Gy for the esophagus, 44.18 Gy vs. 10.16 Gy, 8.55 Gy, and 7.60 Gy for the trachea, P<0.05), and higher in Plans B and C than in Plan D (P<0.05), but there was no difference between Plans B and C (P>0.05). The normal tissue complication probability (NTCP) of the thyroid gland was significantly higher in Plan A than in Plans B, C, and D (7.9% vs. 4.8%, 4.3%, and 3.0%, P<0.05), and higher in Plans B and C than in Plan D, but there was no difference between Plans B and C (P>0.05). There were no difference in the doses for the spinal cord and larynx among the 4 plans. The maximal doses for 50% volumes of target organs (D50) were significantly higher in Plan A than in Plans B, C, and D (49.47 Gy vs. 41.95 Gy, 38.73 Gy, and 26.82 Gy for the thyroid gland, 44.52 Gy vs. 8.41 Gy, 7.03 Gy, and 5.63 Gy for the esophagus, 44.18 Gy vs. 10.16 Gy, 8.55 Gy, and 7.60 Gy for the trachea, P<0.05), and higher in Plans B and C than in Plan D (P<0.05), but there was no difference between Plans B and C (P>0.05). The normal tissue complication probability (NTCP) of the thyroid gland was significantly higher in Plan A than in Plans B, C, and D (7.9% vs. 4.8%, 4.3%, and 3.0%, P<0.05), and higher in Plans B and C than in Plan D, but there was no difference between Plans B and C (P>0.05). There were no difference in the NTCP of other organs at risk among the 4 plans (P>0.05).

CONCLUSIONS

Not obviously increasing the irradiation doses for critical organs at risk, Plan A has the best high dose coverage at the subclinical lesion region of the lower cervical and supraclavicular region, while Plan D the worst. We recommend to use no middle shielding block in the anterior tangential field for the first 40 Gy, then use individual middle shielding blocks of 2.1-2.5 cm in the institutes at where set up error is small.

Expression and distribution of cytokeratins and vimentin in rat larynx and trachea following irradiation

BACKGROUND

External irradiation (IRR) of advanced head and neck tumors often includes tissues of the larynx and trachea unaffected by cancer. In these normal tissues, both single-cell damage (necrosis, apoptosis, functional cell death) and interstitial damage (edema, fibrosis, vascular alterations, cellular infiltrations) resulting in tissue remodeling can occur, depending on various IRR parameters. However, reports on radiogenic intermediate filament protein alterations in laryngeal-tracheal tissues are very rare. In this study, we investigated the phenotypic characterization of the normal integrity-supporting cytokeratins (CK) and vimentin following a clinically relevant IRR protocol in laryngeal-tracheal tissues.

MATERIALS AND METHODS

In 61 laryngo-tracheal specimens from Wistar rats the expression profile and distribution pattern of CK (CK13, CK17/19, CK18) and vimentin were investigated according to IRR dose (fractionated IRR, 2 Gy per day, total dose of 20, 40 or 60 Gy), time from IRR (6 months vs. 12 months) and animal age (1 year vs. 1.5 years) using immunohistochemical methods, semiquantitative assessment and multivariate analysis.

RESULTS

In irradiated specimens, expression of both CK and vimentin showed slight to moderate dose-dependent alterations. The expression differed in frequency and level among the various tissue structures and showed remarkable heterogeneity, with increases, decreases and fluctuations in staining. In the glottic mucosal layer (non-keratinizing squamous epithelium), CK13 expression decreased with increasing dose. The CK17/19 expression of supra- and subglottic respiratory epithelia following 20 and 60 Gy exposure was significantly lower than in controls. The respiratory epithelia and, in part, the cuboidal epithelia of the indifferent type at the inner side of the aryepiglottic fold revealed increasing CK17/19 immunoreactions up to 40 Gy IRR, but a distinct decrease in expression at 60 Gy. In subglottic gland structures, CK18 was detected at significantly higher levels than in controls. There was increasing expression with increasing dose. CK18 reactions of supra- and subglottic respiratory mucosal layer, supraglottic gland structures and thyrocytes tended towards increasing expression with increasing dose and in older animals. Tracheal mucosal epithelia, tracheal glands, and respiratory epithelia of the inner side of the aryepiglottic fold tended towards decreasing expression of CK18 with increasing dose and in older animals. In part, these tissues showed dose-dependent fluctuations. Furthermore, the vimentin reactions showed dose-dependent, heterogeneous patterns, with increases, decreases, and fluctuations in staining. Moreover, there were differences in frequency and intensity of expression among the various tissue structures. Age and time from IRR had no significant effect on immunoreaction.

CONCLUSION

The staining of CK and vimentin predominantly showed a notable dose-dependent heterogeneity, with increases, decreases and fluctuations in expression. The expression pattern persisted for up to 1 year after the completion of irradiation. Thus, these findings must reflect late radiation effects. The altered expression of CK and vimentin may play at least a partial role in structural (e.g. edema) and functional (e.g. voice disorders) changes associated with irradiation of the head and neck.

Fate of mucosal healing in transplanted deep frozen irradiated tracheal homograft

OBJECTIVE

Deep-frozen irradiated tracheal homograft has been successfully employed for subglottic-tracheal reconstruction, as in our previous report. Morphologically, though the transplanted site appeared to have good mucosal healing, the fate of the donor mucosa is not known. The objective of this study was to determine the survival of the mucosa of donor trachea.

STUDY DESIGN AND SETTING

University hospital-based, prospective study.

METHODS

Thirty samples from six sets of specimens, each set consisting of five samples of the tracheal mucosa, were studied. Of five samples in each set, 2 were taken from donors, one from a recipient, and another two from the transplanted sites, eight months postoperatively. The samples in each set of specimens were genetically matched by the process of DNA fingerprinting. Histological studies were done on the mucosa of donor and transplanted sites.

RESULTS

The study demonstrated incompatibility between samples from recipient and transplanted site, and incompatibility between preoperative donor and recipient samples in all sets of specimens.

CONCLUSION

The mucosa of donor trachea did not survive at the transplanted site. The apparently normal postoperative mucosal lining actually represents migration of the recipient mucosa.

SIGNIFICANCE

The fate of transplanted donor tracheal mucosa is elucidated, and may substantially explain the mechanism of rejection resistance.

Low level laser therapy partially restores trachea muscle relaxation response in rats with tumor necrosis factor alpha-mediated smooth airway muscle dysfunction

BACKGROUND AND OBJECTIVE

It is unknown if the decreased ability to relax airway smooth muscles in asthma and other inflammatory airways disorders can be influenced by low level laser therapy (LLLT) irradiation. To investigate if LLLT could reduce impairment in inflamed trachea smooth muscles (TSM) in rats.

STUDY DESIGN/MATERIALS AND METHODS

Controlled rat study where trachea was dissected and mounted in an organ bath apparatus with or without a TNF-alpha solution.

RESULTS

Low level laser therapy administered perpendicularly to a point in the middle of the dissected trachea with a wavelength of 655 nm and a dose of 2.6 J/cm(2), partially restored TSM relaxation response to isoproterenol. Tension reduction was 47.0 % (+/-2.85) in the laser-irradiated group compared to 22.0% (+/-2.21) in the control group (P < 0.01). Accumulation of cAMP was almost normalized after LLLT at 22.3 pmol/mg (+/-2.1) compared to 17.6 pmol/mg (+/-2.1) in the non-irradiated control group (P < 0.01).

CONCLUSION

Low level laser therapy partially restores the normal relaxation response in inflamed TSM and normalizes accumulation of cAMP in the presence of isoproterenol.

The effects of granulocyte colony-stimulating factor on the healing of tracheal anastomosis following radiation therapy in rats

OBJECTIVE

This study evaluates the effects of granulocyte colony-stimulating factor on the healing of tracheal anastomosis following radiation therapy in rats.

METHODS

Fifty-six male Wistar rats were divided into four groups. Group 1 underwent tracheal anastomosis. Group 2 underwent radiation therapy followed by tracheal anastomosis. Group 3 underwent radiation therapy followed by tracheal anastomosis and received granulocyte colony-stimulating factor. Group 4 underwent sham radiation therapy followed by sham tracheal anastomosis. At 10 days following radiation therapy, the trachea was dissected for histopathological, mechanical and biochemical evaluation.

RESULTS

Median scores for inflammation were three points for Group 1, two points for Group 2, two points for Group 3 and one point for Group 4. Median scores for angiogenesis were four points for Group 1, two points for Group 2, three points for Group 3 and one point for Group 4. Median scores for connective tissue regeneration were four points for Group 1, two points for Group 2, three points for Group 3 and one point for Group 4. Median scores for epithelial regeneration were two points for Group 1, one point for Group 2, one point for Group 3 and one point for Group 4. Mean anastomotic bursting pressures were 853 mmHg for Group 1, 293 mmHg for Group 2, 417 mmHg for Group 3 and 966 mmHg for Group 4. Mean hydroxyproline concentrations were 159 microg/mg for Group 1, 177 microg/mg for Group 2, 120 microg/mg for Group 3 and 117 microg/mg for Group 4.

CONCLUSIONS

This study suggests that granulocyte colony-stimulating factor contributes to the healing of tracheal anastomosis following radiation therapy through improved connective tissue regeneration.

Nontraumatic disruption of the fibrocartilaginous trachea: causes and clinical outcomes

BACKGROUND

Nontraumatic disruption of the fibrocartilaginous trachea is rare, and the appropriate management of this condition is not well-characterized.

METHODS

Retrospective analysis of the clinical features, causes, and outcomes with surgical and nonsurgical management in nine adult patients with nontraumatic fibrocartilaginous tracheal disruption identified by bronchoscopy from January 1, 1975, to December 31, 2004, at a single institution.

RESULTS

The most common cause was external beam radiotherapy (RT) in five patients. Other causes included postoperative complications of cervical and superior mediastinal operations in three patients and Aspergillus fumigatus-induced ulcerative tracheobronchitis in one patient post-lung transplantation. Four patients were treated surgically; three because of significant pneumomediastinum and one because the size of the tracheal defect made spontaneous healing seem unlikely. A silicone stent was placed in one patient for concomitant tracheal narrowing, and one patient was treated medically with antifungal agents. The remaining three patients were followed up serially without any intervention. With these treatments, only one patient died as a consequence of tracheal disruption. Repeat bronchoscopies were performed in seven of the remaining eight patients and confirmed healing of the necrotic defect in all.

CONCLUSION

Nontraumatic disruption of the fibrocartilaginous trachea occurs most commonly as a consequence of external beam RT. It can also occur as a complication of cervical and superior mediastinal operations or from A fumigatus-induced ulcerative tracheobronchitis post-lung transplantation. Although surgical treatment has been generally recommended for patients with this condition, patients with contained disruptions without evidence of pneumomediastinum may be managed nonoperatively.

Comparison of dose conversion factors for radon progeny from the ICRP 66 regional model and an airway tube model of tracheo-bronchial tree

Current epidemiological approaches to radon dosimetry yield a dose conversion factor (DCF) of 4 mSv WLM(-1) while the dosimetric approaches give a value closer to 13 mSv WLM(-1). The present study investigated whether the application of compartment models for the bronchial (BB) and bronchiolar (bb) regions, rather than more anatomically realistic airway tube models, has brought the dosimetric DCF to the higher values. The airway tube model of the tracheo-bronchial tree was used to calculate the effective dose per unit radon exposure. All other elements of the human respiratory tract from the reports of the ICRP or NRC were adopted. A dosimetric derivation of the radon DCF using the airway tube model yielded a value of 14.2 mSv WLM(-1). This value is slightly larger than, but not significantly different from, the result obtained through the ICRP 66 approach. It is concluded that utilization of the airway tube model instead of the regional ICRP 66 compartmental model cannot reconcile the gap between dose conversion factors derived from epidemiological and dosimetric approaches.

Prothetische Stimmrehabilitation nach Laryngektomie

BACKGROUND

Indwelling voice prostheses are state of the art for post-laryngectomy voice rehabilitation. The aim of this study was to identify the impact of radiation prior to tracheoesophageal puncture on success rate and complications.

PATIENTS AND METHODS

We undertook a retrospective study of 145 patients who had undergone prosthetic voice restoration between 1990 and 2002 (Provox) and Provox2). Risks of functional failure and complications in 17 patients with previous radiation therapy were compared to those of 128 patients without such therapy.

RESULTS

Previous radiation increased not only the risk of functional failure by 2.9 (P=0.023), but also the risk of shunt-related complications such as aspiration around the prosthesis (1.51; P=0.046), widening of the shunt (2.32; P=0.014), esophageal (2.51; P=0.013) or tracheal (3.29; P=0.0023) dislocation of the prosthesis and spontaneous (2.51; P=0.047) or surgical closure (3.76; P=0.037) of the shunt.

CONCLUSION

Primary tracheoesophageal puncture during laryngectomy is recommended in cases without previous radiation therapy, especially when post-laryngectomy radiation is likely. In patients with previous radiation therapy, generally good success rates decrease, however, without absolute contraindication of tracheoesophageal puncture. These results may affect salvage surgery concepts.

Radiation-induced narrowing of the tracheobronchial tree: An in-depth analysis

PURPOSE

Symptomatic narrowing of the tracheobronchial tree is not a common clinical problem after conventional-dose external beam radiation therapy but has been described when higher doses are utilized. This in-depth study quantifies changes in the caliber of the trachea and mainstem bronchi after high-dose external beam radiation therapy (EBRT).

METHODS AND MATERIALS

As part of an IRB-approved prospective clinical trial to assess for radiation-induced lung injury, patients with thoracic malignancies had pre- and serial post-RT CT scans in the radiation oncology department. This report focuses on 18 enrolled patients who received high-dose (> or = 73.6 Gy) EBRT for NSCLC. The caliber of the trachea, right mainstem bronchus, and left mainstem bronchus were measured utilizing three-dimensional coordinates in axial and coronal planes such that multiple measurements were made of each structure. The decrease in airway caliber was tested for significance using a one-sided Wilcoxon matched-pairs signed-ranks test. The correlation between airway caliber changes, dose, and follow-up interval was tested using the Spearman rank correlation coefficient and the effect of chemotherapy on airway narrowing was evaluated with a one-sided exact Wilcoxon rank sum test.

RESULTS

There was no significant narrowing of the trachea for all dose and time points. There were significant decreases in the caliber of both mainstem bronchi on axial measurements (p = 0.07 and 0.005 for right and left mainstem bronchi, respectively). Decrease in airway caliber ranged from 6 to 57% and appeared to be dose dependent (p = 0.08), progressed with increasing time post-RT (p = 0.04), and was worse in patients who also received chemotherapy (p = 0.04).

CONCLUSION

High-dose EBRT (> or = 73.6 Gy) appears to cause narrowing of the mainstem bronchi as early as 3 months post radiation therapy. Additional study is needed to assess the impact of such narrowing on RT-induced pulmonary symptoms.

Management of Oropharyngeal and Tracheobronchial Secretions in Patients with Neurologic Disease

BACKGROUND

Neurologic disorders may impair the normal clearance of secretions. Effective palliation requires the management of excessive oral, pharyngeal and/or tracheobronchial secretions. This requires an understanding of underlying mechanisms and familiarity with the many available medical and surgical treatment options.

OBJECTIVES

The authors intend to review the relevant anatomy and physiology along with the available medical, surgical and physical therapies available to treat this commonly encountered problem.

DESIGN

A review of current management and the supporting literature.

CONCLUSIONS

Clinicians have many effective therapeutic options to choose from when managing the excessive oral, pharyngeal and/or tracheobronchial secretions caused by neurologic disorders. Treatment choices that are predicated upon pathophysiologic causes and patient status are the most likely to succeed.

Radiation responses of perfused tracheal tissue

We are using a novel perfusion system to examine the effects of radiation on a model respiratory tissue. Tracheas taken from young adult male Fischer 344 rats are embedded in a growth factor-enriched agarose matrix that is mounted in a special apparatus designed to allow growth medium to periodically wash the epithelial surface of the lumen. A comparison of the microarray expression profiles of freshly harvested tracheas and tracheas maintained in perfusion culture for 24 h shows no significant difference except for an increase in expression of a few metabolism- and surfactant-related genes. Perfusion culture samples exposed to 4 Gy of X rays show a lower than expected increase in expression for some cell cycle- and repair-related genes.

Bound PCNA in nuclei of primary rat tracheal epithelial cells after exposure to very low doses of plutonium-238 alpha particles

Bystander effects from ionizing radiation have been detailed for a number of cell systems and a number of end points. We wished to use a cell culture/ex vivo rat model of respiratory tissue to determine whether a bystander effect detected in culture could also be shown in a tissue. Examination by immunofluorescence techniques of tracheal cell cultures after exposure to very low doses of alpha particles revealed a large proportion of cells with proliferating cell nuclear antigen (PCNA) bound in their nuclei. PCNA was selected as an end point because it is involved in both DNA repair and the changes in cell cycle that are typical of many reported bystander effects. Maximum response can be detected in up to 28% of the cells in sub-confluent cultures with a dose of only 2 mGy. At this dose less than 2% of the cell nuclei have experienced a particle traversal and less than 6% of the cells have experienced an alpha-particle traversal through either their nucleus or some part of their cytoplasm. The hypothesis that this bystander response in nontargeted cells is mediated through secreted factor(s) is presented, and supporting evidence was found using partial irradiation and co-culture experiments. Examination of the effect with excised pieces of trachea demonstrated a response similar to that seen in culture.

Expression and distribution of basement membrane proteins in rat larynx and trachea following irradiation

OBJECTIVE

Basement membranes-(BM) influence polarization, differentiation, migration and proliferation of cell and play an important role in maintaining structural and functional tissue integrity. While BM alterations have been reported in various lesions (e.g. inflammation, tumors) of laryngeal-tracheal tissues, reports on radiogenic BM alterations are rare. External irradiation (IRR) of advanced head and neck tumors often includes "normal tissues" (tissues without cancer) of the larynx. In these normal tissues both single-cell damage (necrosis, apoptosis, functional cell death) and interstitial damage (edema, fibrosis, vascular alterations, cellular infiltrations) resulting in tissue remodeling can occur, depending on various IRR parameters. In this study, we set out to add to our knowledge on the phenotypic characterization of the radiogenic BM expression pattern in laryngo-tracheal tissues.

MATERIALS AND METHODS

In 63 laryngo-tracheal specimens from Wistar rats, we investigated the laminin (LA) and collagen IV (CIV) expression profile and distribution pattern depending on the IRR dose (fractionated IRR, 2 Gy/day, up to a total dose of 20, 40, or 60 Gy), the time since IRR (6 months vs 12 months) and animal age (1 year vs 1.5 years) using immunohistochemical methods, semiquantitative assessment, and multivariate analysis.

RESULTS

In specimens irradiated with more than 20 Gy, both BM constituents predominantly showed dose-dependent increases and sometimes fluctuations in staining at slight to moderate levels. The expression differed in frequency and level among the various tissue structures. In some structures there was decreased expression. In the vocalis muscle, laryngeal and esophageal nerve endings, recurrent laryngeal nerve and laryngeal and tracheal muscles, LA was detected at levels significantly stronger than in controls. BM surrounding gland structures, nerve endings of the piriform sinus and esophageal muscles showed a marked tendency towards increased LA expression. However, the BM underlying the mucosal layer of the supra- and subglottic region revealed decreasing LA immunoreaction up to 40 Gy IRR, but a distinct increase in expression at 60 Gy. In the esophageal and tracheal muscles, tracheal perichondrium, recurrent laryngeal nerve and capillaries, CIV was detected at significantly stronger levels than in the controls. The vocal ligament exhibited positive CIV immunoreactions adjacent to interstitial and infiltrate cells and CIV-positive BM condensations, resulting in increased staining of these structures. CIV reactions of laryngeal and hypopharyngeal nerve endings tended towards increased expression. In contrast, BM staining surrounding vocal muscle cells revealed significantly decreased expression. In addition, there was a tendency towards decreased expression for supraglottic, subglottic and hypopharyngeal muscle cells. Age and time since irradiation had no significant effect on staining.

CONCLUSION

The BM constituents laminin and collagen IV showed prominent dose-dependent increases and sometimes fluctuations in expression. This expression pattern persisted up to one year after completion of the irradiation. Thus, these findings must be related to late radiation effects. The altered BM expression may play a role, at least in part, in structural (e.g. laryngeal edema) and functional (voice disorders) changes associated with irradiation of the head and neck area.

Induction and repair of HZE induced cytogenetic damage

Wistar rats were exposed to high-mass, high energy (HZE) 56Fe particles (1000 GeV/AMU) using the Alternating Gradient Synchrotron (AGS). The animals were sacrificed at 1-5 hours or after a 30-day recovery period. The frequency of micronuclei in the tracheal and the deep lung epithelial cells were evaluated. The relative effectiveness of 56Fe, for the induction of initial chromosome damage in the form of micronuclei, was compared to damage produced in the same biological system exposed to other types of high and low-LET radiation. It was demonstrated that for animals sacrificed at short times after exposure, the tracheal and lung epithelial cells, the 56Fe particles were 3.3 and 1.3 times as effective as 60Co in production of micronuclei, respectively. The effectiveness was also compared to that for exposure to inhaled radon. With this comparison, the 56Fe exposure of the tracheal epithelial cells and the lung epithelial cells were only 0.18 and 0.20 times as effective as radon in the production of the initial cytogenetic damage. It was suggested that the low relative effectiveness was related to potential for 'wasted energy' from the core of the 56Fe particles. When the animals were sacrificed after 30 days, the slopes of the dose-response relationships, which reflect the remaining level of damage, decreased by a factor of 10 for both the tracheal and lung epithelial cells. In both cases, the slope of the dose-response lines were no longer significantly different from zero, and the r2 values were very high. Lung epithelial cells, isolated from the animals sacrificed hours after exposure, were maintained in culture, and the micronuclei frequency evaluated after 4 and 6 subcultures. These cells were harvested at 24 and 36 days after the exposure. There was no dose-response detected in these cultures and no signs of genomic instability at either sample time.

In vitro radiation-induced effects on rat tracheal epithelial cells. II) Different preneoplastic cell transformation after alpha and gamma irradiations

In order to compare the cell transformation induced by alpha- and gamma-irradiation, primary cultures of tracheal epithelial cells from two rat strains, Sprague Dawley (SD) and Wistar Furth/Fisher F344 (WF/Fi) rats, were irradiated with 241Am alpha-particles or 60 Co gamma-rays. The relative transformation frequency (RTF) for WF/Fi primary cells was very close to the level of the spontaneous incidence and independent on the two irradiation types used. On the contrary, the RTF for the SD primary cells increased with a decrease of the LET radiation when the relative survival was higher than about 40%. Therefore, the RTF values reached 4-5 for alpha-particles and 10-12 for gamma-rays. The RTF can be related to the intrinsic radiosensitivity of the rat epithelial cells. However, the difference in the radiation-induced RTF for SD or WF/Fi primary cells seems to be due to the development, under genetic control, of the initial lesion to the neoplastic state.

In vitro radiation-induced effects on rat tracheal epithelial cells. I) Different radiosensitivity of cell inactivation after alpha and gamma irradiations

In order to compare the radiotoxicity of alpha- and gamma-irradiations, primary cultures of tracheal epithelial cells from two rat strains, Sprague Dawley (SD) and Wistar Furth/Fisher F344 (WF/Fi) rats, were irradiated with 241Am alpha-particles or 60 Co gamma-rays. The survival ratio for each of the two rat strain cells appeared to be statistically different after high-LET irradiation. WF/Fi rat cells were 1.7-times more radiosensitive than SD rat cells, whereas no difference was observed following low-LET irradiation. A comparison of the cell survival yielded RBEs of 2.8 and 4.5 for SD and WF/Fi rat cells, respectively. As previously observed, with increasing LET of particles, the cell-survival curves approximate an exponential function of the dose. On the contrary, for low-LET, the survival curves showed a marked initial shoulder. This in vitro cellular model, using epithelial cells of the upper airway, provides a suitable system to estimate the mechanism involved in radiosensitivity after high-LET irradiation. The responses to radiation-induced lethal effects within a same type of cell were dependent on the irradiation parameters, but might be modulated by the individual sensitivity under genetic or epigenetic factor controls.

Local deposition distributions of inhaled radionuclides in the human tracheobronchial tree

There is experimental evidence that bronchogenic carcinomas originate mainly at the carinal ridges of the large central airways, where primary hot spots of deposition have been found. However, current lung dosimetry models do not take into consideration the inhomogeneity of deposition within the airways. In this study, computed local distributions of deposited inhaled radionuclides such as radon progenies in morphologically realistic human airway bifurcation models are analysed for different flow rates and particle sizes. Then, local deposition enhancement factors, defined as the ratio of local to average deposition densities, are computed by scanning along the surface of the bifurcation with pre-specified surface area elements. Computed enhancement factors indicate that cells located at carinal ridges or at the inner sides of the progeny branches may receive localised doses which are two orders of magnitude higher than the average values.

Distributions of specific energy in sensitive layers of the human respiratory tract

The purpose of the present work was to calculate the specific energy distribution in sensitive cells of the human lung. Specific energy distributions were calculated by applying Monte Carlo methods and the ICRP 66 model of the human respiratory tract. Specific energies were calculated at various depths in the epithelium and combined according to the relative cell abundance. Distributions are given for various combinations of sources, alpha-particle energies, targets and regions of the lung. The chord length does not follow the triangular distribution when the particle range is comparable to the diameter of the target. The notion of "effective volume" is introduced and defined, which is needed for estimation of hit frequency in some particular targets. It has been shown that basal cells are subjected to a larger proportion of alpha-particle hits with small energy transfer than secretory cells. Small energy transfer events that lead to minor damage of the DNA are more efficient in cancer induction than are hits with large energy deposition that lead to cell killing.

Absorbed fraction and dose conversion coefficients of alpha particles for radon dosimetry

The sensitivity to different relevant parameters of the absorbed fraction of alpha particles emitted from the 222Rn chain in sensitive cells of the tracheo-bronchial tree have been investigated. The structure of the airway wall given by ICRP (ICRP66) has been adopted and employed in the present calculations. The source thickness (mucous gel and sol + cilia), target layer thickness and the depth of the sensitive layers have been varied within reasonable ranges around the default values recommended by ICRP66. The results have shown that the depth of the sensitive layers is the most important parameter in calculating the absorbed fraction. In addition, dose conversion coefficients were calculated and presented along with the absorbed fractions.

Carbon dioxide laser induced airway fire during larynx surgery: case report

The precision intrinsic hemostatic properties of the laser have led to its wide use in modern clinical medicine especially in microscopic airway surgery. However, the intense heat generated by the high energy density of the surgical laser can convert combustible tubes into veritable torches, cause catastrophic fires, and result in severe injury to the patient. This is of particular importance when high energy is used on the continuous mode or when the endotracheal tube is repeatedly hit by the laser at the same spot. Most reported laser-induced complications result from the laser beam inadvertently falling on the areas that are not intended to be exposed. We report a case of a trans-tracheostomy tube fire occurring during carbon dioxide (CO2) laser surgery. Aluminum-tape wrapping did not prevent this complication. It was found that the ignition of a trans-tracheostomy tube was caused by the laser striking an unprotected portion of the tube during resection of granuloma of the trachea.

Alpha hit frequency due to radon decay products in human lung cells

PURPOSE

To calculate the hit probabilities by alpha-particles emitted by radon progeny for basal and secretory cell nuclei in the epithelium of the human tracheobronchial tree.

MATERIALS AND METHODS

The equilibrium activities on the surface of airway tubes were calculated using the ICRP66 model. The stopping-power and ranges of alpha-particles in tissue were adopted from ICRU49. A semi-analytical method for determining the alpha-particle fluence rate in tissue was applied. The distributions of secretory and basal cells throughout the tracheobronchial tree were as given by Mercer et al. (1991).

RESULTS

The probability to hit basal cell nuclei is three-to-four times smaller than for secretory cell nuclei in the bronchial region (BB). However, the total number of traversed basal cell nuclei is greater because of the larger volume abundance of basal cells in BB. The total number of secretory cell nuclei hit in the bronchiolar region (bb) is larger than that in BB because the volume abundance of secretory cells in bb is larger than that in BB.

CONCLUSIONS

Basal cells are more sensitive to alpha-radiation than secretory cells. This finding is based on the analysis of the relative number of cell hits and the relative frequencies of lung cancer induction in BB and bb.

Overexpression of manganese superoxide dismutase (MnSOD) in whole lung or alveolar type II cells of MnSOD transgenic mice does not provide intrinsic lung irradiation protection

Intratracheal (IT) injection of the transgene for human manganese superoxide dismutase in plasmid/liposome (SOD2-PL) complex prior to irradiation protects C57BL/6J mice from whole lung irradiation-induced organizing alveolitis/fibrosis. Transgene mRNA was detected in alveolar type II (AT-II) and tracheobronchial tree cells explanted to culture 48 hours after gene therapy. To determine whether constitutive overexpression of murine MnSOD (Sod2) in whole lung or surfactant promoter-restricted AT-II cells (SP1)-SOD2 mice would provide intrinsic radioresistance, transgenic mice of two strains were compared with age-matched controls. Other groups of surfactant promoter-restricted (SP1)-SOD2 transgenic mice or control FeVB/NHsd mice received IT SOD2-PL gene therapy prior to irradiation. There was no significant intrinsic lung protection in either strain of MnSOD transgenic mice. The SP1-SOD2 transgenic mice were protected from lung damage by IT injection of the human SOD2-PL complex 24 hours prior to irradiation. Thus, overexpression of either human SOD2 or murine Sod2 in the lungs of transgenic mice does not provide intrinsic lung irradiation protection. The overexpression of SOD2 in the SP1-SOD2 mice may have made the mice more sensitive to irradiation.

Relative effectiveness of HZE iron-56 particles for the induction of cytogenetic damage in vivo

One of the risks of prolonged manned space flight is the exposure of astronauts to radiation from galactic cosmic rays, which contain heavy ions such as (56)Fe. To study the effects of such exposures, experiments were conducted at the Brookhaven National Laboratory by exposing Wistar rats to high-mass, high-Z, high-energy (HZE) particles using the Alternating Gradient Synchrotron (AGS). The biological effectiveness of (56)Fe ions (1000 MeV/nucleon) relative to low-LET gamma rays and high-LET alpha particles for the induction of chromosome damage and micronuclei was determined. The mitotic index and the frequency of chromosome aberrations were evaluated in bone marrow cells, and the frequency of micronuclei was measured in cells isolated from the trachea and the deep lung. A marked delay in the entry of cells into mitosis was induced in the bone marrow cells that decreased as a function of time after the exposure. The frequencies of chromatid aberrations and micronuclei increased as linear functions of dose. The frequency of chromosome aberrations induced by HZE particles was about 3.2 times higher than that observed after exposure to (60)Co gamma rays. The frequency of micronuclei in rat lung fibroblasts, lung epithelial cells, and tracheal epithelial cells increased linearly, with slopes of 7 x 10(-4), 12 x 10(-4), and 11 x 10(-4) micronuclei/binucleated cell cGy(-1), respectively. When genetic damage induced by radiation from (56)Fe ions was compared to that from exposure to (60)Co gamma rays, (56)Fe-ion radiation was between 0.9 and 3.3 times more effective than (60)Co gamma rays. However, the HZE-particle exposures were only 10-20% as effective as radon in producing micronuclei in either deep lung or tracheal epithelial cells. Using microdosimetric techniques, we estimated that 32 cells were hit by delta rays for each cell that was traversed by the primary HZE (56)Fe particle. These calculations and the observed low relative effectiveness of the exposure to HZE particles suggest that at least part of the cytogenetic damage measured was caused by the delta rays. Much of the energy deposited by the primary HZE particles may result in cell killing and may therefore be "wasted" as far as production of detectable micronuclei is concerned. The role of wasted energy in studies of cancer induction may be important in risk estimates for exposure to HZE particles.

Monte Carlo simulations for EndoBronchial Photodynamic Therapy: the influence of variations in optical and geometrical properties and of realistic and eccentric light sources

BACKGROUND AND OBJECTIVE

Light dosimetry for endobronchial photodynamic therapy is not very advanced to date. This study investigates the dependency of the fluence rate distribution in the bronchial wall on several parameters.

STUDY DESIGN/MATERIALS AND METHODS

A Monte Carlo model is employed for the illumination of a cylindrical cavity by a linear diffuser to compute the fluence rate distribution in the tissue. The influence of optical and geometrical properties (e.g., the absorption coefficient of the bronchial mucosa and the diameter of the treated lumen) have been investigated, as well as the consequences of varying output characteristics of the diffusers. The optical properties used are those of ex vivo pig bronchial mucosa.

RESULTS

With on-axis linear diffusers that can be modelled as a row of isotropic point sources, a constant fluence rate buildup factor can be employed for varying diffuser lengths and lumen diameters. Extreme off-axis placement of the diffuser causes a highly variable, considerable increase in the maximum fluence rate as well as a highly asymmetrical fluence rate profile on the circumference of the illuminated lumen. The fluence rate profiles resulting from illumination with realistic diffusers can be evaluated by implementing the measured radiance profiles of these diffusers in the model. The changes in fluence rate caused by variations in the optical properties of the bronchial mucosa could be accounted for by diffusion theory. This relationship can be used to extrapolate the ex vivo results to the clinical situation.

CONCLUSION

A set of practical rules of thumb is presented that can help to estimate fluence rate distributions in clinical practice.

Thermal lesions produced by CO2 laser beams: new findings to improve the quality of minimally invasive and transmyocardial laser revascularization protocols

OBJECTIVE

The objective of this study was to investigate the possible existence of a set of critical combinations among medical CO2 laser device set-ups and to compare the resigns of diameter and depth of irradiated tissue. These data are useful to the surgeon to identify a general operative protocol that allows both to forecast the beam behavior on a large variety of operative conditions accurately and to identify the related safety margins. Two methods have been addressed: the more traditional free-air beam delivery to the tissue and the more modern requirements of the minimally invasive surgery concepts, which use fiberoptic-based delivery systems for the CO2 laser beam.

BACKGROUND DATA

In the past many articles have been written about the interaction between laser beams and biological media. However, the CO2 laser beam at 10.6 microm has always challenged research institutions and manufacturers to find the ideal combinations between a suitable fiberoptic-based delivery system concept and the injury threshold conditions recommended for minimally invasive surgery (MIS) and transmyocardial laser revascularization (TMLR) applications. One of the main challenges is to deliver the radiation at 10.6 microm without serious damage to the fiberoptic-based scalpel and the irradiated tissue by the burn of the fiber in use.

METHODS

Five rabbits weighing 3 to 3.5 kg were sacrificed and 60 samples of trachea, myocardium, aorta, and esophagus were immediately excised, trimmed free of the adherent connective tissue, and irradiated in the intima portion of the wall. A commercial TEM medical CO2 laser was coupled to a silver halide fiber (0.9 mm in diameter) and subsequently to regular focusing heads (2.5-inch and 5-inch focal length) for pulsed laser beam delivery. The parameters chosen were: 33, 50, 65, and 100 mJ per pulse, 10 and 20 ms pulse width, delivered in two sets of experiments, one with all the pulsed beam frequencies below 5 Hz, the other between 15 Hz and 20 Hz. The same tests were conducted on 10 blocks of 3 different plastic types to simulate in one single procedure the laser radiation in responses to both hard, low-water content tissues such as bone and of common plastic compounds (such as polymethylmethacrylates [PMMA]) routinely used in orthopedic surgery. An optical microscope was used to measure all the lesions (diameter and depth in millimeters) in all the samples and to identify the smallest and the largest one against which similar thermal injuries found on the other media were compared.

RESULTS

This study demonstrates that for power densities between about 520 and 790 W/cm2 per pulse achieved with the silver halide fiber generated a minimal lesion on the myocardium and aortic tissues. This can be used as reference threshold for MIS and TMLR. The minimal injury threshold on PMMA has been reached at 393 W/cm2 per pulse at 1 Hz. This approached the conditions of a pulsed beam delivered in air on the same medium via a focal spot of an 8.7 inch focal. Surprisingly, all the treated media show lesions that follow similar patterns within a well-defined and limited range of both diameter and depth. This effect was obtained by using power densities ranging from 393 to 6310 W/cm2 per pulse regardless of all the other parameters, including power delivery method, the type of irradiated tissue and the frequency between 0 and 20 Hz. Only the combination power density-type of tissue appears to be decisive. The geometrical convergence of the diameter shows a much smoother pattern than the one of the depth, due to two different irradiation modalities.

CONCLUSIONS

The selection of the CO2 laser beam parameters and the irradiated media reported in this article have allowed identification of a critical set of ablative conditions to be further used in the operating room.

A CT-assisted method of dosimetry in brachytherapy of lung cancer. Rotterdam Oncological Thoracic Study Group

BACKGROUND

The toxicity of endobronchial brachytherapy (EB), in particular fatal haemoptysis and bronchial wall necrosis, has been correlated with the total dose, fraction size, volume encompassed by the 100% isodose, and a proximal tumor location. We describe a CT-based planning method which, by improving target volume definition and volumetric dose information, can improve the therapeutic ratio of EB.

MATERIALS AND METHODS

Sixteen CT-assisted EB procedures were performed in patients who were treated with palliative high-dose rate EB. The CT data were used to analyze applicator position in relation to anatomy. An example of a three-dimensional optimized treatment plan was generated and analyzed using different types of dose-volume histograms.

RESULTS

The procedure was well tolerated by patients and no post-procedure complications were observed. The bronchial applicator was eccentrically positioned at the level of the carina/mainstem bronchus in 12 (of 14) CT scans. A planning CT prior to EB was not found to be useful as the final target volume and/or the final applicator position were not reliably predicted before the therapeutic bronchoscopy. CT-scans performed with the applicator in situ allowed the bronchial segments in the target volume to be identified and enabled dose prescription to the bronchial mucosa.

CONCLUSIONS

CT-assisted EB is feasible and underlines the need for using centered applicators for proximally located tumors. By enabling accurate mucosal dose prescription, CT-assisted EB may reduce the toxicity of fractionated EB in the curative setting. However, faster on-line EB treatment planning is needed for the routine clinical application of this technique.

Evaluation of a commercial three-dimensional electron beam treatment planning system

We evaluated a commercial three-dimensional (3D) electron beam treatment planning system (CADPLAN V.2.7.9) using both experimentally measured and Monte Carlo calculated dose distributions to compare with those predicted by CADPLAN calculations. Tests were carried out at various field sizes and electron beam energies from 6 to 20 MeV. For a homogeneous water phantom the agreement between measured and CADPLAN calculated dose distributions is very good except at the phantom surface. CADPLAN is able to predict hot and cold spots caused by a simple 3D inhomogeneity but unable to predict dose distributions for a more complex geometry where CADPLAN underestimates dose changes caused by inhomogeneity. We discussed possible causes for the inaccuracy in the CADPLAN dose calculations. In addition, we have tested CADPLAN treatment monitor unit and electron cut-out factor calculations and found that CADPLAN predictions generally agree with manual calculations.

The feasibility of high dose iodine 131 treatment as an alternative to surgery in patients with a very large goiter: effect on thyroid function and size and pulmonary function

Some patients with very large goiters (>150 mL) are not candidates for surgery. We evaluated the feasibility of high dose 131I in such patients. Twenty-three patients (2 men and 21 women; median age, 67 yr; range, 42-86 yr) with very large goiter (8 toxic) were treated with calculated high dose 131I [median, 2281 megabecquerels (61.6 mCi); range, 988-4620 megabecquerels (26.7-124.9 mCi)]. During the 12-month observation period, goiter reduction and tracheal anatomy were monitored by magnetic resonance imaging, and the respiratory capacity was monitored by pulmonary function tests. Five patients (22%) developed hypothyroidism. Thyroid volumes were at baseline, after 1 week, and after 1 yr [mean +/- SEM, 311 +/- 28, 314 +/- 26 (P = NS), and 215 +/- 26 (P < 0.01) mL]. The relative changes 1 week after therapy ranged from -14.1% to 15.3%. After 1 yr the mean size was reduced by 33.9% (range, 13.5-61.4%). Only the initial goiter size showed a significant negative correlation to the percent reduction. The smallest cross-sectional area of the trachea decreased 9.2% within 1 week after treatment, but eventually emerged with a 17.9% larger area [mean +/- SEM, 84.3 +/- 4.8, 75.5 +/- 5.1 (P < 0.01), and 98.2 +/- 6.0 (P < 0.01) mm2]. The inspiratory parameter, FIF50%, improved after an initial insignificant decline [baseline therapy, after 1 week, after 3 months, and after 1 yr (mean +/- SEM), 2.37 +/- 0.24, 2.20 +/- 0.21 (P = NS), 2.51 +/- 0.23 (P = NS), and 2.76 +/- 0.25 (P = 0.01) L/s]. FIF50% correlated significantly with the smallest cross-sectional tracheal area (baseline, 1 week, and 1 yr: r = 0.74; P < 0.001, r = 0.63; P < 0.005, and r = 0.46; P < 0.05). Changes in tracheal anatomy did not correlate with changes in either lung dynamics or goiter size. In conclusion, very large goiters can be reduced by a third, on the average, with high dose 131I therapy without any initial clinically significant tracheal compression. Tracheal cross-sectional area as well as pulmonary inspiratory capacity improve. No serious adverse effects are seen.

The midline dose distribution for a three-field radiotherapy technique

At the University of Florida, head and neck cancer often is irradiated using parallel opposed lateral fields (with inferior borders slanted superiorly) and an anterior low neck field. A common criticism is that overlap may occur at the match-line junction of the three fields, resulting in an increased risk of radiation myelitis. One setup for treatment of the oropharynx and two for the larynx were irradiated in an anthropomorphic head and neck phantom made of tissue-equivalent polyacrylamide gel with a two-dimensional thermoluminescent dosimeter array in its sagittal midplane. The results showed that no excess radiation dose was measured at the junction of the three fields. The "spinal cord dose," as percentage of dose to the central axis of the primary field, was as follows: oropharynx setup, 15% to 100%; larynx setup with midline tracheal block, 10% to 90%; larynx setup without tracheal block, 10% to 90%. In conclusion, the University of Florida three-field technique for head and neck cancer produces no measured increase in dose at field junctions.

The study on related genes in the neoplastic transformation of immortalized human fetal tracheal fibroblast cells induced by irradiation

In this study, we investigated the genes related to the transformation of immortalized human fetal tracheal fibroblast cell line induced by alpha particles by means of differential display mRNA method. The result revealed that there were 23 DNA fragments that were expressed intensively in alphaSHTF cells (SHTF cells forming clone on agar after irradiated by alpha particles emitted by 238Pu) only and not in SHTF (SV40-immortalized human fetal tracheal fibroblast) cells. Northern dot confirmed two fragments, C17-5, C23-1 which showed intensive mRNA expression in alphaSHTF cells, but not in SHTF cells. The length of the C17-5 fragment was 310bp. Searching in BLAST database revealed that the C17-5 fragment might be an unknown sequence.

Short- and long-term normal tissue damage with photodynamic therapy in pig trachea: a fluence-response pilot study comparing Photofrin and mTHPC

The damage to normal pig bronchial mucosa caused by photodynamic therapy (PDT) using mTHPC and Photofrin as photosensitizers was evaluated. An endobronchial applicator was used to deliver the light with a linear diffuser and to measure the light fluence in situ. The applied fluences were varied, based on existing clinical protocols. A fluence finding experiment with short-term (1-2 days) response as an end point showed considerable damage to the mucosa with the use of Photofrin (fluences 50-275 J cm(-2), drug dose 2 mg kg(-1)) with oedema and blood vessel damage as most important features. In the short-term mTHPC experiment the damage found was slight (fluences 12.5-50 J cm(-2), drug dose 0.15 mg kg(-1)). For both sensitizers, atrophy and acute inflammation of the epithelium and the submucosal glands was observed. The damage was confined to the mucosa and submucosa leaving the cartilage intact. A long-term response experiment showed that fluences of 50 J cm(-2) for mTHPC and 65 J cm(-2) for Photofrin-treated animals caused damage that recovered within 14 days, with sporadic slight fibrosis and occasional inflammation of the submucosal glands. Limited data on the pharmacokinetics of mTHPC show that drug levels in the trachea are similar at 6 and 20 days post injection, indicating a broad time window for treatment. The importance of in situ light dosimetry was stressed by the inter-animal variations in fluence rate for comparable illumination conditions.

Measurement of tracheobronchial dose from simultaneous exposure to environmental radon and thoron progeny

According to the theory and idea of Hopke et al., a bronchial dosimeter consisting of multiple metal screens has been developed to measure the deposition fractions of radon and thoron progeny in the nasal (N) and tracheobronchial (T-B) regions of the human respiratory tract and to give the dose conversion factors in the T-B region in units of mGy WLM(-1) and mSv y(-1) per Bq m(-3). Different air treatments have been performed in a closed laboratory, which include the use of air conditioning and the application of positive and negative ions for the investigation of the change of the dose conversion factors. At the same time, the radon and thoron gas concentrations have also been measured in the laboratory by active sampling using newly designed activated charcoal canisters connected in series with the bronchial dosimeter for the calculation of the resulted annual effective dose under different air treatments. It is observed that the calculated dose conversion factors derived from the bronchial dosimeter have large discrepancies with those computed using existing lung models. It has also been found that the application of negative ions cannot reduce the annual effective dose in the T-B region; the application of positive ions can lead to a reduction, but not as much as the use of air conditioning. The mitigation of radon effects by air conditioning demonstrated using the bronchial dosimeter is more prominent than that shown by using lung models.

Induction of micronuclei in respiratory tract following radon inhalation

Male Wistar rats were exposed to radon and its progeny (0.0, 60, 262 and 564 working level months, WLM), and the frequency of micronuclei was determined in deep lung fibroblasts, and deep lung, trachea and nasal epithelial cells with slopes of 0.28, 0.67, 0.34 and 0.11 micronuclei/1000 binucleated cells/WLM respectively. Micronuclei in deep lung fibroblasts, isolated and cultured using two methods and media, demonstrated no differences in slopes. Biological damage was used as a biodosimeter to calculate the relationship between dosimetric units: alpha particle traversals or 'nuclear hits', dose in mGy and exposure in WLM. The estimated number of nuclear alpha traversals/Gy was 6.3. Radon exposure to 170 WLM resulted in the same frequency of micronuclei in deep lung epithelial cells as produced by one alpha hit/cell nucleus. Absorbed dose/unit of exposure (mGy/WLM) was estimated assuming the damage was related to absorbed dose or to changes in cell sensitivity and ranged from 1.13 to 1.34 for deep lung epithelial cells, 0.47 to 1.09 for deep lung fibroblasts, 0.34 to 0.67 for tracheal epithelial cells and 0.18 to 0.33 for nasal epithelial cells. Biological dosimetry can be used to relate exposure to damage, compare dosimetric units and validate physical dosimetry models. This approach can be applied to any inhaled material capable of producing biological damage.

Internal dose estimation including the nasal cavity and major airway for continuous inhalation of C15O2, 15O2 and C15O using the thermoluminescent dosimeter method

In the steady state method, 15O-labeled gases (C15O2, 15O2 and C15O) are administered to the body by continuous inhalation in various clinical PET studies. During inhalation, the nasal cavity and major airway may obtain a substantial amount of dose, being the source organs as well as the target organs. The internal absorbed dose to those organs and their contribution to the other target organs have not been calculated by the MIRD method. To calculate the internal dose in the MIRD method, the S values, the absorbed doses per unit of cumulated activities from nasal cavity and major airway to the other organs and vice versa, are needed, and these values are not available.

METHODS

In this study, we introduced a mathematical model of the nasal cavity and major airway to calculate their S values to 23 target organs and from 11 source organs to them. Individual experiments were performed to measure the total uptake percentage and body surface doses of 15O-labeled gases from continuous inhalation.

RESULTS

Using the body surface doses measured by thermoluminescent dosimeters, the cumulated activities of 11 source organs were estimated with the mathematical transformation method, and then the internal absorbed doses in 23 target organs were calculated by the MIRD method. Our experimental results were compared with the other results, and good agreements were observed.

CONCLUSION

Among the target organs, the critical organ is the airway, and the absorbed dose is 2.57 x 10(-2) mGy.MBq-1.

Comparative clastogenic sensitivity of respiratory tract cells to gamma rays

To understand the relationships between exposure and damage to different cell populations in the respiratory tract, methods were developed to culture deep-lung fibroblasts and epithelial cells from the nose, trachea and deep lungs. Female F-344 Fischer and male Wistar rats were exposed to 1-5 Gy of 60Co gamma rays at a dose rate of 0.4 Gy/min. Cells were isolated for short-term culture, and the incidences of binucleated cells and micronuclei were determined. The incidences of micronuclei were determined in cytochalasin-B-induced binucleated cells at 72 h for nasal and tracheal tissue and 96 h for deep-lung fibroblasts and epithelial cells. Maximum frequencies of binucleated cells were found in the control nonirradiated cells at these harvest times, and the frequencies were not significantly affected at these harvest times by radiation exposure. No significant differences were found in the frequencies of micronuclei induced in the nasal epithelial cells isolated from female F-344 Fischer or male Wistar rats. Fibroblasts cultured in different media and isolated from either female F-344 Fischer or male Wistar rats also showed a similar frequency of micronuclei. Over the doses tested, the frequency of micronuclei in the respiratory tract cells increased linearly with the dose. The slopes were 92.2 +/- 9.2, 76.2 +/- 7.9, 32.8 +/- 2.4 and 28.7 +/- 3.4 micronuclei/1000 binucleated cells/Gy for deep-lung epithelial cells, deep-lung fibroblasts, tracheal epithelial cells and nasal epithelial cells, respectively. Deep-lung epithelial or fibroblast cells were about two to three times as sensitive for elastogenic damage as nasal and tracheal epithelial cells. The measurement of micronuclei in isolated respiratory tract cells is very useful in assessing cytogenetic damage induced in different cell types by radiation.

Deposition of monodisperse particles in hollow models representing adult and child-size tracheobronchial airways

A series of experiments was performed to determine deposition efficiencies of four sizes of radiolabeled monodisperse particles in custom-made hollow tracheobronchial models. The particles had geometric diameters of about 1, 5, 10, and 15 microm. The tracheobronchial models, consisting of a trachea and two or more additional generations, had dimensions representative of a typical adult, a 7-y-old child, and a 4-y-old child; the child-size models were appropriately scaled-down replicas of the adult-size model. Each deposition experiment was conducted using a steady inspiratory airflow representative of low physical activity for the appropriate age of individual: 20 L min(-1) for the adult; 9 L min(-1) for the 7-y-old; 5.5 L min(-1) for the 4-y-old. The results indicate that deposition efficiency of the particles increased substantially (up to 35 times) in all three models as particle diameter increased from 1-15 microm, undoubtedly as a result of particle impaction and sedimentation-related phenomena. An analysis of variance demonstrated the occurrence of statistically-significant (p < 0.05) main effects of hollow model size and particle size; the interaction between the two parameters was also significant. In general, deposition efficiencies of the various sizes of particles were greater in the child-size models than in the adult-size model; this effect may have risk assessment implications. In addition, the results obtained experimentally agreed more closely with those predicted using a radiation-protection mathematical particle deposition formulation as the particle size increased for each of the sizes of models.

The infeasibility of using ten-ring irradiated grafts for tracheal allotransplantation even with omentopexy

In our previous study, we demonstrated that high-dose 60Co irradiation was able to prevent rejection of canine tracheal allografts. To determine the maximum possible length of these grafts, in the present study we attempted to transplant five-ring and ten-ring tracheal allografts in two groups of five dogs each. Either five or ten rings were excised from donor tracheas and irradiated with 100,000 cGy of 60Co. The irradiated tracheal grafts were transplanted to replace either five- or ten-ring sections of the mediastinal tracheas removed from the recipient dogs. The grafts were covered with omental pedicles and no immunosuppressants were used. Graft incorporation was achieved in four of the five dogs in the five-ring groups, and three of these dogs survived for more than 700 days. However, four of the five animals in the ten-ring group died from tracheostenosis accompanied by ischemia within 3 weeks. These findings demonstrate the impossibility of performing ten-ring tracheal allotransplantation using irradiated grafts, even with omentopexy.

Effect of inducers of lipid peroxidation on the behavior of ciliated epithelial cells

Television microscope and original image treatment system were used for monitoring and recording the ciliary activity (beat frequency) of gill ciliated epithelia of the mussel Mytilus edulis (Bivalvia) and of the rat tracheal ciliated epithelia in response to the following prooxidants: H2O2, Fe+2, Fe+2 + ascorbic acid and NADP-H + ADP + Fe+2. Mussel ciliated cells proved to be more sensitive to the influence of the prooxidants than rat cells. The reactions of ciliated epithelial cells of mollusks and rats to the inducers of lipid peroxidation were not similar to behavioral responses of these cells under the action of low-dose ionizing radiation.

[State of the lymphoid tissue of tracheobronchial lymph nodes in rats after incorporation in respiratory organs of low-transportable Pu-239]

After single inhalation exposure of rats to low transportable 239Pu the alpha-irradiation doses in tracheo-bronchial lymph nodes (TBLN) were one order of magnitude lower than those in lung. The reduction of cell population in TBLN was observed in late (12-18 month after) post-inhalation period. Dose-response curve for the reduction (as a whole for 12 month) were presented as a line function. Functional abilities of these cells were less damaged and observed in different periods after inhalation. As one of the probable mechanisms of different radiation damage to cells in TBLN population, a variety in their spatial distribution is discussed.

Ex vivo light dosimetry and Monte Carlo simulations for endobronchial photodynamic therapy

The light distribution during photodynamic therapy of the bronchial tree has been estimated by measuring the fluence rate in ex vivo experiments on dissected pig bronchi. The trachea was illuminated (630 nm) with a cylindrical diffuser and the fluence rate was measured with a fibre optic isotropic probe. The experiment with the diffuser on the central axis was also simulated with Monte Carlo techniques using the optical properties that were determined with a double-integrating-sphere set-up. The results from ex vivo experiments and the Monte Carlo simulations were found to agree within the error of measurement (15%), indicating that the Monte Carlo technique can be used to estimate the light distribution for varying geometries and optical properties. The results showed that the light fluence rate in the mucosa of the tracheal tract may increase by a factor of six compared to the fluence rate in air (in the absence of tissue). This is due to the scattering properties of the tissue and the multiple reflections within the cavity. Further ex vivo experiments showed that the positioning of the diffuser is critical for the fluence rate in the lesion to be treated. When the position of the diffuser was changed from the central axis to near the lesion, the fluence rate in the mucosa increased significantly by several orders of magnitude as compared to the initial (central) illumination. The inter- and intraspecimen variations in this increase were large (+/- 35%) because of variations in optical and geometrical properties and light source positioning, respectively. These variations might cause under- or overdosage resulting in either insufficient tumour necrosis or excessive normal tissue damage.