Assessment of radiation-induced otitis media in patients with parotid gland malignancy.

BACKGROUND: Otitis media with effusion (OME) is a known side effect of radiation therapy in patients with head and neck cancer. AIMS/OBJECTIVES: To investigate the incidence rate and clinical course of radiation-induced OME, we have reported on the long-term characteristics of OME in patients with parotid gland malignancy. MATERIAL AND METHODS: This cohort study assessed 200 patients who underwent post-parotidectomy radiation therapy from January 2010 to December 2019 in a tertiary referral center. Postoperative radiation therapy was performed at 6 weeks post-surgery. Serial magnetic resonance images were collected to detect otitis media. Two blinded otologists individually assessed data from radiation therapy initiation to 36 months of post-radiation therapy. RESULTS: A total of 121 patients were enrolled (male, 61 [50.4%]; mean age, 46.98 ± 15.69 years), of which 14 developed otitis media (11.6%) within 6 months after radiation therapy. Spontaneous remission occurred without intervention within 1 year, excluding one patient who sustained otitis media for 2 years. CONCLUSIONS AND SIGNIFICANCE: Radiation-induced OME occurred in 11.6% of patients and it remitted within 1 year without intervention. Therefore, cooperation between otolaryngologists and radiation oncologists is required and invasive intervention should be considered with careful risk-benefit evaluation.

Age and Gender Effects on Wideband Absorbance in Adults With Normal Outer and Middle Ear Function.

PURPOSE: This study examined the effects of age and gender on wideband energy absorbance in adults with normal middle ear function. METHOD: Forty young adults (14 men, 26 women, aged 20-38 years), 31 middle-aged adults (16 men, 15 women, aged 42-64 years), and 30 older adults (20 men, 10 women, aged 65-82 years) were assessed. Energy absorbance (EA) data were collected at 30 frequencies using a prototype commercial instrument developed by Interacoustics. RESULTS: Results showed that the young adult group had significantly lower EA (between 400 and 560 Hz) than the middle-aged group. However, the middle-aged group showed significantly lower EA (between 2240 and 5040 Hz) than the young adult group. In addition, the older adult group had significantly lower EA than the young adult group (between 2520 and 5040 Hz). No significant difference in EA was found at any frequency between middle-aged and older adults. Across age groups, gender differences were found with men having significantly higher EA values than women at lower frequencies, whereas women had significantly higher EA at higher frequencies. CONCLUSIONS: This study provides evidence of the influence of gender and age on EA in adults with normal outer and middle ear function. These findings support the importance of establishing age- and gender-specific EA norms for the adult population.

Imaging Optimization of Temporal Bones With Cochlear Implant Using a High-resolution Cone Beam CT and the Corresponding Effective Dose.

OBJECTIVE: To evaluate the impact of tube voltage, tube current, pulse number, and magnification factor on the image quality of a novel experimental set-up and the corresponding radiation. MATERIALS AND METHODS: Six human temporal bones with cochlear implant were imaged using various tube voltages, tube currents, pulse numbers, and magnification. The effect of radiation was evaluated using a metaloxide semiconductor field-effect transistor (MOSFET) dosimeter device on an anthropomorphic RANDO RAN102 male head phantom. A copper and aluminum combination filter was used for hardware filtration. RESULTS: Overall, 900 frames, 11 mA, and 88 kV provided the best image quality. In temporal bones imaged with the optimized parameters, the cochlea, osseous spiral lamina, modiolus, stapes, round window niche, and oval window landmarks were demonstrated with anatomic structures still fully assessable in all parts and acceptable image quality. The most dominant contributor to the effective dose was bone marrow (36%-37 %) followed by brain (34%-36%), remainder tissues (12%), extra-thoracic airways (7%), and oral mucosa (5%). CONCLUSIONS: By increasing the number of frames, the image quality of the inner ear details obtained using the novel cone-beam computed tomography improved.

Radiation-induced middle ear and mastoid opacification in skull base tumors treated with radiotherapy.

PURPOSE: To assess the incidence of middle ear (ME) pathology in patients treated with radiotherapy (RT) for skull base tumors. METHODS AND MATERIALS: A retrospective analysis of 61 patients treated with RT between 2003 and 2008 for skull base tumors was conducted. Clinical outcomes and demographics were reviewed. Dose-volume histogram analysis was performed on the eustachian canal (EC), ME, mastoid air cells, vestibular apparatus, cochlea, internal auditory canal, lateral and posterior nasopharynx, and temporal lobes to relate doses to symptoms and radiographic change. Otomastoid opacification was rated 0 (none), 1 (mild), 2 (moderate), and 3 (severe) by a neuroradiologist blinded to clinical outcomes and doses. RESULTS: The median prescribed dose was 50.4 Gy (range, 14-74 Gy). The ME mean dose was 14 Gy and 34 Gy for Grade 0-1 and 2-3 opacification, respectively (p<0.0001). The mean mastoid dose was 10 Gy and 26 Gy for Grade 0-1 and 2-3, respectively (p<0.0001). The mean EC dose was 17 Gy and 32 Gy for Grade 0-1 and 2-3, respectively (p=0.0001). Otomastoid opacification resolved in 17 of 40 patients (42.5%), at a mean of 17 months after RT (range, 2-45 months). Otomastoid opacification persisted in 23 of 40 patients (57.5%), with a mean follow-up of 23 months (range, 2-55 months). Multivariate analysis showed that mastoid dose>30 Gy (odds ratio=28.0, p<0.001) and posterior nasopharynx dose of >30 Gy (odds ratio=4.9, p=0.009) were associated with Grade 2-3 effusions, whereas other factors including dose to EC and ME were not significant. CONCLUSIONS: A mean RT dose>30 Gy to the mastoid air cells or posterior nasopharynx is associated with increased risk of moderate to severe otomastoid opacification, which persisted in more than half of patients at 2-year follow-up.

Improved dosimetric and clinical outcomes with intensity-modulated radiotherapy for head-and-neck cancer of unknown primary origin.

PURPOSE: To compare differences in dosimetric, clinical, and quality-of-life endpoints among a cohort of patients treated by intensity-modulated radiotherapy (IMRT) and conventional radiotherapy (CRT) for head-and-neck cancer of unknown primary origin. METHODS AND MATERIALS: The medical records of 51 patients treated by radiation therapy for squamous cell carcinoma of the head and neck presenting as cervical lymph node metastasis of occult primary origin were reviewed. Twenty-four patients (47%) were treated using CRT, and 27 (53%) were treated using IMRT. The proportions of patients receiving concurrent chemotherapy were 54% and 63%, respectively. RESULTS: The 2-year estimates of overall survival, local-regional control, and disease-specific survival for the entire patient population were 86%, 89%, and 84%, respectively. There were no significant differences in any of these endpoints with respect to radiation therapy technique (p>0.05 for all). Dosimetric analysis revealed that the use of IMRT resulted in significant improvements with respect to mean dose and V30 to the contralateral (spared) parotid gland. In addition, mean doses to the ipsilateral inner and middle ear structures were significantly reduced with IMRT (p<0.05 for all). The incidence of severe xerostomia in the late setting was 58% and 11% among patients treated by CRT and IMRT, respectively (p<0.001). The percentages of patients who were G-tube dependent at 6 months after treatment were 42% and 11%, respectively (p<0.001). CONCLUSIONS: IMRT results in significant improvements in the therapeutic ratio among patients treated by radiation therapy for head-and-neck cancer of unknown primary origin.

A study of middle ear function in the treatment of nasopharyngeal carcinoma with IMRT technique.

PURPOSE: This study evaluates the difference in damage to middle ear function with CRT and IMRT techniques in the treatment of nasopharyngeal carcinoma (NPC). We explore the isthmus of the Eustachian tube (ET) as the key anatomic site for the prevention of radiation-induced otitis media with effusion. METHODS AND MATERIALS: Eighty-two patients with NPC were divided into two groups: 40 patients treated with CRT and 42 patients treated with IMRT. The difference between dosage over the middle ear cavity and the isthmus of the ET was evaluated in both CRT group and IMRT group. All patients underwent hearing tests including pure tone audiometry and impedance audiometry before and after RT. RESULTS: The dosage difference to the middle ear cavity and isthmus between these two groups was statistically significant (p<0.05). The difference in hearing test results between these two groups was also statistically significant (p<0.05). If we limited the dose to the middle ear cavity under 34 Gy and the dose to the isthmus under 53 Gy with IMRT, we may decrease radiation-induced OME even with the larger 2.25 Gy fraction size. CONCLUSIONS: IMRT may have better protected the middle ear function compared with the CRT technique, even with larger fraction sizes than for the conventional CRT technique.

Treatment and outcome of advanced external auditory canal and middle ear squamous cell carcinoma.

This is a retrospective study to evaluate the outcomes and complications of combined treatment, surgery with or without adjunctive intraoperative radiotherapy, of locally advanced temporal bone squamous cell carcinoma. A series of 17 patients with locally advanced squamous cell carcinoma of the temporal bone were treated between September 2002 and February 2007. Eleven patients had primary tumors, and 6 patients had recurrences. According to the University of Pittsburgh staging system, 5 patients were stage II (T2 N0), 6 patients were stage III (5, T3 N0 and 1, T1 N1), and 6 patients were stage IV (5, T3 N2b and 1, T4 N0). All patients underwent lateral temporal bone resection and pedicle flap reconstruction. Eight patients received intraoperative and postoperative radiotherapies, 4 patients underwent postoperative radiation alone, whereas 5 patients did not receive any adjunctive treatment. Median follow-up was 29.5 months. No major complications were observed. No patients were found to have residual gross tumor. Disease-free survival was 73.3%, and overall survival was 75.6%. Radical external auditory canal and/or middle ear canal resection is of utmost importance to obtain a good surgical outcome. Postoperative radiotherapy is necessary to obtain good local control; no major adverse effects were observed in the intraoperative radiotherapy patients. The incidence of major complication is minimal after pedicle flap reconstruction.

Analysis of anatomical factors controlling the morbidity of radiation-induced otitis media with effusion.

PURPOSE: To analyze the anatomical factors controlling the morbidity of radiation-induced otitis media with effusion (OME) and determine how to best preserve middle ear function when treating nasopharyngeal carcinoma (NPC). MATERIALS AND METHODS: Forty patients with nasopharyngeal carcinoma undergoing 3-D radiotherapy (RT) planning and curative RT were analyzed retrospectively. The difference in dosage over the middle ear cavity and the isthmus of the Eustachian tube (ET) was evaluated. Pure tone audiometry and impedance audiometry tests were performed before and after RT. RESULTS: Mean dosages over the isthmus of the ET for acoustic impedance and pure tone audiometry were recorded. Differences in dosage among the three classifications of unchanged, improved, and worsened ears were statistically significant. CONCLUSION: There was a correlation between the morbidity of radiation-induced OME and the radiation dosage over the middle ear cavities. Decreased OME morbidity was observed when the dosage over the isthmus of the ET was below 52 Gy and the dosage over middle ear cavity was below 46 Gy.

High-resolution numerical model of the middle and inner ear for a detailed analysis of radio frequency absorption.

In order to enable a detailed analysis of radio frequency (RF) absorption in the human middle and inner ear organs, a numerical model of these organs was developed at a spatial resolution of 0.1 mm, based on a real human tissue sample. The dielectric properties of the liquids (perilymph and endolymph) inside the bony labyrinth were measured on samples of ten freshly deceased humans. After inserting this model into a commercially available numerical head model, FDTD-based computations for exposure scenarios with generic models of handheld devices operated close to the head in the frequency range 400-3700 MHz were carried out. For typical output power values of real handheld mobile communication devices the obtained results showed only very small amounts of absorbed RF power in the middle and inner ear organs. Highest absorption in the middle and inner ear was found for the 400 MHz irradiation. In this case, the RF power absorbed inside the labyrinth and the vestibulocochlear nerve was as low as 166 microW and 12 microW, respectively, when considering a device of 500 mW output power operated close to the ear. For typical mobile phone frequencies (900 MHz and 1850 MHz) and output power values (250 mW and 125 mW) the corresponding values of absorbed RF power were found to be more than one order of magnitude lower than the values given above. These results indicate that temperature-related biologically relevant effects on the middle and inner ear, induced by the RF emissions of typical handheld mobile communication devices, are unlikely.

Ototoxicity after radiotherapy for head and neck tumors.

PURPOSE: To investigate the incidence of radiation-induced ototoxicity according to the total dose delivered to specific parts of the auditory system, fractionation, and chemotherapy. METHODS AND MATERIALS: Records of 325 patients treated for primary extracranial head and neck tumors with curative intent who received radiotherapy between 1964 and 2000 (median follow-up, 5.4 years) were retrospectively reviewed. Reconstructions of the treatment plans were generated to estimate the doses received by components of the auditory system. RESULTS: Radiotherapy-induced morbidity developed in 41.8% of patients (external ear, 33.2%; middle ear, 28.6%; and inner ear, 26.8%). Univariate/multivariate analyses indicate that total dose received by parts of the auditory system seem to be significant, though fractionation and chemoradiation may contribute to the incidence of ototoxicities. Sensorineural hearing loss (SNHL) was observed in 49 patients (15.1%). Univariate and multivariate analyses indicated that age (p = 0.0177 and p = 0.005) and dose to cochlea (p < 0.0001 and p < 0.0001) were significant, and chemoradiation (p = 0.0281 and p = 0.006) may increase the incidence of SNHL. Five-year and 10-year actuarial risk of clinically overt SNHL increased to 37% (p > 0.0001) above doses of 60.5 Gy compared to 3% at doses below 60.5 Gy. For patients treated with adjuvant chemotherapy, clinically overt SNHL increased to 30% compared to 18% in the no-chemotherapy group at 10 years (p = 0.0281). CONCLUSION: Radiotherapy toxicity was observed in all parts of the auditory system with median doses for incidence varying between 60 Gy to 66 Gy. Total dose to organ seems to be a significant factor though fractionation and chemo-radiation may contribute to ototoxicities.

Primary radical radiotherapy for squamous cell carcinoma of the middle ear and external auditory cana--an historical series.

AIMS: To evaluate patients treated with radical radiotherapy alone for squamous cell carcinoma of the middle ear (MEC) and external auditory canal (EAC) in terms of freedom from local recurrence, cancer-specific survival and morbidity. MATERIALS AND METHODS: Between 1965 and 1988, 123 patients were treated, 70 with MEC and 53 with EAC. The median age was 64 years (range 21-86) and 78% presented as late stage. The median dose was 55 Gy (range 39-55) in 16 once daily fractions (range 13-21). RESULTS: At 5 and 10 years, respectively, freedom from local recurrence was 56 and 56%, disease-free survival was 45 and 43%, cancer-specific survival was 53 and 51%, and overall survival was 40 and 21%. Cancer-specific survival was significantly worse with late stage as opposed to early stage (P = 0.0026), as was local recurrence (P = 0.0088). No differences in survival and local control were seen according to site. Radionecrosis developed in 6% of patients. CONCLUSIONS: Combined treatment using radiotherapy and radical surgery is often favoured. This large series shows that radical radiotherapy achieves comparable results in terms of local control and cancer-specific survival. Our radiotherapy regimen is now 55 Gy in 20 daily fractions to reduce late morbidity. Radiotherapy alone remains a viable option, especially as morbidity can be minimised and target volume delineation optimised using computer planning in the future.

[Morphological observation of amifostine's protective effect on radiation induced early middle ear injury].

OBJECTIVE: To assess the radio-protective effect of amifostine on the middle ear in animal models by observing the morphological changes of middle ear mucosa. METHOD: Adult guinea pigs (n=38) were divided into the radiation group, the radiation-amifostine group and the control group. The first two groups were exposed to total 45 Gy of Gamma radiation which was administered to the right ear of each guinea pig with 3.0 Gy/fraction, 5 times per week, using a cobalt-60 machine. And the radiation+amifostine group was pretreated with the radio protector amifostine 100 mg/kg intra-peritoneally 30 min before each fraction of radiation. Sterile saline was administered intra-peritoneally in radiation group before ear irradiation. Two normal guinea pigs given no treatment were chosen as the control. The tympanic bullas were removed and the mucosae was processed for light microscope and scanning electron microscope examination on the 2nd and 30th days post irradiation to observe mucosa thickness, leukocyte and cilia. RESULT: Light microscope and scanning transmission electron microscope examination showed in radiation groups that the middle ear effusion occurred; the cilia and micro cilia fell off, fused or collapsed; their directions changed; the mucosa became thicker; and leukocytes were also found infiltrating into the mucosa. On the 30th day,the damage was more serious. As comparison, there was no manifest damage of the middle ear mucosa in radiation+amifostine group. The mucosa thickness and the leukocyte quantity of radiation group were obviously higher than that of radiation+amifostine group (P < 0.01). CONCLUSION: The middle ear mucosa was found to change over time after irradiation. Amifostine has a protective effect on radiation induced early middle ear injury.

Epithelial internalization of superparamagnetic nanoparticles and response to external magnetic field.

Superparamagnetic magnetite nanoparticles (MNP) coated with silica were synthesized and chronically implanted into the middle ear epithelial tissues of a guinea pig model (n=16) for the generation of force by an external magnetic field. In vivo limitations of biocompatibility include particle morphology, size distribution, composition and mode of internalization. Synthesis of MNP was performed using a modified precipitation technique and they were characterized by transmission electron microscopy, X-ray diffractometry and energy dispersive spectroscopy, which verified size distribution, composition and silica encapsulation. The mechanism for internalizing 16+/-2.3 nm diameter MNP was likely endocytosis, enhanced by magnetically force. Using sterile technique, middle ear epithelia of tympanic membrane or ossicles was exposed and a suspension of particles with fluoroscein isothiocyanate (FITC) label applied to the surface. A rare earth, NdFeBo magnet (0.35 T) placed under the animal, was used to pull the MNP into the tissue. After 8 days, following euthanasia, tissues were harvested and confocal scanning laser interferometry was used to verify intracellular MNP. Displacements of the osscicular chain in response to an external sinusoidal electromagnetic field were also measured using laser Doppler interferometry. We showed for the first time a physiologically relevant, biomechanical function, produced by MNP responding to a magnetic field.

[Carcinoma of the external auditory canal and middle ear: therapeutic strategy and follow up]. / Therapeutisches Management von Gehörgangs- und Mittelohrkarzinomen.

BACKGROUND: Carcinomas of the external auditory canal (EAC) and the middle ear are rare and considered to have a poor prognosis. The recommended therapeutic strategy consists of surgical excision and postoperative radiotherapy. However, there are different opinions about the extend of the primary operation. PATIENTS AND METHODS: A series of 21 patients with carcinoma of the EAC and middle ear were treated at the ENT-Department of the Hospital Fulda from 1985 to 2003. Their records and radiologic findings were reviewed retrospectively with particular reference to tumor type and size, its relation to surrounding tissues, surgical procedures and radiation techniques. The tumors were staged according to the modified Pittburgh staging system for temporal bone carcinomas. The average follow-up time was 6.2 years (range 0.2 - 18.75). RESULTS: 17 patients suffered from carcinoma of the EAC, 4 carcinomas were primarily located in the middle ear. There were 15 squamous cell carcinomas, 3 adenoidcystic carcinomas, 2 adenocarcinomas and one mucoepidermoid carcinoma. 12 patients came primarily to our institution and were staged as follows: pT1 (n = 2), pT3 (n = 2), pT4 (n = 8). 8 patients showed up with recurrent or residual tumors (all of T3 or T4 stage). One patient could not be classified. In 5 cases the tumor was inoperable. These patients underwent combined chemoradiation therapy. All other 16 patients were operated and most of them received adjuvant radiation therapy. In the group of patients who were primarily operated overall 5-year survival rate was 100 %. In contrast, patients who's recurrent or residual tumors were resected had a 5-year survival rate of only 33 %. Patients who received combined chemoradiation therapy showed a 2-year survival rate of 75 %. CONCLUSION: Carcinoma of the EAC and middle ear should be treated primarily by a lateral or subtotal temporal bone resection stage dependent combined with a parotidectomy as well as a neck dissection. Local resection of the EAC is not sufficient, not even in T1 tumors. As from stage T2, in cases of recurrent tumor removal and questionable free margins as well as in cases with lymph node metastases an adjuvant radiation therapy should be added. The most important survival factor is removal of the primary tumor with histologically clear margins.

Radiation-induced otitis media--study of a new test, vestibular-evoked myogenic potential.

PURPOSE: Excluding the radiation history, current physical examination and audiovestibular function tests fail to differentiate radiation-induced otitis media (ROM) from chronic otitis media (COM). This study applied the newly developed vestibular-evoked myogenic potential (VEMP) test to investigate whether the VEMP test can be of help in differentiating between them. METHODS AND MATERIALS: Fourteen irradiated nasopharyngeal carcinoma (NPC) patients with ROM (18 ears) and 14 age-matched, and gender-matched patients with COM (18 ears) were enrolled. Each patient underwent stimulation with a short tone burst initially, and then by tapping the forehead using a tendon hammer. To define the effect of the neck soft tissue on the VEMP response further, an additional two groups (10 non-NPC patients with ROM but no neck fibrosis/edema and 10 non-NPC patients without ROM but with neck fibrosis/edema) were included for comparison. RESULTS: The occurrence of normal VEMPs in the ROM ears (33%) did not differ significantly from that in the COM ears (56%) by tone-burst stimulation. However, using tapping evocation, most (89%) COM ears revealed normal VEMPs, and most (61%) ROM ears demonstrated delayed VEMPs. Furthermore, most (90%) non-NPC patients with ROM but no neck fibrosis/edema revealed delayed or absent VEMPs. In contrast, all non-NPC patients with neck fibrosis/edema but no ROM demonstrated normal VEMPs bilaterally, implying that the effect of neck soft tissue on the VEMP response is less. CONCLUSION: Through tapping evocation, most COM ears revealed normal VEMPs, and most ROM ears demonstrated delayed VEMPs, indicating that ROM is different from COM because of the larger affected areas such as retrolabyrinthine or brainstem involvement. This result can explain why grommet insertion or tympanoplasty is not beneficial to postirradiated ears, possibly because both operations spare the inflammation outside the middle ear cavity.

Radiotherapy-induced ear toxicity.

Despite their particular functional consequences, radiotherapy-induced ear injuries remain under-evaluated and under-reported. These reactions may have acute or late character, may affect all structures of the hearing organ, and result in conductive, sensorineural or mixed hearing loss. Up to 40% of patients have acute middle ear side effects during radical irradiation including acoustic structures and about one-third of patients develop late sensorineural hearing loss (SNHL). Total radiotherapy dose and tumour site seem to be among the most important factors associated with the risk of hearing impairment. Thus, reduction in radiation dose to the auditory structures should be attempted whenever possible. New radiotherapy techniques (3-dimensional conformal irradiation, intensity modulated radiotherapy, proton therapy) allow better dose distribution with lower dose to the non-target organs. Treatment of acute and late external otitis is mainly conservative and includes the anti-inflammatory agents (applied topically and systematically). Post-radiation chronic otitis media and the eustachian tube pathology may be managed with tympanic membrane incision with insertion of a tympanostomy tube (grommet), although the benefit of such approach is controversial and some authors advocate a more conservative approach. In these patients the functional deficit can be alleviated by application of bone conduction hearing aids such as, e.g., the bone anchored hearing aid (BAHA). There is no standard therapy for post-irradiation sudden or progressive SNHL yet corticosteroid therapy, rheologic medications, hyperbaric oxygen or carbogen therapy are usually employed (as for idiopathic SNHL), although controversial data on the efficacy of these treatment modalities have been published. In selected cases with bilateral profound hearing loss or total deafness, cochlear implants may prove effective. Further improvements in radiotherapy techniques and progress in otologic diagnostics and therapy may allow better prevention and management of radiation-related acoustic injury.

[Middle ear adenoma: a case report]. / Przypadek gruczolaka ucha srodkowego.

Middle ear adenoma (MEA) is a rare neoplasm with benign clinical behavior. The immunohistochemical and ultrastructural studies revealed the mixed, bidirectional mucinous and neuroendocrine character. These tumors have been known by many different names, reflecting the controversies relating to their histogenesis and differentiation. The term middle ear adenoma was proposed by Hyams and Michaels in 1976 and since this time over 100 cases were described in the literature. The most often symptoms of the MEA are the unilateral hearing loss and the tinnitus. MEA should be treated by surgery and very attentive postoperative follow-up. The prognosis of these tumors are good. The histological structure of middle ear adenoma, as well as symptomatology, treatment and clinical behavior are discussed on the basis of the literature. A case of histologically confirmed middle ear adenoma in a 34 year old women is presented.

[The results of treatment of middle ear carcinoma with radiotherapy]. / Wyniki leczenia napromienianiem chorych na raka ucha srodkowego.

We have described results of treatment patients with an extremely rare disease--a middle ear carcinoma. Through 25 years we have treated 37 patients. We recommend surgical treatment immediately supplemented by radiotherapy--because of anatomical difficulties in gaining enough histological margins. The median of survival time was 7 months in the group of palliatively treated patients and 14 months in the group of radically treated patients. Three patients had following complications: a necrosis of retromandibular space and mandibular joint, a purulent otitis media and an osteoporosis of the temporal bone.

Cardiovascular and thermal effects of microwave irradiation at 1 and/or 10 GHz in anesthetized rats.

Relatively large thermal gradients may exist during exposure of an animal to microwaves (MWs), particularly at high frequencies. Differences in thermal gradients within the body may lead to noticeable differences in the magnitude of cardiovascular changes resulting from MW exposure. This study compares the thermal distribution and cardiovascular effects of exposure to a single MW frequency with effects of simultaneous exposure to two frequencies. Ketamine-anesthetized male Sprague-Dawley rats (n = 58) were exposed individually to one of three conditions: 1-GHz, 10-GHz, or combined 1- and 10-GHz MWs at an equivalent whole-body specific absorption rate of 12 W/kg. The continuous-wave irradiation was conducted under far-field conditions with animals in E orientation (left lateral exposure, long axis parallel to the electric field) or in H orientation (left lateral exposure, long axis perpendicular to the electric field). Irradiation was started when colonic temperature was 37.5 degrees C and was continued until lethal temperatures were attained. Colonic, tympanic, left and right subcutaneous, and tail temperatures, and arterial blood pressure, heart rate, and respiratory rate were continuously recorded. In both E and H orientations, survival time (i.e., time from colonic temperature of 37.5 degrees C until death) was lowest in animals exposed at 1-GHz, intermediate in those exposed at 1- and 10-GHz combined, and greatest in the 10-GHz group (most differences statistically significant). At all sites (with the exception of right subcutaneous), temperature values in the 1- and 10-GHz combined group were between those of the single-frequency exposure groups in both E and H orientations. During irradiation, arterial blood pressure initially increased and then decreased until death. Heart rate increased throughout the exposure period. The general, overall patterns of these changes were similar in all groups. The results indicate that no unusual physiological responses occur during multi-frequency MW exposure, when compared with results of single-frequency exposure. Bioelectromagnetics 21:159-166, 2000. Published 2000 Wiley-Liss, Inc.