Radiation exposure during midfacial imaging using 4- and 16-slice computed tomography, cone beam computed tomography systems and conventional radiography.

OBJECTIVES: Radiation doses were determined to balance risks against usefulness of the different modalities available for the imaging of the facial skeleton. METHODS: An Alderson Rando Phantom, armed with lithium fluoride thermoluminescent dosemeters (TLDs) was exposed using a set of four conventional radiographs (orbital view, modified Waters view, orthopantomography, skull posterior--anterior 0 degrees ), two different cone beam computed tomography (CBCT) (NewTom 9000 and Siremobil Iso-C3D), and multislice computed tomography (CT) modalities (Somatom VolumeZoom and Somatom Sensation 16). TLDs from 14 well defined anatomical sites lying within the primary beam as well as the TLD corresponding to the thyroid gland were evaluated. RESULTS: Multislice CT showed the highest exposure values. Exposure levels of the CBCT systems lay between CT and conventional radiography. Dose measurement for the 16-slice CT revealed nearly the same radiation exposure as the 4-slice system when adapted examination protocols were used. CONCLUSIONS: Selection of the most appropriate imaging modality should be performed in view of the delivered doses, required image quality and information and the clinical circumstances.

[Radiation exposure and 3 dimensional imaging options of SIREMOBIL Iso-C(3D) for planning surgical dental interventions]. / Strahlenexposition und dreidimensionale Darstellungsmöglichkeiten des SIREMOBIL Iso-C(3D) zur Planung chirurgischer Zahnsanierungen.

BACKGROUND: Preoperative dental X-ray diagnostics of multimorbid, non compliant patients requiring dental surgery are often insufficient. The SIREMOBIL Iso-C(3D) has made intraoperative 3D imaging available, even for the facial skeleton. This modality was used intraoperatively in two patients referred for surgical dental treatment. Furthermore, radiation exposure of the SIREMOBIL Iso-C(3D), an orthopantomography and a complete dental status was compared. MATERIAL AND METHODS: An Alderson-Rando phantom was exposed to ten cycles of the SIREMOBIL Iso-C(3D) using the fast mode (50 projections). In comparison 28 panoramic views of an Orthophos and 10 sets of 14 dental images using the Oralix DC with a quadrate mask were applied. Twenty-five anatomically defined TLD positions were analyzed. Furthermore, SIREMOBIL Iso-C(3D) was used in one patient by performing 100 projections and in a second patient by performing 50 projections. After DICOM-import in eFilm, axial, coronal, and sagittal reconstructions were evaluated by five examiners regarding defined criteria. RESULTS: The radiation exposure level of the SIREMOBIL Iso-C(3D) was lower than in the complete dental status and only slightly higher in comparison with the orthopantomography, although the system requires the highest number of single projections. Quantitative evaluation of the visualization and recognition of defined structures proved to be very good and good in most points. However, limitations of the system became obvious regarding apical processes. CONCLUSION: Because of the dosimetry results and the visualization of the relevant structures, in patients for whom preoperative images cannot sufficiently be performed, the intraoperative use of the SIREMOBIL Iso-C(3D) as a base examination is justified.

[Radiation exposure of the head, midface and pelvis in multi-slice CT (MSCT): comparison with single-slice CT (SSCT)]. / Strahlenexposition bei der Mehrschicht-Spiral-CT (MSCT) von Kopf, Mittelgesicht und Beckenskelett: Vergleich mit dem Einzeilen-Spiral-CT (SSCT).

PURPOSE: Comparison of the radiation exposure of the head, midface and pelvis in multi-slice CT (MSCT) and single-slice CT (SSCT) for manufacturer-implemented standard protocols. MATERIALS AND METHODS: An anthropomorphic Alderson-Rando phantom equipped with LiF-thermoluminescent dosimeters in the head, neck and pelvic region was examined with different MSCT and SSCT protocols, and the measured organ doses were compared. RESULTS: In comparison with the SSCT protocols, the MSCT protocols delivered about twice the organ dose to the head and pelvis and about eight times the organ dose to the midface. The comparison indicates that the parameters (slice collimation, mAs, pitch) used for the MSCT protocols deliver increased radiation doses. CONCLUSIONS: The current standard MSCT protocols generally lead to higher organ doses to the head, midface and pelvis than the SSCT protocols, raising the question whether using the MSCT protocols recommended by the manufacturer can be justified. The dose parameters should be optimized to achieve an acceptable balance of dose reduction and adequate image quality.

Interstitial high dose rate brachytherapy in locally progressive or recurrent head and neck cancer.

In a retrospective study, 19 patients with progressive or recurrent head and neck cancer which had been treated with interstitial high dose rate brachytherapy were analysed. All of them had been previously treated with external radiation. Initial therapy further included surgery in 9 cases and chemotherapy in 3 patients. Staging according to the TNM system revealed advanced stage tumors in the majority of patients. Interstitial brachytherapy was carried out with the isotope Iridium-192. The applied total dose at the reference isodose varied between 10 and 30 Gy. Application was fractionated once a week. A complete tumor remission was achieved in 5 patients and partial remission in 10 patients. In 4 patients the tumor continued to grow despite brachytherapy. The mean follow-up in our collective was 21 months. The calculated local control rate was 34% at 24 months. The survival rate was 49% at 12 months and 35% at 24 months. Interstitial brachytherapy is recommended as a palliative treatment in preirradiated squamous cell carcinoma with local recurrence or progression.

[Salvage therapy of advanced squamous cell carcinoma of the mouth cavity and oropharynx. Results of interstitial high-dose-rate brachytherapy combined with ablative tumor surgery]. / Salvagebehandlung fortgeschrittener Plattenepithel-karzinome der Mundhöhle und des Oropharynx. Ergebnisse der interstitiellen HDR-Brachytherapie in Kombination mit ablativer Tumorchirurgie.

PURPOSE: The clinical effect of high-dose-rate (HDR) interstitial brachytherapy combined with tumor resection was investigated in this retrospective study on patients with recurrent oral and oropharyngeal squamous cell carcinoma. PATIENTS AND METHODS: Oral and oropharyngeal squamous cell carcinoma in 38 patients were treated over a period of 7 years (1988-1994) by HDR interstitial brachytherapy using Gammamed 12i equipment. Pretreatment of patients in terms of irradiation and surgery differed (33 irradiated with a total dose between 60.0 and 75.6 Gy, including 8 patients with additional surgery; 1 patient with surgery alone, and 4 patients without any pretreatment). Indications for interstitial brachytherapy differed according to individual responses to treatment and medical histories. RESULTS: Interstitial brachytherapy was successful in the majority of patients, i.e. complete remission: 12, partial remission: 19, no change: 2, progression: 5. Local control and overall survival including patients with surgical treatment was 59% and 81% at 6 months and 47% and 49% after 12 months, respectively. CONCLUSION: Interstitial HDR brachytherapy with Iridium 192 is recommended in patients with local recurrences or second primary carcinomas after previous external radiotherapy in the head and neck region. Combination of interstitial brachytherapy and surgery is preferable for these patients.