Radiation exposure of patients in comprehensive computed tomography of the head in acute stroke.

BACKGROUND AND PURPOSE: To assess patient radiation exposure in comprehensive stroke imaging using multidetector row CT (MDCT) combining standard CT of the head, cerebral perfusion (CTP), and CT angiography (CTA) studies. METHODS: Examination protocols for CT and CTA of cerebral and cervical vessels, as well as CTP were simulated using a Somatom Sensation Cardiac 64. Effective doses were derived from measurements with the use of lithium-fluoride thermoluminescent dosimeters (LiF-TLD) at several organ sites using an Alderson-Rando phantom. RESULTS: LiF-TLD measurements resulted in effective doses of 1.7 mSv for CT, 1.9 mSv for CTA of intracranial vessels, and 2.8 mSv for CTA of cervical vessels, respectively. Depending on examination parameters, effective doses varied between 1.1 and 5.0 mSv for cerebral CTP. For CTP, local doses in the area of the primary beam ranged between 114 and 444 mGy. CONCLUSIONS: Comprehensive stroke imaging may result in up to 9.5 mSv with possible local doses of 490 mGy. Although critical doses for organ damage (eg, cataract formation or hair loss) are not reached, physicians need to be aware of possible radiation induced sequelae particularly in repetitive examinations.

[Physical brachytherapy planning]. / Physikalische Brachytherapieplanung.

The treatment of prostate cancer, confined to the gland, with high conformal doses to the target volume and sparing of bladder, rectum and urethra at the same time can be achieved by interstitial brachytherapy. Close cooperation of urologist and radiologist, together with the physical treatment planning have improved the clinical results significantly. The ongoing development of new radioactive isotopes and of dedicated computerized treatment planning systems have resulted in a renaissance of the interstitial treatment. "Preplanning" i.e. preoperative treatment planning can be performed precisely and fast. Improved ultrasound techniques allow during the perineal template guided seed implantation a realtime dose calculation resulting in an improved seed placement. CT- or MRI based "postplanning" guarantees for early postoperative dose documentation and quality assurance. 2-dimensional as well as 3-dimensional dose distributions superposed to anatomical structures and dose volume histograms (DVH) allow for dose optimization and quality decision. 192Ir with high activity is used for the high dose rate (HDR) afterloading treatment as a boost after external radiotherapy. 125I and 103Pd as well are used as permanent implants to boost external irradiation. If fast growing low grade tumors should be treated with 103Pd permanent implant and slow growing tumors with 125I is discussed controversialy. About 50 to 100 seeds are implanted. The implanted patients are allowed to leave the hospital as there is sufficient shielding by the surrounding normal tissue. Postplanning is based on CT- or MRI for dose documentation and quality assurance. For 125I treatments the activity-dose-relation was redefined since 1995 (TG43 protocol). Similar corrections seem to be necessary for 103Pd treatments.

The role of CT simulation in whole-brain irradiation.

PURPOSE: Evidence is growing that incorrect field-shaping is a major cause of treatment failure in whole-brain irradiation (WBI). To evaluate the potential benefits of CT simulation in WBI we compared field-shaping based on 3D CT simulation to conventional 2D simulation. METHODS: CT head scans were obtained from 20 patients. Conventional 2D planning was imitated by drawing the block contours on digitally reconstructed radiographs (DRR) by four radiotherapists. Critical parts of the target and the eye lenses were subsequently marked and planning was repeated using 3D information ("3D planning"). The results of both methods were compared by evaluation of the minimal distance from the field edge according to each site. RESULTS: In conventional planning using DRR, major geographic mismatches (< -3 mm) occurred in the subfrontal region and both eye lenses with 1% each location. Minor mismatches (-3 to 0 mm) predominantly occurred in the contralateral lens (21%), ipsilateral lens (10%), and subfrontal region (9%). Close margins (0-5 mm) were most frequently noted at the contralateral lens (49%), ipsilateral lens (35 %), and the subfrontal region (28%). When 3D planning was used, mismatches were not found. However, close margins were inevitable at the ipsilateral lens (5%), subfrontal region (30%), and contralateral lens (70%). CONCLUSIONS: CT simulation in WBI is significantly superior to conventional simulation with respect to complete coverage of the target volume and protection of the eye lenses. The narrow passage between the ocular lenses and lamina cribrosa represents a serious limitation. These patients are safely identified with CT simulation and can be referred for modified irradiation techniques.

Induction chemotherapy and radiotherapy to avoid mastectomy in stage IIA-IIIA breast cancer.

The aim of the presented protocol was to investigate tumour remission and breast conservation rates with and without flap supported surgery after preoperative chemotherapy, radiotherapy and hyperthermia. 101 patients with stage IIA-IIIA breast cancers were initially treated with chemotherapy, radiotherapy and hyperthermia. 96 patients underwent salvage surgery. Complete pathologic response was not related to tumour diameter at diagnosis, the applied chemotherapy regime, number of chemotherapy cycles, overall radiation treatment time and time interval between radiotherapy and surgery. A breast conserving approach was possible in 55 patients (54%). After a median follow-up of 18 months no patient developed an isolated local recurrence.

[Preoperative irradiation and interstitial radiotherapy-hyperthermia boost in breast tumors > or = 3 cm. The Düsseldorf experience]. / Präoperative Bestrahlung mit interstitiellem Radio-hyperthermie-Boost bei Mammatumoren > or = 3 cm. Düsseldorfer Ergebnisse.

AIM: The aim of this protocol was to investigate breast conservation rates with and without flap-supported surgery after preoperative chemotherapy, radiotherapy and hyperthermia. PATIENTS AND METHODS: One hundred and fifty-eight patients with stage IIA-IV breast cancers were initially treated with chemotherapy, radiotherapy and hyperthermia. Radiation treatment consisted of an interstitial boost of 10 Gy 192Ir-afterloading therapy and a course of external beam radiotherapy of 50 Gy, using 5 x 2 Gy/week. Local hyperthermia with 43.5-44.5 degrees C over 60 minutes was delivered immediately before interstitial radiotherapy. RESULTS: One hundred and forty-two patients underwent salvage surgery. A breast-conserving approach was possible in 74 patients (52%). Fifty-three patients (37%) underwent flap-supported surgery. After a median follow-up of 20 months, one patient developed isolated local recurrence. In 14 cases, locoregional recurrences occurred in combination with distant metastases. CONCLUSION: In about 50%, breast conservation was achieved by chemotherapy, radiotherapy and hyperthermia. The low isolated local recurrence rate of 0.6% (1/158) has to be substantiated by further follow-up.

[Radiotherapy following a breast-preserving operation in breast carcinoma]. / Strahlentherapie nach brusterhaltender Operation beim Mammakarzinom.

Between 1980 and 1988, 116 patients with invasive breast cancer were treated by limited surgery with axillary node dissection followed by radiation therapy. Radiotherapy was performed by individually computerized treatment planning. The target volume dose was 50 Gy to the whole breast followed by an electron boost of 10 Gy to the tumor bed. The median follow-up period was 59 months. The actuarial overall survival rate is 93%, and the disease-free survival 75.2%. Ten (8.6%) breast recurrences occurred. Analysis of clinical and pathological prognostic factors revealed that local control was impaired by young age, negative hormone receptors, G3-4 tumors and intraductal growth. The recurrence rate for T3- and T4-tumors was 12.5%.

Dosimetry and physical treatment planning for iodine eye plaque therapy.

The dosimetry of eye plaques loaded with iodine-125 seeds (type 6702) was performed by means of computer calculations and measurements with thermoluminescent dosimeters (TLD). Measurements of the depth dose distribution (2-25.5 mm) along the transverse axis of a single seed were performed in water equivalent phantom material. The transverse axis attenuation and geometry factor F(r) was obtained by applying a least squares fit to the measured data. Based on the resulting radial dose function, a computer program was developed which calculates dose distributions within the eye for arbitrary loading and placement of the eye plaque. The computational results were verified by TLD measurements in an eye phantom.

[Development and dosimetry of a 125 iodine applicator for brachytherapy of intraocular tumors]. / Entwicklung und Dosimetrie eines 125Jod-Applikators zur Brachytherapie intraokularer Tumoren.

Due to the low gamma energy (27-35 ke V), iodine 125 is especially suitable for brachytherapy of intraocular tumors. 125I is available as encapsulated seeds. Applicators can be individually loaded with these seeds to accommodate the shape of the tumor as much as possible. To measure the depth-dose distribution LiF thermoluminence detectors (TLDs, 1 mm3) are embedded in an RW-1 eye phantom at various distances and directions from the high active plaque positioned at the top of the phantom. To obtain the three-dimensional dose distribution, the TLDs are read after exposure for the appropriate time period. Based on experimental measurements of the 125I plaque, a computer program is developed to calculate the dose distribution within the eye and the radiation time for intraocular tumors. These results are very similar to those obtained when using mathematical equations published in the literature. In summary, three-dimensional dose distribution at various distances from an 125I eye plaque has been experimentally determined using a new method. This is an important prerequisite for introducing 125I plaques into the treatment of intraocular tumors.

[Dosimetry of ruthenium applicators with an eye phantom and small volume thermoluminescence detectors]. / Dosimetrie von Rutheniumapplikatoren mit einem Augenphatom und kleinvolumigen Thermolumineszenzdetektoren (TLD).

Even though 106Ru/106Rh applicators have been in clinical use over more than two decades for the radiotherapy of malignant uveal melanomas, the dosimetry of emitted beta radiation is still a physical problem. The dose rate at the applicator surface and the depth dose in tissue equivalent material can be determined only within +/- 30% error. Using new cubic-shaped thermoluminescence detectors (TLD) with small volume the dose distribution is examined in water equivalent material (RW-1). The spatial resolution is 14 times better compared to the previous technique. From dose measurements in an eye phantom the homogeneity of nuclide deposition and the depth dose distribution of a 106Ru/106Rh applicator are determined.