Biomedical subjects

F Lohr

Publications and source records attributed to F Lohr.

At least 19 recordsLinked to original sources

PubMed2005

IMRT for breast. a planning study.

BACKGROUND AND PURPOSE: To evaluate the performance of ten different treatment-planning systems when intensity modulated (IMRT) plans are designed for breast treatments that include the irradiation of the internal mammary chain. PATIENTS AND METHODS: A dataset of five patients (CT images and volumes of interest) was distributed to design IMRT plans on the ten systems. To minimise biases, the same geometry and clinical planning aims were imposed on the individual plans. Results were analysed in terms of dose distributions and dose volume histograms. RESULTS AND CONCLUSIONS: For target coverage, the volume receiving more than 95% of the prescribed dose ranged from 77% (OTP) to 91% (Eclipse and Pinnacle), the volume receiving more than 107% ranged from 3.3% (Hyperion) to 23.2% (OTP). The mean dose to ipsilateral lung ranged from 13 Gy (Eclipse) to 18 Gy (OTP). The volume of the contralateral breast receiving more than 10 Gy ranged from 3% (Pinnacle) to 26% (Precise). The volume of heart receiving more than 20 Gy ranged from 7% (Eclipse) to 47% (Precise), the maximum significant dose to heart ranged from approximately 27 Gy (XiO) to approximately 49 Gy (Precise). The maximum significant dose to healthy tissue ranged from approximately 51 Gy (Eclipse) to approximately 62 Gy (OTP). It was also possible to show that the treatment geometry proposed here enables to minimise contralateral breast irradiation while keeping minimal ipsilateral lung (or heart) involvement and satisfactory target coverage.

Breast Neoplasms↗

PubMed2004

[Intensity modulated radiotherapy (IMRT) of head and neck tumors. Increased biological effectiveness in high-risk situations by "integrated boost" therapy].

Primary tumors of the paranasal sinuses are rare entities which, because of precarious localization and frequently diffuse propagation into neighbouring cavities and the skull base, pose a significant therapeutic problem. Even after complete surgical resection, local relapses are frequent. Postoperative radiotherapy is therefore usually indicated. Intensity modulated radiotherapy (IMRT) is a new technique that helps creating dose distributions that conform closely to the target volume while maximally sparing the organs at risk. This results in the possibility of applying escalated doses to the target while still keeping the incidence of side effects low. What is especially appealing is the possibility of shaping the dose distribution within the target in such a way that areas with a presumably high tumor cell load receive increased doses, a concept which is best described by the term "integrated boost". We present the case of a patient with a sinunasal carcinoma and describe the implications of the clinical implementation of this technique.

Biopsy↗

PubMed2004

[Optimizing the use of radiotherapy with IMRT and image guided location of advanced prostate cancer].

Intensity modulated radiotherapy (IMRT) combined with recently developed noninvasive image-guided targeting techniques for tumor localization/repositioning provide a means to further improve on conformal radiotherapy of prostate cancer by optimally sparing the rectum. This refined approach may potentially improve treatment results for locally advanced prostate cancer while reducing side effects. This review summarizes the clinical requirements for effective prostate radiotherapy and describes the new technology that helps to better fulfil these requirements. These noninvasive developments, their potential benefit as well as their limitations, together with new data on fractionation sensitivity of prostate cancer that may lead to shortened overall treatment times may be of interest for all physicians treating patients with prostate cancer.

Humans↗

PubMed2001

Effective tumor therapy with plasmid-encoded cytokines combined with in vivo electroporation.

Plasmids may have unique advantages as a gene delivery system. However, a major obstacle is the low in vivo transduction efficiency. In this study, an electroporation-based gene transduction approach was taken to study the effect of interleukin (IL)-2 or IL-12 gene transduction on the growth of experimental murine tumors. Significant intratumoral gene transduction was achieved by electroporation of tumors that had been injected with naked plasmids encoding reporter genes and cytokine genes (IL-2 and IL-12) under the control of a constitutive cytomegalovirus promoter. In addition, significant tumor growth delay could be achieved in a murine melanoma line B16.F10 with the cytokine genes. Most importantly, systemic transgene levels were negligible when compared with intratumoral adenovirus-mediated IL-12 gene delivery, which leads to significantly higher systemic cytokine levels. Therefore, naked plasmid- and in vivo electroporation-mediated cancer gene therapy may be therapeutically efficacious while maintaining low systemic toxicity.

Adenoviridae↗

PubMed2001

Stereotactic single-dose radiation therapy of liver tumors: results of a phase I/II trial.

PURPOSE: To investigate the feasibility and the clinical response of a stereotactic single-dose radiation treatment for liver tumors. PATIENTS AND METHODS: Between April 1997 and September 1999, a stereotactic single-dose radiation treatment of 60 liver tumors (four primary tumors, 56 metastases) in 37 patients was performed. Patients were positioned in an individually shaped vacuum pillow. The applied dose was escalated from 14 to 26 Gy (reference point), with the 80% isodose surrounding the planning target volume. Median tumor size was 10 cm(3) (range, 1 to 132 cm(3)). The morbidity, clinical outcome, laboratory findings, and response as seen on computed tomography (CT) scan were evaluated. RESULTS: Follow-up data could be obtained from 55 treated tumors (35 patients). The median follow-up period was 5.7 months (range, 1.0 to 26.1 months; mean, 9.5 months). The treatment was well tolerated by all patients. There were no major side effects. Fifty-four (98%) of 55 tumors were locally controlled after 6 weeks at the initial follow-up based on the CT findings (22 cases of stable disease, 28 partial responses, and four complete responses). After a dose-escalating and learning phase, the actuarial local tumor control rate was 81% at 18 months after therapy. A total of 12 local failures were observed during follow-up. So far, the longest local tumor control is 26.1 months. CONCLUSION: Stereotactic single-dose radiation therapy is a feasible method for the treatment of singular inoperable liver metastases with the potential of a high local tumor control rate and low morbidity.

Adult↗

PubMed2001

[Stereotactic irradiation of liver metastases].

PURPOSE: A number of minimal-invasive methods have been developed for the treatment of non-resectable liver metastases. A focused high dose can be delivered to a liver tumor with sparing of surrounding normal liver tissue using non-invasive stereotactic techniques. METHODS: Sixty-six metastases were treated stereotactically in 43 patients during a phase 2 trial. RESULTS: There were no major side effects observed. The actuarial local control was 82% after 18 months. The median actuarial survival was 24 months. However, there was a significantly improved survival in patients without additional extrahepatic tumor manifestation at the time of treatment compared to those, who were treated in palliative intention (87% vs. 24% after 18 months, p = 0.001 (log-rank). CONCLUSION: Stereotactic single dose irradiation is a non-invasive and safe treatment option for patients with inoperable liver metastases. Phase III studies will further evaluate this new approach.

Actuarial Analysis↗

PubMed2001

Systemic vector leakage and transgene expression by intratumorally injected recombinant adenovirus vectors.

Interleukin 12 is a heterodimeric cytokine that exhibits potent immunostimulatory effects. It has shown some promise in preclinical and clinical studies but was accompanied by serious systemic toxicity such as flu-like syndromes, a rapid transient leukopenia, elevated liver transaminases, gastrointestinal toxicity, and/or liver dysfunction. Gene therapy with intratumorally injected recombinant adenoviral vectors offers the potential to restrict therapeutic gene expression in the tumor. Here we show that a substantial amount of adenoviral vectors disseminates into the systemic circulation and infects parenchymal organs. We further show that this results in high systemic levels of potentially toxic transgene products. To reduce potential toxicity, we tested an inducible promoter based on the heat shock proteins (hsp70B) and present evidence that high intratumoral levels of a therapeutic transgene can be obtained while systemic expression is reduced to a minimum, increasing the safety of adenovirus-based tumor gene therapy.

Adenoviridae↗

PubMed2000

Prospective evaluation of delayed central nervous system (CNS) toxicity of hyperfractionated total body irradiation (TBI).

PURPOSE: Prospective evaluation of chronic radiation effects on the healthy adult brain using neuropsychological testing of intelligence, attention, and memory. METHODS AND MATERIALS: 58 patients (43 +/- 10 yr) undergoing hyperfractionated total body irradiation (TBI) (TBI, 14.4 Gy, 12 x 1.2 Gy in 4 days) before bone marrow or peripheral blood stem cell transplantation were prospectively included. Twenty-one recurrence-free long-term survivors were re-examined 6-36 months (median 27 months) after completion of TBI. Neuropsychological testing included assessment of general intelligence, attention, and memory using normative, standardized psychometric tests. Mood status was controlled, as well. Test results are given as IQ scores (population mean 100) or percentiles for attention and memory (population mean 50). RESULTS: The 21 patients showed normal baseline test results of IQ (101 +/- 13) and attention (53 +/- 28), with memory test scores below average (35 +/- 21). Test results of IQ (98 +/- 17), attention (58 +/- 27), and memory (43 +/- 28) showed no signs of clinically measurable radiation damage to higher CNS (central nervous system) functions during the follow-up. The mood status was improved. CONCLUSION: The investigation of CNS toxicity after hyperfractionated TBI showed no deterioration of test results in adult recurrence-free patients with tumor-free CNS. The median follow-up of 27 months will be extended.

Adult↗

PubMed2000

Comparison of intensity-modulated radiotherapy with conventional conformal radiotherapy for complex-shaped tumors.

PURPOSE: Conformal and intensity-modulated radiotherapy (IMRT) plans for 9 patients were compared based on characterization of plan quality and effects on the oncology department. METHODS AND MATERIALS: These clinical cases, treated originally with conformal radiotherapy (CRT), required extraordinary effort to produce conformal treatment plans using nonmodulated, shaped noncoplanar fields with multileaf collimators (MLCs). IMRT plans created for comparison included rotational treatments with slit collimator, and fixed-field MLC treatments using equispaced coplanar, and noncoplanar fields. Plans were compared based upon target coverage, target conformality, dose homogeneity, monitor units (MU), user-interactive planning time, and treatment delivery time. The results were subjected to a statistical analysis. RESULTS: IMRT increased target coverage an average of 36% and conformality by 10%. Where dose escalation was a goal, IMRT increased mean dose by 4-6 Gy and target coverage by 19% with the same degree of conformality. Rotational IMRT was slightly superior to fixed-field IMRT. All IMRT techniques increased integral dose and target dose heterogeneity. IMRT planning times were significantly less, whereas MU increased significantly; estimated delivery times were similar. CONCLUSION: IMRT techniques increase dose and target coverage while continuing to spare organs-at-risk, and can be delivered in a time frame comparable to other sophisticated techniques.

Carcinoma, Adenoid Cystic↗

PubMed2000

Enhancement of radiotherapy by hyperthermia-regulated gene therapy.

PURPOSE: Interleukin 12 (IL-12) has shown strong antitumoral effects in numerous pre-clinical studies and appears to act synergistically with radiation in murine tumors. The major impediment to its clinical use has been its systemic toxicity. While using intratumorally injected viral gene therapy vectors encoding IL-12 reduces systemic side effects substantially, elevated systemic transgene levels are still observed because adenovirus can reach the circulation. Further restricting IL-12 expression in the tumor is therefore desirable in a combined radiation and adenovirus mediated cancer gene therapy regimen. METHODS AND MATERILAS: Hyperthermia-regulated gene therapy was tested in a nonimmunogenic B16.F10 melanoma line that is syngeneic with C57BL/6 mice. For hyperthermic gene therapy, an adenoviral vector coding for IL-12 under the control of the promoter of the human heat shock protein 70B (hsp70B) was used. One week after transplantation (at a 5-7 mm diameter), tumors were irradiated with 3 x 11 Gy (mo-we-fri). Adenovirus was injected at 3 x 10(8) pfu/tumor 24 h before the last radiation fraction or 3 days afterwards. Hyperthermia was performed 24 h later at 42.5 degrees C. Growth delay to reaching 3 times initial tumor volume was chosen as the biologic endpoint. IL-12 levels in tumor and serum were determined by using the enzyme-linked immunosorbant assay (ELISA). RESULTS: Adenovirus mediated intratumoral expression of IL-12 under the control of a heat inducible promoter in combination with hyperthermia is almost as effective as that under the control of a constitutive cytomegaly virus (CMV) promoter while systemic transgene levels are substantially reduced with the heat inducible promoter. The response to radiotherapy is improved considerably when combined with heat inducible gene therapy without apparent systemic toxicity. When used as a single dose, applying IL-12 gene therapy after completion of radiotherapy appears to be beneficial. CONCLUSIONS: Hyperthermia-regulated gene therapy in combination with radiation is feasible and therapeutically effective in murine tumors with no apparent systemic toxicity.

Adenoviridae↗

PubMed2000

Conventionally fractionated stereotactic radiotherapy (FSRT) for acoustic neuromas.

PURPOSE: Analysis of local tumor control and functional outcome following conventionally fractionated stereotactic radiotherapy (FSRT) for acoustic neuromas. PATIENTS AND METHODS: From 11/1989 to 9/1999 51 patients with acoustic neuromas have been treated by FSRT. Mean total dose was 57.6 +/- 2.5 Gy. Forty-two patients have been followed for at least 12 months and were subject of an outcome analysis. Mean follow-up was 42 months. We analyzed local control, hearing preservation, and facial and trigeminal nerve functional preservation. We evaluated influences of tumor size, age, and association with neurofibromatosis Type 2 (NF2) on outcome and treatment related toxicity. RESULTS: Actuarial 2- and 5-year tumor control rates were 100% and 97.7%, respectively. Actuarial useful hearing preservation rate was 85% at 2 and 5 years. New hearing loss was diagnosed in 4 NF2 patients. Pretreatment normal facial nerve function was preserved in all cases. Two cases of new or impaired trigeminal nerve dysesthesia required medication. No other cranial nerve deficit was observed. In Patients without NF2 tumor size or age had no influence on tumor control and cranial nerve toxicity. Diagnosis of NF2 was associated with higher risk of hearing impairment (p = 0.0002), the hearing preservation rate in this subgroup was 60%. CONCLUSION: FSRT has been shown to be an effective means of local tumor control. Excellent hearing preservation rates and 5th and 7th nerve functional preservation rates were achieved. The results support the conclusion that FSRT can be recommended to patients with acoustic neuromas where special attention has to be taken to preserve useful hearing and normal cranial nerve function. For NF2 patients, FSRT may be the treatment of choice with superior functional outcome compared to treatment alternatives.

Actuarial Analysis↗

PubMed2000

Conformal radiotherapy of challenging paraspinal tumors using a multiple arc segment technique.

PURPOSE: Target volumes that wrap around the spinal cord are difficult to treat. We present and evaluate a refined multiple arc segment (MAS) technique that is applicable with standard three-dimensional (3D) radiotherapy equipment and may be a solution for facilities that do not yet have full access to intensity-modulated radiotherapy (IMRT). METHODS AND MATERIALS: The presented technique consisted of 13 isocentric coplanar beam's eye view shaped fields, delivered as 20 degrees or 10 degrees arc segments with an integrated multileaf collimator (MLC) using automatic sequential field delivery. Dose-volume histograms (DVH) for this technique were compared to a modified bar-arc technique (MBA) modeled as 30 static fields and to an inverse planned IMRT technique using 7 coplanar, equispaced beams delivered with the same MLC. RESULTS: Compared to the MBA technique, maximum dose and target coverage were similar when using 80% of the maximum dose as the reference dose. However, the MAS technique reduced the maximum doses (to > or = 1% of the organs at risk [OAR]) by 9% for the spinal cord, 17% for the esophagus, and 25% for the trachea, as well as the mean doses. Although inverse planned IMRT could further reduce exposure of OAR except for the spinal cord and improve target coverage, our forward planned MAS technique seems to achieve clinically comparable results. CONCLUSION: Substituting a series of small split-field arc segments for large static fields and using additional narrow paraspinal segments significantly improves the sparing of organs at risk for paraspinal targets. Although these results are not quite as good as those achieved with IMRT, for facilities not yet equipped with inverse treatment planning capability, the presented technique enables dose escalation for primary paraspinal tumors and retreatment of recurrent lesions.

Esophagus↗

PubMed2000

Heat-induced gene expression as a novel targeted cancer gene therapy strategy.

One of the main advantages of gene therapy over traditional therapy is the potential to target the expression of therapeutic genes in desired cells or tissues. To achieve targeted gene expression, we experimented with a new approach based on the long-established phenomenon of the heat shock response. By using the green fluorescence protein as a reporter gene, it was demonstrated that expression of a heterologous gene with a heat shock protein 70 promoter could be elevated to 500-1000-fold over background by moderate hyperthermia (39 degrees C to 43 degrees C) in tissue cultured cells. The heat-induced green fluorescence protein expression was first detectable at 3 h after heating and reached a maximum at 18-24 h. The expression dropped back to baseline within 72 h. In addition, when cells were infected with adenovirus vectors containing the heat-inducible interleukin 12 or tumor necrosis factor alpha genes and then heated (42 degrees C, 30 min), expression was at least 13,600- or 6.8 x 10(5)-fold over background, respectively. Intralesion injection of the interleukin-12-carrying adenovirus vector in a mouse melanoma tumor model caused significant tumor growth delay only with hyperthermia treatment. Our results therefore support heat-induced gene expression as a feasible approach for targeted cancer gene therapy.

Adenoviridae↗

PubMed2000

Extracranial stereotactic radiation therapy: set-up accuracy of patients treated for liver metastases.

PURPOSE: Patients with liver metastases might benefit from high-dose conformal radiation therapy. A high accuracy of repositioning and a reduction of target movement are necessary for such an approach. The set-up accuracy of patients with liver metastases treated with stereotactic single dose radiation was evaluated. METHODS AND MATERIALS: Twenty-four patients with liver metastases were treated with single dose radiation therapy on 26 occasions using a self-developed stereotactic frame. Liver movement was reduced by abdominal pressure. The effectiveness was evaluated under fluoroscopy. CT scans were performed on the planning day and directly before treatment. Representative reference marks were chosen and the coordinates were calculated. In addition, the target displacement was quantitatively evaluated after treatment. RESULTS: Diaphragmal movement was reduced to median 7 mm (range: 3-13 mm). The final set-up accuracy of the body was limited to all of median 1.8 mm in latero-lateral direction (range: 0.3-5.0 mm) and 2.0 mm in anterior-posterior direction (0.8-3.8 mm). Deviations of the body in cranio-caudal direction were always less than the thickness of one CT slice (<5 mm). However, a repositioning was necessary in 16 occasions. The final target shift was median 1.6 mm (0.2-7.0 mm) in latero-lateral and 2.3 mm in anterior-posterior direction (0.0-6.3 mm). The median shift in cranio-caudal direction was 4.4 mm (0.0-10.0 mm). CONCLUSIONS: In patients with liver metastases, a high set-up accuracy of the body and the target can be achieved. This allows a high-dose focal radiotherapy of these lesions. However, a control CT scan should be performed directly before therapy to confirm set-up accuracy and possibly prompt necessary corrections.

Aged↗

PubMed2000

Neurobehavioral toxicity of total body irradiation: a follow-up in long-term survivors.

PURPOSE: Total body irradiation (TBI) in preparation for bone marrow transplantation (BMT) is a routine treatment of hematological malignancy. A retrospective and a prospective group study of long-term cerebral side effects was performed, with a special emphasis on neurobehavioral toxicity effects. METHODS AND MATERIALS: Twenty disease-free patients treated with hyperfractionated TBI (14.4 Gy, 12 x 1.2 Gy, 4 days), 50 mg/kg cyclophosphamide, and autologous BMT (mean age 38 years, range 17-52 years; age at TBI 35 years, 16-50 years; follow-up time 32 months, 9-65 months) participated in a neuropsychological, neuroradiological, and neurological examination. Data were compared to 14 patients who were investigated prior to TBI. Eleven patients with renal insufficiencies matched for sex and age (38 years, 20-52 years) served as controls. In a longitudinal approach, neuropsychological follow-up data were assessed in 12 long-term survivors (45 years, 23-59 years; follow-up time 8.8 years, 7-10.8 years; time since diagnosis 10.1 years, 7.5-14.2 years). RESULTS: No evidence of neurological deficits was found in post-TBI patients except one case of peripheral movement disorder of unknown origin. Some patients showed moderate brain atrophy. Neuropsychological assessment showed a subtle reduction of memory performance of about one standard deviation. Cognitive decline in individual patients appeared to be associated with pretreatment (brain irradiation, intrathecal methotrexate). Ten-years post disease onset, survivors without pretreatment showed behavioral improvement up to the premorbid level. CONCLUSION: The incidence of long-term neurobehavioral toxicity was very low for the present TBI/BMT regimen.

Adolescent↗

PubMed2000

Cataract incidence after total-body irradiation.

PURPOSE: The aim of this retrospective study was to evaluate cataract incidence in a homogeneously-treated group of patients after total-body irradiation (TBI) followed by autologous bone marrow transplantation or peripheral blood stem cell transplantation. METHODS AND MATERIALS: Between 1982 and 1994, a total of 260 patients received either autologous bone marrow or blood stem cell transplantation for hematological malignancy at the University of Heidelberg. Two hundred nine of these patients received TBI in our hospital. Radiotherapy was applied as hyperfractionated TBI, with a median dose of 14.4 Gy in 12 fractions over 4 days. Minimum time between fractions was 4 h. Photons with an energy of 23 MeV were used with a dose rate of 7-18 cGy/min. Ninety-six of the 209 irradiated patients were still alive in 1996; 86 of these patients (52 men, 33 women) answered a questionnaire and could be examined ophthalmologically. The median age at time of TBI was 38.5 years, with a range of 15-59 years. RESULTS: The median follow-up is now 5.8 years, with a range of 1.7-13 years. Cataract occurred in 28/85 patients (32.9%) after a median of 47 months (1-104 months). In 6 of 28 patients who developed a cataract, surgery of the cataract was performed. Whole-brain irradiation prior to TBI had been performed more often in the group of patients developing cataract (14.3%) versus 10.7% in the group of patients without cataract. However, there was no statistical difference (Chi-square, p>0.05). CONCLUSION: Cataract is a common side effect of TBI. Cataract incidence found in our patients is comparable to results of other centers using a fractionated regimen for TBI. To assess the incidence of cataract after TBI, a long-term follow-up is required.

Adult↗

PubMed2000

Combination treatment of murine tumors by adenovirus-mediated local B7/IL12 immunotherapy and radiotherapy.

Failure of local tumor control still poses a problem for radiotherapy and translates into reduced survival. Combining radiation with chemotherapy or other newer modalities has shown promising results. Immunological approaches to tumor therapy have found renewed interest due to improved insight into mechanisms involved in the immune response to tumors. In this paper, we studied tumor growth delay after various combination regimens of locally injected adenovirus constitutively expressing IL12 and B7.1 (AdIL12/B7.1) and fractionated radiotherapy in two nonimmunogenic murine tumor models, 4T1 and B16.F10. Effects of radiation and virus infection on surface antigen expression in these tumor lines were assessed. Mechanisms of action of AdIL12/B7.1 were studied by conducting additional experiments with and without depletion of NK-cells and/or T-cells, and by cytotoxic T-lymphocyte assays, and immunohistochemical evaluation of tumor blood vessels. Both B7.1 and IL12 were effectively expressed in both irradiated and unirradiated 4T1 and B16.F10 tumor cells but did not add significantly to radiation-induced cell killing in vitro. However, local tumor infection by AdIL12/B7.1 after irradiation significantly increases the effectiveness of radiotherapy when applied after completion of radiotherapy. The mechanism appears to be complicated, involving a host of factors that included the ability of IL12 to activate T-cells and NK-cells and to inhibit angiogenesis and the ability of radiation to induce apoptosis or necrosis among tumor cells. These data support the combination of radiotherapy with adenovirus-mediated immunotherapy and suggest that the concept of adding genetic immunotherapy after radiotherapy in a combined regimen merits further study.

Adenoviridae↗

PubMed2000

[First experiences with a noninvasive patient set-up system for radiotherapy of the prostate].

PURPOSE: Highly conformal radiotherapy techniques require precise patient positioning. We report our first experience with a new cast system for fixation of the pelvis during stereotactically guided intensity modulated radiotherapy (IMRT) of the prostate with respect to positioning accuracy of the prostate. MATERIAL AND METHODS: The immobilization device consists of a custom-made wrap-around body cast that extends from the abdomen to the thighs and a separate head mask, both made from Scotchcast, and attaches to a frame for extracranial stereotaxy. Sixteen CT-studies (> or = 25 slices, thickness: 3 mm) of 2 patients who were immobilized for IMRT of prostate tumors were evaluated with respect to set-up accuracy of bony structures and the prostate itself. CT-studies were performed immediately before or after a treatment fraction. Deviations of bony landmarks and anatomical landmarks inside the planning target volume were measured in all 3 dimensions. RESULTS: Mean patient movements of 0.15 +/- 0.3 mm (latero-lateral), 0.9 +/- 1 mm (anterior-posterior), 1 +/- 1 mm (tranversal vectorial error) and < 3 mm slice thickness (craniocaudal) were recorded using bony landmarks and 0.9 +/- 0.9 mm (latero-lateral), 1.8 +/- 1.5 mm (anterior-posterior), 2.2 +/- 1.5 mm (transversal vectorial error) and < 3 mm (craniocaudal) using the confines of, or landmarks within the prostate. Standard deviations of absolute positioning error as an often used metric for positioning accuracy ranged between 0.3 and 1.7 mm in the transversal plane. The worst case transversal vectorial deviation for the prostate was 4.4 mm. Figure 4 summarizes the set-up accuracy of bony landmarks and the prostate. CONCLUSION: The presented combination of a body cast and head mask system in a rigid stereotactic body frame ensures reliable noninvasive patient fixation for fractionated extracranial stereotactic radiotherapy. It provides precise and reliable positioning of the prostate and meets the requirements for highly conformal radiotherapy such as IMRT. No further improvement of repositioning can be achieved with external immobilization devices since the positioning error of the target relative to the skeleton exceeds the accuracy of the positioning of the skeleton itself.

Humans↗