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The Delta(4) diode array phantom (Scandidos, Uppsala, Sweden) was evaluated for verification of segmental intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) on an Elekta linear accelerator (Crawley UK). The device was tested for angular sensitivity by irradiating it from 36 different gantry angles, and the responses of the device to various step-and-shoot segment doses and dose rates were evaluated using an ionization chamber as a comparison. The phantom was then compared with ionization chamber and film results for two prostate and pelvic nodes IMRT plans, two head and neck IMRT plans and two lung VMAT plans. These plans were calculated using Pinnacle(3) (Philips Radiation Oncology Systems, Madison, WI). The uniformity of angular response was better than 0.5% over the range of gantry angles. The uniformity of response of the Delta(4) to different segment monitor units and dose rates was better than 0.5%. The assessment of the IMRT and VMAT plans showed that the Delta(4) measured a dose within 2.5% of the ionization chamber, and compared to film recorded a slightly larger region (range -2% to +7%) agreeing with the planned dose to within 3% and 3 mm. The Delta(4) is a complex device and requires careful benchmarking, but following the successful completion of these measurements, the Delta(4) has been introduced into clinical use.

Background and purpose: Intensity modulated radiotherapy (IMRT) allows the delivery of higher and more homogeneous radiation dose to head and neck tumours. This study aims to determine the safety of dose-escalated chemo-IMRT for larynx preservation in locally advanced head and neck cancer. Methods: Patients with T2–4, N1–3, M0 squamous cell carcinoma of the larynx or hypopharynx were treated with a simultaneous-boost IMRT. Two radiation dose levels (DL) were tested: In DL 1, 63 Gy/28F was delivered to primary tumour and involved nodes and 51.8 Gy/28F to elective nodes. In DL 2, the doses were 67.2 Gy/28F and 56 Gy/28F, respectively, representing a 9% dose escalation for the primary. All patients received 2 cycles of neoadjuvant cisplatin and 5-fluorouracil, and concomitant cisplatin. Acute (NCICTCv.2.0) and late toxicity (RTOG and modified LENTSOM) were collected. Results: Thirty patients were entered, 15 in each dose level. All patients completed the treatment schedule. In DL 1, the incidences of acute G3 toxicities were 27% (pain), 20% (radiation dermatitis), 0% (xerostomia) and 67% required gastrostomy tubes. For DL 2 the corresponding incidences were 40%, 20%, 7%, and 87%. G3 dysphagia and pain persisted longer in DL 2. With regard to mucositis, a prolonged healing time for DL 2 was found, with prevalence of G2 of 58% in week 10. No acute grade 4 toxicity was observed. At 6 months, 1 patient in DL 2 had G3 late toxicity (dysphagia). No dose limiting toxicity was found. Complete response rates were 80% in DL 1, and 87% in DL 2. Conclusion: Moderately accelerated chemo-IMRT is safe and feasible with good compliance and acceptable acute toxicity. Dose escalation was possible without a significant difference in acute toxicity. Longer follow-up is required to determine the incidence of late radiation toxicities, and tumour control rates. c 2007 Elsevier Ireland Ltd. All rights reserved. Radiotherapy and Oncology 85 (2007) 36–41.

Purpose: This study assesses the accuracy of NOMOS B-mode acquisition and targeting system (BAT) compared with computed tomography (CT) in localizing the prostate. Methods and Materials: Twenty-six patients were CT scanned, and the prostate was localized by 3 observers using the BAT system. The BAT couch shift measurements were compared with the CT localization. Six of the patients had gold markers present in the prostate, and the prostate movement determined by BAT was compared with the movement determined by the gold markers. Results: Using the BAT system, the 3 observers determined the prostate position to be a mean of 1-5 mm over all directions with respect to the CT. The proportion of readings with a difference >3 mm between the observers was in the range of 25% to 44%. The prostate movement based on gold markers was an average of 3-5 mm different from that measured by BAT. The literature assessing the accuracy and reproducibility on BAT is summarized and compared with our findings. Conclusions: We have found that there are systematic differences between the BAT-defined prostate position compared with that estimated on CT using gold grain marker seeds.

Background and purpose : Two systems have been developed for treating patients with locally advanced prostate cancer using intensity-modulated radiotherapy (IMRT): one using dynamic multi-leaf collimator delivery and the other using step-and-shoot. This paper describes the clinical implementation of these two techniques, and presents results from the first 14 patients treated in a clinical setting (nine dynamic, five step-and-shoot). Patients and methods : Dynamic treatments were planned using Corvus, and step-and-shoot using Helax-TMS; all were delivered using Elekta accelerators. Prior to the first clinical treatments, validation measurements were carried out for each system, including measurements for a complete IMRT treatment. The reproducibility of dynamic delivery and the characteristics of the accelerator for low-monitor-unit (MU) deliveries were also assessed. An extensive quality assurance (QA) program was performed for each of the patients. Additionally, timing measurements were carried out to assess the practicalities of the technique. Results : The planning objectives were met in most cases. Absolute doses for complete IMRT treatments were within 2%, on average, with dose distributions generally showing agreement within 3% or 3 mm. Beam modulation measurements made throughout each patient's treatment indicated that both delivery methods were reproducible. The dynamic plans required an average of 765MU per beam, with a treatment delivery time of 14 min; corresponding results for step-and-shoot plans were 105MU and 10 min. Conclusions : Two IMRT techniques for this group of patients have been successfully implemented in the clinic. The more complex dynamic treatments showed no advantages over the step-and-shoot approach. QA results have shown accurate and reproducible delivery for both techniques, giving increased confidence in the techniques and allowing a reduction in the QA program.

Purpose: To describe the rationale, technique, and early results of stereotactically guided conformal radiotherapy (SCRT) in the treatment of progressive or inoperable low-grade gliomas (LGGs) of childhood. Methods and Materials: Between September 1994 and May 1999, 14 children (median age 6 years, range 5–16) with LGG were treated with SCRT at the Royal Marsden NHS Trust. Tumors were located at the optic chiasm ( n = 9), third ventricle ( n = 2), hypothalamus, craniocervical junction, and pineal region (each n = 1). Four patients received chemotherapy before SCRT. Immobilization was in a Gill-Thomas-Cosman frame ( n = 12) and subsequently in a specially designed pediatric version of the frame ( n = 2). Stereotactic coordinates and the tumor were defined by CT scanning with a fiducial system and MRI fusion. The median tumor volume was 19.5 cm 3 (range 7.5–180). The planning target volume was defined as the area of enhancing tumor plus a 5–10-mm margin. The treatment technique consisted of 4 isocentric, noncoplanar, conformal, fixed fields. Treatment was delivered in 30–33 daily fractions to a total dose of 50–55 Gy. Results: SCRT was well tolerated, with transient hair loss the only acute toxicity. The median follow-up was 33 months (range 2–53). At 6 months after SCRT, 4 of 12 children with neurologic deficits improved and 5 remained stable. Twelve children were available for MRI evaluation. Two had a complete response, 6 a partial response, and 4 stable disease. One child with optic chiasm glioma had local progression at 25 months, and 1 developed diffuse leptomeningeal disease without local progression at 27 months. The 3-year local progression-free survival and overall survival rate after SCRT was 87% and 100%, respectively, compared with 89% and 98% for an historic control treated with conventional RT. New endocrine deficiencies were noted in 2 children after a follow-up of 20 and 23 months. Conclusion: SCRT is a feasible, high-precision technique of RT for children with LGGs for whom RT is considered appropriate. The local control and acute toxicity of SCRT are comparable to a historic control of patients with conventionally delivered RT. The frequency of delayed hypothalamic-pituitary axis dysfunction reflects tumor location adjacent to the hypothalamus and pituitary. Additional follow-up is required to demonstrate that SCRT contributes to a reduction in treatment-related late toxicity, while maintaining the local control achieved with conventionally delivered RT in children with progressive LGGs.

Purpose: To investigate the optimal treatment plan for stereotactically-guided conformal radiotherapy (SCRT) of sellar and parasellar lesions, with respect to sparing normal brain tissue, in the context of routine treatment delivery, based on dose volume histogram analysis. Methods and Materials: Computed tomography (CT) data sets for 8 patients with sellar- and parasellar-based tumors (6 pituitary adenomas and 2 meningiomas) have been used in this study. Treatment plans were prepared for 3-coplanar and 3-, 4-, 6-, and 30-noncoplanar-field arrangements to obtain 95% isodose coverage of the planning target volume (PTV) for each plan. Conformal shaping was achieved by customized blocks generated with the beams eye view (BEV) facility. Dose volume histograms (DVH) were calculated for the normal brain (excluding the PTV), and comparisons made for normal tissue sparing for all treatment plans at ≥80%, ≥60%, and ≥40% of the prescribed dose. Results: The mean volume of normal brain receiving ≥80% and ≥60% of the prescribed dose decreased by 22.3% (range 14.8–35.1%, standard deviation σ = 7.5%) and 47.6% (range 25.8–69.1%, σ = 13.2%), respectively, with a 4-field noncoplanar technique when compared with a conventional 3-field coplanar technique. Adding 2 further fields, from 4-noncoplanar to 6-noncoplanar fields reduced the mean normal brain volume receiving ≥80% of the prescribed dose by a further 4.1% (range −6.5–11.8%, σ = 6.4%), and the volume receiving ≥60% by 3.3% (range −5.5–12.2%, σ = 5.4%), neither of which were statistically significant. Each case must be considered individually however, as a wide range is seen in the volume spared when increasing the number of fields from 4 to 6. Comparing the 4- and 6-field noncoplanar techniques to a 30-field conformal field approach (simulating a dynamic arc plan) revealed near-equivalent normal tissue sparing. Conclusion: Four to six widely spaced, fixed-conformal fields provide the optimum class solution for the treatment of sellar and parasellar lesions, both in terms of normal brain tissue sparing and providing a relatively straightforward patient setup. Increasing the number of fields did not result in further significant sparing, with no clear benefit from techniques approaching dynamic conformal radiotherapy in the cases examined.

Purpose : Stereotactically guided conformal radiotherapy, (SCRT) is a high precision technique of conformal radiotherapy (RT) which reduces the volume of normal tissue irradiated compared to conventional RT and may lead to a reduction in long-term toxicity We describe the technique and the preliminary results in patients with inoperable, residual or recurrent meningiomas. Material and methods : From July 1993 to November 1997, 24 patients (median age: 56 years, range: 28–72) with base of skull ( n =21), falx or upper skull ( n =3) meningiomas were treated with SCRT. The technique employed immobilization in a Gill-Thomas-Cosman (GTC) frame and CT localization with a Brown-Roberts-Wells (BRW) fiducial system for stereotactic space definition. The planning target volume (PTV) was defined as gross tumour volume (GTV) and a 0.5–1 cm margin. Treatment was delivered with three (12 patients) or four non-coplanar conformal fixed fields (12 patients) Conformal blocking was achieved either with lead alloy blocks ( n =11) or with a multi-leaf collimator (MLC) ( n =13). Patients were treated on a 6 MV linear accelerator to doses of 50–55 Gy, in 30–33 daily fractions. The treatments were carried out as part of a routine work of a busy radiotherapy department. Results : Median GTV for 24 meningiomas was 21.7 cm 3 (range: 4.4–183 cm 3 ). SCRT was well tolerated with minimal toxicity Three months after the end of radiotherapy, seven of 15 patients with neurological deficit had an improvement and eight remained unchanged. Two patients experienced early side effects (one VII nerve palsy, one Addisonian state). At a median follow-up of 13-months (range: 3–43) the 1 year progression free survival and overall survival are 100%, which is within the range expected for conventional fractionated radiotherapy for meningiomas. Conclusions : SCRT is a feasible technique of high precision conformal RT for patients with meningiomas. Potential advantages in tumour control, survival and toxicity over conventional RT, require evaluation in long-term prospective studies.

OBJECTIVES: Volumetric modulated arc therapy (VMAT) is a novel form of intensity-modulated radiation therapy that allows the radiation dose to be delivered in a single gantry rotation using conformal or modulated fields. The capability of VMAT to reduce heart and cord dose, while maintaining lung receiving 20 Gy

The recent development of fractionated stereotactic radiotherapy (SRT), which utilises the relocatable Gill-Thomas-Cosman frame (GTC ‘repeat localiser’), requires comprehensive quality assurance (QA). This paper focuses on those QA procedures particularly relevant to fractionated SRT treatments, and which have been derived from the technique used at the Royal Marsden Hospital. They primarily relate to the following: (i) GTC frame fitting, initially in the mould room, and then at each imaging session and treatment fraction; (ii) checking of the linear accelerator beam geometry and alignment lasers; and (iii) setting up of the patient for each fraction of treatment. The precision of the fractionated technique therefore depends on monitoring the GTC frame relocation at each fitting, checking the accuracy of the radiation isocentre of the treatment unit, its coincidence with the patient alignment lasers and the adjustments required to set the patient up accurately. The results of our quality control checks show that setting up to a mean radiation isocentre using precisely set-up alignment lasers can be achievable to within I mm accuracy. When this is combined with a mean GTC frame relocatability of I mm on the patient, a 2-mm allowance between the prescribed isodose surface and the defined target volume is a realistic safety margin for this technique.

The precision of patient repositioning and the firmness of immobilization are among the major determinants of the accuracy of radiation treatment delivery. A relocatable Gill-Thomas localizer (GTL) developed for neurosurgery and stereotactic radiotherapy achieves highly accurate relocation and immobilization and has been used successfully for fractionated stereotactic radiotherapy of intracranial lesions. The feasibility of using GTL for immobilization in conventional fractionated external beam radiotherapy was assessed by comparison with conventional Cabulite shell head fixation. The GTL was well tolerated at the time of preparation and during a 5 week course of radiotherapy. The principal advantage was superior relocation accuracy maintained throughout the course of treatment, high precision of field set-up and markedly reduced production time. In addition the time taken to position the patient in the treatment room was also marginally shortened. GTL is therefore a feasible method of head fixation for conventional cranial irradiation providing patients have adequate dentition. With further development the relocatable method of immobilization originally designed for stereotactic radiotherapy may become the preferred technique particularly in situations where high accuracy is desirable, such as stereotactically guided conformal radiotherapy.

Purpose To develop and compare a volumetric modulated arc therapy (VMAT) technique with conventional radiotherapy for craniospinal irradiation with respect to improved dose conformity and homogeneity in the planning target volume (PTV) and to reduced dose to organs at risk (OAR). Methods and Materials Conventional craniospinal axis radiotherapy plans of 5 patients were acquired. The median (range) length of the PTV was 58.9 (48.1–83.7) cm. The 6-MV VMAT plans were inversely planned with one isocenter near the base of the brain and the minimum number of isocenters required for the specified lengths of spine. The plans were optimized with high weighting for PTV coverage and low weighting for OAR sparing. Conformity and heterogeneity indices, dose–volume histograms, mean doses, and non-PTV integral doses from the two plans (prescription dose 23.4 Gy in 13 fractions) were compared. Results The median (range) conformity index of VMAT was 1.22 (1.09–1.45), compared with 1.69 (1.44–2.67) for conventional plans ( p = 0.04). The median (range) heterogeneity index was also lower for VMAT compared with conventional plans: 1.04 (1.03–1.07) vs. 1.12 (1.09–1.19), respectively ( p = 0.04). A significant reduction of mean and maximum doses was observed in the heart, thyroid, esophagus, optic nerves, and eyes with VMAT when compared with conventional plans. A decrease in body V 10Gy was observed, but for 4 of 5 patients non-PTV integral dose was increased with VMAT when compared with the conventional plans. Conclusions A VMAT technique to treat the craniospinal axis significantly reduces OAR dose, potentially leading to lower late organ toxicity. However, this is achieved at the expense of increased low-dose volumes, which is inherent to the technique, carrying a potentially increased risk of secondary malignancies.

A non-invasive head fixation system is described which is accurately relocatable and enables the transfer of stereotactic positions between a variety of radiodiagnostic images and therapeutic procedures. The system can be simply and repeatedly applied for planning stereotactic radiation therapy from one or more diagnostic images and for repeated treatment with a conventional linear accelerator. In addition, the long-term effects of therapy can be objectively monitored by relocating the frame and repeating images in an identical way, months or years later.

Purpose. To evaluate the efficacy and toxicity of hypofractionated stereotactic radiotherapy in the management of locally recurrent or residual central nervous system (CNS) primitive neuroectodermal turners (PNETs). Patients and Methods. Between 1991 and 2005, 12 patients with locally recurrent medulloblastoma and two patients with residual supratentorial PNET were treated with hypofractionated stereotactic conformal radiotherapy (SCRT). Nine patients were treated for first recurrence, two patients after the 2nd, and one patient after 3rd recurrence. Median age at diagnosis was 20 years (range: 4-35 years) and median age at SCRT 25 years (range: 7-41 years). Nine of 12 patients underwent resection at recurrence and 13 patients received at least one cyCIe of chemotherapy prior to SCRT. All received focal SCRT (30-40 Gy/6-8 #) using non-coplanar arcs (n = 6) or fixed conformal non-coplanar fields (n = 8). Results. Median overall Survival was 29 months (95% CI: 6-51 months) and median progression-free survival was 12 months (95% CI: 5-19 months). Local progression-free survival at 1 and 3 years was 80% (95% CI: 55-100%) and 48% (95% CI: 11-85%). Causes of death were recurrent CNS disease (n = 7), herpes encephalitis (n = 1), and metastatic PNET outside the CNS (n = 1). ConCIusion. Hypofractionated SCRT provides effective local control with acceptable toxicity for patients with recurrent localized PNET. However, overall long-term disease control is rare and limited by the occurrence of CSF mediated relapses, which thus could benefit from intensive systemic chemotherapy as part of the primary relapse strategy even in local recurrences. Larger multi-national studies will be necessary to assess the value of such combined treatment approaches.

Background and purpose Full inverse planned intensity modulated radiotherapy (IMRT) may be indicated to treat concave targets like prostate and pelvic nodes, because concave dose distributions cannot be generated with conformal radiotherapy (CRT). We investigated whether this concave dose distribution can be produced using simplified forward planned multi segment radiotherapy (MSRT). Patients and methods CRT, MSRT and IMRT dose distributions were calculated and compared for five patients treated in our current IMRT prostate and pelvic node dose escalation trial. The same beam arrangement was used for CRT, MSRT and IMRT, increasing the number of segments. The MSRT concave dose distribution was realised regarding left and right pelvic nodes as two separate targets. The IMRT dose distribution had been used to treat the patients using a step and shoot delivery. Results Contrary to CRT, forward planned MSRT concave dose distributions had improved target coverage at lower or equivalent bowel doses than inverse planned IMRT. The five MSRT beams had a maximum of three segments per beam. Both lateral beams had two segments to deliver the two dose levels to prostate and nodes. The posterior field needed a third segment to avoid using a central block. The two anterior oblique beams needed a third segment to account for the different beam weighting because the nodes were irradiated partially using four and partially using five beams. Inverse planned IMRT used up to 15 segments in any one beam, with an average of 11.4 per beam. Conclusions Concave dose distributions for prostate and pelvic node treatment were generated using forward planned multi segment techniques. The plans met clinical constraints used in our IMRT protocol. MSRT presented a significant advantage over both CRT and IMRT.

This study aimed to assess the efficacy and toxicity of hypofractionated stereotactic radiotherapy (SRT) in the management of patients with recurrent glioma.From January 1989 to July 1994, 36 patients with glioma were treated at the time of recurrence. Twenty-nine had recurrent high-grade astrocytoma, 3 high-grade oligodendroglioma, 1 high-grade ependymoma, and 3 pilocytic astrocytoma. Hypofractionated stereotactic radiotherapy was given using either three noncoplanar arcs or four to six noncoplanar fixed beams at 5 Gy/fraction, to doses ranging from 20 to 50 Gy initially on a dose escalation program. Two patients received 20 Gy, 8 received 30 Gy, 10 received 35 Gy, 10 received 40 Gy, 5 received 45 Gy, and 1 received 50 Gy, treating 5 days/week.The median survival of 29 patients with recurrent high-grade astrocytoma was 11 months from the time of SRT. This compared to a median survival of 7 months for a cohort matched for age, performance status, and initial histologic grade who received nitrosourea-based chemotherapy at recurrence (p0.05). Initial low-grade astrocytoma histology was the only favorable prognostic factor for survival on univariate analysis. Three patients with recurrent oligodendroglioma remain alive 11, 23, and 34 months after SRT. Three children treated for recurrent pilocytic astrocytoma remain alive 14, 41, and 55 months following SRT. Presumed radiation damage, defined as reversible steroid-dependent toxicity, was observed in 13 patients (36%) and required reoperation in 2 (6%). A total dose of40 Gy was a major predictor of radiation damage (p0.005).Hypofractionated SRT is a noninvasive, well-tolerated, outpatient-based method of delivering palliative, high-dose, focal irradiation.

Purpose : To determine the radiation tolerance of the lens of the eye and the incidence of radiation-induced lens changes in patients treated by fractionated supervoltage radiation therapy for orbital tumors. Methods : Forty patients treated for orbital lymphoma and pseudotumour with tumour doses of 20–40 Gy were studied. The lens was partly shielded using lead cylinders in most cases. The dose to the germinative zone of the lens was estimated by measurements in a tissue equivalent phantom using both film densitometry and thermoluminescent dosimetry. Ophthalmological examination was performed at 6 monthly intervals after treatment. Results : The lead shield was found to reduce the dose to the germinative zone of the lens to between 36–50% of the tumor dose for Cobalt beam therapy, and to between 11–18% for 5 MeV x-rays. Consequently, the lens doses were in the range 4.5–30 Gy in 10–20 fractions. Lens opacities first appeared from between 3 and 9 years after irradiation. Impairment of visual acuity ensued in 74% of the patients who developed lens opacities. The incidence of lens changes was strongly dose-related. None was seen after doses of 5 Gy or lower, whereas doses of 16.5 Gy or higher were all followed by lens opacities which impaired visual acuity. The largest number of patients received a maximum lens dose of 15 Gy; in this group the actuarial incidence of lens opacities at 8 years was 57% with visual impairment in 38%. Conclusion : The adult lens can tolerate a total dose of 5 Gy during a fractionated course of supervoltage radiation therapy without showing any changes. Doses of 16.5 Gy or higher will almost invariably lead to visual impairment. The dose which causes a 50% probability of visual impairment is approximately 15 Gy.