The value of CT scanning in radiation therapy treatment planning: a prospective study

Support and Assessment for Fall Emergency Referrals (SAFER 1): cluster randomised trial of computerised clinical decision support for paramedics

Objective

To evaluate effectiveness, safety and cost-effectiveness of Computerised Clinical Decision Support (CCDS) for paramedics attending older people who fall.

Design

Cluster trial randomised by paramedic; modelling.

Setting

13 ambulance stations in two UK emergency ambulance services.

Participants

42 of 409 eligible paramedics, who attended 779 older patients for a reported fall.

Interventions

Intervention paramedics received CCDS on Tablet computers to guide patient care. Control paramedics provided care as usual. One service had already installed electronic data capture.

Main Outcome Measures

Effectiveness: patients referred to falls service, patient reported quality of life and satisfaction, processes of care.

Safety

Further emergency contacts or death within one month.

Cost-Effectiveness

Costs and quality of life. We used findings from published Community Falls Prevention Trial to model cost-effectiveness.

Results

17 intervention paramedics used CCDS for 54 (12.4%) of 436 participants. They referred 42 (9.6%) to falls services, compared with 17 (5.0%) of 343 participants seen by 19 control paramedics [Odds ratio (OR) 2.04, 95% CI 1.12 to 3.72]. No adverse events were related to the intervention. Non-significant differences between groups included: subsequent emergency contacts (34.6% versus 29.1%; OR 1.27, 95% CI 0.93 to 1.72); quality of life (mean SF12 differences: MCS −0.74, 95% CI −2.83 to +1.28; PCS −0.13, 95% CI −1.65 to +1.39) and non-conveyance (42.0% versus 36.7%; OR 1.13, 95% CI 0.84 to 1.52). However ambulance job cycle time was 8.9 minutes longer for intervention patients (95% CI 2.3 to 15.3). Average net cost of implementing CCDS was £208 per patient with existing electronic data capture, and £308 without. Modelling estimated cost per quality-adjusted life-year at £15,000 with existing electronic data capture; and £22,200 without.

Conclusions

Intervention paramedics referred twice as many participants to falls services with no difference in safety. CCDS is potentially cost-effective, especially with existing electronic data capture.

Trial Registration

ISRCTN Register ISRCTN10538608

Quality, technology and outcomes: evolution and evaluation of new treatments and/or new technology

The pace of technological innovation and adoption continues to increase each year, and the field of Radiation Oncology struggles to react appropriately to the changes and potential improvements in treatment which hopefully will result from this innovation. The standard methods used in the past to test new technology and treatment techniques are often no longer appropriate for this fast-changing environment. This paper uses examples from radiotherapy technological developments over the last decades to illustrate issues which need to be solved in order to study and evaluate potential advances, and then describes several improved ways to study new techniques and technology. Design of appropriate studies can help us improve patient care while at the same time documenting which new clinical strategies, enabled by new technology, lead to improved patient outcomes.

Radiotherapeutic techniques for prostate cancer, dose escalation and brachytherapy

There is evidence to confirm a dose-response relationship in prostate cancer. The relative benefit is dependent on the clinical prognostic risk factors (T stage, Gleason score and presenting prostate-specific antigen [PSA]) being more favourable for intermediate-risk patients. Refinement of prognostic groups and clinical threshold parameters is ongoing. Escalation of dose in prostate radiotherapy using conventional techniques is limited by rectal tolerance. Substantial advances have been made in radiotherapy practice, such as the development of conformal radiotherapy (CFRT) and intensity-modulated radiotherapy (IMRT). Randomised data support the value of CFRT in reducing rectal toxicity. IMRT can permit higher-dose escalation while still respecting known rectal tolerance thresholds. Brachytherapy is a recognised alternative for low-risk prostate cancer subgroups. New radiotherapeutic strategies for prostate cancer include pelvic nodal irradiation, exploiting the presumed low alpha/beta ratio in prostate cancer for hypofractionation and combining external beam with high-dose-rate brachytherapy boosts. New image-guided methodologies will enhance the therapeutic ratio of any radiotherapy technique or dose escalation programme by enabling more reliable and accurate treatment delivery for improved patient outcomes.

Characteristics and clinical application of a treatment simulator with Ct-option

BACKGROUND AND PURPOSE

The integration of a scanner for computed tomography (CT) and a treatment simulator (Sim-CT, Elekta Oncology Systems, Crawley, UK) has been studied in a clinical situation. Image quality, hounsfield units (HU) and linearity have been evaluated as well as the implications for treatment planning. The additional dose to the patient has also been highlighted.

MATERIAL AND METHODS

Image data is acquired using an array of solid state X-ray detectors attached externally to the simulator's image intensifier. Three different fields of view (FOV: 25.0 cm, 35.0 cm and 50.0 cm) with 0.2 cm, 0.5 cm and 1.0 cm slice thickness can be selected and the system allows for an aperture diameter of 92.0 cm at standard isocentric height. The CT performance has been characterized with several criteria: spatial resolution, contrast sensitivity, geometric accuracy, reliability of hounsfield units and the radiation output level. The spatial resolution gauge of the nuclear associates quality phantom (NAQP) as well as modulation transfer functions (MTF) have been applied to evaluate the spatial resolution. Contrast sensitivity and HU measurements have been performed by means of the NAQP and a HU conversion phantom that allows inserts with different electron densities. The computed tomography dose index (CTDI) of the CT-option has been monitored with a pencil shaped ionization chamber. Treatment planning and dose calculations for heterogeneity correction based on the Sim-CT images generated from an anthropomorphic phantom as well as from ten patients have been compared with similar treatment plans based on identical, yet diagnostic CT (DCT) images.

RESULTS

The last row of holes that are resolved in the spatial resolution gauge of the NAQP are either 0.150 cm or 0.175 cm depending on the FOV and the applied reconstruction filter. These are consistent with the MTF curves showing cut-off frequencies ranging from 5.3 lp/cm to 7.1 lp/cm. Linear regression analysis of HU versus electron densities revealed a correlation coefficient of 0.99. Contrast, pixel size and geometric accuracy are within specifications. Computed tomography dose index values of 0.204 Gy/As and 0.069 Gy/As have been observed with dose measurements in the center of a 16 cm diameter and 32 cm diameter phantom, respectively for large FOV. Small FOV yields CTDI values of 0.925 Gy/As and 0.358 Gy/As which is a factor ten higher than the results obtained from a DCT under similar acquisition conditions. The phantom studies showed excellent agreement between dose distributions generated with the Sim-CT and DCT HU. The deviations between the calculated settings of monitor units as well as the maximum dose in three dimensions were less than 1% for the treatment plans based on either of these HU both for pelvic as well as thoracic simulations. The patient studies confirmed these results.

CONCLUSIONS

The CT-option can be considered as an added value to the simulation process and the images acquired on the Sim-CT system are adequate for dose calculation with tissue heterogeneity correction. The good image quality, however, is compromised by the relative high dose values to the patient. The considerable load to the conventional X-ray tube currently limits the Sim-CT to seven image acquisitions per patient and therefore the system is limited in its capability to perform full three-dimensional reconstruction.

A solid water pelvic and prostate phantom for imaging, volume rendering, treatment planning, and dosimetry for an RTOG multi-institutional, 3-D dose escalation study. Radiation Therapy Oncology Group

PURPOSE

With increased interest in 3-D conformal radiation therapy and dose escalation, it is necessary to provide advanced techniques to assure quality in treatment delivery. Multi-institutional trials for these newer treatment techniques require methods of verifying the consistency of treatments between the participating institutions. For this reason, a phantom was designed to address the quality and consistency of Radiation Therapy Oncology Group (RTOG) 3-D prostate treatment protocol.

METHODS AND MATERIALS

A solid water pelvic and prostate phantom for imaging, volume rendering, treatment planning, and dosimetry applications for performing comprehensive quality assurance has been designed and fabricated. Its configuration was based upon CT slices obtained from a patient study. Individual slices were machined with corresponding contours of the prostate, bladder, rectum, and the left and right femurs. Most of the phantom is made of solid water (Gammex/RMI, Middleton, WI), while the femurs are made of bone-equivalent material. The CT numbers from patient images were used to adjust the solid water composition within the organ volumes, providing image contrast from the remainder of the phantom. Cylindrical insertion grooves are machined in the phantom to allow placement of ionization chambers and thermal luminal dosimeters (TLDs) for dosimetry applications. During imaging, the cavities are filled with rods fabricated from solid water material.

RESULTS

The phantom is being used to evaluate the consistency of a range of processes in radiation therapy simulation, planning, and delivery of 3-D-based treatments for prostate cancer.

CONCLUSION

The ultimate study objective is to use the phantom to evaluate the accuracy and consistency of treatments delivered by institutions participating in national collaborative clinical trials involving 3-D conformal dose escalation.

High-dose conformal radiotherapy influenced the pattern of failure but did not improve survival in glioblastoma multiforme

BACKGROUND AND PURPOSE

Although glioblastoma multiforme is clearly radiation-resistant, there is evidence of a dose-dependent response relationship. The purpose of the study was to evaluate the impact of higher dose by rotational multileaf collimator (MLC) conformal radiation therapy.

MATERIALS AND METHODS

From 1984 to 1995, 38 consecutive cases with intracranial glioblastoma multiforme were treated using the rotational MLC conformal therapy. There were 25 men and 13 women with a median age of 47 years (12-73 years, mean 46.5 years). Median Karnofsky performance score was 80 (30-100, mean 78.2). Median tumor volume was 64 cc (8-800 cc, mean 110.3 cc). All underwent surgical intervention (only biopsy in 1, partial resection in 13, subtotal resection in 21, and gross total resection in 3). Radiation dose to was 60 to 80 Gy (median 68.5 Gy, mean 68.3 Gy) in 21 patients treated before 1990 and 90 Gy in the 17 patients thereafter. Biweekly i.v. chemotherapy was also administered for both arms.

RESULTS

The 1-year, 2-year, 5-year, and 10-year overall survival rates were 75%, 42%, 20%, and 15%, respectively. Univariate analysis showed the initial tumor volume, residual tumor volume, and Karnofsky performance score were statistically significant factors for survival. Only the residual tumor volume was statistically significant by multivariate analysis. The 5-year survival rate of patients with residual tumors of 5 cc or less in volume was as good as 37%. Survival of the 90-Gy Group appeared inferior to that of the Low-Dose Group, though no statistical difference was seen (the 3-year survival was 40% vs. 22%). Local failure was observed in 16 of the 19 recurrences in the Low-Dose Group, whereas it was observed in only 4 of the 13 recurrences in the 90-Gy Group. The difference in pattern of failure was statistically significant. Two patients of the High-Dose Group developed radiation necrosis and one died of it.

CONCLUSIONS

The high-dose conformal radiotherapy did not improve survival in the disease, but did change the pattern of failure.

T classification and clivus margin as risk factors for determining locoregional control by radiotherapy of nasopharyngeal carcinoma

BACKGROUND

The purpose of this study was to determine risk factors that affect locoregional control of nasopharyngeal carcinoma (NPC) after radiotherapy. Computed tomography (CT) is utilized for radiotherapy planning and for identifying high risk anatomic areas.

METHODS

Between April 1990 and December 1993, 40 consecutive patients (1 in Stage I, 3 in Stage II, 5 in Stage III, and 31 in Stage IV) who had locoregional NPC were given definitive radiotherapy at the Koo Foundation Sun Yat-Sen Cancer Center in Taipei, Taiwan. All patients had individualized CT treatment planning. The dimension of each tumor as shown on the treatment planning CT were mapped on conventional simulation films. The extent of each tumor was further affirmed by magnetic resonance imaging (MRI) and the tumor map revised as necessary. The primary radiation fields were designed to include the primary tumor and potential spread areas with appropriate margins. Concurrent chemotherapy was also given to 35 patients (87.5%) who had positive cervical lymph nodes or primary tumors extending beyond the nasopharynx.

RESULTS

By the end of December 1995, after a median follow-up of 42 months and minimal follow-up of 24 months, the locoregional control rate at 4 years was 84.8% (95% confidence interval [CI], 72.3-97.3), disease free survival 68.4% (95% CI, 52. 1-84.7), and overall survival 76.7% (95% CI, 63.4-90.0). The radiation field margin near the sphenoid sinus averaged 1.9 cm, the clivus margin 1.1 cm, the pterygoid fossa margin 2.0 cm, and the oral cavity margin 1.7 cm. Risk factor analysis revealed that T classification and the radiation field margin at the clivus were the most important factors for locoregional control of the tumor. The locoregional control rates were 92.6% (25/27) for T1-T3 patients and 76.9% (10/13) for T4 patients (P = 0.03). The locoregional control rates were 71.4% (5/7) for patients with a clivus margin < 1 cm and 90.6% (29/32) for patients with a clivus margin > or = 1 cm (P = 0.08).

CONCLUSIONS

The excellent locoregional control observed in this series may be attributed to the concurrent chemotherapy and radiotherapy as well as meticulous treatment planning with CT and MRI. The precise delineation of the involved area with the aid of CT, which is taken while the patient is in the position for irradiation, serves to define the necessary safety margin of the radiation field. T classification and clivus margin are the most important factors in determining locoregional control of radiotherapy of NPC. The statistical trend observed in this study indicated that the clivus margin should be adequate to reduce the failure around the clivus, as all local recurrences were observed in this area.

Three dimensional conformal radiation therapy in pediatric parameningeal rhabdomyosarcomas

PURPOSE

We evaluated the utility of three dimensional (3D) treatment planning in the management of children with parameningeal head and neck rhabdomyosarcomas.

METHODS AND MATERIALS

Five children with parameningeal rhabdomyosarcoma were referred for treatment at our radiation oncology center from May 1990 through January 1993. Each patient was evaluated, staged, and treated according to the Intergroup Rhabdomyosarcoma Study. Patients were immobilized and underwent a computed tomography scan with contrast in the treatment position. Tumor and normal tissues were identified with assistance from a diagnostic radiologist and defined in each slice. The patients were then planned and treated with the assistance of a 3D treatment planning system. A second plan was then devised by another physician without the benefit of the 3D volumetric display. The target volumes designed with the 3D system and the two-dimensional (2D) method were then compared. The dosimetric coverage to tumor, tumor plus margin, and normal tissues was also compared with the two methods of treatment planning.

RESULTS

The apparent size of the gross tumor volume was underestimated with the conventional 2D planning method relative to the 3D method. When margin was added around the gross tumor to account for microscopic extension of disease in the 2D method, the expected area of coverage improved relative to the 3D method. In each circumstance, the minimum dose that covered the gross tumor was substantially less with the 2D method than with the 3D method. The inadequate dosimetric coverage was especially pronounced when the necessary margin to account for subclinical disease was added. In each case, the 2D plans would have delivered substantial dose to adjacent normal tissues and organs, resulting in a higher incidence of significant complications.

CONCLUSIONS

3D conformal radiation therapy has a demonstrated advantage in the treatment of sarcomas of the head and neck. The improved dosimetric coverage of the tumor and its margin for subclinical extensions may result in improvement in local control of these tumors. In addition, lowering of radiation dose to adjacent critical structures may help lower the incidence of adverse late effects in children.

Quality assessment of medical decision making in radiation oncology: variability in target volume delineation for brain tumours

The enormous developments in radiation technology open new horizons for improvements in local tumour control. However, the evolution from conventional external beam radiotherapy planning to conformal therapy might be hampered by the potential risk of over-reliance on the physician's capability of estimating the tumour extent from imaging modalities. The variability between 12 volunteering physicians in the delineation of tumour and target volume on the lateral orthogonal localisation radiograph from CT was assessed for 5 brain tumours. The estimated tumour and target sizes varied, respectively with a factor of 1.3-2.6 and with a factor of 1.3-2.1. The anatomical location of the volumes showed maximum variations from 11 to 27 mm in the cranio-caudal direction and from 14 to 21 mm in the fronto-occipital direction. For the 5 test cases, the tumour area on which all radiation oncologists agreed, represented only 25-73% of the corresponding mean tumour area. Although the introduction of computed tomography in radiation treatment planning was proved to be a major step forwards for treatment planning in many tumour sites, the results of the present study on brain tumours demonstrate that the subjective interpretation of the tumour extent based on CT images might be one of the largest factors contributing to the overall uncertainty in radiation treatment planning. Moreover, this study endorses the need for uncertainty analysis of the medical decision-making process. It may be that the process of making uncertainties explicit can contribute to the improvement of our present concept of radiation treatment planning.(ABSTRACT TRUNCATED AT 250 WORDS)

Postoperative radiotherapy after pneumonectomy: impact of modern treatment facilities

PURPOSE

The present study was undertaken to see how modern treatment facilities, computed tomography (CT)-based treatment planning and linear accelerator, have modified the results of postoperative irradiation after a pneumonectomy for lung cancer.

METHODS AND MATERIALS

Between 1970-1985, 103 patients were treated in our department after a pneumonectomy: 50 patients with a T1T2N0 tumor and 53 patients with a T3, N1 or N2 tumor. Three groups were considered: 27 patients had only surgical resection, 51 patients were irradiated postoperatively with a Co60 source, and 25 patients were treated using those modern facilities.

RESULTS

The 5-year survival varies from 4% to 31% according to the tumor extent but also to the radiation technique. Patients treated with a Co60 source had a dismal 5-year survival rate (8%) whereas patients treated with the modern facilities had a 5-year survival rate of 30% similar to the 31% of the control surgical group including less advanced tumors.

CONCLUSION

Linear accelerator and computed tomography-based treatment planning improved the accuracy of postoperative thoracic irradiation and allow to deliver high doses to the mediastinum even after a pneumonectomy.

The value of routine computed tomography scanning of the chest in patients presenting with supradiaphragmatic Hodgkin's disease

Six patients presenting with supradiaphragmatic Hodgkin's disease are presented to demonstrate the potential benefits of chest computed tomography (CT) scanning as a routine staging procedure. These cases show that CT scanning can detect mediastinal and lung involvement not readily detected by other investigations, and that such findings can influence the radiotherapy plan, the need for extended radiotherapy fields or the use of chemotherapy. Following treatment, CT scanning can be useful to assess treatment response and may permit earlier detection of relapse. The use of chest CT scanning as a routine staging procedure in all patients with supradiaphragmatic Hodgkin's disease is advocated.

CT-based radiotherapy treatment planning for cancer of the nasopharynx

We analysed 32 cases of nasopharyngeal carcinoma (NPC) treated with radiotherapy trying to define the role of CT scan during radiotherapy planning, as well as radiation treatment and the follow-up of the patients. CT scan was found to help 15 cases with low-parapharyngeal involvement and/or bone erosion. Persistent abnormal CT findings at 2 mo after the end of radiation treatment were related to a 30% local recurrence rate. This rate went up to 100% in case of skull-base destruction.

Does improved depth dose characteristics and treatment planning correlate with a gain in therapeutic results? Evidence from past clinical experience using conventional radiation sources

Experience with the use of external beam conventional radiation over a period of several decades has shown that in every instance where there has been a major advance in the physical delivery of radiation to the tumor (beam energy and characteristics and precise tumor dose delivery) there has been a corresponding major improvement in the treatment results. The advent of megavoltage sources following the invention and use of Cobalt 60 and medical linear accelerator units during the late 1940's and early 1950's and their major impact on tumor control and patient survival in solid tumors such as carcinoma of the prostate, Hodgkin's Disease, head and neck tumors and cancer of the cervix are being discussed. Most recently, the use of computerized tomography and computer systems for treatment planning is likely to show a further improvement in the therapeutic results.

The clinical utility of magnetic resonance imaging in 3-dimensional treatment planning of brain neoplasms

Results of the clinical experience gained since 1986 in the treatment planning of patients with brain neoplasms through integration of magnetic resonance imaging (MRI) into computerized tomography (CT)-based, three-dimensional treatment planning are presented. Data from MRI can now be fully registered with CT data using appropriate three-dimensional coordinate transformations allowing: (a) display of MRI defined structures on CT images; (b) treatment planning of composite CT-MRI volumes; (c) dose display on either CT or MRI images. Treatment planning with non-coplanar beam arrangements is also facilitated by MRI because of direct acquisition of information in multiple, orthogonal planes. The advantages of this integration of information are especially evident in certain situations, for example, low grade astrocytomas with indistinct CT margins, tumors with margins obscured by bone artifact on CT scan. Target definitions have repeatedly been altered based on MRI detected abnormalities not visualized on CT scans. Regions of gadolinium enhancement on MRI T1-weighted scans can be compared to the contrast-enhancing CT tumor volumes, while abnormalities detected on MRI T2-weighted scans are the counterpart of CT-defined edema. Generally, MRI markedly increased the apparent macroscopic tumor volume from that seen on contrast-CT alone. However, CT tumor information was also necessary as it defined abnormalities not always perceptible with MRI (on average, 19% of composite CT-MRI volume seen on CT only). In all, the integration of MRI data with CT information has been found to be practical, and often necessary, for the three-dimensional treatment of brain neoplasms.

Beams eye view-based photon radiotherapy I

Geographic miss, dosimetric miss (underdosing), and proximity of the tumor to sensitive normal tissues are some of the causes of inadequate radiation dose delivery; this is one of many causes of failure after radiotherapy. In the past decade, computerized tomography (CT)-based treatment planning has helped to overcome some of these problems. Beam's eye view (BEV)-based radiotherapy planning is an improvement over CT-based treatment planning that may further increase the therapeutic ratio. Since January 1988, we have treated 198 patients with BEV-based photon radiotherapy. About 40% of our patients treated with radical radiotherapy undergo BEV-based treatment, and about 70% of patients who undergo planning CT in the treatment position receive BEV-based radiotherapy. Our findings are as follows: (a) routine use of BEV-based RT (BEVRT) is possible in a busy radiation oncology department; (b) BEVRT improves geometric coverage of tumors; (c) BEVRT is extremely useful in the design of oblique portals; (d) time commitments for various members of the RT treatment-planning team are reasonable; (e) BEVRT helps individualize RT technique; (f) preliminary data suggest decreased acute toxicity with the use of BEVRT for prostate cancer patients. Whether these advantages will help to improve the outcome (i.e., improve local control and survival) and/or decrease the long-term toxicity is not yet known.

State-of-the-art of external photon beam radiation treatment planning. Photon Treatment Planning Collaborative Working Group

A virtual revolution in computer capability has occurred in the last few years, largely based on rapidly decreasing costs and increasing reliability of digital memory and mass-storage capability. These developments have now made it possible to consider the application of both computer and display technologies to a much broader range of problems in radiation therapy, including planning of treatment, dose computation, and treatment verification. Several methods of three-dimensional dose computations in heterogeneous media capable of 3% accuracy are likely to be available, but significant work still remains, particularly for high energy x-rays where electron transport, and possibly pair production, need to be considered. Innovative display and planning techniques, as well as plan evaluation schemes, are emerging and show great promise for the future. No doubt these advances will lead to substantially improved treatment planning systems in the next few years. However, it must be emphasized that for many of these applications a tremendous software and hardware development effort is required.

MRI treatment planning for CNS neoplasm: graphic display of target volume using boxed cursor

Treatment planning systems are now capable of interfacing with MRI units, however, reconstructing images in multiple planes remains a laborious process. We have described the construction of contrast markers used with MRI imaging to determine the isocenter coordinates of preplanned CNS treatment fields. Currently existing software was then used to reconstruct the patients target volume by centering a box cursor of appropriate size over the predetermined coordinate representing isocenter. Off axis views of the target volume were easily reconstructed, as were images in the coronal and axial planes. The box cursor technique was useful in making modifications to field placement and field size.

Full integration of the beam's eye view concept into computerized treatment planning

A complete set of beam's eye view (BEV) and beam portal design features have been integrated into a computerized 3-dimensional radiotherapy treatment planning system. Among the features implemented is the ability to mix BEV graphics with gray-scale images such as simulator and verification radiographs, and digital reconstructed radiographs. Image processing techniques have been developed to both enhance verification images and to detect radiation field boundaries. These portal simulation and presentation techniques are being used clinically to design and verify radiation fields with manual or automatically-designed field shaping blocks. The ability to perform computer dose calculations for planes which are parallel or perpendicular to a specified beam's central axis is available and this feature has also proven useful for treatment plan evaluation and optimization. Finally, direct comparison of computer-generated portal images with actual simulation and verification radiographs is also possible. These techniques allow the direct integration of "CT-directed treatment planning" with block design, simulator films and port films, and other Beam's Eye View-type displays.

Analysis of movement of intrathoracic neoplasms using ultrafast computerized tomography

Twenty patients with intrathoracic neoplasms were evaluated with ultrafast (cine) computerized tomography to determine the contribution of tumor motion to geographic errors. The treatment portals were setup with conventional simulation techniques and then scanned with cine computerized tomography. Eight tomographic levels were studied, 10 images per level over 7 seconds time. Major geographic misses were detected in three patients (15%), and minor geographic misses in an additional three (15%). The greatest tumor movement was noted in lesions located adjacent to the heart or aorta or near the diaphragm. Five of six hilar lesions showed significant lateral motion (average = 9.2 mm) with cardiac contraction, and three of four lower lobe lesions showed significant craniocaudal movement with respiration. Mediastinal lesions moved an average of 8.7 mm laterally. Lesions in the upper lobes showed minimal movement (average = 2.2 mm), and tumors attached to the chest wall showed no measurable movement.

Localizing the spinal cord in oblique off-cord lung boosts

We present a method to accurately localize the spinal cord in oblique projections on plain radiographs. Utilizing a CT scan done with the patient in the treatment position, a template is generated to localize the spinal cord. The technique involves analyzing successive axial CT slices and locating cord position relative to the beam central axis. The template is then placed on the simulator fiducial plate at the time of verification simulation. Cord position is documented in the "beam's eye view" on the radiograph. Utilizing this technique, our radiation oncologists are more comfortable defining the medial field border in oblique setups. In most cases, this technique will minimize the perceived need to add superfluous spinal cord blocks that compromise tumor dose.

The value of treatment planning using CT and an immobilizing shell in radiotherapy for paranasal sinus carcinomas

This article describes a method which uses CT scans and immobilizing shells radiation treatment planning (CT-assisted planning) for paranasal sinus carcinomas and the value of this method on the treatment outcome. Results of the treatment for 82 patients who had CT-assisted planning were compared with that of 88 patients who had no such treatment planning. It has been concluded that the combined use of CT and the shell in treatment planning permitted a 3-dimensional localization of both the tumor and critical normal structures with great accuracy, leading to an improved long-term survival and a reduced complication rate. The multivariate regression analysis for predicting significant prognostic factors also confirmed the valuable role of CT in terms of survival and primary tumor control. The actuarial 5-year survival rate was 51% in all patients, whereas, by using CT-assisted planning, it was improved to 61%. The improved survival was observed among the patients with tumors of the suprastructures where tumors were located adjacent to the critical organs (brain and eye). Major complications attributable to radiation have included instances of brain and ocular damage. CT-assisted planning, however, has been proven effective in avoiding brain necrosis and preserving eye sight.

Dose to the cardiac vascular and conduction systems in primary breast irradiation

Using computerized tomography (CT) in which cardiac anatomy was defined, doses delivered to the cardiac compartments, vascular and conduction systems were assessed for various standard techniques of primary breast irradiation. Included in the analysis were 6 MV photon tangents (T) alone, or in conjunction with a separate internal mammary field (IMF). Beams evaluated in the IMF were 6 MV photons, 12 MeV electron beam, and mixed photon/electron beam; Cobalt 60 was also analyzed as an alternate photon beam. Treatment of the IMF with photons, either alone or in combination with electron beam, delivered doses ranging between 30 Gy to 50 Gy to all chambers of the heart, coronary arteries and branches of the conduction system. Complete sparing of the posterior cardiac structures and volume is accomplished with treatment plans using tangents alone or in combination with 12 MeV electron beam irradiation to the IMF. Sparing of the anterior wall of the left ventricle, Bundle of His and left anterior descending coronary artery is also achieved in treatment with tangents and 12 MeV electron beam IMF. Doses to this region with tangents alone ranged from 20 Gy to 45 Gy compared to 0 to 30 Gy with tangents and 12 MeV electron beam IMF. Clinical significance of these findings will be discussed.

Improved radiotherapy treatment planning for spinal cord tumors using gadolinium enhanced MR imaging

Primary intramedullary spinal cord tumors are frequently difficult to localize for radiation treatment planning. Conventional imaging techniques, including unenhanced magnetic resonance (MR) scans, cannot clearly distinguish residual tumor from surrounding normal spinal cord. Recently, contrast agents have been developed for MR that have considerable promise for improving tumor volume definition. This report describes the impact of contrast-enhanced MR on the treatment planning process for four patients with primary spinal cord tumors and discusses the significance of this technique for patients with these neoplasms.

A coordinate transfer of anatomical information from CT to treatment simulation

Use of CT in treatment planning requires that the anatomical information obtained from the CT scans can be transferred accurately to the treatment geometry. We have developed a technique which transfers the CT data to the simulation data and vice versa. The method uses skin marks and digital radiographs reconstructed from CT scans to reproduce the patient's position. The technique has been studied with a special phantom. Based on 10 phantom set-ups, CT coordinates can be transferred to simulation coordinates with a standard deviation of 0.25 cm. This method has been applied on a number of clinical cases that involve different disease sites. For these cases, comparisons of set-up films taken at the simulator and the digital radiographs reconstructed from CT data indicate that patient position can be reproduced to within 0.5 cm.

Progress in 3-D treatment planning for photon beam therapy

The purpose of this report is to study the feasibility of improving dose distributions using non-coplanar photon beams from a linear accelerator. Non-coplanar beams may enter the patient in any arbitrary configuration. This type of treatment technique requires a three-dimensional (3-D) planning system. Clinical examples are used to illustrate the general problems in 3-D treatment planning, and the potential improvement over coplanar beam treatments. Features of a treatment planning system for 3-D planning are discussed.

Locate: An application of computed tomography in radiation therapy treatment planning with emphasis on tumor localization

Computed tomography can provide precise information for radiation therapy treatment planning. However, inaccuracies in radiation field design may occur when the radiation oncologist attempts to transfer information about tumor location from the transverse plane of the CT scan to the longitudinal plane of the simulation film. This report describes a new computer program, LOCATE, which addresses this problem. The program uses operator generated information from the cross sectional CT images to draw an outline of tumor on AP and lateral longitudinal scanned projection radiographs. The resultant images are useful because they are in the same plane as radiographs obtained on a therapy simulator. The impact of LOCATE on radiation treatment planning for 26 patients is discussed along with several cases in which LOCATE was particularly helpful.

Impact of CT-based treatment planning on radiation therapy of carcinoma of the bladder

Computed tomography (CT) has been an integrated step in the treatment planning of radiation therapy of carcinoma of the bladder in stages T1-T3 in 49 consecutive patients referred to Radiumstationen in Aarhus. The introduction of this technique has led to a considerable increase (26 +/- 4%) in the mean effective target volume of these patients compared with that of 51 conventionally simulated patients. The largest field expansions have been performed in the cranial and ventral directions. The field margins to the bladder have been correlated with the position of the tumour mass. The findings are compared with previously published results on CT-based treatment planning of patients with bladder carcinoma.

The use of CT in radiotherapy treatment planning

A prospective study is reported comparing conventional localisation with computed tomography (CT) localisation of tumours for radiotherapy treatment planning. One hundred and five out of 320 (33%) patients had an alteration in treatment plan and details are given according to the tumour site. CT planning enables more accurate localisation of both tumour and normal organs in addition to providing an accurate body contour and inhomogeneity corrections. Implications for integration of CT into radiotherapy planning practice are discussed and the impact of CT on treatment policy evaluated.

Computed tomography and radiotherapy in the treatment of cancer

Computed tomography (CT) has shown to be of great value in the treatment of cancer with radiation therapy. It is used more and more in the estimation of tumor volume and for treatment planning, with the aid of the computerized treatment unit. At the James Graham Brown Cancer Center, Department of Radiation Oncology, CT has been used routinely for the treatment planning. From October 1, 1981 to June 30, 1982, we performed 180 CT scans for the treatment planning, 380 simple dose calculations, 237 complex treatment plans, and 42 intracavitary dosimetry using the treatment planning unit. This is a review of our experience with some illustrations. Accurate tumor dose can be delivered with reducing the complications with the use of CT and the computerized treatment unit.

The role of CT scanning in the radiotherapy planning of pelvic tumors

In order to assess the place of computed tomography (CT) in radiotherapy planning, the tumor volumes are localized both by conventional techniques and with CT scanning under conditions simulating the radiotherapy. A comparison between the two methods has been made in a group of 55 patients with tumors in the pelvis. CT scanning was found to be of such value in 64% of the treatment series, in improving both the accuracy of localization of the target volume (48% of the patients) and the calculation of the dose distribution (31% of the patients) that its use is recommended during the radiotherapy planning of pelvic tumors.

Has CT scanning a role to play in the radiotherapy planning of palliative treatment?

Radiotherapy is useful in the palliative treatment of many large incurable tumours. This study evaluates the effectiveness of computed tomography (CT) as an adjunct in the radiotherapy planning of these patients. Forty-five patients had their treatment fields simulated using findings from physical examination, x-rays etc. The patients were then scanned under conditions simulating the radiotherapy and the dosimetry was recalculated. CT scanning was found to be valuable in the radiotherapy planning in 56% of the treatment series (field geometry: 27% dosimetry: 46%).

Long-term survivors after preoperative pelvic radiation therapy for locally unresectable rectal and sigmoid carcinoma: an assessment of late results

From 1972 to 1976, 11 patients received moderate-dose pelvic preoperative radiation therapy (4500-4600 rad +/- 500 rad boost) for initially unresectable rectal or sigmoid carcinoma. Of six patients subsequently explored, five had radical surgery and are alive without disease at least five years later. Comparison of the present long-term follow-up series with prior (short-term follow-up) series suggests that moderate-dose preoperative pelvic radiation therapy can convert many of these lesions to being resectable ones for which long-term survival-without-disease can be achieved. Attention to irradiation dose and field size is stressed, and a suggestion is made that patients whose tumors at final pathology still demonstrate extrarectal extension receive postoperative small-field boost irradiation.

Using the CT-scanner to explore and circumnavigate current inadequacies in radiotherapy planning

Successful radiotherapy practice depends on the irradiation of tumours such that their destruction follows without unacceptable damage of the surrounding normal tissues. Until recently the accurate acquisition of data concerning the tumour anatomy lagged behind other developments in radiotherapy. Since the arrival of the CT scanner, these anatomical data can be displayed ideally for transmission into a computerised treatment planning system. The CT scan information concerning tumour location, irradiation volume and dosimetry was compared with results obtained using traditional planning methods. In this series, CT scanning appears to be useful in 65 of the 126 patients (52%).