Impact on reproducibility of the treatment position by improving immobilization device in image guided radiation therapy

The immobilization device for treatment becomes important to obtain fixation and reproducibility of the treatment position. It was confirmed that reproducibility of the treatment position obtains higher accuracy by the method of using immobilization device. Methods: We divided into three terms by the methods of immobilization. An infrared reflective marker performs the setup of a position at the start of treatment, and setup of the patient in a fixed implement is performed by ExacTrac. Difference between coordinates of the immobilization device and the patient position was calculated by the vector in three directions. We estimated the position error index (PE(index)) by using the square root of the sum of square of each vectors, and evaluated the amount of differences of patient position at three terms. Results: Mean and standard deviation of index values were 9.53 ± 7.21, 8.50 ± 5.93, and 6.42 ± 3.80 at each three terms. With every passing year, the amount of gap and difference of the patient fixation has decreased. Conclusion: By the improvement of the use of the immobilization device, gap and difference of fixation has decreased. Accordingly, we could obtain better accuracy of fixation.     

A technique for evaluating cast foam positioning and immobilization devices used in breast cancer radiotherapy

Patient setup reproducibility when Alpha Cradles* are used is not well documented. A simple technique is described that localizes longitudinal and transverse planes in breast setups utilizing 4 mm lead-sphere markers embedded in a modified HS-2 Alpha Cradle. The markers are positioned in the cradle coincident with the projected simulator central axis crosshair when the x-ray beam is directed vertically down through a setup point on the patient. A reference film recording patient position relative to the Alpha Cradle is taken through the setup point at the end of the simulation procedure. On the treatment machine, the images of the lead markers on the portal film, taken through the same setup point, indicate longitudinal and transverse planes. These planes are then used to correlate and quantitate the reproducibility of the original reference planes. This technique is easily initiated, and when used in conjunction with a careful analysis of conventional treatment portal films, is very useful in determining the accuracy of patient repositioning in the Alpha Cradle, and precise field placement. Results of a study utilizing a modified HS-2 Alpha Cradle will be presented.     

First place 1989 Alpha Cradle Award winner. Positioning and immobilization device for patients receiving radiation therapy for carcinoma of the breast

Careful treatment planning and dose calculation, combined with effective positioning and immobilization, may improve the probability of tumor control. Modern radiation therapy equipment has had a significant impact on the accuracy of dose calculation and delivery. However, the problems of patient repositioning and immobilization, which may represent the area of the greatest variance in precise treatment delivery, still need much improvement. On this premise, many site specific repositioning and immobilizing devices have been developed in our institution for radiation therapy. Alpha Cradles have been used for positioning of patients undergoing irradiation for carcinoma of the breast at our institution for several years but did not provide adequate support for the arm. A modification of an Alpha Cradle was developed specifically for breast treatments and is described in this report. The modification, which is easily made, consists of a mold which conforms tightly to the arm and allows minimal variation in repositioning of the arm. A handle, built into the device, offers the patient a comfortable resting place for the hand and also fixes the orientation of the hand during the treatments. This device offers a very comfortable support for the elevated arm and greatly improves the accuracy of repositioning the patient.     

Positioning and immobilization of patients undergoing radiation therapy for Hodgkin's disease

The prognosis for patients with Hodgkin's disease is largely determined by the initial management, therefore, special attention must be given to the precision of the often complex treatment in these relatively young and curable patients. Positioning and immobilization is extremely important and may have a role in the final outcome of the treatment. Alpha Cradles, along with laser alignment systems, have been routinely used for these patients in our institution for approximately 10 years. Despite these efforts, difficulties are encountered in precisely reproducing the setup. A modification was therefore made to an Alpha Cradle to include an arm support with handles that fix the position of the patient's elevated arms during the treatment. This modification provides improved repositioning and alignment of the patients, which may have an impact on the final outcome of the treatment. The positioning device also offers improved patient comfort, and, as a result, reduced patient motion as evidence by the reduced number of adjustments required when port films are examined. Additionally, the described technique reduces the risks of over- or underdosage at the junction between the mantle and the para-aortic fields.     

Immobilization and treatment of patients receiving radiation therapy for extremity soft-tissue sarcoma.

The treatment of extremity soft-tissue sarcoma has evolved considerably over the years. Previously, the preferred treatment was radical resection or amputation. Recently, radiation therapy combined with conservative resection has been shown to provide adequate tumor control while preserving a functional limb. Often, a large volume of tissue is irradiated in a manner that requires the patient to be in a reproducible position. Minimizing patient movement is imperative to ensure that the prescribed dose is delivered to the designated target volume. At our institution, Alpha Cradles have been routinely used for eight years to aid in positioning extremity sarcoma patients. The positioning of the patient for tumors at different locations in the extremity and the Alpha Cradle fabrication is described. The positioning device is comfortable for the patient and the accuracy is verified by comparison of simulation films with weekly port films.     

Impact of the “Belly Board” Device on Treatment Reproducibility in Preoperative Radiotherapy for Rectal Cancer

BACKGROUND: The use of the belly board device (BBD) in the prone position has gained acceptance to spare small bowel in rectal cancer patients irradiated postoperatively, but there are few data in the preoperative setting, and the advantages of the BBD regarding normal tissue sparing may be counteracted by problems of patient positioning. This study was undertaken to investigate prospectively the influence of the BBD on treatment reproducibility in patients irradiated preoperatively in the prone position. PATIENTS AND METHODS: 23 patients with rectal carcinoma in clinical stages II/III were included in this study. Axis displacement was evaluated in 14 patients treated without the BBD and nine with. The BBD is a commercial device (Belly Board, Radiation Products Design, Albertville, MN) made of a 17-cm thick hard sponge with an opening of 42 x 42 cm2. No specific patient immobilization devices were used. During radiotherapy, twelve patients had four control films, while eleven patients had three. The mean treatment position deviation was calculated for the medio-lateral, cranio-caudal and antero-posterior directions. RESULTS: When comparing the first control film to the corresponding simulation film for patients without the BBD and with the BBD, the mean lateral displacements were 1.5 mm and 3.2 mm (p = 0.26), the mean cranio-caudal displacements were 1.55 mm and 4.2 mm (p = 0.13), and the mean antero-posterior displacements were 1.8 mm and 4.5 mm (p = 0.04), respectively. When considering all control films, for the three directions, the amplitudes of the displacements were greater when using the BBD, particularly for the antero-posterior direction where the difference was highly significant (p = 0.0006). CONCLUSIONS: Our data show that, in patients treated prone for rectal cancer, the use of the BBD in the preoperative setting without immobilization devices was associated with problems of patient position reproducibility, particularly for the antero-posterior direction. Thus, the use of patient immobilization devices and/or individual custom-made BBD may be recommended if a decision to treat the patient with a BBD is taken.     

Evaluation of positioning reproducibility using a re-locatable head frame for stereotactic radiotherapy

In fractionated stereotactic radiotherapy (SRT), the accuracy of patient relocation is very important. The Gill-Thomas-Cosman (GTC) re-locatable stereotactic frame is used for patient immobilization. A depth helmet and measuring probe are used to check the stability of the patient's head position relative to the GTC frame. However, displacement error caused by rotation of the patient's head is not considered in the depth-helmet measurement. Consequently, displacement of the isocenter position cannot be confirmed by the measurement obtained from the depth helmet. In this study, we evaluated the precision of reproducibility by comparing measurement values of the depth helmet with the displacement of anatomical position on a CT image. We analyzed 21 setups of 8 patients immobilized for SRT using the GTC frame, between June 2001 and June 2003. The reproducibility of the GTC frame was checked at each treatment by comparing it with the treatment planning position. The average discrepancy of the GTC frame set-up measured by the depth helmet was 0.6 mm, with a standard deviation of 0.3 mm. The result measured by CT was 0.7 mm, with a standard deviation of 0.4 mm. When the error of each measurement point was within 1.0 mm, the accuracy of relocation of the patient could be considered clinically acceptable. Displacement error not considered in the measurement of the depth helmet could be evaluated by using CT.     

Upright 3D Treatment Planning Using a Vertical CT

In this report, we describe a novel technique used to plan and administer external beam radiation therapy to a patient in the upright position. A patient required reirradiation for thymic carcinoma but was unable to tolerate the supine position due to bilateral phrenic nerve injury and paralysis of the diaphragm. Computed tomography (CT) images in the upright position were acquired at the Northern Illinois University Institute for Neutron Therapy at Fermilab. The CT data were imported into a standard 3-dimensional (3D) treatment planning system. Treatment was designed to deliver 24 Gy to the target volume while respecting normal tissue tolerances. A custom chair that locked into the treatment table indexing system was constructed for immobilization, and port films verified the reproducibility of setup. Radiation was administered using mixed photon and electron AP fields.     

Incorporation of patient immobilization, tissue compensation and matchline junction technique for three-field breast treatment

A protocol for the treatment of the intact breast was developed to maximize dose homogeneity and reproducibility. This protocol uses patient and breast immobilization, three-dimensional tissue compensators, and a technique for geometric matching of fields when the supraclavicular area is treated. A series of phantom measurements and analysis of patient port films was performed to evaluate dose homogeneity and reproducibility using this technique, and the potential adverse effect of loss of skin sparing from the immobilization device was investigated. Dose homogeneity throughout the phantom breast was within +/- 6% of the prescribed central axis dose, and homogeneity at the supraclavicular match line was +/- 10%. This represented a significant improvement over techniques not using tissue compensation or geometrically matched fields. Reproducibility of patient treatments was not significantly improved from previous non-immobilized treatment techniques, but there was no loss of skin sparing from the device, and other advantages of immobilization were observed. Details of the protocol are discussed together with changes that are currently being made to improve the results obtained thus far.     

Who says you can’t treat pituitary carcinoma on a breast board?

A hospital-manufactured aquaplast head and neck immobilization system was constructed in tandem with a unique custom-built breast board. It was developed in conjunction with the breast board for patients unable to achieve and maintain the desired head flexion needed in the treatment of pituitary lesions. (This custom design provides an alternative to accomplishing this desired head angle needed to position the patient’s eyes out of the treatment area, realizing that the lenses are situated in the anterior 1 cm of the globes.) By using the angled breast board, reproducibility of setup and patient comfort were addressed throughout the simulation, computed tomography planning and treatment process. The custom designed boards were constructed with available materials at relatively low cost to the department.     

Immobilization techniques and dosimetric aspects for pituitary tumors

Twelve percent of all intracranial tumors arise in the pituitary fossa. The management of pituitary tumors is a complex process that may combine several treatment modalities including radiation therapy. Minimizing patient movement during the course of radiation therapy treatment is imperative to ensure both the delivery of the prescribed dose to the small target volume and to minimize the radiation dose to critical structures. Several alternative types of immobilization devices are being used for this purpose; these include biteblocks, thermal plastics, and polyurethane molds (Alpha Cradle). The advantages and disadvantages of each of these devices are reviewed and the fabrication process of the pituitary immobilization mold that we are currently using is described. Dosimetric aspects of the treatments using these devices is addressed.     

Third place 1989 Alpha Cradle Award winner. Technical aspects in the use of "belly boards" for small bowel minimization

The position in which a patient is treated for pelvic irradiation has been shown to have dramatic significance in regard to the volume of small bowel within the treatment field. Previous studies in the literature have repeatedly supported the fact that volume may be the leading factor in both acute and chronic morbidity. We have prospectively evaluated and treated 30 patients utilizing a custom-made polyurethane foam and styrofoam "belly board" with a dropout cut from the level of the xyphoid process to the superior border of the treatment field, specifically designed to allow maximal superior and anterior displacement of small bowel by bladder distention and gravity, while allowing reliable daily reproducibility, accurate immobilization and equally important, increased patient comfort and compliance. By evaluating all patients (in both the supine position alone, and prone in the "Belly Board") with a dedicated treatment planning CT scanner, we have been able to achieve 80-100% reduction in the volume of small bowel within the radiation portals. We will discuss data on the technical set-up, cost, and variations which allow the "Belly Board" to be specifically tailored for use when treating other intraabdominal sites. This technique is simple, inexpensive, highly reproducible, and permits maximal bowel displacement outside the treatment fields.     

Alpha Cradles in breast cancer treatment: easy immobilization for the potentially difficult breast set up

Due to the preference of the present multimodality treatment of breast cancer, we have found the need for a more customized approach to our patient set-up position. Using Smithers Medical Alpha Cradle Kits (AC 325) we have been able to achieve individual casts for our physically challenging patients. The results are a comfortable, easily reproducible position for a technically involved isocentric set-up which requires little additional simulation time and allows the majority of the allotted time for physics measurements and patient interaction. Examples of patient set-ups and consistent treatment field verification are discussed in the following pages.     

A head immobilization system for radiation simulation, CT, MRI, and PET imaging

An aquaplast mask/marker immobilization system for the routine radiation therapy treatment of head and neck disease is described. The system utilizes a commercially available thermoplastic mesh indexed and mounted to a rigid frame attached to the therapy couch. The apparatus is designed to permit CT, MRI, and PET diagnostic scans of the patient to be performed in the simulation and treatment position utilizing the same mask, thereby facilitating image correlation. Studies employing weekly simulation indicate that patient treatment position movement can be restricted to 3 mm over the course of treatment. This easily constructed system permits rapid mask formation to be performed on the treatment simulator, resulting in an immobilization device comparable to masks produced with vacuum-forming techniques. Details of construction, verification, and central axis CT, MRI, PET markers are offered.     

A comparison of surface doses for two immobilizing systems

To achieve accurate and reproducible treatments, many types of immobilizing systems have been used. Two of these systems: Alpha Cradle^™ and VacFix^™, conform around the patient to improve day-to-day treatment repositioning. The Alpha Cradle^™ system has been in clinical use for several years. The system involves tow polyurethane chemicals which upon mixing in a latex bag will expand and harden around the patient. The second system (VacFix^™) uses a 0.15 mm thick plastic bag loosely filled with 1 mm polysterol spheres. The patient lays on the bag in the treatment position and the air is evacuated from the bag. This system retains its shape for the entire treatment and can be re-used. In some patient set-ups, it is possible that the beam is modified as it passes through these devices, causing a potential change in the target dose and an increase in the patient surface dose. CT scans of the Alpha Cradle^™ and VacFix^™ systems were performed and relative densities were calculated and compared to air. Material densities and surface dose data for a Cobalt-60 teletherapy unit and a dual photon linear accelerator are presented.     

Frame-based immobilization and targeting for stereotactic body radiation therapy.

Frame-based stereotactic body radiation therapy (SBRT), such as that conducted with Elekta's Stereotactic Body Frame, can provide an extra measure of precision in the delivery of radiation to extracranial targets, and facilitates secure patient immobilization. In this paper, we review the steps involved in optimal use of an extra-cranial immobilization device for SBRT treatments. Our approach to using frame-based SBRT consists of 4 steps: patient immobilization, tumor and organ motion control, treatment/planning correlation, and daily targeting with pretreatment quality assurance. Patient immobilization was achieved with the Vac-Loc bag, which uses styrofoam beads to conform to the patient's shape comfortably within the body frame. Organ and motion control was assessed under fluoroscopy and controlled via a frame-mounted abdominal pressure plate. The compression screw was tightened until the diaphragmatic excursion range was < 1 cm. Treatment planning was performed using the Philips Pinnacle 6.2b system. In this treatment process, a 20 to 30 noncoplanar beam arrangement was initially selected and an inverse beam weight optimization algorithm was applied. Those beams with low beam weights were removed, leaving a manageable number of beams for treatment delivery. After planning, daily targeting using computed tomography (CT) to verify x-, y-, and z-coordinates of the treatment isocenter were used as a measure of quality assurance. We found our daily setup variation typically averaged < 5 mm in all directions, which is comparable to other published studies on Stereotactic Body Frame. Treatment time ranged from 30 to 45 minutes. Results demonstrate that patients have experienced high rates of local control with acceptable rates of severe side effects - by virtue of the tightly constrained treatment fields. The body frame facilitated comfortable patient positioning and quality assurance checks of the tumor, in relation to another set of independent set of coordinates defined by the body frame fiducials. The ability to impose abdominal compression proved to be a simple way to reduce target and tissue motion. SBRT with Stereotactic Body Frame enables comfortable patient immobilization and facilitates repeated registering and re-registering of the patient to the frame. With the body frame, large-dose-per fraction treatment is possible for localized tumor deposits with the aim of attaining a more therapeutic result.     

Evaluation of interbreath-hold lung tumor position reproducibility with vector volume histogram using the breath-hold technique

Tumor geometric reproducibility for lung stereotactic body radiotherapy (SBRT) is an important issue in the breath-hold (BH) technique. We investigated the inter-BH reproducibility of the tumor position in expiratory BH using our proposed vector volume histogram (VVH) method. Subjects comprising 14 patients with lung cancer who were treated with lung SBRT under expiratory BH conditions were monitored by the Abches system. Multiple computed tomography (CT) scans were performed to evaluate the inter-BH reproducibility of the tumor position at the expiratory BH in the simulation session. Gross tumor volume was delineated by a physician. Deformable image registration was used to deform the images from the 3 expiratory BH-CTs to the treatment planning expiratory BH-CT. To evaluate the inter-BH reproducibility of the tumor positions, we measured the largest motion extent within the organ of 3 dimensions (left-right, LR; anterior-posterior, AP; cranio-caudal, CC) and a 3D vector using the VVH method. The average and standard deviations of the inter-BH reproducibility of the tumor position in the LR, AP, and CC directions, and the 3D vector were 1.7 ± 0.5, 2.0 ± 0.7, 2.1 ± 0.7, and 2.7 ± 0.7 mm, respectively. Ten patients exhibited inter-BH displacements of the lung tumor >3 mm in the 3D vector. No displacement >5 mm was observed in any direction for all patients. Our study indicated that the inter-BH variation of the tumor position was small for lung cancer patients, using the Abches system and the VVH method.     

Functional cast immobilization of thumb metacarpophalangeal joint injuries

A prospective study was performed on 40 patients who were treated with a modified thumb spica cast (MTSC) for injuries involving the region of the metacarpophalangeal joint of the thumb. Twenty-seven of these injuries occurred during sports participation. The immobilization consisted of a fiberglass cast which incorporated the thumb in a balanced position and allowed full flexion and extension of the wrist. Twenty patients had injuries involving the ulnar collateral ligament (five surgical). Three patients had radial collateral ligament injuries (two surgical). Fourteen patients had fractures of the proximal phalanx, including five epiphyseal plate injuries. Two patients had dorsal dislocations and one patient had a metacarpal fracture. One patient with a nondisplaced distal metacarpal fracture was treated with simple immobilization. All patients had successful completion of their treatment within the usual time frame. There was no recurrence or increase in symptomatology during the treatment. There was no residual discomfort, loss of position or malunion of the fractures treated. The advantages of the MTSC include improved functional capabilities during immobilization, good patient acceptance, and no period of limited wrist motion or atrophy of forearm musculature. Our experience has been that the MTSC has been a reliable form of immobilization for treating injuries of the metacarpophalangeal joint of the thumb.     

Implementation of the three-field electron wraparound technique for extensive recurrent chest wall carcinoma: dosimetric and clinical considerations

Treatment of extensive recurrent chest wall carcinoma is a challenge for the radiation oncologist as well as the physics team responsible for setup, computer planning, and daily reproducibility. While electron arc therapy is desirable, unfortunately, most sites do not have this capability. The alternative method of treatment discussed here involves the use of a three-field electron wraparound technique for the chest wall when electron arc therapy is not available. This technique yields an excellent alternative treatment modality with flexibility to accommodate multiple electron energies to compensate for varying chest wall thickness. An additional anterior photon beam is used when skin lesions extend superiorly to the clavicle and along the proximal aspect of the arm. Computerized tomography (CT) interfaced radiotherapy computer planning is used to precisely calculate the sequential gantry angles, skin gaps for adjacent electron fields, and the appropriate junction moves to create a feathering effect of all overlap areas. Treatment aids include extensive shaping of electron and photon fields and the application of bolus material on all four fields. A Smithers Medical Products' Alpha Cradle is used to make this intricate setup possible, providing patient comfort and daily reproducibility for a more efficient treatment.     

Erste Erfahrungen mit computerunterstützter stereotaktischer interstitieller Brachytherapie

Purpose

To reach an optimal treatment result and to avoid damage to critical structures a homogenous dose distribution in the tumor volume with a rapid decreasing dose to the surrounding structures is necessary. Fractionated interstitial brachytherapy of tumors in the ENT region employing needles depends on exact localization of the target volume during all fractions. Therefore reproducibility of positioning of the needle(s) plays an important role.

Material and Methods

We used the ISG Viewing Wand system in combination with the Vogele-Bale-Hohner (VBH) head holder and a new targeting device. Point of entrance, pathway, and target point of the needle were planned and insertion of the needle simulated in advance. To date we have treated 7 patients with inoperable tumors in the ENT region. The actual position of the needle in the control CT was compared to the planned position.

Results

The accuracy of positioning of the needle depended on the location of the tumor. In a patient with a recurrent retroorbital adenocarcinoma the mean accuracy was 1 mm. Due to soft tissue displacement in the neck region and the resulting necessity to readjust the targeting device the needle was placed with a mean deviation of 15 mm between the planned and the actual position.

Conclusions

Computer-assisted frameless stereotactic interstitial brachytherapy allows for precise, reproducible and preplanned insertion of hollow needles into target structures closely adherent to the surrounding tissue, thus avoiding damage of neighbouring structures. This technique is of great advantage in treating deeply seated tumors which are fixed to bony structures, especially at the skull base. Inaccuracy in the neck region caused by soft tissue shift requires improvement of the immobilization in this region.