Can we predict radiation-induced changes in pulmonary function based on the sum of predicted regional dysfunction?

PURPOSE: To determine whether changes in whole-lung pulmonary function test (PFT) values are related to the sum of predicted radiation therapy (RT)-induced changes in regional lung perfusion. PATIENTS AND METHODS: Between 1991 and 1998, 96 patients (61% with lung cancer) who were receiving incidental partial lung irradiation were studied prospectively. The patients were assessed with pre- and post-RT PFTs (forced expiratory volume in one second [FEV1] and diffusion capacity for carbon monoxide [DLCO]) for at least a 6-month follow-up period, and patients were excluded if it was determined that intrathoracic recurrence had an impact on lung function. The maximal declines in PFT values were noted. A dose-response model based on RT-induced reduction in regional perfusion (function) was used to predict regional dysfunction. The predicted decline in pulmonary function was calculated as the weighted sum of the predicted regional injuries: equation [see text] where Vd is the volume of lung irradiated to dose d, and Rd is the reduction in regional perfusion anticipated at dose d. RESULTS: The relationship between the predicted and measured reduction in PFT values was significant for uncorrected DLCO (P = .005) and borderline significant for DLCO (P = .06) and FEV1 (P = .08). However, the correlation coefficients were small (range,.18 to.30). In patients with lung cancer, the correlation coefficients improved as the number of follow-up evaluations increased (range,.43 to.60), especially when patients with hypoperfusion in the lung adjacent to a central mediastinal/hilar thoracic mass were excluded (range,.59 to.91). CONCLUSION: The sum of predicted RT-induced changes in regional perfusion is related to RT-induced changes in pulmonary function. In many patients, however, the percentage of variation explained is small, which renders accurate predictions difficult.

Postmastectomy radiotherapy: toxicities and techniques to reduce them.

The role of locoregional radiation therapy after mastectomy is controversial. It reduces the risk of tumor relapse, improves breast cancer-specific survival and possibly overall survival, but has potential morbidity. This article reviews the technical aspects of postmastectomy radiation therapy and its associations with treatment-related morbidity. We consider common problems that arise in the technical setup of radiation fields. Adverse effects of postmastectomy radiation therapy may be reduced or prevented by careful radiation treatment planning.

Functional imaging of normal tissues with nuclear medicine: applications in radiotherapy.

Functional imaging techniques are gaining significant interest from radiation oncologists. Many now claim the need for physical and physiological information during both treatment planning and in the study of normal tissue injury. Toward this goal, the nuclear medicine functional imaging modalities, single-photon emission computed tomography and positron-emission computed tomography, have been used. This article reviews the studies performed in radiotherapy that used these modalities, and attempts to stimulate further interest in this topic.

A simple device to position large/flaccid breasts during tangential breast irradiation.

PURPOSE: It is technically difficult to irradiate large pendulous or flaccid breasts with tangential photon fields because they often lie very high or lateral on the chestwall. We, therefore, designed a device to reposition the breast on the chestwall to facilitate treatment. METHODS AND MATERIALS: A device to aid in repositioning the breast on the chestwall has been designed. The device consists of a reinforced polyvinylchloride tube formed into a ring that is placed around the breast. A strap around the patient's chest holds the ring in place. The breast tissue is manually moved to the desired position on the chestwall, whereafter the strap is tightened to maintain the position. Treatment setup marks are placed on the skin peripheral to the breast and on the immobilization mold. RESULTS: Twelve patients with large/flaccid breasts were successfully treated with this device. The technical and physician staff find the reproducibility and acute treatment reactions to be acceptable. Anatomically, the use of this device reduces the volume of lung tissue otherwise included in the tangential fields in patients where the breast lies far lateral. In patients where the breast lies too far cephalad on the chestwall for tangential fields to clear the arm, repositioning of the breast with this device makes tangential fields possible. CONCLUSION: This repositioning appliance aids in the radiation treatment of patients with large or flaccid breasts and, in some instances, renders otherwise nontreatable patients treatable with radiation therapy.

Impact of cradle immobilization on setup reproducibility during external beam radiation therapy for lung cancer.

PURPOSE: To compare the setup accuracy during fractionated radiation therapy for two patient groups with lung cancer treated with and without an immobilization cradle. METHODS: Three hundred ninety-seven port films from 30 patients immobilized in the Alpha Cradle were compared with 329 port films from 30 patients who were not immobilized with the cradle. All patients were treated with curative intent for nonmetastatic lung cancer. The frequency of physician-requested isocenter shifts were compared in the two groups using a two-tailed chi-square test. Initial port films taken on the first day of treatment, routine films taken usually weekly during radiation therapy, and requested films taken after a requested shift were considered separately. The immobilization device consisted of a custom-made foam cradle that extended from above the head to the knees. Patients were generally treated with their arms above their heads, and treatment setup marks in the immobilized patients were placed on both the patients' skin and the immobilization cradle. For the noncradle patients, setup marks were placed only on the patients' skin. RESULTS: For the routine films, the frequency of physician-requested isocenter shifts was lower in immobilized patients than in the nonimmobilized group (p = 0.139). Most of this reduction was seen on oblique fields (p = 0.038). No benefits were seen among initial or requested films. The two groups were well balanced with regard to stage, age, field size, and total dose. CONCLUSIONS: The use of aggressive immobilization improves the setup reproducibility in patients receiving external beam radiation therapy for lung cancer, especially during treatment with oblique fields. This improvement in treatment accuracy might improve the therapeutic ratio.

Design of a plastic minicolpostat applicator with shields.

A plastic intracavitary applicator system for the treatment of cancer of the uterine cervix is described. This applicator has a minicolpostat and a mechanism for affixing the tandem to the colpostats. Traditional afterloading refers only to the radioactive source. Both the source and the ovoid shield are afterloaded together in this applicator in contrast to traditional afterloading systems which afterload the source alone. A potential advantage of our applicator system is that it allows high quality CT localization because the sources and shields can be removed and the applicator is made of plastic. The advantages and disadvantages of this variation to the Fletcher system as well as other aspects of applicator design are discussed. An experimentally verified dose calculation method for shielded sources is applied to the design problems associated with this applicator. The dose distribution calculated for a source-shield configuration of the plastic applicator is compared to that obtained with a commercial Fletcher-Suit-Delclos (FSD) applicator. Significant shielding improvements can be achieved for the smallest diameter ovoid, that is, in the minicolpostat. The plastic minicolpostat dose distributions are similar to those produced by the conventional larger diameter colpostats. In particular, the colpostat shielding for rectum and bladder, which is reduced in the metal applicator's minicolpostat configuration, is maintained for the plastic minicolpostat. Further, it is shown that, if desired, relative to the FSD minicolpostat, the mucosa dose can be reduced by a suitable change of the minicolpostat source position.

Radiation therapy treatment planning in supratentorial glioblastoma multiforme: an analysis based on post mortem topographic anatomy with CT correlations.

In a previous study of the brains of 15 adults with glioblastoma multiforme who received minimal or no radiotherapy we determined the topographic distribution of tumor cells. All 15 brains had been fixed and then cut in the coronal or horizontal plane. The distribution of neoplastic cells was determined and entered onto tracings of the whole mount histologic sections. The last CT scans obtained prior to death of 11 of the patients were reviewed independently by a neuroradiologist who traced, on the CT scans, the outer edge of both the contrast-enhancing area and the peritumoral low density "edema". Presented with the neuroradiologist's assessment of the contrast enhancing rim of tumor and of the "edema", a radiotherapist and a radiation dosimetrist, in the present study, prepared treatment plans for a 6 MeV linear accelerator. In 9 of the 11 cases in which immediately antemortum CT scans were available, radiation treatment of the contrast enhancing area alone with a 1 cm margin would have missed portions of the histologically identified tumor. Treatment of the contrast enhancing area along with the peritumoral "edema", with a 1 cm margin, would have covered histologically identified tumor in six of the 11 cases. Treatment of the contrast enhancing area, all "edema", and a 3 cm margin around the "edema" would have covered histologically identified tumor in all cases. Tumors tended to track along nerve pathways. In those lesions near the midline it was common for tumor to cross the corpus callosum. We conclude that radiotherapy with fields designed to treat the contrast enhancing region alone or this region plus "edema" with a tight margin will frequently miss tumor which can be histologically identified by our technique.

Comparison of two repositioning devices used during radiation therapy for Hodgkin's disease.

PURPOSE: Patients irradiated for Hodgkin's disease are fixed in an immobilization cradle to improve repositioning. In the early 1990s, we changed our cradle system from a "short" upper torso cradle to an extended near-total body cradle that also includes the lower torso and thighs. In this study, we assess the impact of the extended cradle on the reproducibility of patient repositioning during irradiation of Hodgkin's disease. METHODS AND MATERIALS: A total of 782 port films of 56 patients treated immediately before and after the change-over were studied to assess positioning reproducibility. Patients treated prior to 1993 were positioned in the short cradle, while those treated 1993 and later were positioned in the extended cradle. All treatment were delivered via anterior and posterior fields and treatment areas above and below the diaphragm were considered separately and together. All treatment fields were simulated and the field shape was designed on anterior and posterior radiographs. Discrepancies in field placement between the simulation radiographs and subsequent port films were noted by a radiation oncologist and requests for position adjustment (both translational and rotational shifts) were noted. The number, magnitude, and direction of any physician-requested position adjustment on port films were retrospectively reviewed. For the purpose of scoring the frequency of field misplacements, when an adjustment was noted on two port films taken during the same treatment session (i.e., a left shift on both an anterior and a posterior port film), it was scored as only one event. A two-tailed chi-square test was used to compare the differences in requested shifts in the two patient groups. RESULTS: The study population consisted of 56 patients (31 short and 25 extended cradle) representing 92 treatment sites. A total of 782 port films representing 450 treatment setups were analyzed (292 above and 158 below the diaphragm). When all port films above the diaphragm (mostly mantle fields) are considered, position adjustments were requested in 13.4% (21 out of 157) of treatment setups with the upper torso cradle and in 5.9% (8 out of 135) of treatment setups with the extended cradle (p = 0.054). When all port films below the diaphragm (mostly paraaortic/spleen and pelvic fields) are considered, position adjustments were requested in 33.8% (27 out of 80) of treatment setups with the upper torso cradle and in 16.7 % (13 out of 78) of treatment setups with the extended cradle (p = 0.056). A reduction in the frequency of both translational and rotational adjustments were seen. When both treatment sites are combined, position adjustments were requested in 20.3% (48 out of 237) of treatment setups with the upper torso cradle and in 9.9% (21 out of 213) of treatment setups when the extended cradle was used (p = 0.0086). CONCLUSIONS: The extended cradle provides superior repositioning of patients undergoing radiation therapy for Hodgkin's disease. Differences observed in setup accuracy in this study underscore the importance of aggressive immobilization of patients with Hodgkin's disease. Increased accuracy of daily setup may provide an opportunity to improve the therapeutic ratio both by increased likelihood of tumor control and decreased risk of normal tissue complications.

Comparison of two head and neck immobilization systems.

PURPOSE: Accurate and reproducible patient positioning is fundamental to the success of fractionated radiotherapy. Concurrent with the introduction of three-dimensional treatment planning capabilities at our institution, a head and neck immobilization system consisting of a standard foam rubber head support and three casting strips was replaced by a customized mask-based device. This study was performed to analyze the impact of the customized immobilization system on the reproducibility of patient setup during irradiation of head and neck and brain tumors. METHODS AND MATERIALS: Patients treated from 1989-1991 were immobilized with the strip system while those treated from 1991-1995 were immobilized with the mask. All treatment fields were simulated and were treated on a 4 MV (where the strip, but not the mask, system was fixed to the treatment couch) or > or = 6 MV (where both the strip and the mask systems were fixed to the couch) accelerator. Port films were taken on the initial treatment day, routinely during treatment, and following shifts (requested). The number, magnitude, and direction of any isocenter shifts were retrospectively reviewed. A two-tailed chi square test was used to compare the differences in requested shifts in the strip and mask groups. RESULTS: The study population consisted of 69 brain tumor (35 strip, 34 mask) and 71 head and neck (37 strip, 34 mask) patients. A total of 1575 port films representing 1070 isocenter placements were analyzed. No differences between the immobilization systems was seen on the 4-MV accelerator (where the mask system was not fixed to the couch). On the > or = 6-MV units, the frequency of shifts was 16.1% versus 6.2% (p = 0.002) with the strips and mask, respectively. Almost all of the benefit was seen in the routine films, where the corresponding rates were 13.2% and 4.1% (p = 0.007). For the mask system, the rate of requested shifts on routine films was 4.1% (8/197) for the > or = 6-MV units and 14.5% (24/166) for the 4-MV unit (p = 0.001). CONCLUSION: Using the frequency of physician-requested isocenter shifts as an indicator of the accuracy of patient repositioning, the newer mask system appears to be an improvement over the previously used strip system, provided that the immobilization device is secured to the treatment couch. Increased accuracy of daily setup provides an opportunity to improve the therapeutic ratio both by increased likelihood of tumor control and decreased risk of normal tissue complications.

Impact of setup variability on incidental lung irradiation during tangential breast treatment.

PURPOSE: This study aimed to determine the variability in treatment setup during a 5-week course of tangential breast treatment for patients immobilized in a customized hemibody cradle, to assess the relationship between the height of the lung shadow on the tangential port film and the percentage of lung volume irradiated, and to estimate the impact of setup variabilities on irradiated lung volume. METHODS: One hundred seventy-two port films were reviewed from 20 patients who received tangential beam treatment for breast cancer. The height of the lung shadow at the central axis (CLD) on each port film was compared to the corresponding simulator film as an assessment of setup variability. A three-dimensional dose calculation was performed, and the percentage of total lung volume within the field was correlated with the CLD. The three-dimensional dose calculation was repeated for selected patients with the location of the treatment beams modified to reflect typical setup variations. RESULTS: The CLD measured on the port films was within 3 mm of that prescribed on the simulator film in 43% (74 of 172) of the port films. The variation was 3-5 mm in 26%, 5-10 mm in 25%, and >10 mm in 6%. The height of the lung shadow correlated with the percentage of lung volume included in the radiation field (r2 = 0.6). Typical variations in treatment setup resulted in < or = 5% fluctuation in the absolute volume of ipsilateral lung irradiated. CONCLUSION: The current immobilization system used in our clinic provides a clinically acceptable reproducibility of patient setup. The height of the lung shadow is reasonably well correlated with the percentage of irradiated lung volume. During a typical 5-week course of radiotherapy, the ipsilateral irradiated lung volume fluctuates <5%.

Variability of the location of internal mammary vessels and glandular breast tissue in breast cancer patients undergoing routine CT-based treatment planning.

PURPOSE: To determine the variability of position of internal mammary vessels (IMV) and glandular breast tissue (GBT) in patients undergoing breast-conserving radiation therapy. To assess the frequency and magnitude of tangential field border shifts based on preradiation therapy (RT) computed tomography (CT) imaging in breast cancer patients. METHODS AND MATERIALS: Five hundred and ninety breast cancer patients irradiated between 9/94 and 3/98 underwent routine CT-based treatment planning. Two analyses were performed. First, the position of IMV and GBT, outlined on the central axis CT image, was determined relative to the midsternum in 111 patients irradiated during a 12-month period. In the second analysis, the difference between anticipated (pre-CT) and actual (CT-based) tangential field borders was assessed in 254 patients irradiated during a 2-year period. RESULTS: In the first analysis, the depth of the IMVs varied from 1 to 6 cm (median 2.4 cm). The lateral distance from the midsternum also varied widely (range 1.7 to 3.7 cm, median 2.5 cm). Similar variability was found in the position of the GBT. In the second analysis, CT information led to changes of anticipated field borders in 65% of patients. The lateral border was shifted in 56% of patients (anteriorly 18%, posteriorly 38%). When the patients were segregated based on internal mammary node (IMN) treatment, the medial border was shifted in 49% of patients when the IMNs were treated in the tangential fields and in 24% when the GBT only was treated. The frequency of lateral field border shifts was similar in both groups. CONCLUSIONS: The position of IMVs and GBT varies widely in breast cancer patients. Tangential field borders based on surface anatomy may not be ideal. Among 254 breast cancer patients, the field borders were shifted in 65% of patients when CT information was available. Thus, in most breast cancer patients, field borders are shifted when CT-based treatment planning is used.

Defining the superior border of posterior fossa radiation treatment fields.

PURPOSE: Lateral posterior fossa treatment fields are usually defined on traditional simulation films based on bony landmarks. The superior field border, intended to include the apex of the tentorium cerebelli, is frequently difficult to define. While sagittal magnetic resonance imaging (MRI) images or three-dimensional treatment planning tools are good means to locate the tentorial apex, these are not always available. We herein describe a method for locating the tentorial apex based on bony landmarks. METHODS AND MATERIALS: Midsagittal magnetic resonance images of 53 patients were reviewed. Using a Cartesian grid, the geometric relationship between the tentorial apex and several bony landmarks was assessed. Two lines were defined: the first connected the posterior clinoid and the internal occipital protuberance (AB). The second was perpendicular to the first, included the tentorial apex, and extended from the base of the skull inferiorly to the "crown" of the skull superiorly (DE). Relationships between measurements were made using linear regression and least square fits. RESULTS: Line DE was within 5 mm of the perpendicular bisector of line AB in 83% (44/53) of patients. The tentorial apex was located within 10 mm of the midpoint of DE in 91% (48/53) of patients. CONCLUSION: In the majority of patients, the location of the tentorial apex can be estimated based on bony landmarks, to within approximately 10 mm. The technique described is a useful means of estimating the location of the tentorial apex in patients where sagittal MRI imaging or three-dimensional treatment planning tools are not available.

A customized head and neck support system.

PURPOSE: To describe a customized head and neck immobilization system for patients receiving radiotherapy including a head support that conforms to the posterior contour of the head and neck. METHODS: The system includes a customized headrest to support the posterior head and neck. This is fixed to a thermoplastic face mask that molds to the anterior head/face contours. The shape of these customized head and neck supports were compared to "standard" supports. RESULTS: This system is comfortable for the patients and appears to be effective in reproducing the setup of the treatment. CONCLUSIONS: The variability in the size and shape of the customized posterior supports exceeded that of "standard" headrests. It is our clinical impression that the customized supports improve reproducibility and are now a standard part of our immobilization system. The quantitative analysis of the customized headrests and some commonly used "standard" headrests suggests that the customized supports are better able to address variabilities in patient shape.

The effectiveness of immobilization during prostate irradiation.

PURPOSE: To evaluate the effect of a hemibody foam cradle on the reproducibility of patient setup during external beam radiation treatment of prostate cancer. METHODS AND MATERIALS: Between January 1992 and April 1993, 74 patients received external beam radiation treatment to the prostate +/- nodes, generally with a four-field box technique. Forty-four of the 74 patients had a custom-made hemibody foam cast used in an attempt to improve setup accuracy. A review of the routine weekly port films was performed following the completion of therapy to determine the reproducibility of patient setup in all 74 patients. The physician's request of an isocenter shift was used as an indicator of reproducibility. Neither the treating technologists nor the physicians knew at the time the films were taken that the port films would be reviewed for setup reproducibility at a later date. The results were compared between the patients treated with (44) and without (30) an immobilization device. RESULTS: In the 44 immobilized patients, 213 routine checks of the isocenter were performed during the 7-week course of radiation therapy. In 17.4% of these instances (37 out of 213), an isocenter shift was requested. This rate is compared to 23.1% (30 out of 130) in the 30 patients who did not have the immobilization device (p < 0.2). There was a statistically significant reduction in isocenter shifts requested in the anterior to posterior direction in the patients who were immobilized, 5.1% (9 out of 175) vs. 12.6% (13 out of 103) (p < 0.05, two tailed chi-square test). There was no significant improvement in the reproducibility of isocenter placement in the cephalad to caudal or right to left directions. CONCLUSIONS: This custom-made hemibody foam cradle appears to improve the reproducibility of patient setup during the 7-week course of fractionated external beam irradiation for patients with adenocarcinoma of the prostate. This type of immobilization device is now routinely used in our clinic and is recommended for all patients receiving pelvic radiotherapy. These devices are likely to be particularly useful when contemplating dose escalation to minimize the volume of bladder and rectum included in the treatment fields.

Changes in plasma transforming growth factor beta during radiotherapy and the risk of symptomatic radiation-induced pneumonitis.

PURPOSE: To determine whether changes in the plasma Transforming Growth Factor beta1 (TGF beta1) concentration during radiotherapy could identify patients at risk for developing symptomatic radiation pneumonitis. METHODS AND MATERIALS: Thirty-six patients who received radiation therapy with curative intent for lung cancer (n = 31), Hodgkin's disease (n = 4), or thymoma (n = 1) were evaluated prospectively. All patients had serial plasma TGF beta1 measurements obtained before, during, and after treatment. Plasma TGF beta1 was quantified using an enzyme-linked immunosorbent assay. Pneumonitis was defined clinically. Plasma TGF beta1 levels were considered to have normalized if the following occurred: the last on-treatment TGF beta1 level was both <7.5 ng/ml and lower than the pretreatment level. RESULTS: Thirteen of these 36 patients developed pneumonitis. Significant changes in plasma TGF beta1 levels during treatment were seen only in the subset of patients whose TGF beta1 levels were >7.5 ng/ml at baseline (n = 22). Failure of plasma TGF beta1 to normalize by the end of treatment, as defined above, much more accurately identified patients at risk for symptomatic pneumonitis if their baseline TGF beta1 was >7.5 ng/ml than if it was <7.5 ng/ml. CONCLUSIONS: Changes in plasma TGF beta1 levels during radiotherapy appears to be a useful means by which to identify patients at risk for the development of symptomatic radiation pneumonitis, particularly in the subset of patients whose pretreatment TGF beta1 levels are >7.5 ng/ml.

The effect of pressure from the table top and patient position on pelvic organ location in patients with prostate cancer.

PURPOSE: To assess the impact of pressure from the table top and patient position on the relationship of the prostate, rectum, and bladder to the bony pelvis. METHODS AND MATERIALS: In 9 patients with prostate cancer (3 status postprostatectomy), computed tomography (CT) scans were obtained in four positions: supine with and without false table top under the buttocks, prone with and without false table top under the lower abdomen. In four patients, a fifth scan was obtained in the first position (supine with table top in place) to assess the impact of changes in bladder/rectal fullness over time. Urination and defecation were not permitted between scans. For each patient, the four (or five) CT scans were registered to each other. RESULTS: The anal canal and the rectum caudal to the coccyx shifted posteriorly in 7/9 patients when the support under the buttocks was removed in the supine position. When pressure from the table top was removed in the prone position, the anterior bladder extension increased. The superior rectum was adjacent to the prostate in all scans and the prostate/superior rectum/bladder generally moved together. Rectal fullness changed with time and rectal gas position was gravity-dependent and shifted with patient position. Bladder volume increased with time. Organs had shifted and/or changed fullness between the first and fifth scan obtained in the same patient position approximately 90 min apart, mostly due to increase in bladder volume. All patients found the supine position most comfortable. CONCLUSIONS: The bladder and rectal fullness vary with time, confounding the ability to attribute changes in organ location to positional factors. Pressure from the table top affects the relative location of pelvic organs and, in part, is responsible for changes previously attributed to position/gravity.

Variability of the depth of supraclavicular and axillary lymph nodes in patients with breast cancer: is a posterior axillary boost field necessary?

PURPOSE: To determine the variability of the depth of supraclavicular (SC) and axillary (AX) lymph nodes in patients undergoing radiation therapy for breast cancer and to relate this variability with the patient's anterior/posterior (A/P) diameter. The dosimetric consequences of the variability in depth are explored and related to the need for a posterior axillary boost field. METHOD AND MATERIALS: In 49 patients undergoing treatment-planning computed tomography (CT) scanning in the treatment position, the maximum depth of the SC and AX lymph nodes was measured on CT images. The A/P diameter was measured at the location of the SC and AX, respectively. The relationship between the SC/AX lymph node depth and patient diameter was determined using linear regression. For an anterior SC and AX field, the relative dose to the SC and AX lymph nodes were calculated for a 6 MV photon beam. RESULTS: The maximum depth of the SC lymph nodes ranged from 2.4 to 9.5 cm (median, 4.3 cm). The depth was less than 3 cm in 4 patients, 3-6 cm in 39 (80%), and greater than 6 cm in 6 patients. There was a linear relationship between the SC lymph node depth and the A/P diameter. The depth of the SC lymph nodes in cm equals approximately one-half of the A/P diameter minus 3.5 (r(2) = 0.69). In 94% (46 of 49) of patients, the SC lymph node depth was between one-fifth and one-half of the A/P diameter. The depth of the axillary lymph nodes ranged from 1.4 to 8 cm (median, 4.3 cm). The depth was less than 3 cm in 8 patients, 3-6 cm in 32 (65%), and greater than 6 cm in 9 patients. The AX lymph node depth in cm equals approximately one-half of the A/P diameter minus 3 (r(2) = 0.81). In all patients, the AX lymph nodes were shallower than mid-depth. The depth of the SC and AX lymph nodes was within +/- 1 cm in 53% (26 of 49) of patients. The AX lymph nodes were located at >/= 1 cm shallower or greater depth than the SC in 24.5% (12 of 49) and 22.5% (11 of 49) of patients, respectively. If an anterior 6-MV beam only is used to treat the SC and AX lymph nodes in these 49 patients, the dose to the AX is within +/- 5% of the SC dose in 53% (26 of 49) patients and is 90% or more of the dose delivered in the SC in 90% (44 of 49) of patients. CONCLUSION: The maximum depth of the SC and AX lymph nodes varies widely and is related to the patient's size represented by the A/P diameter. In most patients, the AX lymph nodes lie at approximately the same depth or shallower than the SC. Therefore, the rationale for a posterior axillary boost field needs to be further assessed. When the AX and SC lymph nodes are deep, opposed supraclavicular and axillary fields and/or the use of a higher energy beam might be reasonable.

Differences in gross target volumes on contrast vs. noncontrast CT scans utilized for conformal radiation therapy treatment planning for prostate carcinoma.

PURPOSE: To compare the gross target volumes (GTVs) (prostate and seminal vesicles) defined on noncontrast and contrast-enhanced computed tomography (CT) images used for three-dimensional conformal treatment planning (3DCRT). METHODS AND MATERIALS: From 1993 to 1996, 39 patients referred for radiation therapy for adenocarcinoma of the prostate underwent pretreatment pelvic CT scanning with and without intravenous (i.v.) contrast for treatment planning purposes. Seven patients were excluded because of incomplete data sets. The prostate and seminal vesicles were outlined by the same physician on all images of 32 patients. On 18 CT exams, the prostate and seminal vesicles were blindly outlined a second time by the same physician to evaluate intraphysician consistency. Discrepancies between the GTVs outlined with and without contrast and between the first and second outline on the same study were assessed by calculating the projected area in the anterior-to-posterior (AP) and right lateral (RLAT) beam's-eye view (BEV). To assess the magnitude, frequency, and direction of discrepancies between the two GTVs, the extension of the GTVs in six directions (right, left, anterior, posterior, cephalad, and caudal) was determined. RESULTS: The GTV outlined with contrast was larger in all directions, except caudal, in the majority of patients. The change in the GTV with contrast was significant in the cephalad (p=0.0003) and right (p=0.0007) directions, but not in the other directions. Although the increase with contrast in any direction was usually small (average < or =5 mm), these changes resulted in a significant increase in GTV area in both the AP and RLAT BEV (9.0%, p=0.0017 and 8.2%, p=0.023, respectively). The intraphysician variability in outlining the prostate/ seminal vesicles was minimal. CONCLUSIONS: The addition of i.v. contrast does appear to make a significant difference in how the prostate and seminal vesicles are outlined by an experienced observer. The increase in area of the target, found when contrast is used, should be taken into consideration when designing the treatment fields for patients with carcinoma of the prostate.

Transperineal templates for brachytherapy treatment of pelvic malignancies--a comparison of standard and customized templates.

A technique is described for the design and construction of customized templates for transperineal implants and interstitial hyperthermia of pelvic malignancies. The design of the template and the distribution of the transperineal Iridium-192 seed ribbons are based on prior optimization of the dose distribution. The target volume is defined by means of pelvic examination and pertinent radiographic studies including a CT. The pelvic CT study is obtained with a plastic obturator in the rectum or the vagina. The obturator is used as a reference structure for aligning the target contour from each image plane to form a composite 2-dimensional contour of maximum tumor extent in a plane perpendicular to the obturator. Dose distributions are calculated to determine the placement of the Iridium-192 seed ribbons in the template. Laparoscopic guidance is used for actual placement of brachytherapy source needles together with a rectal or vaginal obturator to stabilize the template and to assure that the needle placement conforms with the planned geometry. Dose distributions for 10 consecutive patients calculated for customized templates as well as for five commercially available standard templates show that the customized templates are superior to standard templates in that the planned dose distribution matches the configuration of the target volume and is more uniform than with standard templates.

Tandem tip fracture: a rare complication of intracavitary therapy of cervix cancer and how to avoid its occurrence.

A case is described in which the distal tip of a tandem fractured off in a patient's uterus during an intracavitary application of a tandem and ovoids. Potential contributing factors are evaluated. Methods to prevent and detect structural defects in tandems before they become clinically manifest are discussed.