Volume Of Bowel Research Articles

Mapping pelvic lymph nodes: Guidelines for delineation in intensity-modulated radiotherapy

To establish guidelines for delineating the clinical target volume for pelvic nodal irradiation by mapping the location of lymph nodes in relation to the pelvic anatomy. Twenty patients with gynecologic malignancies underwent magnetic resonance imaging with administration of iron oxide particles. All visible lymph nodes were outlined. Five clinical target volumes were generated for each patient using modified margins of 3, 5, 7, 10, and 15 mm around the iliac vessels. The nodal contours were then overlaid and individual nodes analyzed for coverage. The volume of normal tissue within each clinical target volume and planning target volume was also measured to aid selection of the margin that could provide maximal nodal, but minimal normal tissue, coverage. In total, 1216 nodal contours were evaluated. The nodal coverage was 56%, 76%, 88%, 94%, and 99% using vessel margins of 3, 5, 7, 10, and 15 mm, respectively. The mean volume of bowel within the planning target volume was 146.9 cm3 with a 7-mm margin, 190 cm3 with a 10-mm margin, and 266 cm3 with a 15-mm margin. Minor modification to the 7-mm margin ensured 99% coverage of the pelvic nodes. Blood vessels with a modified 7-mm margin offer a good surrogate target for pelvic lymph nodes. By making appropriate adjustments, coverage of specific nodal groups may be increased and the volume of normal tissue irradiated decreased. On the basis of these findings, recommended guidelines for outlining pelvic nodes have been produced.

Pelvic Nodal Dose Escalation with Prostate Hypofractionation Using Conformal Avoidance Defined (H-CAD) Intensity Modulated Radiation Therapy

The management of prostate cancer patients with a significant risk of pelvic lymph node involvement is controversial. Both whole pelvis radiotherapy and dose escalation to the prostate have been linked to improved outcome in such patients, but it is unclear whether conventional whole pelvis doses of only 45-50 Gy are optimal for ultimate nodal control. The purpose of this study is to examine the dosimetric and clinical feasibility of combining prostate dose escalation via hypofractionation with conformal avoidance-based IMRT (H-CAD) dose escalation to the pelvic lymph nodes. One conformal avoidance and one conventional plan were generated for each of eight patients. Conformal avoidance-based IMRT plans were generated that specifically excluded bowel, rectum, and bladder. The prostate and lower seminal vesicles (PTV 70) were planned to receive 70 Gy in 2.5 Gy/fraction while the pelvic lymph nodes (PTV 56) were to concurrently receive 56 Gy in 2 Gy/fraction. The volume of small bowel receiving >or=45 Gy was restricted to 300 ml or less. These conformal avoidance plans were delivered using helical tomotherapy or LINAC-based IMRT with daily imaging localization. All patients received neoadjuvant and concurrent androgen deprivation with a planned total of two years. The conventional, sequential plans created for comparison purposes for all patients consisted of a conventional 4-field pelvic box prescribed to 50.4 Gy (1.8 Gy/fraction) followed by an IMRT boost to the prostate of 25.2 Gy (1.8 Gy/fraction) yielding a final prostate dose of 75.6 Gy. For all plans, the prescription dose was to cover the target structure. Equivalent uniform dose (EUD) analyses were performed on all targets and dose-volume histograms (DVH) were displayed in terms of both physical and normalized total dose (NTD), i.e. dose in 2 Gy fraction equivalents. H-CAD IMRT plans were created for and delivered to all eight patients. Analysis of the H-CAD plans demonstrates prescription dose coverage of >95% of both the PTV 70 (prostate) and PTV 56 (nodes). The EUDs for PTV 70 and PTV 56 were greater than prescription dose for all eight plans. Analysis of bio-effective DVHs demonstrated similar amounts of small bowel receiving >or=45 Gy for H-CAD and sequential plans, in spite of the significantly higher dose to which H-CAD treated the pelvic nodes. The treatment was well tolerated in the eight treated patients in that no grade 2 or higher acute gastrointestinal toxicities were seen. Prostate hypofractionation with concurrent conformal avoidance-based pelvic IMRT for high risk prostate cancer represents an efficient and promising method for achieving dose escalation both of pelvic lymph nodes and the prostate with modest acute toxicity. Unlike a vascular-guided targeting approach, conformal avoidance has the potential advantage of also encompassing at-risk nodes that are not contained within major nodal chains. A phase II trial to more thoroughly examine this treatment approach is currently underway.

To Determine the Volume of Bowel and Dose Received in the Pelvic Radiation Field for Rectal Cancer in the Prone and Supine Position

To Determine the Volume of Bowel and Dose Received in the Pelvic Radiation Field for Rectal Cancer in the Prone and Supine Position

Variation of small bowel sparing with small bowel displacement system according to the physiological status of the bladder during radiotherapy for cervical cancer

Objective. To evaluate the reproducibility of small bowel displacement system (SBDS) volumetrically using weekly CT throughout a regimen of radiotherapy for the treatment of cervical cancer. Methods. From October 2004 to January 2005, 10 consecutive patients who received pelvic radiation therapy for uterine cervical carcinoma with the SBDS were included in this study. With the patient laid prone on the conventional simulator table, the Styrofoam compression device is placed under the lower abdomen of the patient. Next, CT scan images, first two sets of without and with the SBDS, followed by with SBDS once a week for 3 weeks consecutively after the beginning of radiotherapy, were taken. Radiation planning was performed using standard pelvic box fields in 3-dimensional radiation treatment planning system. In each CT sets, we measured the identified organ volumes and the volume of small bowel irradiated in treatment portals. We used the regression analysis to know the correlation of the volume of small bowel irradiated according to the volume variation of bladder during radiotherapy. Results. The mean small bowel volume with SBDS of 10 patients during radiotherapy was reduced by 60.5% (from 32.5% to 78.2%), comparing to the small bowel volume without SBDS. The variation of small bowel volume reduction in each patient was ranged from 7.3% to 38.5% (mean: 20.5%). In spite of using the SBDS, the volume reduction of small bowel irradiated was affected significantly by the volume of bladder during radiotherapy. The variation of small bowel irradiated for five patients who had more than 10% small bowel volume variation was significantly correlated with the volume of bladder, but not for five patients less than 10% small bowel volume variation. Conclusion. We confirm that in spite of the variation of bladder volume during radiotherapy, the SBDS is an effective method that can be used to displace the small bowel continuously away from the irradiated field for cervical cancer.

Comparative Analysis of the Effects of Belly Board and Bladder Distension in Postoperative Radiotherapy of Rectal Cancer Patients

To compare the effect of reducing the irradiated small-bowel volume with the use of belly board, bladder distension or both methods combined, in patients with rectal cancer undergoing postoperative pelvic radiotherapy. This study enrolled 20 consecutive patients with rectal cancer who were scheduled to receive postoperative pelvic radiotherapy. All patients underwent four sets of CT scans under four different methods as follows: group I: empty bladder without the use of a belly board; group II: empty bladder with the use of a belly board; group III: bladder distension without the use of a belly board; group IV: bladder distension with the use of a belly board. The conventional three-field treatment plan was made using a three-dimensional treatment planning system. The irradiated small-bowel volume was calculated at 10% intervals from 10% to 100% of the prescribed dose. The volume of the irradiated small bowel decreased in the order of group I, group II, group III, and group IV at all dose levels (p < 0.001). In comparison to group I, the mean absolute volume reductions (relative volume reduction) of the irradiated small bowel were 41.5 +/- 20.1 cm(3) (33.9 +/- 12.9%) in group II, 76.6 +/- 30.5 cm(3) (55.1 +/- 17.8%) in group III, and 98.5 +/- 36.7 cm(3) (70.7 +/- 14.5%) in group IV. Bladder distension was a more effective method than the belly board for reducing the irradiated small-bowel volume in postoperative pelvic radiotherapy of rectal cancer patients. The combination of the belly board and bladder distension showed an additive effect and was the most effective method for reducing the irradiated small-bowel volume.

Intensity modulated radiotherapy for high risk prostate cancer based on sentinel node SPECT imaging for target volume definition

BackgroundThe RTOG 94-13 trial has provided evidence that patients with high risk prostate cancer benefit from an additional radiotherapy to the pelvic nodes combined with concomitant hormonal ablation. Since lymphatic drainage of the prostate is highly variable, the optimal target volume definition for the pelvic lymph nodes is problematic. To overcome this limitation, we tested the feasibility of an intensity modulated radiation therapy (IMRT) protocol, taking under consideration the individual pelvic sentinel node drainage pattern by SPECT functional imaging.MethodsPatients with high risk prostate cancer were included. Sentinel nodes (SN) were localised 1.5–3 hours after injection of 250 MBq 99mTc-Nanocoll using a double-headed gamma camera with an integrated X-Ray device. All sentinel node localisations were included into the pelvic clinical target volume (CTV). Dose prescriptions were 50.4 Gy (5 × 1.8 Gy / week) to the pelvis and 70.0 Gy (5 × 2.0 Gy / week) to the prostate including the base of seminal vesicles or whole seminal vesicles. Patients were treated with IMRT. Furthermore a theoretical comparison between IMRT and a three-dimensional conformal technique was performed.ResultsSince 08/2003 6 patients were treated with this protocol. All patients had detectable sentinel lymph nodes (total 29). 4 of 6 patients showed sentinel node localisations (total 10), that would not have been treated adequately with CT-based planning ('geographical miss') only. The most common localisation for a probable geographical miss was the perirectal area. The comparison between dose-volume-histograms of IMRT- and conventional CT-planning demonstrated clear superiority of IMRT when all sentinel lymph nodes were included. IMRT allowed a significantly better sparing of normal tissue and reduced volumes of small bowel, large bowel and rectum irradiated with critical doses. No gastrointestinal or genitourinary acute toxicity Grade 3 or 4 (RTOG) occurred.ConclusionIMRT based on sentinel lymph node identification is feasible and reduces the probability of a geographical miss. Furthermore, IMRT allows a pronounced sparing of normal tissue irradiation. Thus, the chosen approach will help to increase the curative potential of radiotherapy in high risk prostate cancer patients.

Conventional, conformal, and intensity-modulated radiation therapy treatment planning of external beam radiotherapy for cervical cancer: The impact of tumor regression

Investigating the impact of tumor regression on the dose within cervical tumors and surrounding organs, comparing conventional, conformal, and intensity-modulated radiotherapy (IMRT) and the need for repeated treatment planning during irradiation. Fourteen patients with cervical cancer underwent magnetic resonance (MR) imaging before treatment and once during treatment, after about 30 Gy. Target volumes and critical organs were delineated. First conventional, conformal, and IMRT plans were generated. To evaluate the impact of tumor regression, we calculated dose-volume histograms for these plans, using the delineations of the intratreatment MR images. Second conformal and IMRT plans were made based on the delineations of the intratreatment MR images. First and second plans were compared. The average volume receiving 95% of the prescribed dose (43 Gy) by the conventional, conformal, and IMRT plans was, respectively, for the bowel 626 cc, 427 cc, and 232 cc; for the rectum 101 cc, 90 cc, and 60 cc; and for the bladder 89 cc, 70 cc, and 58 cc. The volumes of critical organs at this dose level were significantly reduced using IMRT compared with conventional and conformal planning (p < 0.02 in all cases). After having delivered about 30 Gy external beam radiation therapy, the primary gross tumor volumes decreased on average by 46% (range, 6.1-100%). The target volumes on the intratreatment MR images remained sufficiently covered by the 95% isodose. Second IMRT plans significantly diminished the treated bowel volume, if the primary gross tumor volumes decreased >30 cc. Intensity-modulated radiation therapy is superior in sparing of critical organs compared with conventional and conformal treatment, with adequate coverage of the target volumes. Intensity-modulated radiation therapy remains superior after 30 Gy external beam radiation therapy, despite tumor regression and internal organ motion. Repeated IMRT planning can improve the sparing of the bowel and rectum in patients with substantial tumor regression.

Whole pelvic radiotherapy for prostate cancer using 3D conformal and intensity-modulated radiotherapy

To investigate the correlations between observed clinical morbidity and dosimetric parameters for whole pelvic radiotherapy (WPRT) for prostate cancer using either three-dimensional conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT). Between December 1996 and January 2002, 27 patients with prostate adenocarcinoma were treated with conformal WPRT as part of their definitive treatment. WPRT was delivered with 3D-CRT in 14 patients and with IMRT in 13 patients. For each of the patients treated with IMRT, optimized conventional two-dimensional (2D) and 3D-CRT plans were retrospectively generated for the whole pelvic phase of the treatment. Dose-volume histograms for the bowel, bladder, and rectum were compared for the three techniques. Acute toxicities were evaluated for all 27 patients, and late toxicities were evaluated for 25 patients with sufficient follow-up. Toxicities were scored according to the Radiation Therapy Oncology Group morbidity grading scales. Median follow-up was 30 months. Three-dimensional-CRT resulted in a 40% relative reduction (p < 0.001) in the volume of bowel receiving 45 Gy compared with 2D, and IMRT provided a further 60% reduction relative to 3D-CRT (p < 0.001). Compared with either 2D or 3D-CRT, IMRT reduced the volume of rectum receiving 45 Gy by 90% (p < 0.001). Overall, 9 patients (33%) experienced acute Grade 2 gastrointestinal (GI) toxicity, and only 1 of these patients was treated with IMRT. Antidiarrhea medication was required for 6 patients (22%). However, 5 of these 6 patients also received chemotherapy, and none were treated with IMRT. No Grade 3 or higher acute or late GI toxicities were observed. No cases of late radiation enteritis were observed. Acute and late genitourinary toxicity did not appear significantly increased by the addition of conformal WPRT. Compared to conventional 2D planning, conformal planning for WPRT resulted in significant reductions in the doses delivered to the bowel, rectum, and bladder. IMRT was superior to 3D-CRT in limiting the volume of bowel and rectum within high-dose regions. These dosimetric findings correlated with low rates of acute and late GI morbidity.

Intensity-modulated radiation therapy after hysterectomy: Comparison with conventional treatment and sensitivity of the normal-tissue–sparing effect to margin size

To determine the influence of target-volume expansion on the reduction in small-bowel dose achieved with use of intensity-modulated radiation therapy (IMRT) vs. standard conformal treatment of the pelvis after hysterectomy, and to investigate the influence of patient body habitus on the normal-tissue sparing achieved with use of IMRT. A clinical target volume (CTV) was contoured on each of 10 planning computed tomography scans of patients who had been treated for cervical or endometrial cancer after a hysterectomy. Treatment planning was based on vaginal CTVs and regional nodal CTVs. To account for internal motion, margins were added to form an initial planning target volume (PTVA) as follows: 0.0 mm were added to the regional nodal CTV; 10 mm were added anteriorly to the vaginal CTV; and 5 mm were added to the vaginal CTV in all other directions. Two further PTVs (PTVB and PTVC) were produced by a 5-mm expansion of PTVA to give PTVB and a further 5-mm expansion to give PTVC. Treatment plans for all 3 PTVs were produced by use of 2 conformal fields (2FC), 4 conformal fields (4FC), or IMRT to deliver 45 Gy to more than 97% of the PTV. The primary goal of IMRT was to spare small bowel. The change in sparing that accompanied the increase in margin size was assessed by comparison of dose-volume histograms that resulted from PTVA, PTVB, and PTVC. Measured patient dimensions were correlated with bowel sparing. Significantly less small bowel was irradiated by IMRT than by 2FC (p < 0.0001) or 4FC (p < 0.0001) for doses greater than 25 Gy. Significantly less rectum was irradiated by IMRT than by 2FC (p < 0.0001) or 4FC (p < 0.0001). Significantly less bladder was irradiated by IMRT than by 2FC (p < 0.0001). However, the magnitude of the sparing achieved by use of IMRT decreased as margins increased. In particular, the volume of small bowel spared by IMRT vs. 2FC or 4FC decreased as margin size increased (p = 0.0002 and p = 0.008 for 2FC and 4FC, respectively). The amount of normal-tissue sparing achieved by use of IMRT vs. 4FC was inversely correlated with patient body mass index. Because the small-bowel sparing achieved with use of IMRT is markedly reduced by relatively small expansions of the target volume, accurate target delineation, highly reproducible patient immobilization, and a clear understanding of internal-organ motion are needed to achieve optimal advantage in the use of IMRT over conventional methods of posthysterectomy pelvic radiation therapy.

Feasibility of dose escalation using intensity-modulated radiotherapy in posthysterectomy cervical carcinoma

To evaluate retrospectively the utility of intensity-modulated radiotherapy (IMRT) in reducing the volume of normal tissues receiving radiation at varying dose levels when the female pelvis after hysterectomy is treated to doses of 50.4 Gy and 54 Gy. Computed tomography scans from 10 patients who had previously undergone conventional postoperative RT were selected. The clinical tumor volume (vaginal apex and iliac nodes) and organs at risk were contoured. Margins were added to generate the planning tumor volume. The Pinnacle and Corvus planning systems were used to develop conventional and IMRT plans, respectively. Conventional four-field plans were prescribed to deliver 45 Gy (4F(45 Gy)) or 50.4 Gy; eight-field IMRT plans were prescribed to deliver 50.4 Gy (IMRT(50.4 Gy)) or 54 Gy (IMRT(54 Gy)) to the planning tumor volume. All plans were normalized so that > or =97% of the planning tumor volume received the prescribed dose. Student's t test was used to compare the volumes of organs at risk receiving the same doses with different plans. The mean volume of bowel receiving > or =45 Gy was lower with the IMRT(50.4 Gy) (33% lower) and IMRT(54 Gy) (18% lower) plans than with the 4F(45 Gy) plan. The mean volume of rectum receiving > or =45 Gy or > or =50 Gy was also significantly reduced with the IMRT plans despite an escalation of the prescribed dose from 45 Gy with the conventional plans to 54 Gy with IMRT. The mean volume of bladder treated to 45 Gy was the same or slightly lower with the IMRT(50.4 Gy) and IMRT(54 Gy) plans compared with the 4F(45 Gy) plan. Compared with the 4F(45 Gy) plan, the IMRT(50.4 Gy) plan resulted in a smaller volume of bowel receiving 35-45 Gy and a larger volume of bowel receiving 50-55 Gy. Compared with the 4F(45 Gy) plan, the IMRT(54 Gy) plan resulted in smaller volumes of bowel receiving 45-50 Gy; however, small volumes of bowel received 55-60 Gy with the IMRT plan. Intensity-modulated RT may permit an increase in the radiation dose that can safely be delivered to the central pelvis and pelvic lymph nodes after hysterectomy. However, dose-volume calculations using individual CT scans do not account for internal organ motion. Detailed data concerning the relationships among radiation dose, treatment volume, and treatment effects are lacking, and prospective studies of pelvic IMRT are needed to determine the safety and efficacy of this treatment.

Comparison of the belly board device method and the distended bladder method for reducing irradiated small bowel volumes in preoperative radiotherapy of rectal cancer patients

To determine the most effective method to reduce the irradiated small bowel volume when using a belly board device (BBD), a distended bladder (DB), or both in patients with rectal cancer undergoing preoperative pelvic radiotherapy (RT). The study involved 20 patients with rectal cancer who were scheduled to receive preoperative pelvic RT. Patients were asked to empty their bladders and then drink 300 mL of water 2 h before the treatment planning computed tomographic (CT) scan. To identify the small bowel, an oral contrast solution (450 mL) was given 1 h before the CT scan. Two sets of transverse images were taken at 1-cm-thickness intervals with patients in the prone position with or without the BBD. After voiding, two additional sets of CT scans were obtained in prone positions with or without BBD. The conventional three-field treatment plan, composed of a 6-MV photon posterior-anterior field and 15-MV photon opposed lateral fields with wedges of 45 degrees, was made using a three-dimensional treatment planning system. The beam weights of the three-field plan were equal. The volume of irradiated small bowel was calculated for doses between 10% and 100% of the prescribed dose at 10% intervals. For each 10% dose increment, the effect of the BBD and the DB on the irradiated volume was analyzed using Kruskal-Wallis, Wilcoxon signed rank, and Wilcoxon rank-sum tests. All patients underwent four sets of CT scan under the conditions of four different methods as follows: Group I = empty bladder without the use of belly board; Group II = empty bladder with the use of belly board; Group III = distended bladder without the use of belly board; Group IV = distended bladder with the use of belly board. We found that the volume of irradiated small bowel decreased in the order of Group I, Group II, Group III, and Group IV at all dose levels (p < 0.05). Compared with Group I, the mean volume reduction rate (reduced volume) of irradiated small bowel in Group II varied between 14.5% and 65.4% (15.5-80.4 cm(3)), in Group III it varied between 48.1% and 82.0% (21.6-163.1 cm(3)), and in Group IV between 51.4% and 96.4% (28.6-167.1 cm(3)). The DB was more effective than the BBD for reducing the volume of irradiated small bowel in rectal cancer patients receiving pelvic RT. The combination of the BBD and DB showed an additive effect and was the most effective method for reducing the irradiated small bowel volume.

Acute diarrhea during pelvic irradiation: is small-bowel volume effect different in gynecologic patients with prior abdomen operation or not?

Objective To evaluate volume effect of small bowel for diarrhea during pelvic irradiation in gynecologic patients with or without prior abdomen operation. Methods From January 1996 through December 2003, 759 patients undergoing 4-field pelvic irradiation for cervical or uterine cancer were analyzed. Whole pelvic (WP), modified whole pelvic (MWP), or lower pelvic (LP) irradiation were delivered initially. According to contrast medium within small bowel in simulation films, we categorized the small-bowel volume of full dose related to WP fields as small-volume and large-volume groups. We recorded the severity of diarrhea until 39.6 Gy/22 fractions of pelvic irradiation. The actuarial rates of overall and moderate to severe diarrhea were compared among different groups. Results Significantly more large-volume distribution (85%) was noted in patients >60 years without prior operation ( P < 0.001). Large-volume distribution was 53%, 65%, and 82% in post-operative patients with no diarrhea, mild diarrhea, and moderate to severe diarrhea ( P = 0.002), respectively. The corresponding rate was 79%, 77%, and 80% in patients without prior abdomen operation ( P = 0.869). In multivariate analysis, prior operation with LP fields ( P = 0.005) and prior operation with small volume ( P = 0.031) were significantly protective factors for overall diarrhea. The latter was also a protective factor for moderate to severe diarrhea ( P = 0.026). Prior operation could diminish overall diarrhea in patients without simultaneous large-field (WP or MWP) and large-volume. Large volume was a significant factor of overall ( P = 0.014) and moderate to severe ( P = 0.004) diarrhea in large-field patients with operation. The volume effect did not exist in those patients without operation. Conclusion Age and operation can change small-bowel distribution. Prior operation may attenuate diarrhea if irradiated volume of small bowel is small. There is a volume effect in post-operative rather than non-operative patients receiving large-field irradiation. More practical dose-volume evaluation of small bowel may be applied for volume effect in gynecologic patients without prior operation.

Treatment with a belly-board device significantly reduces the volume of small bowel irradiated and results in low acute toxicity in adjuvant radiotherapy for gynecologic cancer: results of a prospective study

Background and purpose To determine whether treatment prone on a belly-board significantly reduces the volume of small bowel irradiated in women receiving adjuvant radiotherapy for gynecologic cancer, and to prospectively study acute small bowel toxicity using an accepted recording instrument. Material and methods Thirty-two gynecologic patients underwent simulation with CT scanning supine and prone. Small bowel was delineated on every CT slice, and treatment was prone on the belly-board using 3–5 fields—typically Anterior, Right and Left Lateral, plus or minus Lateral Boosts. Median prescribed dose was 50.4 Gy and all treatments were delivered in 1.8 Gy fractions. Concomitant Cisplatin was administered in 13 patients with cervical carcinoma. Comparison of small bowel dose–volumes was made between supine and prone, with each subject acting as their own matched pair. Acute small bowel toxicity was prospectively measured using the Common Toxicity Criteria: Version 2.0. Results Treatment prone on the belly-board significantly reduced the volume of small bowel receiving ≥100; ≥95; ≥90; and ≥80% of the prescribed dose, but not ≥50%. This was found whether volume was defined in cubic centimeters or % of total small bowel volume. Of 29 evaluable subjects, 2 (7%) experienced 1 episode each of grade 3 diarrhoea. All other toxicity events were grade 2 or less and comprised diarrhoea (59%), abdominal pain or cramping (48%), nausea (38%), anorexia (17%), vomiting (10%). There were no Grade 4 events and no treatment days were lost due to toxicity. Conclusions Treatment prone on a belly-board device results in significant small bowel sparing, during adjuvant radiotherapy for gynecologic cancer. The absence of Grade 4 events or Treatment Days Lost compares favorably with the published literature.

The influence of small bowel motion on both a conventional three-field and intensity modulated radiation therapy (IMRT) for rectal cancer

To investigate the reduction of irradiated small bowel volume with intensity modulated radiation therapy (IMRT) planning in rectal cancer and to asses the variability of the irradiated small bowel in the conventional planning as in the IMRT planning (IMPlan) by obtaining weekly CT scans. Twelve patients with rectal cancer had treatment planning CT scans of the pelvis with small bowel contrast obtained for planning and once a week during treatment (65 CT scans total). The scans were registered using the bony structures. The clinical target volume (CTV), small bowel, large bowel and bladder were outlined on each slice. The first CT scan was used for IMPlan and conventional three-field planning (ConPlan), which were then applied to the CT scans obtained during therapy. The median value among patients of the mean volume over a patient's scan of small bowel irradiated > or =95% was 112 cm3 (standard deviation (SD): 31 cm3) for the ConPlan and 42 cm3 (SD: 17 cm3) for the IMPlan. The median total bladder volume was 148 cm3 (SD: 130 cm3). There was a good correlation between the volume of irradiated small bowel and the bladder volume for IMPlan with <50 cm3 irradiated small bowel and ConPlan with <150 cm3 (p = 0.002). The use of IMRT led to a potentially clinically meaningful reduction in the volume of small bowel irradiated, even when accounting for small bowel motion. A full bladder was of greatest benefit in individuals with the smallest volume of small bowel in the treatment field.

Small-bowel displacement system for the sparing of Small bowel in three-dimensional conformal radiotherapy for cervical cancer

The efficacy of the small-bowel displacement system (SBDS) in three-dimensional conformal radiotherapy (3-D CRT) planning for sparing the volume of small bowel is presented for cervical cancer. Ten consecutive patients, who received pelvic radiation therapy for uterine cervical cancer with the SBDS from January to March 2003, were included in this study. The SBDS consists of a customised Styrofoam compression device, which can displace the small bowel out of the radiation fields, and an individualised immobilisation board. With oral contrast before scanning, computed tomography was taken in the prone position with and without the SBDS. 3-D conformal planning was carried out, and dose distribution was compared in the target volumes and in the organs-at-risk with and without the SBDS. In all patients, the SBDS significantly reduced the small-bowel volume within radiation fields. The median small-bowel volume with SBDS was reduced by 56.4% compared with the small-bowel volume without SBDS (from 491 to 214 cm3; P = 0.004). Among the 10 patients, the highest small-bowel volume reduction was 70.2% (from 544 to 62 cm3). At the prescription dose, the median volume of small bowel irradiated was reduced significantly with SBDS (9.8% vs 1.2%; P = 0.005). Differences in the dose-volume histogram for the rectum and the bladder between the 3-D CRT plans with and without SBDS were not statistically significant (P > 0.1). All patients completed radiotherapy without a break in treatment. The SBDS is a novel method that can be used to displace the small bowel away from the 3-D CRT fields effectively, and reduce radiation therapy morbidity.

Delineation of a reference target volume for pelvic lymph node irradiation using MR imaging with ultrasmall superparamagnetic iron oxide particles

Materials/Methods: 20 patients with gynaecological cancer had a pre-operative MRI with USPIO administration. Common iliac, presacral, external iliac, internal iliac and obturator nodes were measured and outlined. Five clinical target volumes (CTV) were generated for each patient by expanding blood vessels by 3mm, 5mm, 7mm, 10mm and 15mm. Nodal contours were overlaid on every CTV and analysed for coverage. Planning target volumes (PTV) were created by adding a margin of 1cm to the CTV. The volume of bowel, bladder and rectum within each CTV and PTV was measured to aid selection of the appropriate margin for each nodal group. Results: 1216 nodal contours were evaluated. The mean number per patient was 61 (range 30‐101) and the mean short axis diameter was 3.6mm. Nodal coverage was 56%, 76%, 88%, 94% and 99% nodes by 3mm, 5mm, 7mm, 10mm and 15mm vessel expansion respectively. The mean volume of bowel within the PTV was 96cm3 (15.4%) with a 3mm vessel margin, 121cm3 (19.4%) with a 5mm margin, 146.9cm3 (23.7%) with a 7mm margin, 190cm3 (30.8%) with a 10mm margin and 266cm3 (42.9%) with a 15mm margin. Conclusions: MR imaging with USPIO is an innovative technique to localise and stage lymph nodes. It has enabled the production of reference CT images delineating the pelvic lymph node regions. Guidelines have been developed for pelvic nodal irradiation with IMRT using a modified 7mm margin, with proposed adjustments to improve coverage of specific target nodal groups. These guidelines enable a reduction in the volume of bowel within the PTV by 23% without compromising tumour coverage.

Plasma citrulline concentration: A surrogate end point for radiation-induced mucosal atrophy of the small bowel. A feasibility study in 23 patients

Purpose Plasma citrulline, a nitrogen end product of glutamine metabolism in small-bowel enterocytes, was suggested as a marker of radiation-induced small-bowel epithelial cell loss in mice after single-dose whole-body irradiation. Our objective was to evaluate the feasibility of citrulline as a marker for radiation-induced small-intestinal mucosal atrophy in patients during and after abdominal fractionated radiotherapy. Methods and materials Twenty-three patients were studied weekly during treatment and at intervals of 2 weeks and 3 and 6 months after treatment by postabsorptive plasma citrulline concentration and clinical toxicity grading. The interrelationship between these variables and the correlation with small-bowel dose and volume parameters were investigated. Results During fractionated radiotherapy, citrulline concentration significantly decreased as a function of the radiation dose ( p < 0.001) and the volume of small bowel treated ( p = 0.001). The plasma citrulline concentration correlated with clinical toxicity during the last 3 weeks of treatment. As a whole, citrulline concentration correlated better with radiation dose and volume parameters than clinical toxicity grading. Conclusions In patients treated with fractionated radiation therapy for abdominal or pelvic cancer sites, plasma citrulline concentration may be a simple objective marker for monitoring epithelial cell loss, a major event in acute radiation-induced small-bowel toxicity.

Magnetic resonance lymphography to localise pelvic lymph nodes for intensity-modulated radiotherapy in gynaecological cancer

5070 Background: Intensity-modulated radiotherapy (IMRT) for gynaecological tumours requires accurate target volume delineation. Pelvic lymph nodes are poorly visualised on CT and MRI. Blood vessels with a 1–2cm margin are currently used as surrogate targets. A significant volume of small bowel is potentially irradiaited due to uncertainty about the exact lymph node position. Ultrasmall superparamagnetic iron oxide (USPIO), a novel MR contrast agent, localises in macrophages causing normal lymph nodes to appear black on MR images. This study used USPIO to determine the position of pelvic lymph nodes in relation to anatomic structures and develop guidelines for nodal irradiation. Methods: 15 patients with endometrial or cervical cancer had a diagnostic MRI (4mm slices) with subsequent USPIO administration and a repeat scan after 24 hours. All common iliac, presacral, external iliac, internal iliac and obturator nodes were outlined. On 10 scans, vessels were expanded by a margin of 15mm, 10mm, 7mm, 5mm and 3mm. The obturator and upper sacral regions were included with a corresponding margin. Nodal contours were overlaid on each expanded volume and analysed for coverage. Small bowel within each planning target volume (PTV) was measured. The resulting nodal irradiation guidelines were applied to the next 5 patients. Results: 836 nodal contours were evaluated. The mean number per patient was 56 (range 29–106). Contours covered by 15mm, 10mm, 7mm, 5mm and 3mm expansion were 99%, 96%, 90%, 77% and 63% respectively. The mean PTV bowel volume was 284, 204, 159, 130 and 102cm3. From these results, volume guidelines using an adjusted 7mm margin were applied to a further 5 patients resulting in 97% nodal coverage. Conclusions: MR lymphography with USPIO is an innovative technique to locate pelvic lymph nodes. Guidelines have been developed from these data for pelvic nodal irradiation with IMRT and conformal radiotherapy. A modified 7mm margin around vessels is recommended. This reduction in the margin reduces the small bowel volume within the PTV by 22% without compromising tumour coverage. No significant financial relationships to disclose.

Magnetic resonance lymphography to localise pelvic lymph nodes for intensity-modulated radiotherapy in gynaecological cancer

5070 Background: Intensity-modulated radiotherapy (IMRT) for gynaecological tumours requires accurate target volume delineation. Pelvic lymph nodes are poorly visualised on CT and MRI. Blood vessels with a 1–2cm margin are currently used as surrogate targets. A significant volume of small bowel is potentially irradiaited due to uncertainty about the exact lymph node position. Ultrasmall superparamagnetic iron oxide (USPIO), a novel MR contrast agent, localises in macrophages causing normal lymph nodes to appear black on MR images. This study used USPIO to determine the position of pelvic lymph nodes in relation to anatomic structures and develop guidelines for nodal irradiation. Methods: 15 patients with endometrial or cervical cancer had a diagnostic MRI (4mm slices) with subsequent USPIO administration and a repeat scan after 24 hours. All common iliac, presacral, external iliac, internal iliac and obturator nodes were outlined. On 10 scans, vessels were expanded by a margin of 15mm, 10mm, 7mm, 5mm and 3mm. The obturator and upper sacral regions were included with a corresponding margin. Nodal contours were overlaid on each expanded volume and analysed for coverage. Small bowel within each planning target volume (PTV) was measured. The resulting nodal irradiation guidelines were applied to the next 5 patients. Results: 836 nodal contours were evaluated. The mean number per patient was 56 (range 29–106). Contours covered by 15mm, 10mm, 7mm, 5mm and 3mm expansion were 99%, 96%, 90%, 77% and 63% respectively. The mean PTV bowel volume was 284, 204, 159, 130 and 102cm3. From these results, volume guidelines using an adjusted 7mm margin were applied to a further 5 patients resulting in 97% nodal coverage. Conclusions: MR lymphography with USPIO is an innovative technique to locate pelvic lymph nodes. Guidelines have been developed from these data for pelvic nodal irradiation with IMRT and conformal radiotherapy. A modified 7mm margin around vessels is recommended. This reduction in the margin reduces the small bowel volume within the PTV by 22% without compromising tumour coverage. No significant financial relationships to disclose.

Incorporation of magnetic resonance imaging into intensity modulated whole-pelvic radiation therapy treatment planning to reduce the volume of pelvic bone marrow irradiated

Intensity modulated radiation therapy (IMRT) has been used to reduce the volume of small bowel irradiated in gynecology patients. We are currently exploring IMRT as a means of reducing the volume of pelvic bone marrow (BM) irradiated and thus the risk of hematologic toxicity in this patient group. While CT is commonly used for treatment planning, it is not sensitive enough to distinguish between active and nonactive BM. The purpose of this study is to examine the feasibility of incorporating T1-weighted MR imaging into the planning process to aid in the delineation of active BM. A planning CT scan was obtained with a patient in the treatment position. The same patient also had a T1-weighted pelvic MR scan. Using image fusion software, the CT and MR scans were aligned. BM regions having a pixel value on the MR scan similar to muscle were used to define the active BM. Three treatment plans were then generated for this patient. In the conventional plan (non-IMRT), the majority of the active BM sites were included within the high isodose (70–100%) lines. In contrast, the IMRT plan (without BM sparing) reduced the volume of pelvic BM irradiated by the 90–100% isodoses. When the BM was entered as a constraint in the treatment plan (BM-sparing plan), a reduction in the volume of BM irradiated was observed from 50% to 100% of the prescription dose. Our results suggest that MR imaging is a useful adjunct to IMRT planning in gynecology patients and offers the possibility of customizing treatment based upon an individual patient's BM distribution.