http://www.tomotherapy.com/index.php en mike@imagehat.com Copyright 2008 2008-03-20T16:21:00-06:00 http://www.tomotherapy.com/clinician/case_studies/flexibility/ http://www.tomotherapy.com/clinician/case_studies/flexibility/#When:16:21:00Z The TomoTherapy® Hi·Art® treatment system's sophisticated delivery method allows tremendous planning flexibility and lessens the need for planning trade-offs between target coverage and critical structure avoidance.BACKGROUND For any given case, there is no single plan that defines the capability of TomoTherapy®. Depending on the relative priorities given to achieving certain clinical goals, dosimetric planning results can differ. Three clinical cases were included in an article in the September 2007 edition of the International Journal Radiation Oncology · Biology · Physics (Volume 69, No. 1, pp. 240–250). The intent of the article was to compare intensity modulated arc therapy (IMAT) and helical TomoTherapySM treatments. TomoTherapy Incorporated obtained the original case files from one of the paper’s authors and below demonstrates the fact that—for any given case—there is no single plan that defines the capabilities of TomoTherapy. Depending on the relative priorities given to achieving certain clinical goals, dosimetric planning results can differ significantly. CASE STUDIES SBRT Lung Case Original Plan   |   Plan Revision 1   |   Plan Revision 2   |   Summary of Organ Sparing Results Left Orbit Case Original Plan   |   Plan Revision   |   Summary of Organ Sparing Results Posterior Brain Case Original Plan   |   Plan Revision   |   Summary of Organ Sparing Results SBRT LUNG CASE Original Plan Planning was performed for a small left lung tumor (20.4 cm3 PTV) to be treated with 60 Gy in three fractions. This is regarded as a stereotactic body radiotherapy (SBRT) treatment due to the high dose per fraction. The original plan called for 95% of the PTV to be covered by the prescription dose. The planner chose to maintain a uniform dose within the PTV by making this a high priority during plan optimization. The GTV, being within the PTV, naturally receives an even more uniform dose and a higher mean dose. Critical structures to be spared include both lungs and the spinal cord. PTV: Min/Max dose = 58/62 Gy Lungs: Mean dose = 10.4 Gy; V20Gy = 14.8% Cord: Max dose = 4.7 Gy PTV dose is very uniform (dose spread only 4 Gy), at some expense to the degree of lung and cord sparing. This plan used a 2.5 cm collimator width, rather than a 1 cm width as used for the first revised plan below. Back to top SBRT LUNG CASE - PLAN REVISION 1 For this plan a 1 cm collimator width was used to maximize the ability of the system to achieve a uniform PTV dose while achieving a very high degree of organ at risk sparing. In particular, the smaller collimator width increases the dose gradient superiorly and inferiorly to the PTV. As is shown here, target dose coverage and uniformity is maintained, or even slightly improved, over the original plan but with lower mean lung and maximum cord doses. PTV: Min/Max dose = 60/63 Gy Lungs: Mean dose = 7.4 Gy; V20Gy = 10.4% Cord: Max dose = 1.3 Gy This plan achieved a fast dose falloff outside the PTV while maintaining a uniform dose inside the PTV. An alternative technique for creating a fast dose falloff is to relax the priority of achieving target dose uniformity, as demonstrated by the second revised plan below. Back to top SBRT LUNG CASE - PLAN REVISION 2 Increasing the priority for lung sparing relative to PTV dose uniformity creates a faster dose gradient in the lung. This plan uses a 2.5 cm collimator yet achieves slightly better lung and cord sparing than with the 1 cm collimator plan above. The tradeoff is target dose uniformity, but since the intent of an SBRT treatment is target ablation there is good clinical rationale for allowing dose near the center of the PTV to be considerably higher than the minimum dose. PTV: Min/Max dose = 56/75 Gy Lungs: Mean dose = 7.2 Gy; V20Gy = 9.8% Cord: Max dose = 1.2 Gy A very rapid dose falloff was achieved in this plan via maximum PTV dose being allowed to rise to 125% of the prescription dose. This takes advantage of the fact that dose gradients are greater at dose levels well below the maximum dose. Such an effect can be created in a TomoTherapySM treatment without the use of a smaller collimator. This TomoTherapySM plan achieves significantly better lung and cord sparing than the IMAT plan. Back to top SBRT LUNG CASE - SUMMARY OF ORGAN SPARING RESULTS   IMAT TomoSM original Tomo rev 1 Tomo rev 2 Mean lung dose (Gy) 9.3 10.4 (12) 7.4 (-20) 7.2 (-23) Max cord dose (Gy) 4.7 4.7 (0) 1.3 (-72) 1.2 (-74) Mean lung and maximum cord doses for the original IMAT plan, original TomoTherapy plan, and revised TomoTherapy plans. For the TomoTherapy plans, percent differences compared to the IMAT plan are shown in parentheses. Back to top LEFT ORBIT CASE Original Plan For this case, a volume including the left orbit forms the GTV, to which the prescription dose is 70 Gy. The IMAT plan used four sagittal arcs (couch angle 90 degrees) in order to better spare the right eye, brain stem and optic apparatus than if axial arcs (couch angle 0 degrees) were used. This is an obvious strategy of trying to keep incoming beam paths away from these structures. The TomoTherapy system uses axial, helical gantry rotations but has the advantage of a very high modulation capability. In the original plan comparison, similar target dose coverage was achieved with the two techniques, but the IMAT plan achieved better critical structure sparing due to the use of sagittal arcs. GTV: Min/Max dose = 67/75 Gy Right eye: Mean/Max dose = 7.1/13.1 Gy Optic apparatus: Mean/Max dose = 21.7/38 Gy Brain stem: Max dose = 46.7 Gy The TomoTherapy plan can be improved by setting more aggressive critical tissue constraints and making use of higher beam modulation. Back to top LEFT ORBIT CASE - PLAN REVISION Placing more aggressive dose constraints on critical structures, results in dramatically reduced maximum dose levels. The modulation factor was also increased, enabling the optimization algorithm to conform dose to the target volume more effectively. GTV: Min/Max dose = 68/75 Gy Right eye: Mean/Max dose = 2.8/5.5 Gy Optic apparatus: Mean/Max dose = 12.2/18 Gy Brain stem: Max dose = 23.5 Gy Note: No primary dose in oral cavity, in contrast to the IMAT plan In this revised plan, the TomoTherapy® optimizer was able to create a plan with axial arcs that has significantly improved critical organ sparing compared to that achieved with non-axial arcs in the IMAT plan. The key enabler for this is the very high degree of modulation available. Back to top LEFT ORBIT CASE - SUMMARY OF ORGAN SPARING RESULTS   IMAT Tomo original Tomo revised Mean Rt eye dose (Gy) 3.4 7.1 (109) 2.8 (-18) Max Rt eye dose (Gy) 10.9 13.1 (20) 5.5 (-50) Mean optic apparatus dose (Gy) 15 21.7 (45) 12.2 (-19) Max optic apparatus dose (Gy) 28.5 38 (33) 18 (-37) Mean and maximum doses for the right eye and optic apparatus for the original IMAT plan, original TomoTherapy plan, and the revised TomoTherapy plan. For the TomoTherapy plans, percent differences compared to the IMAT plan are shown in parentheses. Back to top POSTERIOR BRAIN CASE Original Plan Plans for a glioblastoma multiforme in the left posterior part of the brain were generated using IMAT and TomoTherapy. Prescription dose was 46 Gy. The IMAT plan included four non-axial couch angles, each with four overlapping arcs (16 arcs in total). The rationale for this significant increase in plan complexity was again better critical structure sparing, in particular brain stem, optic nerve and both eyes. In the original plan comparison, critical structure sparing was better with IMAT, but at the expense of target dose uniformity. PTV: Min/Max dose = 46/47 Gy Brain stem: Mean/Max dose = 18.7/39 Gy Optic nerve: Mean/Max dose = 3.9/8.1 Gy As with the other case examples, the TomoTherapy system was able to achieve much better critical structure sparing with more aggressive optimization parameters and increased modulation. Back to top POSTERIOR BRAIN CASE - PLAN REVISION Brain stem and optic nerve sparing are both greatly improved with this revised plan. PTV coverage and dose uniformity are not compromised in this case. PTV: Min/Max dose = 46/47 Gy Brain stem: Mean/Max dose = 2.8/11 Gy Optic nerve: Mean/Max dose = 1.4/2.2 Gy The revised TomoTherapySM plan achieves much better brain stem sparing and similar optic nerve sparing compared with the IMAT plan, without sacrificing target dose uniformity. Back to top POSTERIOR BRAIN CASE - SUMMARY OF ORGAN SPARING RESULTS   IMAT Tomo original Tomo revised Mean brain stem dose (Gy) 6.1 18.7 (207) 2.8 (-54) Max brain stem dose (Gy) 29.2 39 (34) 11 (-62) Mean optic nerve dose (Gy) 1.0 3.9 (290) 1.4 (40) Max optic nerve dose (Gy) 2.4 8.2 (242) 2.2 (-8) Mean and maximum doses for the brain stem and optic nerve, for the original IMAT plan, the original TomoTherapy plan, and the revised TomoTherapy plan. For the TomoTherapy plans, percent differences compared to the IMAT plan are shown in parentheses. Back to top The three original TomoTherapy plans presented above were originally included in an article in the September 2007 edition of the International Journal Radiation Oncology · Biology · Physics (Volume 69, No. 1, pp. 240–250). Assurance 2008-03-20T16:21:00-06:00 http://www.tomotherapy.com/clinician/case_studies/tomotherapy_ctrue_adaptive_lung_st_agnes/ http://www.tomotherapy.com/clinician/case_studies/tomotherapy_ctrue_adaptive_lung_st_agnes/#When:15:28:00Z This clinical case study demonstrates how the TomoTherapy® Hi·Art® treatment system's CTrue™ technology provides true dose guidance. Only TomoTherapy's daily 3D imaging reveals anatomical changes and their dosimetric impact at every fraction.Original Treatment Plan 50 Gy in 25 fractions is prescribed to a mass in the right posterior lung. Excellent cord sparing (maximum of approx. 8 Gy) is achieved via optimization of a helical IMRT delivery.   Hypothetical Delivery Original plan image Five days into treatment (~1cGy MVCT) Registered image(Green= Daily CT;Grey=Planning CT) Over a one week period, a progressive posterior shift of the tumor occurs due to reduced pleural effusion. Daily patient alignment via external marks or bony anatomy would lead to a severe under-dosage of the tumor due to geographic miss. Dose calculation showing the results if treated by aligning to bone   Actual Delivery Using CTrue Technology Registered images using PTV contour & dose to position tumor for treatment Using CTrue technology, the shifting tumor can be correctly aligned before every fraction and dose can be overlaid to check target coverage and organ sparing. Spinal cord dose remains within tolerance thanks to the TomoTherapy Hi·Art system’s helical delivery, and treatment is continued with the initial plan up to and including the 5th fraction. Taking advantage of CTrue images and adaptive therapy technology, the clinician decided that after the 5th treatment session, the plan will be re-optimized for the remaining fractions. Dose calculated on the daily CT image.   Adapted Plan Using CTrue technology, every daily image is suitable for treatment planning since pixel values are true representations of tissue density. The day-5 CTrue image is used to re-plan the case using the true anatomy. After re-optimization, the cord is once again spared effectively along with excellent dose coverage of the target at its new location. DVH for re-optimized plan, showing low cord dose and homogeneous target dose.   * Original treatment plan and images courtesy of Richard Hudes, MD, St. Agnes Cancer Center, Baltimore, MD. Used by permission. Assurance 2007-01-19T15:28:00-06:00 http://www.tomotherapy.com/clinician/case_studies/tomotherapy_prostate_cancer/ http://www.tomotherapy.com/clinician/case_studies/tomotherapy_prostate_cancer/#When:14:05:00Z This simulated treatment plan demonstrates how the TomoTherapy® Hi·Art® treatment system can be used to focus the radiation dose on the target area of the prostate, while avoiding sensitive structures close by. The Plan Figure 1: TCS views of TomoTherapy treatment plan for prostate cancer. Figure 1 shows transverse, coronal and sagittal (TCS) image planes in a prostate cancer treatment plan. Colors show the planned dose distribution overlaid on the images. The plan involves irradiating the prostate with a dose high enough to control the cancer while limiting dose to the bladder and rectum. One of the biggest challenges for treating prostate cancer is movement of the target area from day to day due to influences such as rectal and bladder filling. The TomoTherapy Hi·Art treatment system's on-board CTrue™ imaging capability helps ensure the prostate is accurately positioned every day. The Goals Prostate: 72 Gy to at least 98% of its volume Rectum: no more than 20% of the rectum to receive more than 36 Gy Bladder: no more than 30% of the bladder to receive more than 36 Gy The Results The Dose Volume Histogram in Figure 2 demonstrates how the TomoTherapy Hi·Art treatment system is able to meet or exceed each of these objectives.   Figure 2: DVH of a TomoTherapy treatment plan for prostate cancer. Accuracy 2007-05-08T14:05:00-06:00 http://www.tomotherapy.com/clinician/case_studies/tomotherapy_multiple_metastases/ http://www.tomotherapy.com/clinician/case_studies/tomotherapy_multiple_metastases/#When:18:22:00Z This simulated treatment plan demonstrates how the TomoTherapy® Hi·Art® system can be used to treat multiple lesions without the need to change isocenters.The Plan Figure 1: TCS views of TomoTherapy treatment plan for multiple metastases. Figure 1 shows the TCS views for treating multiple lesions of the right kidney, liver, lung and spine in a single treatment plan without irradiating a large volume of healthy tissue. The TomoTherapy Hi·Art treatment system can deliver conformal doses to multiple lesions and dose levels while sparing surrounding normal tissue. The Goals GTV1 (liver lesion): 45 Gy GTV2 (liver lesion): 39 Gy Kidney lesion: 30 Gy 1st Spinal lesion: 30 Gy 2nd Spinal lesion: 35 Gy Lung lesion: 35 Gy The Results The DVH in Figure 2 demonstrates how the TomoTherapy Hi·Art treatment system is able to meet each of these objectives. Tolerance for the right kidney is maintained (no more than 15% of the structure received 20 Gy), while less than 25% of the liver received 10 Gy (well below tolerance).   Figure 2: DVH of TomoTherapy treatment plan for multiple metastases. Precision 2007-02-04T18:22:00-06:00 http://www.tomotherapy.com/clinician/case_studies/tomotherapy_scalp_carcinoma_froedtert_mcw/ http://www.tomotherapy.com/clinician/case_studies/tomotherapy_scalp_carcinoma_froedtert_mcw/#When:02:07:00Z This clinical case study demonstrates the TomoTherapy® Hi·Art® system's ability to treat a large, irregular lesion on the scalp in lieu of electron therapy.The Plan Figure 1: TCS views of TomoTherapy treatment plan for scalp carcinoma. Figure 1 shows the TCS views for treating a large, irregularly-shaped superficial lesion of the scalp. The TomoTherapy Hi·Art treatment system® can deliver conformal doses to superficial targets better than conventional electron therapy. The Goals Tumor: 60 Gy Minimal dose to brain, optic nerves and lenses The Results The DVH in Figure 2 demonstrates how the TomoTherapy Hi·Art system is able to deliver a highly-conformal dose of 60 Gy to the target area, while limiting dose to both ocular orbits to less than 7 Gy each, and limiting dose to both lenses to less than 2 Gy each.   Figure 2: DVH of TomoTherapy treatment plan for scalp carcinoma. Treatment plan and case study summary courtesy of Froedtert Hospital and Medical College of Wisconsin. Used by permission. Precision 2007-02-04T02:07:00-06:00 http://www.tomotherapy.com/clinician/case_studies/tomotherapy_sbrt_for_lung_metastasis_uva/ http://www.tomotherapy.com/clinician/case_studies/tomotherapy_sbrt_for_lung_metastasis_uva/#When:15:53:00Z This clinical case study demonstrates the TomoTherapy® Hi·Art® system's ability to deliver stereotactic body radiation therapy (SBRT), in which very high doses are delivered to a precisely-defined target volume in a single or a few treatment fractions. A high degree of conformality and targeting accuracy are of paramount importance.The Plan Figure 1: Frames from an MRI sequence used to define the range of motion for the primary tumor volume. Figure 2: TomoTherapy treatment plan for SBRT to lung metastasis. In this case, the Hi·Art treatment system was used to deliver SBRT to a 1 cm breast cancer metastasis in the right lung, which was the only site of disease. The target volume was defined with the help of dynamic MRI, in order to account for the full range of tumor motion (Figure 1). Treatment was in three fractions of 12.5 Gy, and the heart, bronchi, esophagus, and spinal cord were designated as sensitive structures (Figure 2). The Results CT images taken two, three and six months after treatment show the tumor’s response and the accuracy of treatment delivery (Figure 3). The six-month scan shows a small region of pulmonary fibrosis surrounding the remaining 2 mm nidus, indicating that targeting was accurate.   Figure 3: CT scans showing tumor response and treatment accuracy of TomoTherapy SBRT. Treatment plan and case study summary courtesy of University of Virginia. Used by permission. Accuracy 2007-01-19T15:53:00-06:00 http://www.tomotherapy.com/clinician/case_studies/tomotherapy_planned_adaptive_mdacc/ http://www.tomotherapy.com/clinician/case_studies/tomotherapy_planned_adaptive_mdacc/#When:15:30:00Z This clinical case study demonstrates the TomoTherapy® Hi·Art® treatment system's Planned Adaptive™ feature, which the clinician can use to evaluate how changes in anatomy and patient positioning impact the delivered dose.The Plan The initial treatment plan involves irradiating the head and neck region while limiting dose to the brain, spinal cord, and parotid glands. Using the Planned Adaptive software, the clinician can calculate the dose on the daily CT (verification dose) and evaluate how changes in anatomy (in this case, weight loss) impact the delivered dose. The DVH in Figure 1 shows how the first fraction verification dose (dashed lines) closely matches the planned dose (solid lines). Figure 1: DVH comparing planned dose vs. verification dose for first treatment fraction. Figure 2: DVH of 15th fraction verification dose indicates increasing dose to right parotid due to patient’s weight loss.   The Goals Tumor: 70 Gy Minimal dose to brain, spinal cord, and parotid glands Calculate accumulated verification dose using the daily CT scans Adapt plan to accommodate changes in patient anatomy as necessary After 34 Gy, comparison of verification doses vs. original planned dose show increased dose to right parotid due to anatomical changes (Figure 3). The clinician used the Hi·Art treatment system’s Planned Adaptive software to isolate the hot areas and convert them to ROIs (Figure 4), which were then used to generate a new plan compensating for the changes. The remaining 26 Gy was delivered using the parotid-sparing adaptive plan (Figure 5). The Results Figure 3: Planned Adaptive software highlights “hot spots” where verification dose differs from planned dose. Figure 4: Clinician uses Planned Adaptive software to convert hot spots to ROIs, then generates new plan based on new contours.   Figure 5: After adapting the plan, the treatment is brought back in line with the original plan goals. *Treatment plan and case study summary courtesy of M. D. Anderson Cancer Center - Orlando. Used by permission. Assurance 2007-01-19T15:30:00-06:00