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Intensity modulated radiation therapy (IMRT) has become standard of care for most cancer sites that are managed by radiation therapy. This book documents the evolution of this technology over 35 years to the current level of volumetric arc modulated therapy (VMAT). It covers every aspect of this radiation treatment technology, including the fundamentals of IMRT/VMAT, basic principles and advanced processes for implementation. The physics of IMRT is followed by the clinical application in major disease sites such as central nervous system, head and neck, breast, lung, prostate and cervix. It also provides updated references on each component of IMRT/VMAT. This book is written by leading experts in the field with extensive clinical experience in the practice and implementation of this technology. Part of IPEM-IOP Series in Physics and Engineering in Medicine and Biology.

Radiotherapy represents an important therapeutic option in the management of prostate cancer (PCa). As helical tomotherapy may improve toxicity outcomes, we aimed to evaluate and report the toxicity and clinical outcomes of localized PCa patients treated with moderately hypofractionated helical tomotherapy. We retrospectively analyzed 415 patients affected by localized PCa and treated with moderately hypofractionated helical tomotherapy in our department from January 2008 to December 2020. All patients were stratified according to the D'Amico risk classification: low-risk 21%, favorable intermediate-risk 16%, unfavorable intermediate-risk 30.4%, and high-risk 32.6%. The dose prescription for high-risk patients was 72.8 Gy to the prostate (planning tumor volume-PTV1), 61.6 Gy to the seminal vesicles (PTV2), and 50.4 Gy to the pelvic lymph nodes (PTV3) in 28 fractions; for low- and intermediate-risk patients 70 Gy for PTV1, 56 Gy for PTV2, and 50.4 Gy for PTV3 in 28 fractions. Image-guided radiation therapy was performed daily in all patients by mega-voltage computed tomography. Forty-one percent of patients received androgen deprivation therapy (ADT). Acute and late toxicity was assessed according to the National Cancer Institute's Common Terminology Criteria for Adverse Events v.5.0 (CTCAE). Median follow-up was 82.7 months (range=12-157 months) and the median age of patients at diagnosis was 72.5 years (range=49-84 years). The 3, 5, and 7 yr overall survival (OS) rates were 95%, 90%, and 84%, respectively, while 3, 5, and 7 yr disease-free survival (DFS) were 96%, 90%, and 87%, respectively. Acute toxicity was as follows: genitourinary (GU) G1 and G2 in 35.9% and 24%; gastrointestinal (GI) in 13.7% and 8%, with G3 or more acute toxicities less than 1%. The late GI toxicity G2 and G3 were 5.3% and 1%, respectively, and the late GU toxicity G2 and G3 were 4.8% and 2.1%, respectively, and only three patients had a G4 toxicity. Hypofractionated helical tomotherapy for PCa treatment appeared to be safe and reliable, with favorable acute and late toxicity rates and encouraging results in terms of disease control.

Introduction This study aimed to perform a rigorous dosimetric comparison of three advanced radiotherapy techniques—Volumetric Modulated Arc Therapy(VMAT), Helical Tomotherapy (TOMO), and Intensity-Modulated Radiation Therapy(IMRT)—for nasopharyngeal carcinoma (NPC), with particular emphasis on target coverage homogeneity, organ-at-risk (OARs) sparing, and the impact of using a unified treatment planning system (TPS) to eliminate inter-platform biases. Methods A total of 62 non-metastatic NPC patients were included in this retrospective study. All plans were re-optimized and calculated using a single TPS (RayStation 10B) with identical dose calculation algorithms to ensure comparability. Each patient underwent planning with dual-arc VMAT, helical TOMO, and 9-field IMRT techniques. Plans were evaluated based on homogeneity index (HI), conformity index (CI), and dose-volume parameters for multiple serial and parallel OARs. Statistical analyses included ANOVA with post-hoc Tukey tests. Results All techniques achieved adequate target coverage. VMAT yielded significantly superior homogeneity across all target volumes (HI = 0.06 ± 0.01 for PGTV70, p < 0.05), with no significant differences in CI among techniques. Both VMAT and TOMO significantly reduced doses to serial OARs such as the brainstem and spinal cord compared to IMRT (p < 0.05). TOMO provided the best parotid glands sparing (mean dose 26.13 ± 1.76 Gy), outperforming both VMAT and IMRT (p < 0.01). VMAT achieved the lowest brainstem mean dose (21.43 ± 4.47 Gy), while TOMO excelled in reducing high-dose volumes for most parallel OARs. Conclusion VMAT offers superior dose homogeneity and reduced delivery time, making it a highly efficient and dosimetrically favorable option for NPC radiotherapy. TOMO demonstrates advantages in sparing critical OARs, particularly in high-dose regions. The use of a unified TPS platform confirms that observed differences are technique-derived rather than planning-system artifacts. These findings support technique selection based on institutional resources and clinical priorities.

Background To treat multiple targets separated in the craniocaudal direction within a short time, we invented a new technique using multiple static‐port tomotherapy with the dynamic‐jaw mode and named it the pseudo‐DJDC (pDJDC) technique. We compared the pDJDC plans and helical tomotherapy plans using the dynamic‐jaw mode (HDJ) for multiple targets. In the pDJDC plans, we used a beam set with 2–7 ports to the targets at the same level in the craniocaudal direction, and employed another beam set for other targets using different port angles (9–12 angles in total). Methods In seven patients, two plans using the pDJDC and HDJ techniques were compared. For multiple targets (n = 2–6), 20–60 Gy in 2‐ to 7.5‐Gy fractions were prescribed for the planning target volumes at D50%. The conformity index, uniformity index (D5%/D95%), dose distribution in the lung, and treatment time were evaluated. Results The median conformity index of all seven patients was 3.0 for the pDJDC plans and 2.4 for the HDJ plans (P = 0.031). The median uniformity indices of the planning target volume (n = 25) for the two plans were 1.048 and 1.057, respectively (P = 0.10). For five patients with thoracic targets, the median mean lung doses were 2.6 Gy and 2.4 Gy, respectively (P = 0.63). The median V5Gy and V20Gy of the lungs in the five patients were 11.8% and 8.5% (P = 0.63), and 1.6% and 2.1% (P = 0.31), respectively. The pDJDC plans reduced the treatment time by 48% compared to the HDJ plans (median: 462 and 884 sec, respectively, P = 0.031). Conclusion The pDJDC technique allows treatment of multiple targets in almost half the time of the HDJ technique. The pDJDC plans were comparable to the HDJ plans in dose distribution, although the conformity index deteriorated.

ClearRT helical kVCT imaging for the Radixact helical tomotherapy system recently received FDA approval and is available for clinical use. The system is intended to enhance image fidelity in radiation therapy treatment planning and delivery compared to the prior MV‐based onboard imaging approach. The purpose of this work was to characterize the imaging performance of this system and compare this performance with that of clinical systems used in image‐guided and/or adaptive radiotherapy (ART) or computed tomography (CT) simulation, including Radixact MVCT, TomoTherapy MVCT, Varian TrueBeam kV OBI CBCT, and the Siemens SOMATOM Definition Edge kVCT. A CT image quality phantom was scanned across clinically relevant acquisition modes for each system to evaluate image quality metrics, including noise, uniformity, contrast, spatial resolution, and CT number linearity. Similar noise levels were observed for ClearRT and Siemens Edge, whereas noise for the other systems was ∼1.5–5 times higher. Uniformity was best for Siemens Edge, whereas most scans for ClearRT exhibited a slight “cupping” or “capping” artifact. The ClearRT and Siemens Edge performed best for contrast metrics, which included low‐contrast visibility and contrast‐to‐noise ratio evaluations. Spatial resolution was best for TrueBeam and Siemens Edge, whereas the three kVCT systems exhibited similar CT number linearity. Overall, these results provide an initial indication that ClearRT image quality is adequate for image guidance in radiotherapy and sufficient for delineating anatomic structures, thus enabling its use for ART. ClearRT also showed significant improvement over MVCT, which was previously the only onboard imaging modality available on Radixact. Although the acquisition of these scans does come at the cost of additional patient dose, reported CTDI values indicate a similar or generally reduced machine output for ClearRT compared to the other systems while maintaining comparable or improved image quality overall.

Background Helical TomoTherapy ® is widely used for total body irradiation as a component of conditioning regimens before allogeneic bone-marrow transplantation. However, this technique limits the maximum length of a planning target volume to 135 cm. Therefore, patients taller than 135 cm require two planning computed tomography scans and treatment plans. The junctional target between these two treatment plans is thus a critical region for treatment planning and delivery. Here, we compare radiation coverage of the junctional target between helical and static approaches to treatment planning and delivery to determine which approach allows high quality irradiation planning and provides more robustness against patient movement. Methods We retrospectively analyzed 10 patients who underwent total body irradiation using a static four-field box planning approach and nine patients who underwent total body irradiation using a helical planning approach. All patients were taller than 135 cm. The junctional target volume was divided into 10 slices of 1 cm thickness (JT 1 –JT 10 ) for analysis. Dosimetric parameters and dose-volume histograms were compared to assess the quality of coverage of the junctional target between the helical and static planning approaches. Results The D 50 for the total junctional target was slightly higher than the prescribed dose for both helical and static approaches, with a mean of 108.12% for the helical group and 107.81% for the static group. The mean D 95 was 98.44% ± 4.19% for the helical group and 96.20% ± 4.59% for the static group. The mean homogeneity index covering the entire junctional target volume was 1.20 ± 0.04 for the helical group and 1.21 ± 0.05 for the static group. The mean homogeneity index ranged from 1.08 ± 0.01 in JT 1 to 1.22 ± 0.06 in JT 6 for the helical group and from 1.06 ± 0.02 in JT 1 to 1.19 ± 0.05 in JT 6 for the static group. There were no significant differences in parameters between helical and static groups. However, the static approach provided robustness against up to 30 mm of lateral movement of the patient. Conclusions As long as TBI using helical TomoTherapy ® is limited to a maximum length of 135 cm, the junctional target must be addressed during treatment planning. Our analysis shows that the static four-field box approach is viable and offers higher robustness against lateral movement of the patient than the helical approach.

The Radixact® linear accelerator contains the motion Synchrony system, which tracks and compensates for intrafraction patient motion. For respiratory motion, the system models the motion of the target and synchronizes the delivery of radiation with this motion using the jaws and multi‐leaf collimators (MLCs). It was the purpose of this work to determine the ability of the Synchrony system to track and compensate for different phantom motions using a delivery quality assurance (DQA) workflow. Thirteen helical plans were created on static datasets from liver, lung, and pancreas subjects. Dose distributions were measured using a Delta4® Phantom+ mounted on a Hexamotion® stage for the following three case scenarios for each plan: (a) no phantom motion and no Synchrony (M0S0), (b) phantom motion and no Synchrony (M1S0), and (c) phantom motion with Synchrony (M1S1). The LEDs were placed on the Phantom+ for the 13 patient cases and were placed on a separate one‐dimensional surrogate stage for additional studies to investigate the effect of separate target and surrogate motion. The root‐mean‐square (RMS) error between the Synchrony‐modeled positions and the programmed phantom positions was <1.5 mm for all Synchrony deliveries with the LEDs on the Phantom+. The tracking errors increased slightly when the LEDs were placed on the surrogate stage but were similar to tracking errors observed for other motion tracking systems such as CyberKnife Synchrony. One‐dimensional profiles indicate the effects of motion interplay and dose blurring present in several of the M1S0 plans that are not present in the M1S1 plans. All 13 of the M1S1 measured doses had gamma pass rates (3%/2 mm/10%T) compared to the planned dose > 90%. Only two of the M1S0 measured doses had gamma pass rates > 90%. Motion Synchrony offers a potential alternative to the current, ITV‐based motion management strategy for helical tomotherapy deliveries.

With the newly-developed static-port forward-planning (FP) mode of tomotherapy, the ratio of the dose of the planning target volume (PTV) periphery to the maximum dose can be easily adjusted by modifying leaf margins when planning stereotactic body radiotherapy (SBRT). The purpose of this study was to evaluate the characteristics of FP plans compared to helical intensity-modulated radiotherapy (IMRT) and helical 3D conformal radiotherapy (3DCRT) plans of SBRT for lung tumors. The three plans were created for 14 tumors in 11 patients. For 13 tumors, 60 Gy in 7.5-Gy fractions was prescribed for a minimum coverage dose of 95% of the PTV (D95). The prescribed isodose line (PIL) was intended to be 60–80% of the maximum dose. Nine angles were used for the FP plans. The median D98 and D50 of the internal target volume for FP, helical-IMRT and helical-3DCRT plans were 70.4, 71.4 and 60.5 Gy, respectively (P < 0.001), and 77.7, 75.7 and 62.3 Gy, respectively (P < 0.0001). The median PIL and the lung volume receiving ≥20 Gy (V20) were 73.4, 73.4 and 94.3%, respectively (P < 0.0001), and 4.7, 4.0 and 5.7%, respectively (P < 0.0001). These parameters were not significantly different between the FP and helical-IMRT plans. The median beam-on times were 238.6, 418.9 and 197.1 s, respectively (P < 0.0001). The FP plans reduced the beam-on time by 43% compared to the helical-IMRT plans. The dose distribution of the FP plans was comparable to that of the helical-IMRT plans. The helical-3DCRT plans could not adjust PIL to be 60–80%.

IntroductionSpatially Fractionated Radiotherapy (SFRT) delivers intentionally heterogeneous dose distributions with alternating high- and low-dose regions and has been widely applied in the management of bulky tumors. In SFRT, high-dose sub-volumes (referred to as vertices) are distributed within the gross tumor volume (GTV) to create a spatial peak-valley dose pattern. However, studies of SFRT using the TomoTherapy platform remain limited. This study evaluates the dosimetric performance of GRID and lattice vertex designs using TomoHelical and TomoDirect techniques.MethodsA phantom-based planning study was performed with two simulated GTV representing medium- and large-sized tumors. Cylindrical GRID vertices and spherical lattice vertices were created with diameters of 1.00 cm and 1.25 cm and corresponding center-to-center spacings of 3.0 cm and 2.5 cm, respectively. Treatment plans were created using TomoHelical and TomoDirect techniques with identical prescription criteria, requiring at least 50% of the target volume to receive 15 Gy in a single fraction. Beam-on time, normal tissue dose metrics (V30% and V50%), homogeneity index, conformity index, peak-to-edge dose ratio (PEDR), and peak-to-valley dose ratio (PVDR) were evaluated. Delivery accuracy was assessed using ArcCHECK measurements with a 3%/2 mm gamma criterion.ResultsAll plans met prescription and delivery accuracy requirements, with gamma passing rates exceeding 95%. TomoHelical produced higher PVDR and PEDR values, improved conformity, and lower V50% compared with TomoDirect. TomoDirect achieved shorter beam-on times but showed greater variability in vertex mean dose. Lattice configurations yielded higher PVDR values than GRID, while vertex diameter had minimal impact on most dosimetric parameters.ConclusionTomoHelical delivery combined with lattice designs provided superior dose modulation and normal tissue sparing for SFRT, while requiring longer delivery times. In contrast, GRID designs enabled faster treatment delivery. These findings provide practical guidance for optimizing SFRT planning using the TomoTherapy platform.

IntroductionThe optimal management of localized prostate cancer (PCa) in the \"oldest-old\" demographic presents a unique clinical challenge, requiring a careful balance between oncological control and the preservation of quality of life. This study aims to evaluate the safety, toxicity profile, and clinical outcomes of moderately hypofractionated helical tomotherapy (HT) in a cohort of patients aged 75 years and older with localized PCa.Materials and MethodsIn this retrospective cohort study, we analyzed 51 consecutive patients with a median age of 79 years treated between 2016 and 2022. All patients received 69 Gy in 25 fractions (2.76 Gy/fraction) via the HT platform. Risk stratification was performed using the D'Amico classification, revealing that the majority were high-risk (52.9%) or intermediate-risk (43.1%). Clinical outcomes included biochemical relapse-free survival (BRFS), cancer-specific survival (CSS), and overall survival (OS). Toxicity grading followed CTCAE v4.0 criteria, and Quality of Life (QoL) was evaluated through the International Prostate Symptom Score (IPSS) and a single-item index.ResultsAt a median follow-up of 38 months, the 5-year BRFS, CSS, and OS rates were 83.3%, 80.1%, and 68.8%, respectively. Acute Grade 2 genitourinary and gastrointestinal toxicities occurred in 25.5% and 27.5% of the subjects. Late Grade 3 complications were rare (1 GU, 4 GI). Significant longitudinal improvements in IPSS and QoL were observed within 3 months post-treatment ( ).ConclusionModerately hypofractionated HT may be a safe and effective treatment for elderly PCa patients, suggesting potential for excellent oncological control and symptomatic relief.