Judit Boda-Heggemann

kV cone-beam CT-based IGRT: a clinical review.

AbstractAims and Methods:Delivery of high radiation doses while simultaneously sparing organs at risk requires advanced imaging for target volume definition, highly conformal dose distributions of intensity modulated radiotherapy (IMRT), and narrow planning target volume (PTV) margins. Three-dimensional image-guided radiotherapy (IGRT) with cone-beam computer tomography (CBCT), which results in more precise target localization, is quickly replacing two-dimensional (2D) IGRT. An overview on the clinical applications of kilovoltage gantry-mounted CBCT systems with emphasis on the most frequently targeted body sites (prostate, lung, head and neck) is provided based on a review of the relevant literature. Alternative imaging methods and their advantages/disadvantages are discussed.Results:IGRT with soft tissue detection improves set-up accuracy and is currently replacing 2D verification and frame-based stereotactic treatments; safety margins are significantly reduced by this IGRT technology. In addition, systematic changes of tumor volume and shape and of the normal tissue can be monitored allowing for adaptation of radiotherapy. IGRT in combination with conformal treatment planning allows for hypofractionated dose escalation, which results in improved rates of local tumor control with low rates of toxicity.Conclusion:CBCT allows for daily pretreatment position verification and online correction of set-up errors which improves the precision of patient repositioning with the possibility of shrinking safety margins, sparing organs at risk, and escalating radiation doses. A trend for better clinical outcome can be observed.ZusammenfassungHintergrund und Methodik:Die Verwendung von eskalierten Bestrahlungsdosen bei gleichzeitiger Schonung der Risikoorgane setzt multimodale Bildgebung zur Zielvolumendefinition, hochkonformale Bestrahlungsplanung mittels intensitätsmodulierter Radiotherapie und enge Sicherheitssäume voraus. Bildgeführte Strahlentherapie (IGRT) dient der präzisen Lokalisation des Zielvolumens, und konventionelle 2D Techniken wie Feldkontrollaufnahmen werden aktuell insbesondere durch dreidimensionale Cone-beam-(CBCT-)Technik ersetzt. Dieser Artikel gibt einen Literaturüberblick über den aktuellen Stand der IGRT mittels CBCT. Schwerpunkte sind die praktische Anwendung und klinischen Resultate bei Prostatakarzinom, Bronchialkarzinom und Kopf-Hals-Tumoren. Ergebnisse: Schlussfolgerungen: Schlüsselwörter: Ergebnisse:IGRT mittels CBCT ist hocheffektiv zur Verifikation der Patientenpositionierung und insbesondere zur Verifikation der Tumorposition. Rahmenbasierte Stereotaxie kann durch IGRT ersetzt werden, sowohl kraniell als auch extrakraniell. Bei Verwendung von IGRT-Techniken ohne ausreichenden Weichteilkontrast müssen größere Sicherheitssäume verwendet werden, um ein Verfehlen des Zielvolumens zu vermeiden. Zusätzlich sind mittels 3D IGRT systematische Veränderungen von Tumorvolumen, Tumorform und Lagebeziehung zu Risikoorganen darstellbar, was zur Adaption des Bestrahlungsplanes genutzt werden kann. Mittels konformaler IMRT-Bestrahlungstechniken und präziser IGRT konnten hypofraktionierte, eskalierte Bestrahlungsdosen sicher appliziert werden, was in verbesserter lokaler Tumorkontrolle ohne erhöhte Toxizität resultierte.Schlussfolgerungen:CBCT ermöglicht die Verifikation der Tumorposition zur Online-Korrektur von Positionsfehlern vor der Behandlung, was die Anwendung von kleinen Sicherheitssäumen, Normalgewebsschonung und Dosiseskalation ermöglicht. Die Verbesserung klinischer Ergebnisse wird durch diese Techniken erwartet und ist z.T. bereits in der Literatur dokumentiert.

kV Cone-Beam CT-Based IGRT

AbstractAims and Methods:Delivery of high radiation doses while simultaneously sparing organs at risk requires advanced imaging for target volume definition, highly conformal dose distributions of intensity modulated radiotherapy (IMRT), and narrow planning target volume (PTV) margins. Three-dimensional image-guided radiotherapy (IGRT) with cone-beam computer tomography (CBCT), which results in more precise target localization, is quickly replacing two-dimensional (2D) IGRT. An overview on the clinical applications of kilovoltage gantry-mounted CBCT systems with emphasis on the most frequently targeted body sites (prostate, lung, head and neck) is provided based on a review of the relevant literature. Alternative imaging methods and their advantages/disadvantages are discussed.Results:IGRT with soft tissue detection improves set-up accuracy and is currently replacing 2D verification and frame-based stereotactic treatments; safety margins are significantly reduced by this IGRT technology. In addition, systematic changes of tumor volume and shape and of the normal tissue can be monitored allowing for adaptation of radiotherapy. IGRT in combination with conformal treatment planning allows for hypofractionated dose escalation, which results in improved rates of local tumor control with low rates of toxicity.Conclusion:CBCT allows for daily pretreatment position verification and online correction of set-up errors which improves the precision of patient repositioning with the possibility of shrinking safety margins, sparing organs at risk, and escalating radiation doses. A trend for better clinical outcome can be observed.ZusammenfassungHintergrund und Methodik:Die Verwendung von eskalierten Bestrahlungsdosen bei gleichzeitiger Schonung der Risikoorgane setzt multimodale Bildgebung zur Zielvolumendefinition, hochkonformale Bestrahlungsplanung mittels intensitätsmodulierter Radiotherapie und enge Sicherheitssäume voraus. Bildgeführte Strahlentherapie (IGRT) dient der präzisen Lokalisation des Zielvolumens, und konventionelle 2D Techniken wie Feldkontrollaufnahmen werden aktuell insbesondere durch dreidimensionale Cone-beam-(CBCT-)Technik ersetzt. Dieser Artikel gibt einen Literaturüberblick über den aktuellen Stand der IGRT mittels CBCT. Schwerpunkte sind die praktische Anwendung und klinischen Resultate bei Prostatakarzinom, Bronchialkarzinom und Kopf-Hals-Tumoren. Ergebnisse: Schlussfolgerungen: Schlüsselwörter: Ergebnisse:IGRT mittels CBCT ist hocheffektiv zur Verifikation der Patientenpositionierung und insbesondere zur Verifikation der Tumorposition. Rahmenbasierte Stereotaxie kann durch IGRT ersetzt werden, sowohl kraniell als auch extrakraniell. Bei Verwendung von IGRT-Techniken ohne ausreichenden Weichteilkontrast müssen größere Sicherheitssäume verwendet werden, um ein Verfehlen des Zielvolumens zu vermeiden. Zusätzlich sind mittels 3D IGRT systematische Veränderungen von Tumorvolumen, Tumorform und Lagebeziehung zu Risikoorganen darstellbar, was zur Adaption des Bestrahlungsplanes genutzt werden kann. Mittels konformaler IMRT-Bestrahlungstechniken und präziser IGRT konnten hypofraktionierte, eskalierte Bestrahlungsdosen sicher appliziert werden, was in verbesserter lokaler Tumorkontrolle ohne erhöhte Toxizität resultierte.Schlussfolgerungen:CBCT ermöglicht die Verifikation der Tumorposition zur Online-Korrektur von Positionsfehlern vor der Behandlung, was die Anwendung von kleinen Sicherheitssäumen, Normalgewebsschonung und Dosiseskalation ermöglicht. Die Verbesserung klinischer Ergebnisse wird durch diese Techniken erwartet und ist z.T. bereits in der Literatur dokumentiert.

Local tumor control probability modeling of primary and secondary lung tumors in stereotactic body radiotherapy

BACKGROUND AND PURPOSE To evaluate whether local tumor control probability (TCP) in stereotactic body radiotherapy (SBRT) varies between lung metastases of different primary cancer sites and between primary non-small cell lung cancer (NSCLC) and secondary lung tumors. MATERIALS AND METHODS A retrospective multi-institutional (n=22) database of 399 patients with stage I NSCLC and 397 patients with 525 lung metastases was analyzed. Irradiation doses were converted to biologically effective doses (BED). Logistic regression was used for local tumor control probability (TCP) modeling and the second-order bias corrected Akaike Information Criterion was used for model comparison. RESULTS After median follow-up of 19 months and 16 months (n.s.), local tumor control was observed in 87.7% and 86.7% of the primary and secondary lung tumors (n.s.), respectively. A strong dose-response relationship was observed in the primary NSCLC and metastatic cohort but dose-response relationships were not significantly different: the TCD90 (dose to achieve 90% TCP; BED of maximum planning target volume dose) estimates were 176 Gy (151-223) and 160 Gy (123-237) (n.s.), respectively. The dose-response relationship was not influenced by the primary cancer site within the metastatic cohort. CONCLUSIONS Dose-response relationships for local tumor control in SBRT were not different between lung metastases of various primary cancer sites and between primary NSCLC and lung metastases.

Accuracy of Ultrasound-Based (BAT) Prostate-Repositioning: A Three-Dimensional On-Line Fiducial-Based Assessment With Cone-Beam Computed Tomography

PURPOSE To assess the accuracy of ultrasound-based repositioning (BAT) before prostate radiation with fiducial-based three-dimensional matching with cone-beam computed tomography (CBCT). PATIENTS AND METHODS Fifty-four positionings in 8 patients with 125I seeds/intraprostatic calcifications as fiducials were evaluated. Patients were initially positioned according to skin marks and after this according to bony structures based on CBCT. Prostate position correction was then performed with BAT. Residual error after repositioning based on skin marks, bony anatomy, and BAT was estimated by a second CBCT based on user-independent automatic fiducial registration. RESULTS Overall mean value (MV+/-SD) residual error after BAT based on fiducial registration by CBCT was 0.7+/-1.7 mm in x (group systematic error [M]=0.5 mm; SD of systematic error [Sigma]=0.8 mm; SD of random error [sigma]=1.4 mm), 0.9+/-3.3 mm in y (M=0.5 mm, Sigma=2.2 mm, sigma=2.8 mm), and -1.7+/-3.4 mm in z (M=-1.7 mm, Sigma=2.3 mm, sigma=3.0 mm) directions, whereas residual error relative to positioning based on skin marks was 2.1+/-4.6 mm in x (M=2.6 mm, Sigma=3.3 mm, sigma=3.9 mm), -4.8+/-8.5 mm in y (M=-4.4 mm, Sigma=3.7 mm, sigma=6.7 mm), and -5.2+/-3.6 mm in z (M=-4.8 mm, Sigma=1.7 mm, sigma=3.5 mm) directions and relative to positioning based on bony anatomy was 0+/-1.8 mm in x (M=0.2 mm, Sigma=0.9 mm, sigma=1.1 mm), -3.5+/-6.8 mm in y (M=-3.0 mm, Sigma=1.8 mm, sigma=3.7 mm), and -1.9+/-5.2 mm in z (M=-2.0 mm, Sigma=1.3 mm, sigma=4.0 mm) directions. CONCLUSIONS BAT improved the daily repositioning accuracy over skin marks or even bony anatomy. The results obtained with BAT are within the precision of extracranial stereotactic procedures and represent values that can be achieved with several users with different education levels. If sonographic visibility is insufficient, CBCT or kV/MV portal imaging with implanted fiducials are recommended.

Frameless stereotactic radiosurgery of a solitary liver metastasis using active breathing control and stereotactic ultrasound.

Background and Purpose:Radiosurgery of liver metastases is effective but a technical challenge due to respiration-induced movement. The authors report on the initial experience of the combination of active breathing control (ABC®) with stereotactic ultrasound (B-mode acquisition and targeting [BAT®]) for frameless radiosurgery.Patients and Methods:A patient with a solitary, inoperable liver metastasis from cholangiocellular carcinoma is presented (Figure 4). ABC® (Figure 3) was used for tumor/liver immobilization. Tumor/liver position was controlled and corrected using ultrasound (BAT®; Figure 1). The tumor was irradiated with a single dose of 24 Gy.Results:Using ABC®, the motion of the tumor was significantly reduced and the overall positioning error was < 5 mm (Figure 2). BAT® allowed a rapid localization of the lesion during breath hold which could be performed without difficulties for 20 s. Overall treatment time was acceptable (30 min).Conclusion:Frameless stereotactic radiotherapy with the combination of ABC® and BAT® allows the delivery of high single doses to targets accessible to ultrasound with high precision comparable to a frame-based approach.Hintergrund und Ziel:Die Radiochirurgie solitärer Lebermetastasen ist effektiv, stellt jedoch aufgrund der Atembewegung des Targets eine technische Herausforderung dar. Die Autoren berichten über die initiale Erfahrung mit der rahmenlosen Radiochirurgie durch die Kombination einer aktiven Atmungskontrolle („active breathing control“ [ABC®]) mit dem stereotaktischen Ultraschall („B-mode acquisition and targeting“ [BAT®]).Patient und Methodik:Präsentiert wird ein Patient mit einer solitären Lebermetastase bei cholangiozellulärem Karzinom (Abbildung 4). ABC® (Abbildung 3) wurde zur Immobilisation des Tumors bzw. der Leber verwendet. Die Position des Tumors bzw. der Leber wurde mit Ultraschall (BAT®) kontrolliert und ggf. korrigiert (Abbildung 1). Der Tumor wurde mit einer Einzeldosis von 24 Gy konformal bestrahlt.Ergebnisse:Durch ABC® konnte die Leber-/Tumorbewegung minimiert werden, die gesamte Positionierungsunsicherheit betrug < 5 mm (Abbildung 2). BAT® erlaubte eine schnelle Lokalisierung des Zielvolumens unter Atemanhalt, was wiederholt über 20 s vom Patienten problemlos ausgeführt wurde. Die Gesamtbehandlungszeit war gegenüber einer ungetriggerten Behandlung kaum verlängert (30 min).Schlussfolgerung:Die rahmenlose Stereotaxie durch Kombination von ABC® und BAT® erlaubt, bei sonographisch zugänglichen Zielvolumina hohe Dosen zu applizieren. Die erreichte Präzision liegt im Bereich jener von rahmenbasierten Verfahren.

Deep Inspiration Breath Hold-Based Radiation Therapy: A Clinical Review.

Several recent developments in linear accelerator-based radiation therapy (RT) such as fast multileaf collimators, accelerated intensity modulation paradigms like volumeric modulated arc therapy and flattening filter-free (FFF) high-dose-rate therapy have dramatically shortened the duration of treatment fractions. Deliverable photon dose distributions have approached physical complexity limits as a consequence of precise dose calculation algorithms and online 3-dimensional image guided patient positioning (image guided RT). Simultaneously, beam quality and treatment speed have continuously been improved in particle beam therapy, especially for scanned particle beams. Applying complex treatment plans with steep dose gradients requires strategies to mitigate and compensate for motion effects in general, particularly breathing motion. Intrafractional breathing-related motion results in uncertainties in dose delivery and thus in target coverage. As a consequence, generous margins have been used, which, in turn, increases exposure to organs at risk. Particle therapy, particularly with scanned beams, poses additional problems such as interplay effects and range uncertainties. Among advanced strategies to compensate breathing motion such as beam gating and tracking, deep inspiration breath hold (DIBH) gating is particularly advantageous in several respects, not only for hypofractionated, high single-dose stereotactic body RT of lung, liver, and upper abdominal lesions but also for normofractionated treatment of thoracic tumors such as lung cancer, mediastinal lymphomas, and breast cancer. This review provides an in-depth discussion of the rationale and technical implementation of DIBH gating for hypofractionated and normofractionated RT of intrathoracic and upper abdominal tumors in photon and proton RT.

Intrafraction motion of the prostate during an IMRT session: a fiducial-based 3D measurement with Cone-beam CT.

BackgroundImage-guidance systems allow accurate interfractional repositioning of IMRT treatments, however, these may require up to 15 minutes. Therefore intrafraction motion might have an impact on treatment precision. 3D geometric data regarding intrafraction prostate motion are rare; we therefore assessed its magnitude with pre- and post-treatment fiducial-based imaging with cone-beam-CT (CBCT).Methods39 IMRT fractions in 5 prostate cancer patients after 125I-seed implantation were evaluated. Patient position was corrected based on the 125I-seeds after pre-treatment CBCT. Immediately after treatment delivery, a second CBCT was performed. Differences in bone- and fiducial position were measured by seed-based grey-value matching.ResultsFraction time was 13.6 ± 1.6 minutes. Median overall displacement vector length of 125I-seeds was 3 mm (M = 3 mm, Σ = 0.9 mm, σ = 1.7 mm; M: group systematic error, Σ: SD of systematic error, σ: SD of random error). Median displacement vector of bony structures was 1.84 mm (M = 2.9 mm, Σ = 1 mm, σ = 3.2 mm). Median displacement vector length of the prostate relative to bony structures was 1.9 mm (M = 3 mm, Σ = 1.3 mm, σ = 2.6 mm).Conclusiona) Overall displacement vector length during an IMRT session is < 3 mm.b) Positioning devices reducing intrafraction bony displacements can further reduce overall intrafraction motion.c) Intrafraction prostate motion relative to bony structures is < 2 mm and may be further reduced by institutional protocols and reduction of IMRT duration.

Stereotactic body radiotherapy (SBRT) for medically inoperable lung metastases—A pooled analysis of the German working group “stereotactic radiotherapy”

OBJECTIVES The current literature on stereotactic body radiotherapy (SBRT) for oligometastatic disease is characterized by small patient cohorts with heterogeneous primary tumors, metastases location and dose regimes. Hence, this study established a multi-institutional database of 700 patients treated with SBRT for pulmonary metastases to identify prognostic factors influencing survival and local control. MATERIALS AND METHODS All German radiotherapy departments were contacted and invited to participate in this analysis. A total number of 700 patients with medically inoperable lung metastases treated with SBRT in 20 centers between 1997 and 2014 were included in a database. Primary and metastatic tumor characteristics, treatment characteristics and follow-up data including survival, local control, distant metastases, and toxicity were evaluated. Lung metastases were treated with median PTV-encompassing single doses of 12.5Gy (range 3.0-33.0Gy) in a median number of 3 fractions (range 1-13). RESULTS After a median follow-up time of 14.3 months, 2-year local control (LC) and overall survival (OS) were 81.2% and 54.4%, respectively. In multivariate analysis, OS was most significantly influenced by pretreatment performance status, maximum metastasis diameter, primary tumor histology, time interval between primary tumor diagnosis and SBRT treatment and number of metastases. For LC, independent prognostic factors were pretreatment performance status, biological effective dose (BED) at PTV isocenter (BEDISO) and single fraction (PTV-encompassing) dose in multivariate analysis. Radiation-induced pneumonitis grade 2 or higher was observed in 6.5% of patients. The only factor significantly influencing toxicity was BEDISO (p=0.006). CONCLUSION SBRT for medically inoperable patients with pulmonary metastases achieved excellent local control and promising overall survival. Important prognostic factors were identified for selecting patients who might benefit most from this therapy approach.

Dosimetric consequences of a translational isocenter correction based on image guidance for intensity modulated radiotherapy (IMRT) of the prostate.

Interfractional prostate motion during radiotherapy can have deleterious clinical consequences. It has become clinical practice to re-position the patient according to ultrasound or other imaging techniques. We investigated the dosimetric consequences of the linear translational position correction (isocenter correction) when a conformal IMRT technique with nine fields was used. Treatment plans of seven patients with empty and distended rectums were analyzed. The reference plans were calculated on the CT with an empty rectum. The treatment plans were transferred to a second CT with a distended rectum for an uncorrected setup of the patient referenced to bony anatomy and a corrected setup after translational position correction of the isocenter. The dosimetric consequences (with and without correction) were analyzed. For single treatment fractions, organ motion decreased the volume of the prostate encompassed by the 95% isodose (V95%) by up to -24%-p (percentage points). The mean rectum dose increased by up to 41%-p. Linear translational correction increased V95% of the prostate by up to 17%-p while the mean rectum dose was reduced by up to -23%-p compared to the uncorrected setup. Linear translational correction can improve radiation treatment accuracy for prostate cancer if geometrical changes are within certain limits.

Flattening-filter-free intensity modulated breath-hold image-guided SABR (Stereotactic ABlative Radiotherapy) can be applied in a 15-min treatment slot

Hypofractionated image-guided stereotactic ablative radiotherapy (igSABR) is effective in small lung/liver lesions. Computer-assisted breath-hold reduces intrafraction motion but, as every gating/triggering strategy, reduces the duty cycle, resulting in long fraction times if combined with intensity-modulated radiotherapy (IMRT). 10 MV flattening-filter-free IMRT reduces daily fraction duration to <10 min for single doses of 5-20 Gy.