Quantification Of Organ Motion Research Articles

Quantification of Organ Motion in Male and Female Patients Undergoing Long-Course Radiation Therapy for Rectal Cancer in the Supine Position

PurposePrevious studies have reported data on the internal rectal motion of patients with rectal cancer treated in the prone position. With the introduction of intensity modulated techniques, more patients are treated in the more reproducible supine position. Data informing specific margins for this treatment position are sparse, as are data comparing rectal motion characteristics and factors in male and female patients. The purpose of this retrospective study was to quantify and compare the interfractional rectal movement characteristics of male and female patients with rectal cancer treated with long-course chemoradiation therapy in the supine position. The data will aid the generation of internal target volume margins accounting for this organ's internal physiological movements. Methods and MaterialsCone beam computed tomography (CBCT) images were acquired from 19 male and 16 female patients with rectal cancer on the first 3 days of treatment and weekly thereafter. The rectum, bladder, and femoral heads were delineated on the planning CT (PCT) and 6 CBCT for each patient. Overall, 245 images were analyzed. All patients were treated with a full bladder. The rectum was divided into three 5-cm segments (upper, mid, and lower). The motion of the rectum was quantified by documenting the anteroposterior and lateral distances as measured using fixed anatomic landmarks, namely from the anterior aspect of the sacrum and mid-left femoral head, respectively. These measurements were taken at 1-cm intervals from the inferior border of L5 vertebrae. The sigmoid was excluded from these measurements. Estimations of systematic and random physiological movement error were determined and margins were calculated. ResultsTwo hundred forty-five image sets (19 PCT + 114 CBCT for male, 16 PCT + 96 CBCT for female) on patients who had undergone long-course radiation therapy were analyzed. Rectal tumor location was 31% in the inferior rectum, 46% in the mid rectum, and 23% in the superior rectum. Random rectal motion (mean of the per-patient standard deviation [σ]) was largest for the upper and mid rectum in the anterior direction. There were statistically significant differences in σ between male and female patients in the left lateral motion of the mid and inferior rectum as well as the anterior, posterior, and right motion of the inferior rectum (mid left: P < .0005; lower left: P < .0005; lower posterior: P = .001; lower anterior: P = .032; lower right: P = .001). Suggested internal target volume margin guidelines are therefore nonisotropic and vary per segment of rectum and sex. ConclusionsIn our present study, interfractional rectal motion is shown to be significantly different between male and female patients. Our data suggest that the use of asymmetrical sex-specific margins in patients with rectal cancer treated in the supine position should be considered.

PH-0264 Quantification of organ motion during prolonged breath-holding using deformable image registration

PH-0264 Quantification of organ motion during prolonged breath-holding using deformable image registration

Image-guided Radiotherapy to Manage Respiratory Motion: Lung and Liver

Organ motion as a result of respiratory and cardiac motion poses significant challenges for the accurate delivery of radiotherapy to both the thorax and the upper abdomen. Modern imaging techniques during radiotherapy simulation and delivery now permit better quantification of organ motion, which in turn reduces tumour and organ at risk position uncertainty. These imaging advances, coupled with respiratory correlated radiotherapy delivery techniques, have led to the development of a range of approaches to manage respiratory motion. This review summarises the key strategies of image-guided respiratory motion management with a focus on lung and liver radiotherapy.

Quantification of Organ Motion During Chemoradiotherapy of Rectal Cancer Using Cone-Beam Computed Tomography

There has been no previously published data related to the quantification of rectal motion using cone-beam computed tomography (CBCT) during standard conformal long-course chemoradiotherapy. The purpose of the present study was to quantify the interfractional changes in rectal movement and dimensions and rectal and bladder volume using CBCT and to quantify the bony anatomy displacements to calculate the margins required to account for systematic (Σ) and random (σ) setup errors. CBCT images were acquired from 16 patients on the first 3 days of treatment and weekly thereafter. The rectum and bladder were outlined on all CBCT images. The interfraction movement was measured using fixed bony landmarks as references to define the rectal location (upper, mid, and low), The maximal rectal diameter at the three rectal locations was also measured. The bony anatomy displacements were quantified, allowing the calculation of systematic (Σ) and random (σ) setup errors. A total of 123 CBCT data sets were analyzed. Analysis of variance for standard deviation from planning scans showed that rectal anterior and lateral wall movement differed significantly by rectal location. Anterior and lateral rectal wall movements were larger in the mid and upper rectum compared with the low rectum. The posterior rectal wall movement did not change significantly with the rectal location. The rectal diameter changed more in the mid and upper than in the low rectum. No consistent relationship was found between the rectal and bladder volume and time, nor was a significant relationship found between the rectal volume and bladder volume. In the present study, the anterior and lateral rectal movement and rectal diameter were found to change most in the upper rectum, followed by the mid rectum, with the smallest changes seen in the low rectum. Asymmetric margins are warranted to ensure phase 2 coverage.

SU-FF-J-99: 4D Multi-Organ Motion Analysis in Pancreatic Cancer Patients

Purpose: Center of mass (COM) motion, bounding box motion and volume fluctuation analysis of the clinical target volume (CTV), liver,kidneys, stomach and duodenum in pancreatic cancer patients were measured using 4DCT and deformable registration. Methods and Materials: Eight patients with pancreatic cancer underwent 4DCT for treatment planning. The scans were binned into 10 phases (T00 to T90) and a physician contoured the GTV, CTV, and other abdominal volumes of interest (VOIs) on the T30 phase scan. Deformable registration was applied to propagate the contours to other respiratory phases. Subtraction images were used to validate the registration. We calculated the superior‐inferior (SI), anterior‐posterior (AP), and left‐right (LR) coordinates of the VOIs' center of mass, bounding box margin, as well as volume as a function of respiratory phase. Results: The greatest motion was in the SI axis, with lesser motion in the AP direction. Motion in the LR axis was negligible. Bounding box analysis showed anisotropic movement of the SI and AP edges of organs. The superior margin of the liver showed the greatest movement. In multi‐organ motion analysis, several trends were observed: 1) SI motion of the right kidney and liver were nearly identical; 2) right kidney range of motion was greater than the left kidney motion in 6 of 8 patients 3) Volume fluctuation as a function of respiratory phase of all abdominal organs studied was < 8% of the average organ volume. Conclusion: We have validated and implemented 4D routine motion analysis of abdominal organs. Quantification of organ motion is a necessary step in designing the radiation treatment plan of a moving target. Coupled with dosimetric analysis, it provides metrics for evaluating the need for gated treatment.

Conformal radiotherapy (CRT) planning for lung cancer: analysis of intrathoracic organ motion during extreme phases of breathing

Purpose: Conformal radiotherapy beams are defined on the basis of static computed tomography acquisitions by taking into account setup errors and organ/tumor motion during breathing. In the absence of precise data, the size of the margins is estimated arbitrarily. The objective of this study was to evaluate the amplitude of maximum intrathoracic organ motion during breathing.Methods and Materials: Twenty patients treated for non-small-cell lung cancer were included in the study: 10 patients at the Institut Curie with a personalized alpha cradle immobilization and 10 patients at Tenon Hospital with just the Posirest device below their arms. Three computed tomography acquisitions were performed in the treatment position: the first during free breathing and the other two during deep breath-hold inspiration and expiration. For each acquisition, the displacements of the various intrathoracic structures were measured in three dimensions.Results: Patients from the two centers were comparable in terms of age, weight, height, tumor site, and stage. In the overall population, the greatest displacements were observed for the diaphragm, and the smallest displacements were observed for the lung apices and carina. The relative amplitude of motion was comparable between the two centers. The use of a personalized immobilization device reduced lateral thoracic movements (p < 0.02) and lung apex movements (p < 0.02).Conclusion: Intrathoracic organ movements during extreme phases of breathing are considerable. Quantification of organ motion is necessary for definition of the safety margins. A personalized immobilization device appears to effectively reduce apical and lateral displacement.

Ultrasound-based stereotactic guidance in prostate cancer--quantification of organ motion and set-up errors in external beam radiation therapy.

A mobile transabdominal ultrasound-based targeting system (BAT(R)) has been developed which can stereotactically localize the position of the prostate each treatment day and directly integrate this information into the treatment planning system. Daily target verification facilitates a marked reduction in planning treatment margins by correcting potential organ-motion and set-up errors. Previous studies have been performed to establish the precision of ultrasound localization. This report quantifies the magnitude of the patient isocenter shift parameters encountered during clinical implementation of this system. After five weeks of conformal external beam radiation therapy, 54 patients underwent a second CT simulation. Prostate-only fields based on this scan were created with no PTV margin beyond the CTV. For each of the final conedown treatments (2-4 fractions), patients underwent ultrasound-based stereotactic prostate localization at the treatment machine. The portable system, which electronically imports the CT simulation target-contour and isocenter information, is situated adjacent to the treatment couch. Transverse and sagittal suprapubic ultrasound images are captured, and the system electronically couples this data to the baseline isocenter. The CT contours are maneuvered in three dimensions by a touch-screen menu to visually overlay the ultrasound images. The system then displays the three-dimensional (3D) couch shifts required to produce field alignment. One hundred and eighty-nine daily ultrasound prostate position shifts were recorded for 54 patients. The isocenter field misalignment between the baseline CT and ultrasound ranged from -26.8 to 33.8 mm in the anterior/posterior (A/P) dimension, -10.2 to 30.9 mm in the lateral dimension, and -24.6 to 9.0 mm in the superior/inferior (S/I) dimension. The corresponding directed average disagreements were -3.0 mm (SD 8.3 mm) A/P, 1.86 mm (SD 5.7 mm) lateral, and -2.6 mm (SD 6.5 mm) S/I. The magnitudes of undirected misalignments were frequently larger than 5 mm (51% of A/P, 31% of lateral, and 35% of superior measurements) and oftentimes larger than 10 mm (21% of A/P, 7% of lateral, and 12% of superior measurements). Organ motion and set-up uncertainties limit optimization of 3D treatment planning by expanding the width of PTV margins required to ensure target coverage. Transabdominal ultrasound-based stereotactic guidance is a safe and direct method for correcting patient positioning. Our experience with the BAT system in a large cohort of prostate cancer patients revealed that substantial daily isocenter corrections were encountered in a large percentage of cases. This data would suggest that daily clinical isocenter misalignments are greater than would be expected from published data on organ motion and set-up variations encountered in the study setting.

Ultrasound-Based Stereotactic Guidance in Prostate Cancer—Quantification of Organ Motion and Set-Up Errors in External Beam Radiation Therapy

Objective: A mobile transabdominal ultrasound-based targeting system (BATr`) has been developed which can stereotactically localize the position of the prostate each treatment day and directly integrate this information into the treatment planning system. Daily target verification facilitates a marked reduction in planning treatment margins by correcting potential organ-motion and set-up errors. Previous studies have been performed to establish the precision of ultrasound localization. This report quantifies the magnitude of the patient isocenter shift parameters encountered during clinical implementation of this system.Material and Methods: After five weeks of conformal external beam radiation therapy, 54 patients underwent a second CT simulation. Prostate-only fields based on this scan were created with no PTV margin beyond the CTV. For each of the final conedown treatments (2–4 fractions), patients underwent ultrasound-based stereotactic prostate localization at the treatment machine. The portable system, which electronically imports the CT simulation target-contour and isocenter information, is situated adjacent to the treatment couch. Transverse and sagittal suprapubic ultrasound images are captured, and the system electronically couples this data to the baseline isocenter. The CT contours are maneuvered in three dimensions by a touch-screen menu to visually overlay the ultrasound images. The system then displays the three-dimensional (3D) couch shifts required to produce field alignment.Results: One hundred and eighty-nine daily ultrasound prostate position shifts were recorded for 54 patients. The isocenter field misalignment between the baseline CT and ultrasound ranged from 26.8 to 33.8 mm in the anterior/posterior (A/P) dimension, 10.2 to 30.9 mm in the lateral dimension, and 24.6 to 9.0 mm in the superior/inferior (S/I) dimension. The corresponding directed average disagreements were -3.0 mm (SD 8.3 mm) A/P, 1.86 mm (SD 5.7 mm) lateral, and -2.6 mm (SD 6.5 mm) S/I. The magnitudes of undirected misalignments were frequently larger than 5 mm (51 % of A/P, 31% of lateral, and 35% of superior measurements) and oftentimes larger than 10 mm (21% of A/P, 7% of lateral, and 12% of superior measurements).Conclusions: Organ motion and set-up uncertainties limit optimization of 3D treatment planning by expanding the width of PTV margins required to ensure target coverage. Transabdominal ultrasound-based stereotactic guidance is a safe and direct method for correcting patient positioning. Our experience with the BATr` system in a large cohort of prostate cancer patients revealed that substantial daily isocenter corrections were encountered in a large percentage of cases. This data would suggest that daily clinical isocenter misalignments are greater than would be expected from published data on organ motion and set-up variations encountered in the study setting.

Ultrasound‐based stereotactic guidance in prostate cancer—Quantification of organ motion and set‐up errors in external beam radiation therapy

Ultrasound‐based stereotactic guidance in prostate cancer—Quantification of organ motion and set‐up errors in external beam radiation therapy

Quantification of organ motion during conformal radiotherapy of the prostate by three dimensional image registration

Knowledge about the mobility of organs relative to the bony anatomy is of great importance when preparing and verifying conformal radiotherapy. The conventional technique for measuring the motion of an organ is to locate landmarks on the organ and the bony anatomy and to compare the distance between these landmarks on subsequent computerized tomography (CT) scans. The first purpose of this study is to investigate the use of a three dimensional (3D) image registration method based on chamfer matching for measurement of the location and orientation of the whole organ relative to the bony anatomy. The second purpose is to quantify organ motion during conformal therapy of the prostate. Four CT scans were made during the course of conformal treatment of 11 patients with prostate cancer. With the use of a 3D treatment planning system, the prostate and seminal vesicles were contoured interactively. In addition, bladder and rectum were contoured and the volume computed. Next, the bony anatomy of subsequent scans was segmented and matched automatically on the first scan. The femora and the pelvic bone were matched separately to quantify motion of the legs. Prostate (and seminal vesicle) contours from the subsequent scans were matched on the corresponding contours of the first scan, resulting in the 3D rotations and translations that describe the motion of the prostate and seminal vesicles relative to the pelvic bone. Bone matching of two scans with about 50 slices of 256 x 256 pixels takes about 2 min on a workstation and achieves subpixel registration accuracy. Matching of the organ contours takes about 30 s. The accuracy in determining the relative movement of the prostate is 0.5 to 0.9 mm for translations (depending on the axis) and 1 degree for rotations (standard deviations). Because all organ contours are used for matching, small differences in delineation of the prostate, missing slices, or differences in slice distance have only a limited influence on the accuracy. Rotations of the femora and the pelvic bone are quantified with about 0.4 degree accuracy. A strong correlation was found between rectal volume and anterior-posterior translation and rotation around the left-right axis of the prostate. Consequently, these parameters had the largest standard deviations of 2.7 mm and 4.0 degrees. Bladder filling had much less influence. Less significant correlations were found between various leg rotations and pelvic and prostate motion. Standard deviations of the rotation angles of the pelvic bone were less than 1 degree in all directions. Using 3D image registration, the motion of organs relative to bony anatomy has been quantified accurately. Uncertainties in contouring and visual interpretation of the scans have a much smaller influence on the measurement of organ displacement with our new method than with conventional methods. We have quantified correlations between rectal filling, leg motions, and prostate motion.

28 The use of MRI, CT and spect registration for treatment planning and follow-up

MRI for treatment planning Due to geometric distortions, the use of MRI in radiotherapy planning has been limited. By accurate registration of CT and MRI (e.g., based on the skull) using the chamfer matching algorithm, the geometric accuracy of CT is combined with the diagnostic quality of MRI. This method is mainly in use for tumours in the head but applications for prostate cancer are under development. Follow-up studies Tissue response after radiotherapy is sometimes visible on CT. For lung damage, ventilation and perfusion SPECT scans are the visualisation instrument of choice. By matching the planning CT with follow-up CT or SPECT a correlation of radiation dose and subsequent damage is possible. Organ motion studies Matching of repeat scans of the same patient allows quantification of organ motion. Using this technique, motion of prostate and femurs relative to the pelvis has been measured accurately in 40 scans from 11 patients. Prostate motion was mostly be attributed to rectal volume variations, but femur motion has a small but significant influence on prostate rotation. Conclusion Image registration is an essential tool for precision radiotherapy.