Kidney Motion Research Articles

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.

Improvement of MRI‐functional measurement with automatic movement correction in native and transplanted kidneys

To improve 2D software for motion correction of renal dynamic contrast-enhanced magnetic resonance imaging (DCE-MRI) and to evaluate its effect using the Patlak-Rutland model. A subpixel-accurate method to correct for kidney motion during DCE-MRI was evaluated on native and transplanted kidneys using data from two different institutions with different magnets and protocols. The Patlak-Rutland model was used to calculate glomerular filtration rate (GFR) on a voxel-by-voxel basis providing mean (Kp) and uncertainty (sigma(K(p))) values for GFR. In transplanted kidneys, average absolute variation of Kp was 6.4% +/- 4.8% (max = 16.6%). In native kidneys average absolute variation of Kp was 12.11% +/- 6.88% (max = 25.6%) for the right and 11.6% +/- 6% (max = 20.8%) for the left. Movement correction showed an average reduction of sigma(K(p)) of 6.9% +/- 6.6% (max = 21.4%) in transplanted kidneys, 30.9% +/- 17.6% (max = 60.8%) for the right native kidney, and 31.8% +/- 14% (max = 55.3%) for the left kidney. The movement correction algorithm showed improved uncertainty on GFR computation for both native and transplanted kidneys despite different spatial resolution from the different MRI systems and different levels of signal-to-noise ratios on DCE-MRI.

Dynamic Contrast-Enhanced Magnetic Resonance Images of the Kidney

In this article, an improved method to segment the renal cortex and medulla and to eliminate the influence of kidney motion produced by respiration is proposed. On the basis of an adaptive threshold estimated from the mean gray levels of the grown regions, a region-growing algorithm is presented to produce a three-dimensional (3-D) kidney contour and to segment the renal structures. Moreover, a shell mask of kidney margin is proposed to realize a coarse matching so as to eliminate the image translation, which makes the processing simple and direct in spatial processing without any image transform computations, and a correlation computation can be implemented with great efficiency. Then, a refined matching with a mask of cortex is completed through a 3-D correlation algorithm to ensure the accurate registration of the images in different phases. Comparing with the global mask including the whole kidney, both the shell mask and the cortex mask significantly contribute to decreasing the matching errors for images with nonuniform intensity signals, which much improves the registration quality of renal MR images. In this way, the effect of the respiration motions can be eliminated so that the intensity measurement in different phases becomes accurate within the respective structures.

Intensity-based registration of freehand 3D ultrasound and CT-scan images of the kidney

Objectives This paper presents a method to register a pre-operative computed-tomography (CT) volume to a sparse set of intra-operative ultra-sound (US) slices. In the context of percutaneous renal puncture, the aim is to transfer planning information to an intra-operative coordinate system. Materials and methods The spatial position of the US slices is measured by optically localizing a calibrated probe. Assuming the reproducibility of kidney motion during breathing, and no deformation of the organ, the method consists in optimizing a rigid 6 degree of freedom transform by evaluating at each step the similarity between the set of US images and the CT volume. The correlation between CT and US images being naturally rather poor, the images were preprocessed in order to increase their similarity. Among the similarity measures formerly studied in the context of medical image registration, correlation ratio turned out to be one of the most accurate and appropriate, particularly with the chosen non-derivative minimization scheme, namely Powell-Brent’s. The resulting matching transforms are compared to a standard rigid surface registration involving segmentation, regarding both accuracy and repeatability. Results The obtained results are presented and discussed.

Registration and segmentation of multislice 3DCT images: Application to laparoscopic surgery of the upper urinary system

A clear identification of arteries, veins and urinary tracts, together with their simultaneous visualization in 3D is required when planning laparoscopic surgery on kidneys. To this aim, multiple contrast-enhanced CT scans are acquired at different times during blood circulation, but the kidney motion, among other causes, seriously hampers their direct fusion. This study aims at developing algorithms to represent in 3D, from such images, the kidney surroundings as close as possible to the surgical reality.

Respiration-induced motion of the kidneys in whole abdominal radiotherapy: implications for treatment planning and late toxicity

Purpose: Whole abdominal radiotherapy (WAR) has potential utility in the management of several malignancies. The limited radiation tolerance of the kidneys is an important consideration in the design of WAR fields. Although renal blocking is standard for WAR, few guidelines exist in the literature to factor respiration-induced kidney motion into the design of these blocks. Methods: Radiographs were obtained to measure kidney excursion under forced respiratory conditions in eight patients (14 visualized kidneys). Intravenous contrast was administered and AP films were obtained at maximum inspiration and expiration. Renal excursion was measured relative to a horizontal reference line at the bottom of the L3 vertebral body. The kidney position on the actual treatment simulation film was also determined using this technique. Treatment isodose distributions through the kidneys were obtained for a sample patient using phantom measurements and two blocking schemes: AP/PA and PA only. These provided quantification of the actual dose received by the kidney in a typical WAR treatment. Results: In the worst case scenario, the left kidney block required an additional 10 mm above and 15 mm below the renal silhouette on the simulation film in order to account for all phases of respiration. The corresponding values for the right kidney were 2 mm and 19 mm, respectively. The dose received by the kidney under the center of the block was 20% of prescribed using AP/PA blocks and 50% of prescribed using PA blocks only. However, portions of ‘blocked’ kidney received up to 90% of the prescribed dose with either technique. Conclusions: Although kidney motion under forced respiratory conditions is not representative of typical treatment conditions, the data highlight the possibility of renal movement during treatment. This is particularly important in light of the significant dose (20 to 50%) delivered to the kidney under the center of the kidney block in typical treatments. Given the potential for overdosage of this critical organ, careful prospective documentation of renal function is warranted in patients receiving WAR.

497 Respiration induced motion of the kidneys: Implications for block design in whole abdominal radiotherapy (WAR)

<h3>Purpose</h3> Whole abdominal radiotherapy (WAR) is frequently used in the treatment of tumors of the ovary and endometrium. The limited radiation tolerance of several critical organs, especially the kidneys, is an important consideration in the design of WAR fields. Although renal blocking is standard for WAR, few guidelines exist in the literature to factor respiration-induced kidney motion into the design of these blocks. <h3>Methods</h3> Radiographs were obtained to measure kidney excursion under forced respiratory conditions in 6 patients (10 visualized kidneys). Intravenous contrast was administered and AP films were obtained at maximum inspiration and expiration. A horizontal reference line was drawn at the bottom of the L3 vertebral body and the excursion of each kidney was determined relative to this line. The kidney position on the actual treatment simulation film was also determined using this technique. These excursion movements were incorporated into the design of an idealized block to account for all phases of respiration. <h3>Results</h3> The range of excursion for the left kidney was 1–32mm and for the right kidney was 3–14mm. In a worst case scenario, the left kidney block required an additional 14mm above and 32mm below the renal silhouette on the simulation film. The corresponding values for the right kidney were 17mm and 10mm, respectively. <h3>Conclusions</h3> Although kidney motion under forced respiratory conditions is not representative of typical treatment conditions, the data highlight the possibility of significant renal movement during treatment. These factors must be kept in mind when customizing renal blocks.

The influence of respiration induced motion of the kidneys on the accuracy of radiotherapy treatment planning, a magnetic resonance imaging study

An MRI study has been performed to determine the respiration induced motion of the kidneys. Under normal respiration conditions displacements of the left and right kidney varied from 2 to 24 mm and 4 to 35 mm, respectively. Under forced respiration conditions displacements were larger and ranged from 10 to 66 mm for the left kidney and 10 to 86 mm for the right kidney. The influence of kidney motion on the radiation dose was determined for patients irradiated on the total abdomen for ovarian cancer with shielding of the kidneys during part of the treatment. The kidney motion resulted in a larger fraction of the kidney volume receiving a dose between 20 and 22 Gy.

The influence of respiration induced motion of the kidneys on the accuracy of radiotherapy treatment planning, a magnetic resonance imaging study

An MRI study has been performed to determine the respiration induced motion of the kidneys. Under normal respiration conditions displacements of the left and right kidney varied from 2 to 24 mm and 4 to 35 mm, respectively. Under forced respiration conditions displacements were larger and ranged from 10 to 66 mm for the left kidney and 10 to 86 mm for the right kidney. The influence of kidney motion on the radiation dose was determined for patients irradiated on the total abdomen for ovarian cancer with shielding of the kidneys during part of the treatment. The kidney motion resulted in a larger fraction of the kidney volume receiving a dose between 20 and 22 Gy.