Tumor Phantom Research Articles

Data acquisition system for harmonic motion microwave Doppler imaging.

Harmonic Motion Microwave Doppler Imaging (HMMDI) is a hybrid method proposed for breast tumor detection, which images the coupled dielectric and elastic properties of the tissue. In this paper, the performance of a data acquisition system for HMMDI method is evaluated on breast phantom materials. A breast fat phantom including fibro-glandular and tumor phantom regions is produced. The phantom is excited using a focused ultrasound probe and a microwave transmitter. The received microwave signal level is measured on three different points inside the phantom (fat, fibro-glandular, and tumor regions). The experimental results using the designed homodyne receiver proved the effectiveness of the proposed setup. In tumor phantom region, the signal level decreased about 3 dB compared to the signal level obtained from the fibro-glandular phantom area, whereas this signal was about 4 dB higher than the received signal from the fat phantom.

P-0099 - Computed Tomography Scan and Image Reconstruction Models Affects the Target Volume of Liver Cancer Radiotherapy

Introduction: Evaluation the tumor volume for liver cancer radiotherapy is usually performed by computed tomography scan. However, respiratory motion would cause variations of the position, volume and shape of the tumor on the CT image and result in deviation of target volume. This study will evaluate the influences of different CT scan and image reconstruction models towards target volume for liver cancer radiotherapy. Methods: This study employed a home-made movable platform and liver tumor phantoms to simulate respiratory motion of human body. The movable platform was set up with different amplitudes and periods to explore various CT scan and reconstruction models of 4D CT-MIP, 4D CT-AIP, helical CT and slow CT. The differences among actual tumor volume and the target volumes produced by various CT scan and image reconstruction models were analyzed with a reconstructed 3D image of liver tumor after the scanning. Results: The image reconstruction showed that the 4D CT-MIP provided clear tumor area and detected the tumor boundaries specifically. The area of tumor target was accurately delineated when determining the gross tumor volume in treatment planning system. The differences 4D CT-AIP and 4D CT-MIP for R-L, A-P and S-I directions were less than 0.5cm. When compared with 4D CT-MIP and slow CT were 2.8 cm and 1.6 cm, respectively. The reconstruction images of bigger tumors had greater deviations than the smaller ones. No matter what the volume was, the reconstructed images from 4D CT-MIP were the closest to the actual target volume. Conclusion: 4D CT-MIP could completely define the motion ranges of the tumor during respiration and allow the tumor to receive complete radiation doses and promote the effectiveness of liver cancer radiotherapy.

Three-dimensional confocal imaging for breast cancer detection using CMOS Gaussian monocycle pulse transmitter and 4 × 4 ultra wideband antenna array with impedance matching layer

A time-domain reflectometry breast cancer detection system was developed, which was composed of a Gaussian monocycle pulse (GMP) transmitter circuit fabricated by complementary metal oxide semiconductor (CMOS) 65 nm technology and an ultra wide-band (UWB) planar slot antenna array. The center frequency and bandwidth of the antenna were 6 and 9.2 GHz, respectively. The GMP train having the pulse width of 160 ps was generated by the 65 nm CMOS logic circuit with a core area of 0.0017 mm2 and was emitted by the 4 × 4 planar slot antenna array. The fabricated planar 4 × 4 antenna array with the matching layer could resolve the two separate 5 × 5 × 5 mm3 breast tumor phantoms, which were located at the depth of 22 mm with the spacing of 8 mm.

A Finite Element Model for Recognizing Breast Cancer

Breast cancer recognition is an important issue in elastography diagnostic imaging. Breast tumor biopsy has been for many years the reference procedure to assess histological definition for breast diseases. But biopsy measurement is an invasive method besides it takes larger time. So, fast and improved methods are needed. Using elastography technology, a digital image correlation technique can be used to calculate the displacement of breast tissue after it has suffered a compression force. This displacement is related to tissue stiffness, and breast cancer can be classified into benign or malignant according to that displacement. The value of compression force affects the displacement of tissue, and then affects the results of the breast cancer recognition. Finite element method was being used to simulate a model for the breast cancer as a phantom to be used in measurements and study of breast cancer diagnosis. The breast cancer using this phantom can be recognized within a short time. The proposed work succeeded in recognizing breast tumor phantom by an average correct recognition ratio CRR of about 94.25% on a simulation environment. The strain ratio SR for benign and malignant models is also computed. The result of the simulated breast tumor model is compared with real data of 10 lesion cases (6 benign and 4 malignant). The coefficient of variation CV between the simulated SR and the SR using real data reaches to about 5% for benign lesions and 4.78% for malignant lesions. The results of CRR and CV in this proposed work assure that the proposed breast cancer model using finite element modeling is a robust technique for breast tumor simulation where the behavior of real data of breast cancer can be predicted.

Dosimetry in brain tumor phantom at 15 MV 3D conformal radiation therapy

Glioblastoma multiforme (GBM) is the most common, aggressive, highly malignant and infiltrative of all brain tumors with low rate of control. The main goal of this work was to evaluate the spatial dose distribution into a GBM simulator inside a head phantom exposed to a 15 MV 3D conformal radiation therapy in order to validate internal doses. A head and neck phantom developed by the Ionizing Radiation Research Group (NRI) was used on the experiments. Such phantom holds the following synthetic structures: brain and spinal cord, skull, cervical and thoracic vertebrae, jaw, hyoid bone, laryngeal cartilages, head and neck muscles and skin. Computer tomography (CT) of the simulator was taken, capturing a set of contrasted references. Therapy Radiation planning (TPS) was performed based on those CT images, satisfying a 200 cGy prescribed dose split in three irradiation fields. The TPS assumed 97% of prescribed dose cover the prescribed treatment volume (PTV). Radiochromic films in a solid water phantom provided dose response as a function of optical density. Spatial dosimetric distribution was generated by radiochromic film samples at coronal, sagittal-anterior and sagittal-posterior positions, inserted into tumor simulator and brain. The spatial dose profiles held 70 to 120% of the prescribed dose. In spite of the stratified profile, as opposed to the smooth dose profile from TPS, the tumor internal doses were within a 5% deviation from 214.4 cGy evaluated by TPS. 83.2% of the points with a gamma value of less than 1 (3%/3mm) for TPS and experimental values, respectively. At the tumor, measured at coronal section, a few dark spots in the film caused the appearance of outlier points in 13-15% of dose deviation percentage. And, as final conclusion, such dosimeter choice and the physical anthropomorphic and anthropometric phantom provided an efficient method for validating radiotherapy protocols.

3D viability imaging of tumor phantoms treated with single-walled carbon nanohorns and photothermal therapy

A new image analysis method called the spatial phantom evaluation of cellular thermal response in layers (SPECTRL) is presented for assessing spatial viability response to nanoparticle enhanced photothermal therapy in tissue representative phantoms. Sodium alginate phantoms seeded with MDA-MB-231 breast cancer cells and single-walled nanohorns were laser irradiated with an ytterbium fiber laser at a wavelength of 1064 nm and irradiance of 3.8 W cm−2 for 10–80 s. SPECTRL quantitatively assessed and correlated 3D viability with spatiotemporal temperature. Based on this analysis, kill and transition zones increased from 3.7 mm3 and 13 mm3 respectively to 44.5 mm3 and 44.3 mm3 as duration was increased from 10 to 80 s. SPECTRL provides a quantitative tool for measuring precise spatial treatment regions, providing information necessary to tailor therapy protocols.

SU-E-T-153: Dosimetric Impact in Moving Tumor Under Irradiation Dose by Chasing Its Motion with DMLC

Purpose: The dosimetric error in a moving tumor by delivering the dose with the real-time tumor tracking was evaluated to evidence the clinical efficacy of its new technique. Methods: A spherical tumor phantom (2, 3 and 4cm-diam.), in which a small ionization chamber or a radiation film on coronal plane were inserted, was sinusoidally moved by using the Washington University 4D Phantom. A dynamic MLC motion pattern same with a tumor motion was independently prepared by considering the PTV margin of 0, 0.5 and 1cm, and this chased tumor phantom synchronously by the trigger of RPM system (Varian Medical Systems, Ltd. Co.). The absolute dose at center of tumor and the dose distribution were measured under the delayed dMLC chasing, which was induced by changing the beam-on trigger in RPM, and they were evaluated by comparing with its in static. Results: The significant dosimetric error was not observed with a sinusoidal motion of the amplitude less than ±0.5cm, even if the chasing delay time went over 1sec. A small PTV margin and a large tumor motion caused a large dosimetic error at the range of −5% ∼ −50%. The penumbra of dose distribution at the edge of a tumor was blurred at the error of 5% under the delayed dMLC chasing with 1sec. Conclusion: The dosimetric error in a moved tumor by chasing with dMLC was only observed in an unlikely situation, such as 1sec chasing error, which corresponded to a maximum geometrical discrepancy of 1cm between dMLC and tumor if the tumor moved with an amplitude of 2cm and a period of 4sec. The same evaluation will apply with a human respiratory motion furthermore. Japan Science Promotion Foundation, No:24601001

125 mW 102.4 GS/s Ultra-High-Speed Sampling Circuit for Complementary Metal–Oxide–Semiconductor Breast Cancer Detection System

For application to an impulse-radio ultra-wideband (IR-UWB) portable breast cancer detection system, a 102.4 GS/s sampling circuit is developed. The high sampling rate is realized by an equivalent-time sampling technique and a low-power multi-clock generation circuit using a phase interpolator. The phase interpolator achieved a minimum phase resolution 9.8 ps. Using the sampling circuit, a tumor phantom buried by a breast phantom was detected.

A Compact 4 $\times$ 4 Planar UWB Antenna Array for 3-D Breast Cancer Detection

A compact 4 × 4 planar ultrawideband (UWB) antenna array with the total size of 44 × 52.4 mm was developed for radar-based breast cancer detection system. The center frequency and the bandwidth of the antenna were 6 and 12.5 GHz, respectively. The breast phantom materials were developed to fit the characteristics of the measured human breast tissues. A quasi-three-dimensional confocal imaging was performed using the breast phantoms. It was confirmed that the compact 4 × 4 antenna array could detect a 5 × 5 × 5-mm3 tumor phantom in an inhomogeneous structure with a glandular phantom and resolve the two separate tumor phantoms, which were located at the depth of 23 mm with the spacing of 10 mm.

肺定位放射線治療におけるカーボンファイバカウチの線量影響

The aim of this study was to measure the dose attenuation caused by a carbon fiber radiation therapy table (Imaging Couch Top; ICT, BrainLab) and to evaluate the dosimetric impact of ICT during stereotactic body radiation therapy (SBRT) in lung tumors. The dose attenuation of ICT was measured using an ionization chamber and modeled by means of a treatment planning system (TPS). SBRT was planned with and without ICT in a lung tumor phantom and ten cases of clinical lung tumors. The results were analyzed from isocenter doses and a dose-volume histogram (DVH): D95, Dmean, V20, V5, homogeneity index (HI), and conformity index (CI). The dose attenuation of the ICT modeled with TPS agreed to within ±1% of the actually measured values. The isocenter doses, D95 and Dmean with and without ICT showed differences of 4.1-5% for posterior single field and three fields in the phantom study, and differences of 0.6-2.4% for five fields and rotation in the phantom study and six fields in ten clinical cases. The dose impact of ICT was not significant for five or more fields in SBRT. It is thus possible to reduce the dose effect of ICT by modifying the beam angle and beam weight in the treatment plan.

A gel tumour phantom for assessment of the accuracy of manual and automatic delineation of gross tumour volume from FDG-PET/CT

Introduction. Our primary aim was to make a phantom for PET that could mimic a highly irregular tumour and provide true tumour contours. The secondary aim was to use the phantom to assess the accuracy of different methods for delineation of tumour volume from the PET images. Material and methods. An empty mould was produced on the basis of a contrast enhanced computed tomography (CT) study of a patient with a squamous cell carcinoma in the head and neck region. The mould was filled with a homogeneous fast-settling gel that contained both 18F for positron emission tomography (PET) and an iodine contrast agent. This phantom (mould and gel) was scanned on a PET/CT scanner. A series of reference tumour contours were obtained from the CT images in the PET/CT. Tumour delineation based on the PET images was achieved manually, by isoSUV thresholding, and by a recently developed three-dimensional (3D) Difference of Gaussians algorithm (DoG). Average distances between the PET-derived and reference contours were assessed by a 3D distance transform. Results. The manual, thresholding and DoG delineation methods resulted in volumes that were 146%, 86% and 100% of the reference volume, respectively, and average distance deviations from the reference surface were 1.57 mm, 1.48 mm and 1.0, mm, respectively. Discussion. Manual drawing as well as isoSUV determination of tumour contours in geometrically irregular tumours may be unreliable. The DoG method may contribute to more correct delineation of the tumour. Although the present phantom had a homogeneous distribution of activity, it may also provide useful knowledge in the case of inhomogeneous activity distributions. Conclusion. The geometric irregular tumour phantom with its inherent reference contours was an important tool for testing of different delineation methods and for teaching delineation.

SU‐E‐T‐532: Comparison of Dose Distributions Calculated Using Different Planning Systems with Radiochromic Film Measurements in an Inhomogeneous Phantom

Accurate modeling of the dose distribution in a lung tumor is challenging for traditional dose calculation algorithms. We compare the dose distributions of four commercial dose calculation Methods: Raysearch (Raysearch Laboratories) and Pinnacle (Philips Healthcare) collapsed cone, and Eclipse AAA and Eclipse Acuros,(Varian Medical Systems) with measurements using radiochromic film in a lung tumor phantomMethods: A simple lung tumor phantom was constructed using a thermoplastic cylinder 29 mm diameter and 40mm in length (density 1.3 gm/cc) imbedded in cork phantom 25 × 25 × 20 cm of density 0.32 gm/cc. Nine film layers normal to the axis of the cylinder where placed between layers of cork, above, below and through the cylindrical inhomogeneity. The phantom was irradiated with a single asymmetric 10×10 cm 6 MV field with the central axis collinear with the cylinder axis. Thirteen film exposures at 5 cm depth taken with doses 0-10 Gy were used to calibrate the film. The phantom was CT scanned and the DICOM study loaded into each of the treatment planning systems to calculate the dose distribution in the phantom. Away from cork-poly interfaces, agreement between the four algorithms was within 3% of the film measurements. For Acuros, the dose at the edge of the cylinder was found to be up to 2% lower than that at the center of the cylinder possibly because of the loss of lateral electron equilibrium. All four algorithms achieved remarkable agreement with the radiochromic film measurement. The Acuros algorithm appeared to more accurately model the peripheral dose deficit in the tumor, although a more detailed study is required for confirmation.

Experimental and simulation studies for the optimization of dedicated scintimammography cameras

The main drawback of scintimammography with conventional gamma cameras is the large distance between detector and breast, which limits imaging performance and adds significant background noise from the heart and other organs. These limitations can be minimized by dedicated gamma cameras placed in tight contact with the breast. The purpose of this study was to determine the lowest Tumor-to-Background (T:B) ratio for detectable lesions and the smallest lesions that can be imaged with a dedicated system. The system is based on an R3292 position sensitive photomultiplier tube (PSPMT) from Hamamatsu, coupled to a 10 cm in diameter CsI(Tl) crystal and a general purpose collimator with hexagonal holes. Two crystals were assessed, with pixel size of 2 × 2 mm2 and 3 × 3 mm2. The experimental setup consists of a cylindrical breast phantom, cylindrical tumor phantoms positioned inside the breast phantom at various depths, and a heart phantom. The same setup, as well as some additional tumor phantoms, were modeled with the GATE simulation toolkit, following the validation of the entire system. A 20% energy window and the Dual Energy Window Subtraction Method (DEWSM) for scatter correction were applied in experimental and simulation data. In all measurements 99mTc was used. Signal to Noise Ratio (SNR) and contrast were measured in all experiments and used for quantification of results. Experimental and simulation results show that the lowest T:B ratio that can be detected is 2:1 with tumor phantom volume ⩾ 0.25 ml at 1 cm depth. The smallest volume of a tumor phantom that can be detected is 0.04 ml with T:B ratio equal to 9:1 at 1 cm depth.

IMPROVED THERMAL ABLATION EFFICACY USING MAGNETIC NANOPARTICLES: A STUDY IN TUMOR PHANTOMS

Magnetic heating used for inducing hyperthermia and thermal ablation is particularly promising in the treatment of cancer provided that the therapeutic temperature is kept constant during the treatment time throughout the targeted tissue and the healthy surrounding tissues are maintained at a safe temperature. The present study shows the temperature increment produced by different concentrations of magnetic nanoparticles (ferrofluid and magnetoliposomes) inside a phantom, after irradiating tissuemimicking materials (phantoms)with a minimally invasive coaxial antenna working at a frequency of 2.45GHz. This frequency was chosen because maximum dielectric loss of water molecules begins at 2.4GHz and because this is an ISM (industrial, scientific and medical) frequency. Temperature sensors were placed inside and outside the tumor phantom to assess the focusing effect of heat produced by nanoparticles. Results have shown that the temperature increments depend on the nanoparticles concentration. In this way, a temperature increment of more than 56◦C was obtained with a ferrofluid concentration of 13.2 mg/mL, whereas the increment in the reference phantom was only of ≈ 21◦C. Concerning the magnetoliposomes, the temperature achieved was similar to that obtained with the ferrofluid but at a lesser concentration of nanoparticles. These results Received 1 February 2012, Accepted 27 March 2012, Scheduled 30 May 2012 * Corresponding author: Joan Estelrich (joanestelrich@ub.edu). 230 Garcia-Jimeno et al. demonstrate that it is possible to achieve higher temperatures and to focus energy where the nanoparticles are located.

Breast tumour detection by flexible wearable antenna system

Breast tumour detection using flexible wearable antenna system presented in this paper removes the need for liquid coupling mediums used in conventional systems, leading to a simpler and cost effective imaging device. This is achieved by considering a planar microstrip antenna design on a flexible substrate and optimising the antenna for the skin contact operation. It is shown that systems with a matched coupling medium still have 20% theoretical reflection loss at the skin, which is eliminated in the presented system. Simulation results show three-fold increase in the current densities and electric fields in the tumour. Experimental results with in-house breast and tumour phantoms show that the received signal from a tumour has 33 dB maximum and 19 dB average (over 400 MHz range) amplitude above noise level. Theoretical analysis, simulation models, and experimental results for breast tumour detection using flexible wearable antenna system are presented and discussed.

Effects of probe geometry on transscleral diffuse optical spectroscopy

The purpose of this study was to investigate how the geometry of a fiber optic probe affects the transmission and reflection of light through the scleral eye wall. Two geometrical parameters of the fiber probe were investigated: the source-detector distance and the fiber protrusion, i.e. the length of the fiber extending from the flat surface of the fiber probe. For optimization of the fiber optic probe geometry, fluorescence stained choroidal tumor phantoms in ex vivo porcine eyes were measured with both diffuse reflectance- and laser-induced fluorescence spectroscopy. The strength of the fluorescence signal compared to the excitation signal was used as a measure for optimization. Intraocular pressure (IOP) and temperature were monitored to assess the impact of the probe on the eye. For visualizing any possible damage caused by the probe, the scleral surface was imaged with scanning electron microscopy after completion of the spectroscopic measurements. A source-detector distance of 5 mm with zero fiber protrusion was considered optimal in terms of spectroscopic contrast, however, a slight fiber protrusion of 0.5 mm is argued to be advantageous for clinical measurements. The study further indicates that transscleral spectroscopy can be safely performed in human eyes under in vivo conditions, without leading to an unacceptable IOP elevation, a significant rise in tissue temperature, or any visible damage to the scleral surface.

Pulmonary Tumor Measurements from X-Ray Computed Tomography in One, Two, and Three Dimensions

We evaluated the accuracy and reproducibility of three-dimensional (3D) measurements of lung phantoms and patient tumors from x-ray computed tomography (CT) and compared these to one-dimensional (1D) and two-dimensional (2D) measurements. CT images of three spherical and three irregularly shaped tumor phantoms were evaluated by three observers who performed five repeated measurements. Additionally, three observers manually segmented 29 patient lung tumors five times each. Follow-up imaging was performed for 23 tumors and response criteria were compared. For a single subject, imaging was performed on nine occasions over 2 years to evaluate multidimensional tumor response. To evaluate measurement accuracy, we compared imaging measurements to ground truth using analysis of variance. For estimates of precision, intraobserver and interobserver coefficients of variation and intraclass correlations (ICC) were used. Linear regression and Pearson correlations were used to evaluate agreement and tumor response was descriptively compared. For spherical shaped phantoms, all measurements were highly accurate, but for irregularly shaped phantoms, only 3D measurements were in high agreement with ground truth measurements. All phantom and patient measurements showed high intra- and interobserver reproducibility (ICC >0.900). Over a 2-year period for a single patient, there was disagreement between tumor response classifications based on 3D measurements and those generated using 1D and 2D measurements. Tumor volume measurements were highly reproducible and accurate for irregular, spherical phantoms and patient tumors with nonuniform dimensions. Response classifications obtained from multidimensional measurements suggest that 3D measurements provide higher sensitivity to tumor response.

SU‐E‐T‐856: Investigation of Fluence Parameterization Methods for PARETO Multi‐Objective Radiation Therapy Treatment Planning Software

Purpose: To determine the best parameterization of fluence modulation for PARETO (Pareto‐Aware Radiotherapy Evolutionary Treatment Optimization) multi‐objective treatment planning software, as judged by the complexity of each parameterization, the efficiency, and the quality of the plans produced. Methods: PARETO simultaneously optimizes the number of beams, beam orientations, and fluence modulation. For this investigation, we have tested four fluence parameterizations on a paraspinal tumour phantom and a spine patient data set using a pre‐determined number of beams. The first method applies linear gradients over the projection of Planning Target Volume (PTV) in the beamˈs‐eye‐view plane. The second method applies the two‐dimensional inverse cosine transform of a few low‐frequency parameters. Another method interpolates between the intensities of a coarse grid of square beamlets. Also, an isodose‐based contour method defines regions on the fluence maps that are assigned different intensities. Methods which produce plans of the best quality (as judged by dose‐volume histograms) will have a similar distribution of non‐dominated solutions. The complexity of each parameterization is determined by the number of parameters, and the efficiency is determined by the run time. Results: For both geometries, we found that the set of non‐dominated solutions of each parameterization overlapped in the projection of the PTV conformity fitness function and the quadrature‐averaged Organs‐At‐Risk (OAR) fitness function. The beam group and cosine transform methods produced some plans which did slightly better in simultaneously achieving good PTV conformity and OAR dose sparing. The cosine transform and linear gradient methods proved to be the most efficient. The cosine transform method also has the least number of parameters per beam. Conclusions: We have found that several different parameterizations of fluence modulation produce non‐dominated solutions of similar quality. The cosine transform method is the best choice for efficiently producing solutions that do well in PTV conformity and OAR sparing.

SU‐E‐T‐882: Electron Disequilibrium Pitfalls for Small Megavoltage Photon Fields Incident on Lung Tumors

Purpose: Stereotactic body radiation therapy (SBRT) of lung uses sub‐centimeter MV x‐ray fields. Under these conditions, lateral electron disequilibrium (LED) can occur in lung tissue, which causes perturbations of the dose distribution near the tumor. This purpose of this work is to characterize the LED effect in lung for clinically relevant ranges of beam energies, field sizes, and lung densities. Methods: The MC code DOSXYZnrc (National Research Council of Canada, Ottawa, ON) was employed to simulate two 20×20×25cm3 water‐lung‐water slab phantoms. The two phantoms were identical in composition except that the second phantom also included a 3×3×3cm3 centrally located water cube to mimic a small lung tumor. To characterize LED, dose calculations were performed using combinations of beam energy (Co‐60 up to 18MV), field sizes (1×1cm2 up to 15×15cm2), and lung densities (0.001g/cm3 up to 1g/cm3) for both phantoms. Results: MC lung slab phantom simulations revealed that for each combination of beam energy and field size, a critical lung density (CLD) could be defined to establish LED. For example, a 6MV 5×5cm2 photon field was subject to LED for lung densities of 0.2g/cm3 or lower. On the contrary, employing an 18MV 5×5cm2 photon field increased the CLD to 0.5g/cm3. With regard to the second lung tumor phantom, the LED effect caused major reductions in the calculated dose near to the tumor. For instance, dose reductions of 24% and 16% were found within the distal and proximal tumor surfaces, respectively. Conclusion: We have fully characterized the LED effect and shown that it causes dose reductions in both lung and tumor tissues. To avoid these dose perturbations, SBRT of lung cancer patients should be optimized to select radiation therapy parameters carefully in accordance with patient lung density.Financial support from the Natural Sciences and Engineering Research Council of Canada (NSERC), and the Canadian Institutes of Health Research (CIHR) are gratefully acknowledged.

Reduced Image Noise at Low-Dose Multidetector CT of the Abdomen with Prior Image Constrained Compressed Sensing Algorithm

To assess the effect of prior image constrained compressed sensing (PICCS) on noise reduction and image quality at low-dose computed tomography (CT). This HIPAA-compliant institutional review board-approved retrospective study was performed by using DICOM CT colonography data sets obtained in 20 adult patients. Informed consent was waived. Low-dose CT colonography was performed with 64-detector CT by using the standard protocol with mean effective dose per series of 3.06 mSv (range, 1.4-7.7 mSv). PICCS was applied to standard filtered back-projection (FBP) series. For FBP and PICCS series, mean and standard deviation (SD) of attenuation were obtained with 100-mm(2) circular region of interest (ROI) at six sites (240 soft-tissue, colonic gas, and subcutaneous fat measurements). Two abdominal radiologists reviewed two- and three-dimensional CT colonography displays and graded image quality with a five-point scale. Phantom studies were performed to compare spatial resolution and image quality between FBP and PICCS. Mean image noise and image quality scores were calculated and compared for clinical and phantom data sets. Bland-Altman, generalized estimating equation regression model, and Student t tests were used to obtain limits of agreement and to compare noise ratios and subjective image quality. Mean SD of attenuation (image noise) for ROIs was 38.0 for FBP and 12.2 for PICCS, corresponding to a noise-reduction factor of 3.1 (P < .001). Average noise reduction was 3.3 for soft tissue, 2.8 for air, and 3.0 for fat attenuation. Attenuation did not substantially change between FBP and PICCS images. Average two-dimensional image quality was 2.45 for FBP and 3.4 for PICCS (P < .001). Average three-dimensional image quality at three sites in the colon was 3.5 for FBP and 3.7 for PICCS (P = .34). Phantom data sets revealed no loss of spatial resolution in a line phantom and reduced noise in a liver tumor phantom when PICCS was compared with FBP. Application of PICCS to standard FBP low-dose multidetector CT abdominal images results in substantial noise reduction and improved image quality.