Lesion Detectability and Radiation Dose in Spiral Breast CT With Photon-Counting Detector Technology: A Phantom Study.

OBJECTIVES: The aim of the article was to evaluate the lesion detectability, image quality, and radiation dose of a dedicated clinical spiral breast computed tomography (CT) system equipped with a photon-counting detector, and to propose optimal scan parameter settings to achieve low patient dose levels and optimal image quality. METHODS: A breast phantom containing inserts mimicking microcalcifications (diameters 196, 290, and 400 µm) and masses (diameters 1.8, 3.18, 4.76, and 6.32 mm) was examined in a spiral breast CT system with systematic variations of x-ray tube currents between 5 and 125 mA, using 2 slabs of 100 and 160 mm. Signal-to-noise ratio and contrast-to-noise ratio measurements were performed by region of interest analysis. Two experienced radiologists assessed the detectability of the inserts. The average absorbed dose was calculated in Monte Carlo simulations. RESULTS: Microcalcifications in diameters of 290 and 400 µm and masses in diameters of 3.18, 4.76, and 6.32 mm were visible for all tube currents between 5 and 125 mA. Soft tissue masses in a diameter of 1.8 mm were visible at tube currents of 25 mA and higher. Microcalcifications with a diameter of 196 µm were detectable at a tube current of 25 mA and higher in the small, and at a tube current of 40 mA and higher in the large slab. For the small and large breast, at a tube current of 25 and 40 mA, an average dose value of 4.30 ± 0.01 and 5.70 ± 0.02 mGy was calculated, respectively. CONCLUSIONS: Optimizing tube current of spiral breast CT according to the breast size enables the visualization of microcalcifications as small as 196 µm while keeping dose values in the range of conventional mammography.

Quantitative Computed Tomography (QCT) of the Distal Forearm in Men Using a Spiral Whole-Body CT Scanner - Description of a Method and Reliability Assessment of the QCT Pro Software.

The Mr F study investigates the pathogenesis of low trauma distal forearm fractures in men and includes volumetric bone mineral density (vBMD) measurements at the ultradistal forearm as there are no current data. A standard 64 slice CT scanner was used to determine if it was possible to adapt the existing Mindways quantitative computed tomography Pro software for measuring vBMD values at the hip and spine sites. For calculation of intra- and interobserver reliability 40 forearm scans out of the 300 available were chosen randomly. The images were analyzed using the Slice Pick module and Bone Investigational Toolkit. The 4% length of the radius was chosen by measuring the length of the radius from the scaphoid fossa distally to the radial head. The acquired image then underwent extraction, isolation, rotation, and selection of region of interest in order to generate a report on vBMD. A cross-sectional image was created to allow the generation of data on the cortical and trabecular components separately. Repeat analyses were undertaken by 3 independent observers who were blinded as to whether the image was from a participant with or without fracture. The images were presented in random order at each time point. The following parameters were recorded: cortical cross sectional area, total vBMD, trabecular vBMD, and cortical vBMD (CvBMD). Data were analyzed by calculating intraclass correlation coefficients for intra- and interobserver reliability. The lowest values occurred at the CvBMD with intraobserver reliability of 0.92 (95% confidence interval [CI] of 0.86-0.96) and interobserver reliability of 0.92 (95% CI 0.89-0.96). All other parameters had reliability values between 0.97 and 0.99 with tighter 95% CI than for CvBMD. The method of adapting the Mindways Pro software using a standard CT to produce vBMD and structural data at the ultradistal radius is reliable.

Characterization of dynamic collimation mechanisms for helical CT scans with direct measurements.

Dynamic collimation is an important dose reduction mechanism for helical CT scans, especially for modern wide-beam scanner models. Its implementation and efficacy need to be studied to optimize CT scan protocols and to reduce unnecessary patient dose. The purpose of this study is to evaluate dynamic beam collimation for modern wide-beam CT scanners with direct measurements and to estimate the efficacy for dose reduction. By using a linear-array solid state detector, primary x-ray beam coverage was measured for four CT scanner models: GE Revolution CT, Siemens Somatom Force, Philips iQon, and GE LightSpeed VCT. Supported independently from patient table, the detector remained stationary at the isocenter during helical scans. Data lines were recorded every 0.24 ms throughout one entire helical scan, with a spatial resolution of 0.8 mm along the craniocaudal direction. The measurements were repeated for various scan parameters related to dynamic collimation, including beam collimation width, pitch, rotation time, and scan length. The recorded beam coverage area was used as a surrogate to total primary dose, to model different dynamic collimation mechanisms. The directly measured total radiation range was compared to table travel distance and nominal scan length which equals to the ratio between DLP and CTDIvol. Equations to calculate the percentage dose reduction with dynamic collimation were derived for different mechanisms. Three different dynamic collimation mechanisms were revealed and related linear model parameters were reported for different helical scan parameters. The nominal scan length used to calculate DLP was shown to vary for different dynamic collimation mechanisms. For typical head and abdomen scans with nominal scan lengths of 17.5 cm and 25 cm, percentage dose reduction from dynamic collimation ranged from 2% to 32%. In conclusion, with direct measurements of primary x-ray beam coverage, dynamic collimation mechanisms and related dose reduction effects were characterized for four modern wide-beam CT scanners.

Overranging and overbeaming measurement in area detector computed tomography: A method for simultaneous measurement in volume helical acquisition.

PURPOSE: We propose a novel method to assess overbeaming and overranging, as well as the effect of reducing longitudinal exposure range, by using a dynamic z-collimator in area detector computed tomography. METHODS AND MATERIALS: A 500-mm diameter cylindrical imaging plate was exposed by helical scanning in a dark room. The beam collimation of the helical acquisitions was set at 32 and 80 mm. Overbeaming and overranging with the dynamic z-collimator were measured. RESULTS: The actual beam widths were approximately 39 and 88 mm at 32 and 80 mm collimation, respectively, and were relatively reduced owing to increased beam collimation. Overranging was 27.0 and 48.2 mm with a pitch of 0.83 and 1.49 at 32 mm collimation and 72.5 and 83.1 mm with a pitch of 0.87 and 0.99 at 80 mm collimation. The dynamic z-collimator relatively reduced the overranging by 17.3% and 17.1% for the 32 and 80 mm collimation, respectively. CONCLUSION: We devised a method to simultaneously measure overbeaming and overranging with only one helical acquisition. Although the dynamic z-collimator reduced the overranging by approximately 17%, wider collimation widths and higher pitch settings would increase the exposure dose outside the scan range.

Dedicated Breast Computed Tomography With a Photon-Counting Detector: Initial Results of Clinical In Vivo Imaging.

OBJECTIVES: The purpose of this work is to present the data obtained from the first clinical in vivo application of a new dedicated spiral breast computed tomography (B-CT) equipped with a photon-counting detector. MATERIALS AND METHODS: The institutional review board approved this retrospective study. Twelve women referred for breast cancer screening were included and underwent bilateral spiral B-CT acquired in prone position. Additional sonography was performed in case of dense breast tissue or any B-CT findings. In 3 women, previous mammography was available for comparison. Soft tissue (ST) and high-resolution (HR) images were reconstructed. Two independent radiologists performed separately the readout for subjective image quality and for imaging findings detection. Objective image quality evaluation was performed in consensus and included spatial resolution, contrast resolution, signal-to-noise ratio (SNR), and contrast-to-noise ratio. All women were asked to report about positioning comfort and overall comfort during data acquisition. RESULTS: The major pectoral muscle was included in 15 breast CT scans (62.5%); glandular component was partially missing in 2 (8.3%) of the 24 scanned breasts. A thin "ring artifact" was present in all scans but had no influence on image interpretations; no other artifacts were present. Subjective image quality assessment showed excellent agreement between the 2 readers (κ = 1). Three masses were depicted in B-CT and were confirmed as simple cysts in sonography. Additional 5 simple cysts and 2 solid benign lesions were identified only in sonography. A total of 12 calcifications were depicted with a median size of 1.1 mm (interquartile range, 0.7-1.7 mm) on HR and 1.4 mm (interquartile range, 1.1-1.8 mm) on ST images. Median SNRgl, SNRfat, and contrast-to-noise ratio were significantly higher in ST than in HR reconstructions (each, P < 0.001). A mild discomfort due to positioning of the rib cage on the table was reported by 2 women (16.7%); otherwise, no discomfort was reported. CONCLUSIONS: The new dedicated B-CT equipped with a photon-counting detector provides high-quality images with potential for screening of breast cancer along with minor patient discomfort.

Toward adaptive proton therapy guided with a mobile helical CT scanner.

PURPOSE: To evaluate the feasibility of image-guided adaptive proton therapy (IGAPT) with a mobile helical-CT without rails. METHOD: CT images were acquired with a 32-slice mobile CT (mCT) scanning through a 6 degree-of-freedom robotic couch rotated isocentrically 90 degrees from an initial setup position. The relationship between the treatment isocenter and the mCT imaging isocenter was established by a stereotactic reference frame attached to the treatment couch. Imaging quality, geometric integrity and localization accuracy were evaluated according to AAPM TG-66. Accuracy of relative stopping power ratio (RSPR) was evaluated by comparing water equivalent distance (WED) and dose calculations on anthropomorphic phantoms to that of planning CT (pCT). Feasibility of image-guided adaptive proton therapy was demonstrated on fractional images acquired with the mCT scanner. RESULTS: mCT images showed slightly lower spatial resolution and a higher contrast-to-noise ratio compared to pCT images from the standard helical CT scanner. The geometric accuracy of the mCT was <1 mm. Localization accuracy was <0.4 mm and <0.3° with respect to 2DkV/kV matching. WED differences between mCT and pCT images were negligible, with discrepancies of 0.8 ±â€¯0.6 mm and 1.3 ±â€¯0.9 mm for brain and lung phantoms respectively. 3D gamma analysis (3% and 3 mm) passing rate was >95% on dose computed on mCT, with respect to dose calculation on pCT. CONCLUSION: Our study has demonstrated that the geometric integrity, image quality and RSPR accuracy of the mCT are sufficient for IGAPT.

Hamartoma pulmonar como presentación de un nódulo pulmonar solitario / Pulmonary hamartoma as an example of solitary pulmonary nodule

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Axial or Helical? Considerations for wide collimation CT scanners capable of volumetric imaging in both modes.

PURPOSE: To determine whether axial or helical mode is more appropriate for a 16 cm collimation CT scanner capable of step-and-shoot volumetric axial coverage, in terms of radiation dose, image quality, and scan duration. METHODS: All scans were performed with a Revolution CT (GE Healthcare) operating at 120 kV and 100 mAs. Using calibrated optically stimulated luminescence detectors, radiation dose along the axial scan profile was evaluated at the isocenter, including the overlap region between two axial sections. This overlap region measures 3 cm in the z-axis at the isocenter and is required to obtain sufficient projection data from the relatively large cone-beam angles. Using an image quality phantom (Gammex Model 464), spatial resolution, CT number uniformity, image noise, and low contrast detectability (LCD) were evaluated under five different conditions: in the middle of a helical acquisition, in the middle of a 16 cm axial section, at both ends of an axial section and in the overlap region between two axial sections. Scan durations and dose length products (DLP) were recorded for prescribed scan lengths of 2.5-100 cm. RESULTS: The overlap region between two axial sections received a dose 83% higher than the single-exposure region at the isocenter. Within a single axial section, the dose at the anode end was 37% less than at the cathode end due to the anode heel effect. Image noise ranged from a low of 13 HU for the cathode end of an axial section up to 14.7 HU for the anode end (P < 0.001). The LCD was at lower at the anode end of the axial section compared to both the cathode end (P < 0.05) and the overlap location (P < 0.02). The spatial resolution and CT number uniformity were consistent among all conditions. Scan durations were shorter (0.28 s) for the axial mode compared to the helical mode at scan lengths ≤ 16 cm, and longer at scan lengths ≥ 16 cm where more than one table position was required, up to a difference of 13.9 s for a the 100 cm scan length (3.8 s for helical compared to 17.6 s for axial). DLPs were consistent between scan modes; slightly lower in axial mode at shorter scan lengths due to helical overranging, and slightly higher in axial mode at longer scan lengths due to the axial overlap regions. CONCLUSIONS: To ensure the most consistent radiation dose and image quality along the scan length, we recommend helical mode for scans longer than the 16 cm coverage of a single axial section. For scan lengths ≤ 16 cm, axial scanning is the most practical option, with a shorter scan duration and higher dose efficiency.

Efficacy of a dynamic collimator for overranging dose reduction in a second- and third-generation dual source CT scanner.

OBJECTIVES: The purpose of this study was to assess the efficacy of the renewed dynamic collimator in a third-generation dual source CT (DSCT) scanner and to determine the improvements over the second-generation scanner. METHODS: Collimator efficacy is defined as the percentage overranging dose in terms of dose-length product (DLP) that is blocked by the dynamic collimator relative to the total overranging dose in case of a static collimator. Efficacy was assessed at various pitch values and different scan lengths. The number of additional rotations due to overranging and effective scan length were calculated on the basis of reported scanning parameters. On the basis of these values, the efficacy of the collimator was calculated. RESULTS: The second-generation scanner showed decreased performance of the dynamic collimator at increasing pitch. Efficacy dropped to 10% at the highest pitch. For the third-generation scanner the efficacy remained above 50% at higher pitch. Noise was for some pitch values slightly higher at the edge of the imaged volume, indicating a reduced scan range to reduce the overranging dose. CONCLUSIONS: The improved dynamic collimator in the third-generation scanner blocks the overranging dose for more than 50% and is more capable of shielding radiation dose, especially in high pitch scan modes. KEY POINTS: • Overranging dose is to a large extent blocked by the dynamic collimator • Efficacy is strongly improved within the third-generation DSCT scanner • Reducing the number of additional rotations can reduce overranging with increased noise.

Precisión en la planificación quirúrgica 3D en un paciente con síndrome de Goldenhar / Precision in 3D surgical planning in a patient with Goldenhar syndrome

Objetivo. Presentar un caso clínico de una paciente con síndrome de Goldenhar en el cual se utilizó, para la planificación de la corrección de su asimetría facial, el software Materialise CMF® (Leuven, Bélgica). Caso clínico. aciente de sexo femenino de 27 años que padece síndrome de Goldenhar. Se le realizó cirugía ortognática para corregir su asimetría facial. Para el diagnóstico, planificación y simulación quirúrgica del caso se utilizó el software 3D Materialise CMF® (Leuven, Bélgica). Conclusión. El método de planificación tradicional no es preciso, y estas imprecisiones producen una acumulación de errores en todo el proceso. Estos conceptos cobran gran relevancia en los casos de deformidades asimétricas, en donde los métodos bidimensionales son insuficientes, dejando un gran margen para la intuición, para la habilidad del profesional y, por lo tanto, para el error. El método de planificación 3D facilita el estudio, la planificación y la transferencia de lo planificado a la cirugía, minimizando los errores y logrando la máxima precisión (AU)

Aim. Submit a case of a patient with Goldenhar syndrome. The Materialise CMF® (Leuven, Belgium) software was used for planning her facial asymmetry correction. Case report. Female patient aged 27 who suffers from Goldenhar syndrome. He underwent orthognathic surgery to correct facial asymmetry. For diagnosis, surgical planning and simulation case 3D Materialise CMF® software (Leuven, Belgium) was used. Conclusions. The traditional method of planning is not necessary, these inaccuracies are an accumulation of errors in the whole process. These concepts assume great importance in cases of asymmetric deformities where the 2-dimensional methods are insufficient, leaving much room for intuition, for the professional ability and therefore for error. The method of 3D planning facilitates the study, planning and transfer of what is thought to surgery, minimizing errors and achieving maximum accuracy (AU)

Volumetric CT with sparse detector arrays (and application to Si-strip photon counters).

Novel x-ray medical imaging sensors, such as photon counting detectors (PCDs) and large area CCD and CMOS cameras can involve irregular and/or sparse sampling of the detector plane. Application of such detectors to CT involves undersampling that is markedly different from the commonly considered case of sparse angular sampling. This work investigates volumetric sampling in CT systems incorporating sparsely sampled detectors with axial and helical scan orbits and evaluates performance of model-based image reconstruction (MBIR) with spatially varying regularization in mitigating artifacts due to sparse detector sampling. Volumetric metrics of sampling density and uniformity were introduced. Penalized-likelihood MBIR with a spatially varying penalty that homogenized resolution by accounting for variations in local sampling density (i.e. detector gaps) was evaluated. The proposed methodology was tested in simulations and on an imaging bench based on a Si-strip PCD (total area 5 cm × 25 cm) consisting of an arrangement of line sensors separated by gaps of up to 2.5 mm. The bench was equipped with translation/rotation stages allowing a variety of scanning trajectories, ranging from a simple axial acquisition to helical scans with variable pitch. Statistical (spherical clutter) and anthropomorphic (hand) phantoms were considered. Image quality was compared to that obtained with a conventional uniform penalty in terms of structural similarity index (SSIM), image uniformity, spatial resolution, contrast, and noise. Scan trajectories with intermediate helical width (~10 mm longitudinal distance per 360° rotation) demonstrated optimal tradeoff between the average sampling density and the homogeneity of sampling throughout the volume. For a scan trajectory with 10.8 mm helical width, the spatially varying penalty resulted in significant visual reduction of sampling artifacts, confirmed by a 10% reduction in minimum SSIM (from 0.88 to 0.8) and a 40% reduction in the dispersion of SSIM in the volume compared to the constant penalty (both penalties applied at optimal regularization strength). Images of the spherical clutter and wrist phantoms confirmed the advantages of the spatially varying penalty, showing a 25% improvement in image uniformity and 1.8 × higher CNR (at matched spatial resolution) compared to the constant penalty. The studies elucidate the relationship between sampling in the detector plane, acquisition orbit, sampling of the reconstructed volume, and the resulting image quality. They also demonstrate the benefit of spatially varying regularization in MBIR for scenarios with irregular sampling patterns. Such findings are important and integral to the incorporation of a sparsely sampled Si-strip PCD in CT imaging.

Multi-detector row CT-guided marking technique for breast-conserving therapy of early breast cancer: margin positivity and local control rates.

BACKGROUND: In breast-conserving surgery (BCS), image-guided marking of the tumor border is important for preventing local recurrence and achieving a good cosmetic outcome. The purpose of this study was to evaluate the usefulness of multi-detector row computed tomography (MDCT)-guided marking technique before BCS in patients in whom ultrasound (US)-guided marking was not feasible. METHODS: Between 2004 and 2010, 94 lesions underwent contrast-enhanced MDCT-guided marking. Margin positivity and local control rates were compared with those of 149 lesions undergoing US-guided marking during the same period. RESULTS: In 21 lesions undergoing CT marking (22 %) and 20 lesions undergoing US marking (13 %), a negative resection margin could not be achieved, and hence the marking was judged as unsuccessful. Eighty-four lesions of the CT marking group and 119 of the US marking group received postoperative radiotherapy with 50 Gy in 25 fractions with or without an additional 10-Gy boost to the tumor bed. The remaining 10 and 30 patients, respectively, did not receive radiotherapy. The median follow-up period was 54 and 51 months for patients with CT marking and those with US marking, respectively. At 4 postoperative years, the local control rate was 96.5 % for patients with CT marking and 97.3 % for those with US marking (P = 0.89). CONCLUSIONS: The MDCT marking technique appears to be a valuable tool for determining the surgical margin for BCS in patients in whom ultrasound marking cannot be performed. Combining this technique with appropriate postoperative radiation therapy is expected to yield reasonably high local control rates.

Puesta al día en el estudio radiológico de la tuberculosis pulmonar / Update on the radiological study of pulmonary tuberculosis

La tuberculosis ha mostrado un resurgimiento en los últimos años, fenómeno que se ha atribuido a factores como el aumento de la migración y la epidemia del virus de la inmunodeficiencia humana. La tuberculosis pulmonar primaria se manifiesta desde el punto de vista radiológico con afectación parenquimatosa, linfadenopatías, derrame pleural o enfermedad miliar. En la forma posprimaria, el hallazgo radiológico más precoz son los nodulillos y las lesiones ramificadas centrolobulillares, que aumentan de tamaño y confluyen para dar consolidaciones parcheadas, mal definidas. La presencia de cavitaciones es muy característica de enfermedad activa. El objetivo de este trabajo es describir los hallazgos radiológicos de la tuberculosis pulmonar y sus complicaciones (AU)

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Optimization of the imaging quality of 64-slice CT acquisition protocol using Taguchi analysis: A phantom study.

In this study, the phantom imaging quality of 64-slice CT acquisition protocol was quantitatively evaluated using Taguchi. The phantom acrylic line group was designed and assembled with multiple layers of solid water plate in order to imitate the adult abdomen, and scanned with Philips brilliance CT in order to simulate a clinical examination. According to the Taguchi L8(2(7)) orthogonal array, four major factors of the acquisition protocol were optimized, including (A) CT slice thickness, (B) the image reconstruction filter type, (C) the spiral CT pitch, and (D) the matrix size. The reconstructed line group phantom image was counted by four radiologists for three discrete rounds in order to obtain the averages and standard deviations of the line counts and the corresponding signal to noise ratios (S/N). The quantified S/N values were analyzed and the optimal combination of the four factor settings was determined to be comprised of (A) a 1-mm thickness, (B) a sharp filter type, (C) a 1.172 spiral CT pitch, and (D) a 1024×1024 matrix size. The dominant factors included the (A) filter type and the cross interaction between the filter type and CT slice thickness (A×B). The minor factors were determined to be (C) the spiral CT pitch and (D) the matrix size since neither was capable of yielding a 95% confidence level in the ANOVA test.

Image Quality of 3rd Generation Spiral Cranial Dual-Source CT in Combination with an Advanced Model Iterative Reconstruction Technique: A Prospective Intra-Individual Comparison Study to Standard Sequential Cranial CT Using Identical Radiation Dose.

OBJECTIVES: To prospectively intra-individually compare image quality of a 3rd generation Dual-Source-CT (DSCT) spiral cranial CT (cCT) to a sequential 4-slice Multi-Slice-CT (MSCT) while maintaining identical intra-individual radiation dose levels. METHODS: 35 patients, who had a non-contrast enhanced sequential cCT examination on a 4-slice MDCT within the past 12 months, underwent a spiral cCT scan on a 3rd generation DSCT. CTDIvol identical to initial 4-slice MDCT was applied. Data was reconstructed using filtered backward projection (FBP) and 3rd-generation iterative reconstruction (IR) algorithm at 5 different IR strength levels. Two neuroradiologists independently evaluated subjective image quality using a 4-point Likert-scale and objective image quality was assessed in white matter and nucleus caudatus with signal-to-noise ratios (SNR) being subsequently calculated. RESULTS: Subjective image quality of all spiral cCT datasets was rated significantly higher compared to the 4-slice MDCT sequential acquisitions (p<0.05). Mean SNR was significantly higher in all spiral compared to sequential cCT datasets with mean SNR improvement of 61.65% (p*Bonferroni0.05<0.0024). Subjective image quality improved with increasing IR levels. CONCLUSION: Combination of 3rd-generation DSCT spiral cCT with an advanced model IR technique significantly improves subjective and objective image quality compared to a standard sequential cCT acquisition acquired at identical dose levels.

Lipoma pulmonar intraparenquimatoso con comportamiento clínico de neoplasia maligna / Intraparenchymal pulmonary lipoma clinically mimicking malignant neoplasm

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Silicosis: diferencias relevantes entre marmolistas y mineros / Silicosis: relevant differences between marble workers and miners

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Patient-specific tube-voltage selection at coronary CT angiography based on the combination of X-ray attenuation on scout views and body mass index: how can appropriate radiation dose be achieved?

BACKGROUND: Body weight, body mass index (BMI), and scout X-ray radiographic attenuation can be used to predict image noise on computed tomographic coronary angiography (CTCA) images. PURPOSE: To use a formula to predict patient-specific image noise and then select an appropriate CTCA patient-specific tube voltage for better radiation control. MATERIAL AND METHODS: Forty-eight patients who underwent CTCA imaging at 120 kVp were reviewed, and their patient information and scouting X-ray radiographic attenuations were recorded to identify the best correlations between patient data and image noise and to develop a predicted image noise formula. Subsequently, 54 patients subjected to scanning at 100 or 120 kVp, depending on the noise predicted by our formula, were prospectively studied. Two radiologists visually assessed the image quality of the right coronary artery (RCA), left anterior descending artery (LAD), and left circumflex artery (LCX) by consensus readings. RESULTS: The predicted image noise = 0.939 BMI + 0.025 scouting attenuation + 20.16. The median value of the overall image noise was 30.55 HU at 120 kVp and 29.85 HU at 100 kVp. The mean visual evaluation scores at 100 and 120 kVp were 3.25 and 3.24 for the proximal RCA, 3.40 and 3.26 for the proximal LAD, and 3.30 and 3.15 for the proximal LCX, respectively. CONCLUSION: The BMI and scouting X-ray radiographic attenuation can be combined to predict the CTCA image noise. Our prediction formula is useful for deciding when to switch from the 120- to the 100-kVp technique.

Dosimetric effect of small bowel oral contrast on conventional radiation therapy, linear accelerator-based intensity modulated radiation therapy, and helical tomotherapy plans for rectal cancer.

PURPOSE: This study evaluated the dosimetric effect of small bowel oral contrast on conventional radiation therapy, linear accelerator-based intensity modulated radiation therapy (IMRT), and helical tomotherapy (HT) treatment plans. METHODS AND MATERIALS: Thirteen patients with rectal cancer underwent computed tomography (CT) simulation with oral contrast (CCT) in preparation for chemoradiation therapy. The contrast in the small bowel was contoured, and a noncontrast CT scan (NCCT) was simulated by reassigning a CT number of 0 Hounsfield units to the contrast volume. Conventional, IMRT, and HT plans were generated with the CCT. The plan generated on the CCT was then recalculated on the NCCT, maintaining the same number of monitor units for each field, and the plans were not renormalized. Dosimetric parameters representing coverage of the planning target volume with 45 Gy (D98%, D95%, D50%, and D2%) and sparing of the bladder and peritoneal cavity (D50%, D30%, and D10%) were recorded. The ratio of dose calculated in the presence of contrast to dose with contrast edited out was recorded for each parameter. A paired Student t test was used for comparison of plans. RESULTS: For conventional plans, there was <0.1% variance in the dose ratio for all volumes of interest. For IMRT plans, there was a 1% decrease in the mean dose ratio, and the range of dose ratios for all volumes was greater than that for HT or conventional plans. For HT plans, for all volumes of interest, the mean dose ratio was <0.2%, and the range for all patients was <1%. For all IMRT dosimetric parameters, the difference was in the order of 1% of the mean dose (P < .05). The dose difference was not statistically significant for the conventional or HT plans. CONCLUSIONS: The use of CCT during CT simulation has no clinically significant effect on dose calculations for conventional, IMRT, and HT treatment plans and may not require replacement of the contrast with a CT number of 0 Hounsfield units.

¿Podría englobarse la fibromatosis agresiva dentro del espectro de los tumores del estroma gastrointestinal? / Could aggressive fibromatosis be considered whitin the spectrum of gstrointestinal stromal tumors?

Los tumores desmoides aparecen como resultado de la proliferación fibroblástica, sin signos histológicos de malignidad pero localmente muy agresivos. Se han descrito casos de fibromatosis tras extirpación de GIST. Presentamos el caso de un GIST gástrico operado, que a los 18 meses se realiza laparotomía exploradora por sospecha de recurrencia y tras hallazgos histológicos definitivos, se diagnostica de fibromatosis intra-abdominal agresiva. Se discute la valoración clínico-oncológica de la fibromatosis como forma de recurrencia local del GIST

Desmoid tumors appear as a result of fibroblastic proliferation without histological signs of malignancy but locally aggressive. Fibromatosis have been described after removing a gastrointestinal stromal tumor (GIST). We present a case of a resected gastric GIST and eigthteen months after surgery, a exploratory laparotomy was performed suspecting recurrence and after definitive histological findings, the diagnosis was aggressive intra-abdominal fibromatosis. Clinical-oncological assessment of fibromatosis is discussed as a form of GIST local recurrence