Decellularized tracheal prelamination implant: A proposed bilateral double organ technique.

In tracheal replacement transplantation, prelamination is a critical stage. Nowadays, the most widely used prelamination technique is the prethoracic fascia flap with lateral thoracic artery. We propose a flap based on the internal thoracic artery, which allows a relatively non-aggressive double organ implant, and we have tested its efficacy in decellularized tracheas. Tracheas of albino New Zealand rabbits were decellularized following a protocol that uses detergents and cryogenization, sterilized with 1kGy gamma radiation, and tutorized with a stent. Bilateral pedicled flaps made of pectoral fascia and a muscular component were harvested through a longitudinal 3-cm central thoracic incision, wrapping the tracheas with them in 16 rabbits, remaining them implanted for 2, 4, 8, and 12 weeks. The tracheas were then studied histologically using standard stainings plus immunohistochemistry (CD31). The models were adjusted with Bayesian statistics using ordinal regression; results as odds ratios and credibility intervals. All analysis were performed using R software. Acute inflammatory cell invasion was observed at 2 weeks, which almost disappeared at week 8 after implant. Only macrophages and giant cells increased between Weeks 8 and 12 (OR 10.487, CI [1.603-97.327]). The cartilage maintained its structure, with slight signs of ischemia in a few cases. New CD31-positive vessels were observed from Week 2 and increasing thereafter, reaching a maximum peak at Week 8. We propose a bilateral implant technique that is viable and effective as a prelamination option for two concurrent tracheas, achieving perfect vascularization and integration of the organ with hardly any inflammatory response in the medium or long term.

PERIPHERAL SURFACE DOSE FROM A LINEAR ACCELERATOR: RADIOCHROMIC FILM EXPERIMENTAL MEASUREMENTS OF FLATTENING FILTER FREE VERSUS FLATTENED BEAMS.

There is a growing interest in the use of flattening filter free (FFF) beams due to the shorter treatment times. The reduction of head scatter suggests a better radiation protection to radiotherapy patients, considering the expected decrease in peripheral surface dose (PSD). In this work, PSD of flattened (FF) and FFF-photon beams was compared. A radiochromic film calibration method to reduce energy dependence was used. PSD was measured at distances from 2 to 50 cm to the field border for different square field sizes, modifying relevant clinical parameters. Also, clinical breast and prostate stereotactic body radiotherapy (SBRT) plans were studied. For square beams, FFF PSD is lower compared with FF PSD (differences ranging from 3 to 64%) and 10 MV FFF yields to the lowest value, for distances greater than 5 cm. For SBRT plans, near and far away from the field border, there is a reduction of PSD for FFF-beams, but the behavior at intermediate distances should be checked depending on the case.

Measurement of body composition in cancer patients using CT planning scan at the third lumbar vertebra.

INTRODUCTION: Objective: the main objective was to assess body composition in terms of skeletal muscle index (SMI), myosteatosis, visceral adipose tissue (VAT), subcutaneous adipose tissue (SAT), and intermuscular adipose tissue (IMAT) as an adjunct of information provided by radiotherapy CT planning scan. Material and methods: a sample of 49 patients with lung and digestive cancers underwent a CT scan for radiotherapy treatment, which included measurements at the L3 region. Images were analyzed with a radiotherapy contouring software, using different Hounsfield Unit (HU) settings. Cross-sectional areas (cm2) were automatically computed by summing tissue pixels and multiplying by pixel surface area. Low SMI (cm2/m2) and muscle density (HU) were determined according to the recently established cut-off points. Results: the prevalence of low SMI was detected in 46.94% of patients, being present in 8 women, 4 men with BMI < 25 kg/m2, and 11 men with BMI ≥ 25 kg/m2. The average mean skeletal attenuation of total skeletal muscle area was 29.02 (± 8.66) HU, and myosteatosis was present in 13 women (81.25%) and 31 men (93.94%). Mean SAT was 131.92 (± 76.80) cm2, mean VAT was 133.19 (± 85.28) cm2, and mean IMAT was 11.29 (± 12.86) cm2. Conclusion: skeletal muscle abnormalities are frequently present in cancer patients and a low SMI may also exist even in the presence of overweight. As CT scans are an important tool at any radiation oncology department, they could also be used to offer highly sensitive and specific information about body composition, as well as to detect early malnutrition before starting radiotherapy treatment.

INTRODUCCIÓN: Objetivo: evaluar la composición corporal mediante el índice de músculo esquelético (IME), el tejido adiposo visceral (TAV), el tejido adiposo subcutáneo (TAS) y el tejido adiposo intermuscular (TAIM) o la densidad muscular (DM) en pacientes oncológicos antes de iniciar el tratamiento con radioterapia mediante cortes de TAC. Materiales y métodos: se estudiaron 49 pacientes con cáncer de pulmón y del aparato digestivo sometidos a tomografía computarizada con cortes en L3 para la determinación del tratamiento con radioterapia. El tejido adiposo y muscular se cuantificó mediante distintas Unidades Hounsfield (UH) (-29 a +150 para masa muscular, -190 a -30 para TAIM/TAS y -150 a -50 para TAV). Resultados: la prevalencia de un IME bajo se detectó en el 46,94% de los pacientes, estando presente en 8 mujeres, 6 de ellas con un IMC ≥ 25 kg/m². Según la distribución masculina, se identificaron 4 hombres con IMC < 25 kg/m² y 11 hombres con ≥ 25 kg/m². La DM media fue de 29,02 (± 8,66) UH y la mioesteatosis estuvo presente en 13 mujeres (81,25%) y 31 hombres (93,94%). La media del TAS fue de 131,92 (± 76,80) cm², la del TAV de 133,19 (± 85,28) cm² y la del TAIM de 11,29 (± 12,86) cm². Conclusión: las anormalidades del músculo esquelético y la masa grasa son muy frecuentes en los pacientes con cáncer, pudiendo existir un bajo IME incluso en presencia de sobrepeso u obesidad. Teniendo en cuenta que la TAC es una herramienta importante en cualquier departamento de radioterapia, también podría utilizarse para ofrecer información sensible y específica sobre la composición corporal, así como para detectar la malnutrición precoz.

Performance evaluation of a high resolution dedicated breast PET scanner.

PURPOSE: Early stage breast cancers may not be visible on a whole-body PET scan. To overcome whole-body PET limitations, several dedicated breast positron emission tomography (DbPET) systems have emerged nowadays aiming to improve spatial resolution. In this work the authors evaluate the performance of a high resolution dedicated breast PET scanner (Mammi-PET, Oncovision). METHODS: Global status, uniformity, sensitivity, energy, and spatial resolution were measured. Spheres of different sizes (2.5, 4, 5, and 6 mm diameter) and various 18 fluorodeoxyglucose ((18)F-FDG) activity concentrations were randomly inserted in a gelatine breast phantom developed at our institution. Several lesion-to-background ratios (LBR) were simulated, 5:1, 10:1, 20:1, 30:1, and 50:1. Images were reconstructed using different voxel sizes. The ability of experienced reporters to detect spheres was tested as a function of acquisition time, LBR, sphere size, and matrix reconstruction voxel size. For comparison, phantoms were scanned in the DbPET camera and in a whole body PET (WB-PET). Two patients who just underwent WB-PET/CT exams were imaged with the DbPET system and the images were compared. RESULTS: The measured absolute peak sensitivity was 2.0%. The energy resolution was 24.0% ± 1%. The integral and differential uniformity were 10% and 6% in the total field of view (FOV) and 9% and 5% in the central FOV, respectively. The measured spatial resolution was 2.0, 1.9, and 1.7 mm in the radial, tangential, and axial directions. The system exhibited very good detectability for spheres ≥4 mm and LBR ≥10 with a sphere detection of 100% when acquisition time was set >3 min/bed. For LBR = 5 and acquisition time of 7 min the detectability was 100% for spheres of 6 mm and 75% for spheres of 5, 4, and 2.5 mm. Lesion WB-PET detectability was only comparable to the DbPET camera for lesion sizes ≥5 mm when acquisition time was >3 min and LBR > 10. CONCLUSIONS: The DbPET has a good performance for its clinical use and shows an improved resolution and lesion detectability of small lesions compared to WB-PET.

Tumor bed segmentation: first step for partial breast irradiation.

INTRODUCTION: In breast IMRT simultaneous integrated boost (SIB) treatment and accelerated partial breast irradiation (APBI), proper delineation of the tumor bed is necessary. Conservative oncoplastic surgery causes changes in peritumoral breast tissue that complicates locating the site of the tumor. Nevertheless, there are still centers that do not use surgical clips to delineate the site. This study aims to show how the lack of clips affects the techniques of SIB and APBI in terms of dose distribution and safety margins in the tumor bed. MATERIALS AND METHODS: On 30 patients, the defining of the tumor bed obtained from the pre-surgery CT scan to that outlined on the basis of clips on the post-surgery CT was compared. Tumor bed deviation from the original tumor site was quantified. In addition, the margins to the original tumor site necessary to guarantee the coverage of the tumor bed were calculated. RESULTS: Variations were detected in the distances between geometric centers of the PTV (minimum 0.5-maximum 3 cm). The maximum margin necessary to include the entire tumor bed was 4.5 cm. Lesions located in the upper outer quadrant required the widest margins. If margins are not added, the tumor bed volume defined with clips will be underdosed. CONCLUSIONS: The definition of the tumor bed based on studies before surgery does not have the necessary accuracy. Clips need to be placed in the surgical bed to identify the changes occurring after the restorative mammoplasty. Without clips, SIB and APBI are not safe.