1,721,050 research outputs found
Pediatric vs adult dosimetry in CBCT: a challenge?
No full textConcern about the radiation dose to children from diagnostic radiology examinations has recently been popularly expressed, particularly as related Computed Tomography (CT) procedures. This involves the idea that children can receive higher doses compared to adults. Since the dosimetric quantities are essentially defined for adult patients, if related to effective dose, it becomes important to study and derive methods applicable also to pediatric cases. In fact, the “commonly” statement implies that size, shape, and data for pediatric organs will be derived from adult ones, numerically reducing dosimetric problems to the definition of scaling algorithms. The aim of this study is to analyze the differences in pediatric vs adult dosimetry, starting from measured organ doses in Cone-Beam Computed Tomography (CBCT) procedures for maxilla-facial region. Two different anthropomorphic phantoms (child vs adult phantoms) were scanned, acquiring all data: results will be presented in terms of organ and derived doses, discussing the approach and differences
Radioprotection in CO2 Angiography
No full textWhy to focus on radioprotection in a Conference of biomechanics? Because a deep analysis of the radioprotective problem of this quite new diagnostic procedure, demonstrates that the optimization of radioprotection is strictly related to the optimization of gas injection, which changes in the different biomechanical conditions. A particular attention is focused to the differences, in terms of radiological dose between iodine and CO2, and some protocols are on course to clarify this aspect, frequently with incoherent results. In this paper the radioprotection problem of CO2 angiography will be clearly outlined, with procedural references to vascular biomechanics. It will be demonstrated that the radioprotection problem and imaging results depend only and how the clinicians manage the diagnostic procedure: it depends only a little on the contrast medium, it mostly depends on the scientific knowledge of clinical staff: doctors, technicians and physicists. If everyone plays his role in the best way, knowing that the imaging result is strictly related to the vascular biomechanics, (which has to be deeply known), a global positive result is achieved
Optimization of gas injection in CO2 Angiography
No full textThe use of programmable gas injectors has demonstrated how it is necessary to adapt the parameters (gas pressure and flow) in the particular diagnostic context to obtain the best imaging result with minimum radiological exposure. Imaging of a big vascular cavity, or medium size artery or small peripheral artery is a completely different game, which requires different regulations and management of the instruments. In this paper the focus will be on small peripheral arteries imaging (BTK), where the required low injection gas flow interferes with the low hydraulic resistance of the catheter and the wide arterial pressure pulsatility, producing an irregular gas injection, with reflow and pain. To overcome this problem, a calibrated adjunctive resistance in series of the catheter is proposed, with theoretical analysis and optical simulation
Simulatore cardiaco
No full textL’invenzione riguarda un simulatore cardiaco, utilizzabile per riprodurre nel modo più fedele possibile alla realtà il comportamento strutturale e funzionale del muscolo cardiaco e dei ventricoli durante le fasi di sistole e diastole.
I simulatori biomeccanici del muscolo cardiaco attualmente presenti sul mercato appartengono a due grandi famiglie: 1) simulatori costituiti da una pompa a flusso pulsatile, a stantuffo o peristaltica che generano direttamente sul liquido contenuto pressioni e flussi fisiologici; 2) simulatori basati su una camera elastica contenente liquido, montata all’interno di una camera rigida e chiusa nella quale una pompa esterna introduce ed aspira ciclicamente del liquido, inducendo altrettanto ciclicamente cambiamenti strutturali della parete flessibile con conseguenti variazioni pressorie e volumetriche.
Tali simulatori possono riprodurre fedelmente i flussi e le pressioni sanguigni generati dal muscolo cardiaco, ed in particolare dai ventricoli, ma non consentono riscontri analitici relativi al comportamento meccanico dettagliato di zone specifiche della camera ventricolare.
E’ quindi impossibile, mediate tali simulatori, eseguire valutazioni approfondite per determinare la fattibilità e, soprattutto, l’efficacia funzionale, dell’impianto di dispositivi biomeccanici all'interno dei ventricoli, volti a correggerne patologie che li affliggono come, ad esempio, patologie dilatative, attraverso una modificazione della motilità e degli indici di stress delle pareti muscolari.
Il simulatore Heart String, atttraverso la combinazione di elementi meccanici semplici e di servomotori opportunamente pilotati, è in grado di riprodurre sia il comportamento globale sia il comportamento localizzato delle pareti muscolari durante le fasi di sistole e diastole del ventricolo, ricreando situazioni fisiologiche normali e patologiche.
Il sistema Heart String è un simulatore cardiaco semplice, affidabile ed economico. L’invenzione permette di ottenere i seguenti vantaggi:
- riprodurre in modo fedele il comportamento localizzato contrattile delle pareti ventricolari;
- acquisire ed analizzare parametri fisici del fluido che scorre all’interno del simulatore cardiaco e confrontarli con quelli fisiologici;
- valutare in modo oggettivo il comportamento ventricolare anche se affetto da patologie ed avere riscontri qualitativi e quantitativi sul funzionamento di dispositivi terapeutici impiantati all’interno della camera ventricolare per la correzione di patologie cardiache.
- acquisire informazioni morfologiche statiche e dinamiche della funzionalità ventricolare mediante impiego di raggi x ed ultrasuoni
HEART RATE VARIABILITY ANALYSIS THROUGH WAVELET DECOMPOSITION
No full textparameters (heart rate and blood pressure) at rest and in response to external stimuli. It is composed of two subsystems: the sympathetic and parasympathetic (or vagal) ones, acting
simultaneously but at different rates, the first for increasing and the second one for decreasing the heart rate (HR). To evaluate the activities of the two subsystems spectral analysis of HR
variability is traditionally used. Standard methods (Fourier and autoregressive analysis) require stationary signals and do not allow to analyze short and transitory periods. But applying the
wavelet analysis, it is possible to make a multi-resolution evaluation (in time and frequency) of the activation of the two subsystems and quantify their variations. Since a validated methodology for spectral analysis of transient periods does not exist, we tested the wavelet approach by analysing the Valsalva manoeuvre in healthy and pathologic patients. The physiology of this cardiovascular test is well known and it represents the good target to evaluate the wavelet approach and its feasibility in quantifying sympathetic and vagal activations.
The obtained results demonstrate the goodness of wavelet approach: in healthy subjects the different activations were quantified properly with the right sequence. In pathological patients, our analysis demonstrated the absence of some activations and the results are statistically different from the normal ones
APPLICAZIONE SULLA DISMOTILITÀ INTESTINALE DI ESTRATTI DI FOGLIE DI OLEA EUROPAEA L. E DI PETALI DI HIBISCUS SABDARIFFA L. (HERBAL MIX)
No full textRazionale dello studio: La miscela di erbe (Herbal Mix, HM)
composta da estratti di foglie di Olea europaea L. ed estratti di
petali di Hibiscus sabdariffa L. è stata studiata su alcuni target di
patologie infiammatorie intestinali caratterizzate da dismotilità.
Nello specifico, ne sono stati analizzati gli effetti sulla contrattilità
della muscolatura liscia intestinale e l’azione su iNOS ed eNOS
umana.
Materiali e Metodi: HM è costituito dall’86,67% di estratto
di foglie di Olea europaea L. (principalmente oleuropeina) e dal
13,33% di estratto di fiori di Hibiscus sabdariffa L. (principalmente
acido ibiscico), in rapporto 13:2. Sono stati utilizzati tessuti ex
vivo di ileo e colon per l’analisi degli effetti di HM sulla contrattilità
spontanea e indotta; per la valutazione dell’inibizione della
NOS, è stato seguito il saggio della L-citrullina con rilevamento
fluorimetrico.
Risultati: HM ha mostrato attività spasmolitica con significativa
diminuzione delle contrazioni ad alta e media frequenza su ileo
e colon, sia per quanto riguarda la contrattilità spontanea che
indotta, con un effetto di tipo dose-dipendente. Inoltre, l’estratto
ha provocato un’inibizione dose-dipendente degli enzimi iNOS
ed eNOS, con un effetto massimo del 67% per iNOS e del 64%
per eNOS.
Conclusioni: I risultati mostrano che HM costituisce una formulazione
efficace nella modulazione di alcuni bersagli legati alle
malattie intestinali su base infiammatoria
RADIOLOGICAL OPTIMIZATION OF BUBBLE DYNAMICS IN CARBON DIOXIDE ANGIOGRAPHY
No full textThe using of carbon dioxide as contrast medium (CM) is increasing in the diagnosis of vascular diseases such as peripheral stenosis and fistulae. This radiological technique produces images through a digital subtraction (DS) of the images obtained with CM injected and a series of masks images.
The two phase system (blood, CO2) remain separate by a surface until the gas is been dissolved. The radiological contrast of the xray image is given by integral dose on the pixels under the bubble respect to the pixel’s dose in the surround. Since the bubble is moving in the vessel, the fluoroscopy pulse time and the frame frequency change the contrast to noise ratio (CNR) of the contrast medium. This create moving artifacts that reduce the diagnostic outcome of the exam. To evaluate the best operational procedure we started with a laboratory model of the dynamical system. In this study has been realized a phantom made of 15cm of water with inside different glass vessels of various diameters. The images are taken with a PAXSCAN 4030 FP irradiated with RQR5 and RQR7 (IEC61267) x-ray field in different frame rate and integration time configuration. Moreover an algorithm to find the best radiological parameters has been developed to maximize the image quality indexes with no changing in entrance dose. The image quality improvement is evaluated in term of increment of the figure of merit of the image (CNR^2/Dose). The results shows the limits of the common used stacking technique and find out how long integration time protocols are less efficient than high frame rate protocols even in condition of high frame rate
FEASIBILITY STUDY OF A NECK COLLAR FOR CEREBRAL COOLING
No full textHypothermia is an important neuro-protective strategy for patients with acute brain damage following traumatic brain injury, stroke or sudden cardiac death.. Nowadays, cooling therapy is performed inside the intensive care units with non-invasive systems applied to the body and head
surface or invasively through cooling catheters inserted in the femoral vein. Full body cooling presents criticism still unresolved and a therapy localized in the brain is more effective. External systems (i.e. cool helmets) have a very low efficiency due to the need to overstep the cranial cap.
For this reason we tested the feasibility to reduce the temperature of brain tissues by cooling the blood inside carotid and cervical artery through the neck. A simple mathematical model of heat transfer between neck surface, tissue, blood in the carotid and cervical arteries and then brain was studied and then in-vitro simulated. Cooling was performed with peltier cells opportunely conditioned. Results demonstrate the possibility to reduce the temperature of the brain of 2°C in about 50 minutes. Temperature’s decrease and process duration fit good together with actual first aid times and medical procedures. Moreover, an earlier intervention makes it faster the cooling transfer administered in the intensive units
XXII International Conference on Mechanics in Medicine and Biology - Abstracts Book
No full textThis book contain the abstracts presented the XXII ICMMB, held in Bologna in September 2022. The abstracts are divided following the sessions scheduled during the conference
Cardiac Apex Rotation: a valuable index of global myocardial performance in acute ischemia
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