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PubMed2002

A synthetic aragonite-based bioceramic: influence of process parameters on porosity and compressive strength.

We investigate the influence of process parameters such as weight fraction and particle size of pore-former, and isostatic pressure, on porosity and compressive strength of non-sintered porous calcium carbonate biomaterials compacted at high pressure in uniaxial or isostatic mode. Experiment design and results analysis are performed according to a two-level 2k factorial design method (FDM). Results indicate that only the weight fraction of pore-former (wt fpf) influences significantly the porosity and the compressive strength. The porosity P, is described by a linear function of wt fpf, and the compressive strength sigma(comp), by an exponential one. For materials compacted under uniaxial pressing: P (vol%) = 33.7 + 85.4 (wt fpf) and sigma(comp) (MPa) = 28.8e(-9.2(wt fpf)) with 0.1 < or = wt fpf < or = 0.3. For materials compacted in isostatic mode: P (vol%) = 33.9 + 82.1 (wt fpf) and sigma(comp) (MPa) = 24.0e(-7.0(wt fpf)) with 0.15 < or = wt fpf < or = 0.35. The pore-former particle size has no significant influence on both properties. The increase in isostatic pressure provides slightly lower porosity and better compressive strength. For a fixed fraction of pore-former, isostatic pressing leads to a better compressive strength than uniaxial pressing. This study indicates that, for a constant amount of pore former, the size of macropores can be adjusted to reach optimal bone-ingrowth without change in compressive strength.

Biocompatible Materials↗

PubMed2000

Correlation between drug release kinetics from proteineous matrices and protein folding: elasticity and compressibility study.

Naproxen sodium (NS) release mechanism from proteineous matrices based on egg albumin (EA) and bovine serum albumin (BSA) was investigated by several physico-chemical methods. The gel strength, modulus of elasticity and erosion properties of the matrices were studied and correlated with drug release kinetics. The results revealed that NS release rate from EA and BSA matrices was markedly different, indicating the significant role of protein nature and conformation on matrix behavior. Unexpectedly it was found that incorporation of NS to EA matrix increased gel strength and modulus of elasticity and decreased matrix erosion. This effect was dependent on NS concentration in the matrix. In contrast to EA, BSA behaved as a non-gelling matrix and was unable to retard drug release because of its high solubility. The influence of NS on protein folding and compressibility in protein solutions was studied using densitometric and ultrasonic techniques. Adiabatic compressibility measurements revealed that NS caused unfolding of EA, an effect which led to a decrease in EA intrinsic compressibility and the exposure of atomic side groups buried in protein interior. Unfolding of EA led to an increase of modulus of elasticity in solution (measured by ultrasonic velocimetry technique) which is in correlation with the modulus of elasticity measurements of gelled tablets (measured by Instron). In concentrated EA solutions, the results showed a large increase in EA compressibility and ultrasonic absorption in the presence of NS indicating a strong aggregation of the denatured state of EA. Regarding BSA, the results suggested that NS affected the packing of the protein interior, transforming it to a molten globule intermediate state, an effect that led to an increase in BSA compressibility. At high BSA concentrations, aggregation of the molten globule state was observed as indicated by an increase of BSA compressibility and ultrasonic absorption values.

Algorithms↗

PubMed1998

Ventilatory strategies affect gas exchange in a pig model of closed-chest cardiac compression.

STUDY OBJECTIVE: To identify the arterial and mixed venous blood gas changes caused by different ventilatory strategies during resuscitation from ventricular fibrillation in a pig model of closed-chest cardiac compression. METHODS: A prospective randomized animal study was performed using 27 domestic pigs (body weight, 30 to 35 kg). Pentobarbital-anesthetized pigs were assigned to receive one of three treatments: (1) chest compression without assisted ventilation (n = 8), (2) assisted ventilation with room air (n = 8), and (3) assisted ventilation with 100% oxygen (n = 8). A fourth group, with the airway completely blocked, was added at the end of the experiment (n = 3). After instrumentation, the ventricles were fibrillated, and chest compression was begun 30 seconds after fibrillation with the use of the Thumper Mechanical CPR system (Michigan Instruments). Arterial and mixed venous blood gas samples were collected at 1, 3, 10, and 20 minutes of resuscitation. Defibrillation was attempted after the 20-minute sample was taken. RESULTS: Fibrillation followed by chest compression alone caused a significant drop in arterial and mixed venous partial pressure of oxygen (PO2) and a significant increase in arterial and mixed venous partial pressure of carbon dioxide (PCO2). Compared with the chest compression only, ventilation with room air significantly increased arterial and mixed venous PO2 and decreased arterial and mixed venous PCO2. Ventilation with 100% oxygen further increased arterial and mixed venous PO2 but did not affect PCO2, when compared with room air ventilation. The only successful defibrillations (3 animals) occurred in the group receiving 100% oxygen. CONCLUSION: This study indicates that passive air movement during chest compression does not allow physiologically significant pulmonary gas exchange and that room air ventilation alone is not sufficient to maintain mixed venous PO2.

Animals↗

PubMed2001

The effect of partial removal of the nucleus pulposus from the intervertebral disc on the response of the human annulus fibrosus to compression.

OBJECTIVE: To determine how partial removal of the nucleus changes the response of the annulus to compression. DESIGN: The deformation of the annulus in the mid-sagittal plane, during compression, was determined from digital video images. BACKGROUND: Several studies have shown that removal of the nucleus changes the external behaviour of the intervertebral disc, but few studies have investigated changes to internal behaviour. METHODS: Six frozen human lumbar discs were bisected in the sagittal plane to produce 12 specimens. The cut surfaces were marked with seven dots of Alcian blue stain. The specimens were sealed, enabling their internal structure to be viewed directly by a digital video recording system, and thawed. The video system recorded the response of each specimen as it was compressed by up to 1.8 mm at a rate of 0.2 mm s(-1). The displacements of the Alcian blue marks were measured using an image analysis program. Magnetic resonance imaging was used to investigate the validity of this technique. RESULTS: Partial removal of the nucleus changed the way that the disc deformed under compression. A highly significant change in direction of movement was seen in the inner posterior region of the annulus. CONCLUSIONS: Partial removal of the nucleus changes the response of the annulus to compression. RELEVANCE: Partial denucleation of the human intervertebral disc is shown to change the direction of bulging of the inner annulus when the disc is compressed. Increases in shear stress, arising from these changes, may lead to further disc degeneration in the form of circumferential tears.

Biomechanical Phenomena↗

PubMed1999

Nonlinear analysis of cartilage in unconfined ramp compression using a fibril reinforced poroelastic model.

OBJECTIVE: To develop a biomechanical model for cartilage which is capable of capturing experimentally observed nonlinear behaviours of cartilage and to investigate effects of collagen fibril reinforcement in cartilage. DESIGN: A sequence of 10 or 20 steps of ramp compression/relaxation applied to cartilage disks in uniaxial unconfined geometry is simulated for comparison with experimental data. BACKGROUND: Mechanical behaviours of cartilage, such as the compression-offset dependent stiffening of the transient response and the strong relaxation component, have been previously difficult to describe using the biphasic model in unconfined compression. METHODS: Cartilage is modelled as a fluid-saturated solid reinforced by an elastic fibrillar network. The latter, mainly representing collagen fibrils, is considered as a distinct constituent embedded in a biphasic component made up mainly of proteoglycan macromolecules and a fluid carrying mobile ions. The Young's modulus of the fibrillar network is taken to vary linearly with its tensile strain but to be zero for compression. Numerical computations are carried out using a finite element procedure, for which the fibrillar network is discretized into a system of spring elements. RESULTS: The nonlinear fibril reinforced poroelastic model is capable of describing the strong relaxation behaviour and compression-offset dependent stiffening of cartilage in unconfined compression. Computational results are also presented to demonstrate unique features of the model, e.g. the matrix stress in the radial direction is changed from tensile to compressive due to presence of distinct fibrils in the model. RELEVANCE: Experimentally observed nonlinear behaviours of cartilage are successfully simulated, and the roles of collagen fibrils are distinguished by using the proposed model. Thus this study may lead to a better understanding of physiological responses of individual constituents of cartilage to external loads, and of the roles of mechanical loading in cartilage remodelling and pathology.

Biomechanical Phenomena↗

PubMed2002

Effectiveness of ventilation-compression ratios 1:5 and 2:15 in simulated single rescuer paediatric resuscitation.

Current guidelines for paediatric basic life support (BLS) recommend a ventilation-compression ratio of 1:5 during child resuscitation compared with 2:15 for adults, based on the consensus that ventilation is more important in paediatric than in adult BLS. We hypothesized that the ratio 2:15 would provide the same minute ventilation as 1:5 during single-rescuer paediatric BLS due to the reduced time required to change between ventilations and compressions. Fourteen lay rescuers were trained with both ratios and thereafter performed single rescuer BLS for approximately 4 min with each of the two ratios in random order on a child-sized manikin with a built-in respiratory monitor. Quality of chest compressions was assessed by measurement of the rate, depth and position. There were no significant differences in tidal volumes or minute ventilation between the ratios. Nearly all chest compressions were within acceptable limits for depth and place with both methods, but the mean number of chest compressions per minute was 48+/-15% greater with ratio 2:15. In conclusion, there was no difference in ventilation, but nearly one and a half times as many compressions with a ratio of 2:15 than 1:5 for lay rescuers during single rescuer paediatric CPR. In order to simplify CPR training for laypersons, we recommend a 2:15 ratio for both single- and two-person, adult and paediatric layperson BLS.

Adult↗

PubMed2003

Comparison of standard CPR versus diffuse and stacked hand position interposed abdominal compression-CPR in a swine model.

Interposed abdominal compression cardiopulmonary resuscitation (IAC-CPR) is an innovative basic life support technique requiring no mechanical adjuncts. Optimizing its performance remains a challenge. Hand-position technique over the abdomen during interposed abdominal compression (IAC) may be important. The purpose of this study was to determine if there is a difference in efficacy depending on the type of abdominal hand-position used. Two different hand positions were studied: open hands, placed side by side, resulting in diffuse abdominal compression and stacked hands, with one on top of the other, producing a more focal compression of the abdomen. Thirty swine were cannulated with micromanometer-tipped pressure transducers in the ascending aorta (Ao) and right atrium (RA), and Millar Doppler-tipped catheters in the descending aorta and inferior vena cava (IVC) to determine flow patterns during cardiopulmonary resuscitation (CPR), During CPR there were no differences in aortic systolic or right atrial systolic pressures. Both forms of IAC-CPR produced greater aortic diastolic and right atrial diastolic pressures then standard CPR (STD-CPR) (P<0.05). Coronary perfusion pressures (CPP), however, were not different. Blood flow directions and velocity patterns showed that STD-CPR chest compressions produce caudally directed blood flow in both the descending aorta and the IVC, and that such flows reverse (becoming cranially directed) during the relaxation phase of chest compression. IAC-CPR produced similar blood flow patterns in the aorta and IVC, as seen with STD-CPR. There were no differences in blood flow patterns between the different forms of IAC-CPR. No CPR-produced trauma difference was found. Abdominal hand position (diffuse or stacked) did not affect blood flow in either the aorta or IVC or resuscitation success in this experimental model. There was a trend towards better outcomes with stacked hands IAC-CPR with 90 versus 70% survival with STD-CPR.

Abdomen↗

PubMed1998

Efficacy of chest compression-only BLS CPR in the presence of an occluded airway.

Reluctance of the lay public to perform bystander CPR is becoming an increasingly worrisome problem in the USA. Most bystanders who admit such reluctance concede that fear of contagious disease from mouth-to-mouth contact is what keeps them from performing basic life support. Animal models of prehospital cardiac arrest indicates that 24-h survival is essentially as good with chest compression-only CPR as with chest compressions and assisted ventilation. This simpler technique is an attractive alternative strategy for encouraging more bystander participation. Such experimental studies have been criticized as irrelevant however secondary to differences between human and porcine airway mechanics. This study examined the effect of chest compression-only CPR under the worst possible circumstances where the airway was totally occluded. After 6 min of either standard CPR including ventilation with a patent airway or chest compressions-only with a totally occluded airway, no difference in 24 h survival was found (10/10 vs. 9/10). As anticipated arterial blood gases were not as good, but hemodynamics produced were better with chest compression-only CPR (P < 0.05). Chest compression-only CPR, even with a totally occluded airway, is as good as standard CPR for successful outcome following 6.5 min of cardiac arrest. Such a strategy for the first minutes of cardiac arrest, particularly before professional help arrives, has several advantages including increased acceptability to the lay public.

Airway Obstruction↗

PubMed1999

Chest injuries after active compression-decompression cardiopulmonary resuscitation (ACD-CPR) in cadavers.

In a prospective study of 38 cadavers of patients older than 18 without previous chest injury or cardiopulmonary resuscitation (CPR), active compression-decompression (ACD) resuscitation manoeuvres were performed to determine possible factors influencing sternal and/or rib fractures. ACD was performed for 60 s, with compression and decompression forces being continuously recorded. A stepwise logistic regression analysis was applied. Factors analyzed were age, gender, use of a compression cushion beneath the piston of the ACD device (Ambu CardioPump), and maximal compression and decompression forces. After ACD, the cadavers were autopsied and thoracic injuries were assessed. There was a significant correlation between sternal fractures and gender (P = 0.008), and between rib fractures and age (P = 0.008). Women were found to have a higher risk for sternal fractures, whereas older patients had a higher risk for rib fractures. Maximal compression force was another factor in sternal and/or rib fracture (P = 0.048). Even though a significantly higher incidence of sternal fractures was observed when the compression cushion was used (P = 0.045), inclusion of this variable in the regression analysis only marginally improved the prediction for correct classification of sternal fractures. In conclusion, when well controlled ACD-CPR is performed in cadavers, age is the most important factor determining the incidence of rib fracture. Sternal fractures were more common in female cadavers.

Age Factors↗

PubMed2000

Analysis of compression of polymer mushrooms using self-consistent field theory.

A number of new technologies, including new-generation biomaterials and chromatography resins, are based on passivation and modification of surfaces by terminally attaching polymer chains to the surface. However, little is known about these systems at the molecular level. In this work the compression of a single end-grafted polymer chain (or mushroom) by a disc of finite radius was investigated using a self-consistent field (SCF) lattice model. In accordance with results predicted using scaling theory [Subramanian et al., Europhys. Lett. 29 (1995) 285 and Macromolecules 29 (1996) 4045], the compressed chain undergoes a smooth escape transition. However, under the assumption of angular symmetry, a first-order escape transition of the end-grafted chain is not observed, suggesting that the formation of a tether is required for the predicted phase transition. Segment density distributions and compression energies are calculated in a cylindrical lattice. The energy required to compress a chain increases monotonically as the disc is moved closer to the surface and becomes independent of chain length at strong compressions where the work of compression involves only confinement of the tether joining the escaped chain fraction to the grafting point.

Polymers↗

PubMed2001

Modeling temporal and compressive properties of the normal and impaired auditory system.

Three modifications of a psychoacoustically and physiologically motivated processing model [Dau et al., J. Acoust. Soc. Am. 102 (1997a) 2892-2905] are presented and tested. The modifications aim at simulating sensorineural hearing loss and incorporate a level-dependent peripheral compression whose properties are affected by hearing impairment. Model 1 realizes this difference by introducing for impaired listeners an instantaneous level-dependent expansion prior to the adaptation stage of the model. Model 2 and Model 3 realize a level-dependent compression with time constants of 5 and 15 ms, respectively, for normal hearing and a reduced compression for impaired hearing. In Model 2, the compression occurs after the envelope extraction stage, while in Model 3, envelope extraction follows compression. All models account to a similar extent for the recruitment phenomenon measured with narrow-band stimuli and for forward-masking data of normal-hearing and hearing-impaired subjects using a 20-ms, 2-kHz tone signal and a 1-kHz-wide bandpass noise masker centered at 2 kHz. A clear difference between the different models occurs for the processing of temporally fluctuating stimuli. A modulation-rate-independent increase in modulation-response level for simulating impaired hearing is only predicted by Model 1 while the other two models realize a modulation-rate-dependent increase. Hence, the predictions of Model 2 and Model 3 are in conflict with the results of modulation-matching experiments reported in the literature. It is concluded that key properties of sensorineural hearing loss (altered loudness perception, reduced dynamic range, normal temporal properties but prolonged forward-masking effects) can effectively be modeled by incorporating a fast-acting expansion within the current processing model prior to the nonlinear adaptation stage. Based on these findings, a model of both normal and impaired hearing is proposed which incorporates a fast-acting compressive nonlinearity, representing the cochlear nonlinearity (which is reduced in impaired listeners), followed by an instantaneous expansion and the nonlinear adaptation stage which represent aspects of the retro-cochlear information processing in the auditory system.

Auditory Pathways↗

PubMed2004

[Compressive therapy after varicose vein surgery: results of a French national inquiry].

OBJECTIVES: A survey on postoperative compression after varicose vein surgery was undertaken in 2001 among surgeons of the French-speaking Vascular Surgery Society as well as non-members with a heavy caseload in varicose vein surgery. The aims of the study were to 1) identify the various medical devices and protocols used postoperatively, 2) estimate the frequency and duration of use, and 3) identify the surgeon's rationale for prescribing postoperative compression. The first part of the inquiry was devoted to surgical procedures and has been previously published (J Mal Vasc 2003; 28: 277-86). MATERIAL AND METHODS: A questionnaire with 11 items for postoperative treatments and a patient form was mailed to 675 surgeons. RESULTS: The response rate was 41.5% (280 surgeons). Results were assessed by a scientific committee. Surgeons were classified into different groups according to their membership in the French-speaking Vascular Surgery Society or not, the type of practice (private, public hospital, mixed), and caseload. Compression was widely used (97.1%). It was the only postoperative treatment for 25.2% of the surgeons, was associated with anticoagulant treatment for 38.8% or non-steroidal antiinflammatory drugs for 11.2%. Prescription was evidence-based for only 11.6%. Compression therapy was mainly started postoperatively (93.2%). Elastic bandages (long stretch) were used by 87%. Duration of bandage therapy was variable (less than 8 days for 38.8%, 8-15 days for 24.5%). After bandage therapy, medical compression stockings (above knee 74.7%) or French class II (77.9%) were used. Compression stockings were prescribed for 8-15 days or 15-30 days by 12.7% and 84.6% of the surgeons respectively. Prolonged postoperative treatment was not common (28%) and was prescribed for patients with trophic changes.

Bandages↗

PubMed2001

Biosynthetic response and mechanical properties of articular cartilage after injurious compression.

Traumatic joint injury is known to produce osteoarthritic degeneration of articular cartilage. To study the effects of injurious compression on the degradation and repair of cartilage in vitro, we developed a model that allows strain and strain rate-controlled loading of cartilage explants. The influence of strain rate on both cartilage matrix biosynthesis and mechanical properties was assessed after single injurious compressions. Loading with a strain rate of 0.01 s(-1) to a final strain of 50% resulted in no measured effect on the cells or on the extracellular matrix, although peak stresses reached levels of about 12 MPa. However, compression with strain rates of 0.1 and 1 s(-1) caused peak stresses of approximately 18 and 24 MPa, respectively, and resulted in significant decreases in both proteoglycan and total protein biosynthesis. The mechanical properties of the explants (compressive and shear stiffness) were also reduced with increasing strain rate. Additionally, cell viability decreased with increasing strain rate, and the remaining viable cells lost their ability to exhibit an increase in biosynthesis in response to low-amplitude dynamic mechanical stimulation. This latter decrease in reparative response was most dramatic in the tissue compressed at the highest strain rates. We conclude that strain rate (like peak stress or strain) is an important parameter in defining mechanical injury, and that cartilage injuriously compressed at high strain rates can lose its characteristic anabolic response to low-amplitude cyclic mechanical loading.

Animals↗

PubMed1999

Thrombin injection versus compression of femoral artery pseudoaneurysms.

OBJECTIVE: The compression of femoral artery pseudoaneurysms is a time consuming, painful, and sometimes unsuccessful procedure. Thrombin injection has been advocated as a superior alternative. In this study, we compare our experiences with both techniques. METHODS: All the records of femoral artery false aneurysms that were treated in the vascular laboratory from January 1996 to April 1999 were retrospectively reviewed. Treatment with ultrasound scan-guided compression was compared with treatment with dilute thrombin injection (100 U/mL). RESULTS: Both groups had similar demographics and aneurysm sizes (P >.2). Of the pseudoaneursyms, 88% were caused by cardiac catheterization and the others were the results of femoral artery access for cardiac surgery (6%), arteriography (5%), and renal dialysis (1%). Compression was successful in 25 of 40 patients (63%). Nine persistent aneurysms necessitated operation, and six were treated successfully with thrombin injection. Primary thrombin injection successfully obliterated 21 pseudoaneurysms in 23 patients. Overall, 27 of 29 pseudoaneurysms were treated successfully with thrombin injection (93%). Thrombosis occurred within seconds of the thrombin injection and required, on average, 300 units of thrombin (100 to 600 units). The patients who underwent successful compression required an average of 37 minutes of compression (range, 5 to 70 minutes) and required analgesia on several occasions. No patients in the thrombin group required analgesia or sedation. Neither group had complications. A cost analysis shows that thrombin treatment results in considerable savings in vascular laboratory resource use but not in overall hospital expenditures. CONCLUSION: Ultrasound scan-guided thrombin injection is a safe, fast, and painless procedure that completely obliterates femoral artery pseudoaneurysms. The shift from compressive therapy to thrombin injection reduces vascular laboratory use and is less expensive, although it does not significantly impact hospital costs.

Adult↗

PubMed2002

Effect of Honan balloon compression on peribulbar anesthesia adequacy in cataract surgery.

PURPOSE: To ascertain whether a Honan balloon is necessary to produce effective peribulbar anesthesia in routine cataract surgery by evaluating its effect on intraocular pressure (IOP), surgeon assessment of the anesthesia's effectiveness, and patients' analgesic experience. SETTING: West of England Eye Unit, Royal Devon and Exeter Hospital, England. METHOD: Fifty eyes of 50 patients having routine phacoemulsification cataract extraction and intraocular lens implantation were randomized to have 10-minute ocular compression with the Honan balloon or no compression after peribulbar anesthesia. A single investigator gave all the peribulbar injections using a standard technique. The IOP was measured immediately before and 10 minutes after the injections. Two surgeons who were blinded to the randomization process performed the surgeries and completed an assessment questionnaire on various aspects of the peribulbar block. The patients also scored their level of analgesia during surgery. RESULTS: In the 26 patients who had Honan balloon compression, there was a significant reduction in IOP (mean 6.2 mm Hg; P <.05). In the 24 patients with no balloon compression, there were no significant changes in IOP 10 minutes after the peribulbar injections. There was no statistically significant difference in the surgeons' scores in any aspect of the peribulbar anesthesia (P >.05). All patients experienced a good level of analgesia. CONCLUSIONS: There was a significant reduction in IOP after Honan balloon ocular compression. However, there was no significant increase in IOP without balloon compression. The use of a Honan balloon did not appear to make a significant difference in the effectiveness of the peribulbar anesthesia to the surgeons or patients.

Aged↗

PubMed1989

An historical look at the thoracic outlet compression syndrome.

The story of the thoracic outlet compression syndrome begins with the identification of the anatomical abnormality of the cervical rib, and the symptoms related to it. Resection of the cervical rib, however, was soon followed by the recognition that symptoms could occur in the absence of a cervical rib. The scalenus anticus was then held to be the culprit, although several different mechanisms were advanced to explain the development of symptoms. Subsets of the thoracic outlet compression syndrome were then codified; costoclavicular compression; compression under the coracoid process during hyperabduction; primary symptoms related to arterial compression; and the syndrome that appears when neural and arterial compression are absent but venous occlusion is present. The importance of the first rib as a common denominator has brought about the idea that first rib resection is the best method of extirpating this common anatomic factor. That thesis is not accepted universally, however.

History, 19th Century↗

PubMedDate not supplied

Assessment of commercial compression algorithms, of the lossy DCT and lossless types, applied to diagnostic digital image files.

The need for diagnostic image compression of the lossy or irreversible type has been declining due to the rapid increase in commercially available formatted hard disk capacity. It is estimated that the latter has increased about three orders of magnitude in the past 14 years while the size of diagnostic image files has, of course, remained constant. During the same period, despite claims for significantly improved performance by vendors, it seems that only small progress has been made in commercial lossless and lossy compression algorithms. There is still no consensus for lossy compression to a level acceptable for diagnosis. This is mostly considered to be around a ratio of 10:1. However, acceptable compression ratios depend heavily on the type of images processed and may be compared with the 3:1 ratio produced by lossless algorithms. This last value was shown to increase to more than 5.5:1 for gamma-camera images when corrected for the noise content of individual bit planes and for the display capabilities of computer monitors. Therefore, any possible benefits of lossy over lossless compression become questionable when the currently available hard disk capacity and network transmission speed are considered against the inevitable loss of information in the lossy type of compression.

Algorithms↗

PubMedDate not supplied

A comparison of lossless compression methods for medical images.

In this work, lossless grayscale image compression methods are compared on a medical image database. The database contains 10 different types of images with bit rates varying from 8 to 16 bits per pixel. The total number of test images was about 3000, originating from 125 different patient studies. Methods used for compressing the images include seven methods designed for grayscale images and 18 ordinary general-purpose compression programs. Furthermore, four compressed image file formats were used. The results show that the compression ratios strongly depend on the type of the image. The best methods turned out to be TMW, CALIC and JPEG-LS. The analysis step in TMW is very time-consuming. CALIC gives high compression ratios in a reasonable time, whereas JPEG-LS is nearly as effective and very fast.

Computer Graphics↗