Tissue Oxygen Partial Pressure Research Articles

Brain tissue oxygen partial pressure monitoring and prognosis of patients with traumatic brain injury: a meta-analysis.

To assess whether monitoring brain tissue oxygen partial pressure (PbtO2) or employing intracranial pressure (ICP)/cerebral perfusion pressure (CCP)-guided management improves patient outcomes, including mortality, hospital length of stay (LOS), mean daily ICP and mean daily CCP during the intensive care unit(ICU)stay. We searched the Web of Science, EMBASE, PubMed, Cochrane Library, and MEDLINE databases until December 12, 2023. Prospective randomized controlled and cohort studies were included. A meta-analysis was performed for the primary outcome measure, mortality, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Eleven studies with a total of 37,492 patients were included. The mortality in the group with PbtO2 was 29.0% (odds ratio: 0.73;95% confidence interval [CI]:0.56-0.96; P = 0.03; I = 55%), demonstrating a significant benefit. The overall hospital LOS was longer in the PbtO2 group than that in the ICP/CPP group (mean difference:2.03; 95% CI:1.03-3.02; P<0.0001; I = 39%). The mean daily ICP in the PbtO2 monitoring group was lower than that in the ICP/CPP group (mean difference:-1.93; 95% CI: -3.61 to -0.24; P = 0.03; I = 41%). Moreover, PbtO2 monitoring did not improve the mean daily CPP (mean difference:2.43; 95%CI: -1.39 to 6.25;P = 0.21; I = 56%).Compared with ICP/CPP monitoring, PbtO2 monitoring reduced the mortality and the mean daily ICP in patients with severe traumatic brain injury; however, no significant effect was noted on the mean daily CPP. In contrast, ICP/CPP monitoring alone was associated with a short hospital stay.

253 Tissue Partial Pressure of Oxygen During Spreading Depolarization in Malignant Stroke is Associated With Outcome

INTRODUCTION: Spreading depolarization (SD) describes a propagating neuronal mass depolarization within the cerebral cortex that likely represents a relevant mechanism of secondary lesion progression. METHODS: This prospective observational study included 25 patients with MHS that underwent decompressive hemicraniectomy (DC) followed by subdural placement of an electrocorticography (ECoG) strip electrode and cortical implantation of a PtiO2 probe within in the periinfarct tissue. Continuous ECoG and PtiO2 recordings were obtained at bedside for five days and analyzed for the occurrence of SD and SD-associated PtiO2 changes, as well as their association with clinical outcome at 6 months. RESULTS: The overall simultaneous ECoG and PtiO2 recording time was 2603 hours, during which 796 SDs were detected. The overall SD duration and SD frequency did not correlate with outcome. During the observation period, the overall PtiO2baseline changed significantly with an almost linear increase that reached a peak around 100 hours (*p=0.0055), followed by a PtiO2 drop until the end of the monitoring period (*p = 0.0048). Accordingly, low baseline PtiO2 (&lt;15 mmHg) was mainly noted during the first 24 hours but did not correlate with outcome (p = 0.916). Conversely, 20 out of 25 patients showed SD-associated PtiO2 changes in 363 out of 796 SDs (45.6%), which were categorized as biphasic (222), hypoxic (119) and hyperoxic (22). Among these SD-associated PtiO2 responses, a high occurrence rate, biphasic response pattern and high amplitude correlated significantly with favorable outcome (mRS 1-3) at 6 months. CONCLUSIONS: SD-associated PtiO2 coupling in patients suffering hemispheric stroke appears to be associated with clinical outcome and could reflect the presence of viable and metabolically less impaired peri-infarct tissue.

A portable optical pulsatile flowmetry demonstrates strong clinical relevance for diabetic foot perfusion assessment.

We present a robust, cost-effective (<2000 USD), and portable optical diffuse speckle pulsatile flowmetry (DSPF) device with a flexible handheld probe for deep tissue blood flow measurement in the human foot as well as a first-in-man observational clinical study using the proposed optical device for tissue ischemia assessment and peripheral artery disease (PAD) diagnosis. Blood flow in tissue is inherently pulsatile in nature. However, most conventional methods cannot measure deep tissue-level pulsatile blood flow noninvasively. The proposed optical device can measure tissue-level pulsatile blood flow ∼6 mm underneath the skin surface. A new quantitative tissue perfusion index (TPIDSPF) based on frequency domain analysis of the pulsatile blood flow waveform is defined to assess tissue ischemia status. Through a clinical study involving 66 subjects, including healthy individuals and diabetes patients with and without PAD, TPIDSPF demonstrated strong correlations of 0.720 with transcutaneous tissue partial oxygen pressure (TcPO2) and 0.652 with toe-brachial index (TBI). Moreover, among the three methods, TPIDSPF demonstrated the highest area under the curve for PAD diagnosis among diabetes patients, with a notable value of 0.941. The promising clinical results suggest that the proposed optical method has the potential to be an effective clinical tool for identifying PAD among the diabetic cohort.

Photoacoustic Lifetime Imaging of Hypoxia.

We present an approach based on photoacoustic lifetime imaging (PALI) to map the distribution of oxygen partial pressure (pO2) in tissue. This method utilizes methylene blue, a dye widely used in clinical applications, as an oxygen-sensitive imaging agent. PALI measurement of oxygen relies upon pO2-dependent excitation lifetime of the dye. The technique maps the excited triplet state of oxygen-sensitive dye, thus reflecting the spatial and temporal distributions of tissue oxygen.

Effect of hyperbaric oxygen therapy combined with repetitive transcranial magnetic stimulation on vascular cognitive impairment: a randomised controlled trial protocol

IntroductionVascular cognitive impairment (VCI) has an increasing prevalence worldwide, accounting for at least 20%–40% of all diagnoses of dementia. The decline in cognitive function seriously impairs patients’ activities of daily...

Neuroprotective effects of a hemoglobin-based oxygen carrier (stroma-free hemoglobin nanoparticle) on ischemia reperfusion injury

The application of hemoglobin (Hb)-based oxygen carriers (HBOCs) to the treatment of cerebral ischemia has been investigated. A cluster of 1 Hb and 3 human serum albumins (Hb-HSA3) was found to exert neuroprotective effects on ischemia/reperfusion injury. Stroma-free hemoglobin nanoparticles (SFHbNP), a subsequently developed HBOC consisting of a spherical polymerized stroma-free Hb core with a HSA shell, contains the natural antioxidant enzyme catalase and, thus, is expected to exert additive effects. We herein investigated whether SFHbNP exerted enhanced neuroprotective effects in a rat transient middle cerebral artery occlusion (tMCAO) model. Rats were subjected to 2-hour tMCAO and divided into the following 3 groups with the intravenous administration of the respective reagents: (1) phosphate-buffered saline (PBS), as a vehicle (2) Hb-HSA3, and (3) SFHbNP. After 24-hour reperfusion, infarct and edema volumes decreased in the order of the PBS, Hb-HSA3, and SFHbNP groups, with a significant difference (p < 0.05) between the PBS and SFHbNP groups. Similar reductions were observed in oxidative stress, leukocyte recruitment, and blood–brain barrier disruption in the order of the PBS, Hb-HSA3, and SFHbNP groups. In the early phase of reperfusion within 6 h, microvascular HBOC perfusion and cerebral blood flow were maintained at high levels during the reperfusion period in the Hb-HSA3 and SFHbNP groups. However, a difference was observed in tissue oxygen partial pressure levels, which significantly decreased after 6-hour reperfusion in the Hb-HSA3 group, but remained high in the SFHbNP group. A superior oxygen transport ability appears to be related to the enhanced neuroprotective effects of SFHbNP.

Sononeoperfusion effect by ultrasound and microbubble promotes nitric oxide release to alleviate hypoxia in a mouse MC38 tumor model

Tumor hypoperfusion not only impedes therapeutic drug delivery and accumulation, but also leads to a hypoxic and acidic tumor microenvironment, resulting in tumor proliferation, invasion, and therapeutic resistance. Sononeoperfusion effect refers to tumor perfusion enhancement using ultrasound and microbubbles. This study aimed to further investigate hypoxia alleviation by sononeoperfusion effect and explore the characteristics and mechanism of sononeoperfusion effect. To stimulate the sononeoperfusion effect, mice bearing MC38 colon cancers were included in this study and diagnostic ultrasound for therapy was set at a mechanical index (MI) of 0.1, 0.3, and 0.5, frequency of 3 MHz, pulse length of 5 cycles, and pulse repetition frequency of 2000 Hz. The results demonstrated that a single ultrasound and microbubble (USMB) treatment resulted in tumor perfusion enhancement at MI = 0.3, and nitric oxide (NO) concentration increased at MI = 0.3/0.5 (P < 0.05). However, there were no significant difference in the hypoxia-inducible factor-1α (HIF-1α) or D-lactate (D-LA) (P > 0.05) levels. Multiple sononeoperfusion effects were observed at MI = 0.3/0.5 (P < 0.05). For each treatment, USMB slightly but steadily improved the tumor tissue oxygen partial pressure (pO2) during and post treatment. It alleviated tumor hypoxia by decreasing HIF-1α, D-LA level and the hypoxic immunofluorescence intensity at MI = 0.3/0.5 (P < 0.05). The sononeoperfusion effect was not stimulated after eNOS inhibition. In conclusion, USMB with appropriate MI could lead to a sononeoperfusion effect via NO release, resulting in hypoxia amelioration. The tumors were not resistant to multiple sononeoperfusion effects. Repeated sononeoperfusion is a promising approach for relieving tumor hypoxia and resistance to therapy.

Examination of Lower Limb Microcirculation in Diabetic Patients with and without Intermittent Claudication.

Intermittent claudication is a frequent complaint in lower extremity artery disease, but approximately two thirds of patients are asymptomatic, most of which are diabetic patients. Non-invasive angiological and microrheological tests on diabetic subjects with and without intermittent claudication were performed in the present study. In total, 98 diabetic patients were included and divided into two groups: 20 patients (63.5 ± 8.8 years, 55% men, 45% women) had intermittent claudication, 78 patients (65.5 ± 9.3 years, 61.5% men, 38.5% women) were asymptomatic. Hand-held Doppler ultrasound examination, transcutaneous tissue partial oxygen pressure (tcpO2) measurement, Rydel-Seiffer tuning fork tests, and 6-min walk tests were performed, and erythrocyte aggregation was investigated. Ankle-brachial index (p < 0.02) and tcpO2, measured during provocation tests (p < 0.003) and the 6-min walk test (p < 0.0001), significantly deteriorated in the symptomatic group. A higher erythrocyte aggregation index and faster aggregate formation was observed in claudication patients (p < 0.02). Despite the statistically better results of the asymptomatic group, 13% of these patients had severe limb ischemia based on the results of tcpO2 measurement. Claudication can be associated with worse hemodynamic and hemorheological conditions in diabetic patients; however, severe ischemia can also develop in asymptomatic subjects. Non-invasive vascular tests can detect ischemia, which highlights the importance of early instrumental screening of the lower limbs.

Tissue oxygen partial pressure as a viability metric for ex vivo brain tissue slices

BackgroundDespite the prevalent use of the ex vivo brain slice preparation in neurophysiology research, a reliable method for judging tissue viability ― and thus suitability of a slice for inclusion in an experiment ― is lacking. The utility of indirect electrophysiological measures of tissue health is model-specific and needs to be used cautiously. In this study, we verify a more direct test of slice viability, based on tissue oxygen consumption rate. New methodWe hypothesised that the minimum intra-slice partial pressure of oxygen (pO2min) would correlate with tissue oxygen consumption rate, providing an accessible method for reliably assessing tissue viability status. Using mouse brain cortex slices, we measured tissue oxygen consumption rate using a Fick’s law diffusion–consumption model applied to full intra-tissue pO2 profiles and compared this to pO2min and 2,3,5-triphenol tetrazolium chloride (TTC) viability staining. ResultsTissue pO2min correlated strongly with oxygen consumption rate in both neurophysiological active and quiescent tissue (in “no-magnesium” and “normal” artificial cerebrospinal fluid, respectively) (R2 =49.7% and 42.1%, respectively). Both correlated with TTC viability stain. Oxygen consumption rate was positively related to the frequency of seizure-like event activity in no-magnesium artificial cerebrospinal fluid (R2 = 44.8%). Comparison with existing methodsWhile measurement of tissue oxygen levels and oxygen consumption is not new, intra-tissue pO2min is a novel approach to assess brain slice viability. ConclusionThe results confirm that tissue oxygen minimum pO2min is a robust metric for estimating tissue viability status — the lower the pO2min, the healthier the tissue.

Metabolism changes during direct revascularization in moyamoya disease: illustrative case.

Cerebral revascularization is recommended for patients with moyamoya disease (MMD) with reduced cerebral perfusion reserve and recurrent or progressive ischemic events. The standard surgical treatment for these patients is a low-flow bypass with or without indirect revascularization. The use of intraoperative monitoring of the metabolic profile using analytes such as glucose, lactate, pyruvate, and glycerol has not yet been described during cerebral artery bypass surgery for MMD-induced chronic cerebral ischemia. The authors aimed to describe an illustrative case using intraoperative microdialysis and brain tissue oxygen partial pressure (PbtO2) probes in a patient with MMD during direct revascularization. The patient's severe tissue hypoxia situation was confirmed by a PbtO2:partial pressure of oxygen (PaO2) ratio below 0.1 and anaerobic metabolism by a lactate:pyruvate ratio greater than 40. Following bypass, a rapid and sustained increase in PbtO2 up to normal values (PbtO2:PaO2 ratio between 0.1 and 0.35) and the normalization of cerebral energetic metabolism with a lactate/pyruvate ratio less than 20 was observed. The results show a quick improvement of regional cerebral hemodynamics due to the direct anastomosis procedure, reducing the incidence of subsequent ischemic stroke in pediatric and adult patients immediately.

Hyperbaric oxygen therapy in outpatient care

Hyperbaric oxygen therapy, or high pressure oxygen therapy, is a highly specialised branch of medicine. Applications and results date back to the 1960s and it has been used, researched and developed ever since. During the treatment, patients breathe 100% oxygen in a pressurised chamber. For clinical purposes, as defined, the pressure must equal or exceed 1.4 atmosphera absolute, most of the cases typically higher (2.0-2.5 atmosphera absolute). Oxygen dissolves by pressure in body fluids, transported by circulation to all tissues. Cellular regeneration and tissue processes are induced by both the increased oxygen supply and the intermittent change in tissue partial oxygen pressure associated with treatment. The effect can be used in the treatment of many diseases, usually as part of a complex treatment plan. Additional advantage is that it is a non-invasive and pain-free therapy. Evidence-based indications and general baseline usage are regulated by the European Underwater and Baromedical Society through the European Committee of Hyperbaric Medicine, in accordance with the principles of evidence-based medicine. The authors describe three cases in their publication where hyperbaric oxygen therapy significantly contributed to the success of overall treatment. Orv Hetil. 2023; 164(25): 993-996.

Hyperosmolar therapy for regulation of cerebral edema and intracranial pressure

Background: Hyperosmolar therapy is an essential treatment method for increased intracranial pressure and cerebral edema. Mannitol and hypertonic saline are frequently used in clinical practice; however, more helpful recommendations are needed for the optimal management of cerebral edema in terms of the choice, dosage, and timing of these medications. This study aimed to introduce the characteristics and relative strengths of two agents, i.e., mannitol and hypertonic saline, and review clinical data supporting their use in various diseases.Current Concepts: Hyperosmolar therapy reduces intracranial pressure by removing water from the brain tissue and transferring it to the vascular space by creating an osmotic gradient. Mannitol improves cerebral blood flow by reducing the hematocrit, decreasing blood viscosity, and increasing deformability of red blood cells. Hypertonic saline increases intravascular volume, transiently increases cardiac output, and improves tissue oxygen partial pressure in the brain. Hypertonic saline has several advantages over mannitol, including quicker onset and longer-lasting reduction in intracranial pressure. However, no significant differences are noted in clinical, functional outcomes, or mortality between the two treatment agents.Discussion and Conclusion: Both mannitol and hypertonic saline are effective in reducing increased intracranial pressure. Clinicians should be able to select an appropriate agent in different clinical situations based on available evidence and patients’ individual medical conditions.

Construction of Bone Hypoxic Microenvironment Based on Bone-on-a-Chip Platforms.

The normal physiological activities and functions of bone cells cannot be separated from the balance of the oxygenation level, and the physiological activities of bone cells are different under different oxygenation levels. At present, in vitro cell cultures are generally performed in a normoxic environment, and the partial pressure of oxygen of a conventional incubator is generally set at 141 mmHg (18.6%, close to the 20.1% oxygen in ambient air). This value is higher than the mean value of the oxygen partial pressure in human bone tissue. Additionally, the further away from the endosteal sinusoids, the lower the oxygen content. It follows that the construction of a hypoxic microenvironment is the key point of in vitro experimental investigation. However, current methods of cellular research cannot realize precise control of oxygenation levels at the microscale, and the development of microfluidic platforms can overcome the inherent limitations of these methods. In addition to discussing the characteristics of the hypoxic microenvironment in bone tissue, this review will discuss various methods of constructing oxygen gradients in vitro and measuring oxygen tension from the microscale based on microfluidic technology. This integration of advantages and disadvantages to perfect the experimental study will help us to study the physiological responses of cells under more physiological-relevant conditions and provide a new strategy for future research on various in vitro cell biomedicines.

Hypoxia signaling in cancer: Implications for therapeutic interventions.

Hypoxia is a persistent physiological feature of many different solid tumors and a key driver of malignancy, and in recent years, it has been recognized as an important target for cancer therapy. Hypoxia occurs in the majority of solid tumors due to a poor vascular oxygen supply that is not sufficient to meet the needs of rapidly proliferating cancer cells. A hypoxic tumor microenvironment (TME) can reduce the effectiveness of other tumor therapies, such as radiotherapy, chemotherapy, and immunotherapy. In this review, we discuss the critical role of hypoxia in tumor development, including tumor metabolism, tumor immunity, and tumor angiogenesis. The treatment methods for hypoxic TME are summarized, including hypoxia-targeted therapy and improving oxygenation by alleviating tumor hypoxia itself. Hyperoxia therapy can be used to improve tissue oxygen partial pressure and relieve tumor hypoxia. We focus on the underlying mechanisms of hyperoxia and their impact on current cancer therapies and discuss the prospects of hyperoxia therapy in cancer treatment.

Multimodal Neuromonitoring in Pediatric Neurocritical Care: Current Perspectives.

Children with neurological illness in the critical care unit are always at higher risk of developing secondary brain injury (SBI). Brain insult can lead to changes in cerebral autoregulation, intracranial pressure (ICP), cerebral oxygenation, and metabolism. This can cause a raised ICP, cerebral ischemia, hypoxia, excitotoxicity, cellular energy failure, and nonconvulsive status epilepticus. Simultaneous and continuous assessment of these parameters will help to improve patient care and neurological outcomes. Even thoughclinical examination and neuroimaging can help in the initial diagnosis of the neurological illness, they may not be helpful in continuous monitoring of cerebralpathophysiological changes. The ideal single neuromonitoring device to detect these real-time changes is currently unavailable. However, a range of invasive and noninvasive monitors are available to monitor these cerebral functional parameters. Invasive monitoring techniques include invasive ICP monitoring, cerebral autoregulation monitoring, brain tissue partial oxygen pressure, and cerebral microdialysis. Noninvasive-monitoring techniques include pupillometry, brain and ocular ultrasonography, near-infraredspectroscopy, and electrophysiological monitoring. Multimodal (MM) neuromonitoring involves incorporating these techniques and tools for the early identification and treatment of primary and secondary brain insults. The utility and feasibility of most of these techniques are well described in adult neurocritical care. Even though the evidence on their usage in children is primarily available in pediatric traumatic brain injury, the emerging data help to further expand their utility in pediatric nontraumatic coma. MM neuromonitoring aims to provide clinical and pathophysiological information to the intensivists to improve their understanding of the child's neurological status and to formulate patient-specific treatment approaches.

Tissue partial pressure of oxygen during spreading depolarization in malignant stroke is associated with outcome

Tissue partial pressure of oxygen during spreading depolarization in malignant stroke is associated with outcome

Phosphorescent Microneedle Array for the Measurement of Oxygen Partial Pressure in Tissue.

The knowledge of the exact oxygen partial pressure in tissue is crucial for patient care and in the treatment of ischemic medical conditions. However, current methods to assess oxygen partial pressure in tissue suffer from a variety of disadvantages, including complex equipment and procedures that necessitate trained personnel. Additionally, the barrier function of the stratum corneum reduces oxygen exchange and can consequently hamper surface measurements of rapidly changing oxygen partial pressure in tissue. To overcome these challenges, a novel, easy-to-use technique to monitor the oxygen partial pressure in tissue using microneedle arrays (MNAs) has been developed. The MNAs can be made from poly(ethyl methacrylate) and poly(propyl methacrylate) and overcome the skin's barrier function to measure oxygen in the capillary bed and interstitial fluid of the skin. The MNAs' tips are embedded with an oxygen-sensitive phosphorescent metalloporphyrin, where the oxygen partial pressure inversely correlates to changes in both emission intensity and phosphorescence lifetime of the in-house developed red emitting Pt-core porphyrin. It was demonstrated that the oxygen-sensing MNAs are sufficiently robust to puncture human skin via rupture of the stratum corneum, and that the MNAs can detect changes in oxygen partial pressure in skin within the physiologically relevant range (0-160 mmHg). Additionally, the MNAs can be combined with a wearable wireless optical readout system, making these oxygen-sensing MNAs a novel wearable and portable method for user-friendly monitoring of oxygen partial pressure in skin.

Protoporphyrin IX delayed fluorescence imaging: a modality for hypoxia-based surgical guidance.

.SignificanceHypoxia imaging for surgical guidance has never been possible, yet it is well known that most tumors have microregional chronic and/or cycling hypoxia present as well as chaotic blood flow. The ability to image oxygen partial pressure () is therefore a unique control of tissue metabolism and can be used in a range of disease applications to understand the complex biochemistry of oxygen supply and consumption.AimDelayed fluorescence (DF) from the endogenous molecule protoporphyrin IX (PpIX) has been shown to be a truly unique reporter of the local oxygen partial pressure in tissue. PpIX is endogenously synthesized by mitochondria in most tissues, and the particular property of DF emission is directly related to low microenvironmental oxygen concentration. Here, it is shown that PpIX has a unique emission in hypoxic tumor tissue regions, which is measured as a DF signal in the red to near-infrared spectrum.ApproachA time-gated imaging system was used for PpIX DF for wide field direct mapping of changes. Acquiring both prompt and DF in a rapid sequential cycle allowed for imaging oxygenation in a way that was insensitive to the PpIX concentration. By choosing adequate parameters, the video rate acquisition of images could be achieved, providing real-time tissue metabolic information.ResultsIn this report, we show the first demonstration of imaging hypoxia signals from PpIX in a pancreatic cancer model, exhibiting contrast relative to surrounding normal oxygenated tissues. Additionally, tissue palpation amplifies the signal and provides intuitive temporal contrast based upon neoangiogenic blood flow differences.ConclusionsPpIX DF provides a mechanism for tumor contrast that could easily be translated to human use as an intrinsic contrast mechanism for oncologic surgical guidance.

Mechanism of Anti-Inflammatory Drugs in the Early Treatment of Oral Gingival Mucosa and Soft Tissue Trauma.

Traumatic tissue develops an uncontrolled inflammatory response that causes secondary damage to the injured tissue and other parts of the body. Therefore, preventing wound infection, reducing inflammatory response, and reducing secondary tissue damage are the keys to early treatment of tissue trauma. In the treatment of gingival soft tissue trauma, anti-inflammatory and analgesic drugs are reasonably selected according to the condition, which can effectively reduce inflammation, and they help periodontal tissue regeneration and healing. However, there are few studies on the mechanism of anti-inflammatory drugs in the early treatment of oral gingival mucosal soft tissue trauma, and the specific mechanism is unknown. Therefore, this paper explored the mechanism of anti-inflammatory drugs in the early treatment of oral gingival mucosa and soft tissue trauma through experiments, which provided theoretical support for the clinical treatment of gingival mucosa and soft tissue trauma repair. In this paper, two anti-inflammatory drugs, levofloxacin and metronidazole, were selected to measure their release properties in vitro and in vivo. Then, the white-eared rabbits were treated with gingival wound treatment experiments, and the physiological characteristics, intratissue pressure, tissue partial pressure of oxygen, IL-6 content, and PGE2 content were determined at each postinjury period, and the mechanism of action of anti-inflammatory drugs was determined. Research results have shown that anti-inflammatory drugs can significantly inhibit the content of IL-6 and PGE2 in gingival soft tissue after injury, reduce the local inflammatory response, and accelerate tissue healing.

The imaging of the hypoxic microenvironment in tumorous tissue using PET/CT and PET/MRI

Tissue hypoxia becomes the driver of the micro-environmental transformation of the malignant tumorous tissue in majority of solid tumors. Even more, during the development of solid tumors, a large amount of nutrients is consumed due to rapid proliferation of tumor cells. The way of use of nutrients could be assessed using the probes during positron emission tomography (PET), the most frequent is the use of 18F-fluorodeoxyglucose (18F-FDG) demonstrating the turn-over of glucose exploitation in a manner of Warburg phenomenon. Even tumor cells can undergo metabolic reprogramming by changing the expression of glycolysis-related proteins, development of hypoxic condition increases glucose uptake to promote their growth. The hypoxic conditions are stimulation also the development of drug and/or radiation resistance, thus, the identification of the hypoxic tissue could play an important role in therapy planning. The process that enables use of hypoxia specific PET radiopharmaceutical starts when it enters cell by passive diffusion. Intracellularly, a model substance - 18F-fluoromisonidazol (18F-FMISO) is reduced by nitroreductase enzymes to become trapped in cells within reduced tissue oxygen partial pressure. The identification of the hypoxic tissue aids to plan the target to radiotherapy in squamous cell carcinomas of head and neck or cervical carcinoma, when 18F-FMISO-PET/CT is used as a planning procedure for a target volume, while 18F-FDG-PET/MRI is being the local and whole body staging procedure. Hypoxia imaging helps to identify the high-grade component of an astrocytic tumor before stereotactic biopsy.