Thermal images of somatic sensory cortex obtained through the skull of rat and gerbil

Brugge, John F.; Poon, P.W.F.; So, Albert; Wu, Bangxian; Chan, F.H.Y.; Lam, F.K.

doi:10.1007/bf00241352

Cited by 11 publications

(10 citation statements)

References 28 publications

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“…The stimulation-induced increases in spiking frequency of a small neuronal ensemble (n) in the ROI of the contralateral somatosensory cortex were colocalized with increases in BOLD, CBV, CBF, CMR O 2 , and T t ( Table 1). This multiparametric approach excluded a closed-skull technique, for example, as used by Brugge et al (1995), to selectively measure brain temperature. To account for convective heat loss through the small opening in the skull, we introduced the term Q e (see Theory), which was also measured (see Materials and methods).…”

Section: Resultsmentioning

confidence: 99%

Regional Temperature Changes in the Brain during Somatosensory Stimulation

Trübel

Sacolick

Hyder

2005

J Cereb Blood Flow Metab

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Time-dependent variations in the brain temperature (Tt) are likely to be caused by fluctuations of cerebral blood flow (CBF) and cerebral metabolic rate of oxidative consumption (CMRO2) both of which are seemingly coupled to alterations in neuronal activity. We combined magnetic resonance, optical imaging, temperature sensing, and electrophysiologic methods in alpha-chloralose anesthetized rats to obtain multimodal measurements during forepaw stimulation. Localized changes in neuronal activity were colocalized with regional increases in Tt (by approximately 0.2%), CBF (by approximately 95%), and CMRO2 (by approximately 73%). The time-to-peak for Tt (42+/-11 secs) was significantly longer than those for CBF and CMRO2 (5+/-2 and 18+/-4 secs, respectively) with a 2-min stimulation. Net heat in the region of interest (ROI) was modeled as being dependent on the sum of heats attributed to changes in CMRO2 (Qm) and CBF (Qf) as well as conductive heat loss from the ROI to neighboring regions (Qc) and to the environment (Qe). Although tissue cooling because of Qf and Qc can occur and are enhanced during activation, the net increase in Tt corresponded to a large rise in Qm, whereas effects of Qe can be ignored. The results show that Tt increases slowly (by approximately 0.1 degrees C) during physiologic stimulation in alpha-chloralose anesthetized rats. Because the potential cooling effect of CBF depends on the temperature of blood entering the brain, Tt is mainly affected by CMRO2 during functional challenges. Implications of these findings for functional studies in awake humans and temperature regulation are discussed.

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Section: Resultsmentioning

confidence: 99%

Regional Temperature Changes in the Brain during Somatosensory Stimulation

Trübel

Sacolick

Hyder

2005

J Cereb Blood Flow Metab

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“…Because lanthanide monomers like TmDOTP 5− can reach brain’s interstitial space (23), they report extracellular pH. Temperature and/or pH sensitivities of these paramagnetic complexes are notably better than with other diamagnetic MRS methods (3, 4, 24-30). …”

Section: Discussionmentioning

confidence: 99%

Characterization of a lanthanide complex encapsulated with MRI contrast agents into liposomes for biosensor imaging of redundant deviation in shifts (BIRDS)

et al. 2014

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Purposely-designed magnetic resonance imaging (MRI) probes encapsulated in liposomes, which alter contrast by their paramagnetic effect on longitudinal (T1) and transverse (T2) relaxation times of tissue water, hold promise for molecular imaging. However a challenge with liposomal MRI probes that are solely dependent on enhancement of water relaxation is lack of specific molecular readouts, especially in strong paramagnetic environments, thereby reducing the potential for monitoring disease treatment (e.g., cancer) beyond the generated MRI contrast. Previously it has been shown that molecular imaging with magnetic resonance is also possible by detecting the signal of non-exchangeable protons emanating from paramagnetic lanthanide complexes themselves (e.g., TmDOTP5−, which is a Tm3+-containing biosensor based on a macrocyclic chelate 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrakis(methylene phosphonate), DOTP5−) with a method called Biosensor Imaging of Redundant Deviation in Shifts (BIRDS). Here we show that BIRDS is useful for molecular imaging with probes like TmDOTP5− even when they are encapsulated inside liposomes with ultra-strong T1 and T2 contrast agents (e.g., Magnevist and Molday ION, respectively). We demonstrate that molecular readouts like pH and temperature determined from probes like TmDOTP5− are resilient, because sensitivity of the chemical shifts to the probe’s environment is not compromised by presence of other paramagnetic agents contained within the same nanocarrier milieu. Because high liposomal encapsulation efficiency allows for robust MRI contrast and signal amplification for BIRDS, nanoengineered liposomal probes containing both monomers like TmDOTP5− and paramagnetic contrast agents could allow high spatial resolution imaging of disease diagnosis (with MRI) and status monitoring (with BIRDS).

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“…1,2 Accordingly, in vivo temperature measurements, also called thermometry, have been developed that are based on either invasive 3 or non-invasive 4 techniques. While invasive methods utilize thermocouple wires 5,6 or thermistors, 3 non-invasive techniques include infrared (IR) spectroscopy 7 and Magnetic Resonance (MR) methods, including MRI contrast agents based on paramagnetic metal ion complexes. 8,9 Since the depth range of optical methods is usually limited to 4 mm, the thermometry applications of IR are usually limited to probing tissue close to the exterior or require indwelling catheters containing fiber-optic probes.…”

Section: Introductionmentioning

confidence: 99%

Six-coordinate Iron(II) and Cobalt(II) paraSHIFT Agents for Measuring Temperature by Magnetic Resonance Spectroscopy

et al. 2015

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Paramagnetic Fe(II) and Co(II) complexes are utilized as the first transition metal examples of 1H NMR shift agents (paraSHIFT) for thermometry applications using Magnetic Resonance Spectroscopy (MRS). The coordinating ligands consist of TACN (1,4,7-triazacyclononane) and CYCLEN (1,4,7,10-tetraazacyclododecane) azamacrocycles appended with 6-methyl-2-picolyl groups, denoted as MPT and TMPC, respectively. 1H NMR spectra of the MPT- and TMPC-based Fe(II) and Co(II) complexes demonstrate narrow and highly shifted resonances that are dispersed as broadly as 440 ppm. The six-coordinate complex cations, [M(MPT)]2+ and [M(TMPC)]2+, vary from distorted octahedral to distorted trigonal prismatic geometries, respectively, and also demonstrate that 6-methyl-2-picolyl pendents control the rigidity of these complexes. Analyses of the 1H NMR chemical shifts, integrated intensities, line widths, the distances obtained from X-ray diffraction measurements and longitudinal relaxation time (T1) values allow for the partial assignment of proton resonances of the [M(MPT)]2+ complexes. Nine and six equivalent methyl protons of [M(MPT)]2+ and [M(TMPC)]2+, respectively, produce three-fold higher 1H NMR intensities compared to other paramagnetically shifted proton resonances. Among all four complexes, the methyl proton resonances of [Fe(TMPC)]2+ and [Co(TMPC)]2+ at −49.3 ppm and −113.7 ppm (37 °C) demonstrate the greatest temperature dependent coefficients (CT) of 0.23 ppm/°C and 0.52 ppm/°C, respectively. The methyl groups of these two complexes both produce normalized values of |CT|/FWHM = 0.30 °C−1, where FWHM is full width at half maximum (Hz) of proton resonances. The T1 values of the highly shifted methyl protons are in the range of 0.37–2.4 ms, allowing rapid acquisition of spectroscopic data. These complexes are kinetically inert over a wide range of pH values (5.6–8.6), as well as in the presence of serum albumin and biologically relevant cations and anions. The combination of large hyperfine shifts, large temperature sensitivity, increased signal-to-noise ratio and short T1 values suggests that these complexes, in particular the TMPC-based complexes, show promise as paraSHIFT agents for thermometry.

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Thermal images of somatic sensory cortex obtained through the skull of rat and gerbil

Cited by 11 publications

References 28 publications

Regional Temperature Changes in the Brain during Somatosensory Stimulation

Regional Temperature Changes in the Brain during Somatosensory Stimulation

Characterization of a lanthanide complex encapsulated with MRI contrast agents into liposomes for biosensor imaging of redundant deviation in shifts (BIRDS)

Six-coordinate Iron(II) and Cobalt(II) paraSHIFT Agents for Measuring Temperature by Magnetic Resonance Spectroscopy

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