Application of CT in the investigation of angiogenesis in oncology.
Explore the source record for details and available documents.
Contrast Media↗
Biomedical subjects
K A Miles
Publications and source records attributed to K A Miles.
Assessment of quantitative computed tomographic cerebral perfusion imaging with H2(15)O positron emission tomography.
Assessment of quantitative cerebral blood flow on a conventional fast CT machine without the use of specialized equipment may be valuable in the investigation of acute stroke and head injury. We aimed to compare a single slice CT perfusion sequence with H2(15)O positron emission tomography using the sagittal sinus as an input function, a method that avoids unnecessary orbital irradiation. Eight patients were studied, two patients with gliomas, and six with arteriovenous malformations. The dynamic CT perfusion sequence was performed by acquiring the same 10 mm slice 10 times over 30 sec during a 50 ml bolus of intravenous contrast medium given at a rate of 7.5 ml sec-1 using a power injector. The CT perfusion studies were completed without complication. Co-registration was sub-optimal in one patient. Overall the correlation between the two methodologies was encouraging with an average r2 value of 0.524 for individual analyses. When two patients with high flow arteriovenous malformations were excluded the average r2 value increased to 0.640. The results of this CT perfusion methodology are encouraging. Having shown its feasibility, further studies in conditions with lower rates of cerebral blood flow are warranted.
Adult↗
Blood-brain barrier and blood volume imaging of cerebral glioma using functional CT: a pictorial review.
We present five cases of cerebral glioma that illustrate the benefit of functional CT imaging of blood-brain barrier permeability and cerebral blood volume. Functional CT uses Patlak analysis of a single location dynamic sequence to extract physiological information that is useful clinically in the assessment of cerebral gliomas. Functional CT offers distinct advantages over other functional modalities, including clearer delineation of tumour, tumour grading, measurement of tumour activity and monitoring response to therapy.
Aged↗
Tumour angiogenesis and its relation to contrast enhancement on computed tomography: a review.
Angiogenesis describes the formation of new blood vessels within tumours. The process is essential for tumour growth and metastasis. The development of new vessels leads to physiological changes, specifically increased perfusion, blood volume and capillary permeability, that alter contrast enhancement during computed tomography (CT). Functional CT techniques that quantify these physiological changes can provide greater insight into how angiogenesis alters contrast enhancement in routine practice and also serve as diagnostic tools in their own right. The functional information obtained can aid with tissue characterisation, such as type or grade of tumour, improve the detection of hepatic metastases, produce clearer delineation of tumours with benefits for radiotherapy planning and biopsy, and provide prognostic information. By providing a marker for tumour angiogenesis, quantitative contrast enhanced CT can improve the diagnostic assessment of patients with cancer.
Contrast Media↗
Hepatic metastases: the value of quantitative assessment of contrast enhancement on computed tomography.
OBJECTIVE: Occult and overt hepatic metastases have been the target of research in an effort to improve detection and characterisation of cancer spread and, consequently, guidance of treatment. This paper aims to illustrate the value of two quantitative techniques for assessing contrast enhancement during CT in the detection of hepatic metastases. It outlines the applications to which they can be put, and the ease of incorporation into current protocols. METHODS AND MATERIAL: The first technique, perfusion CT, uses a single location dynamic CT sequence to obtain time attenuation data whilst a short, high concentration IV bolus of contrast passes through the abdominal vasculature. Quantitative hepatic arterial and portal values are calculated, along with a perfusion image map. The second technique uses densitometric analysis during a modified contrast enhanced dual-phase liver CT examination. Semi-quantitative values are calculated from the images obtained at the 25 and 40 s times. RESULTS: Both perfusion CT and densitometric analysis have been to shown to differentiate between normal and tumour-bearing liver as defined by structural CT. Hepatic metastases are associated with increased arterial perfusion and arterial phase enhancement. Increased arterial phase enhancement on densitometric analysis in the absence of overt lesions heralds the onset of visible metastases in the liver in the ensuing 18 months. Perfusion CT has also demonstrated a correlation between high arterial perfusion around a visible metastasis and increased survival. CONCLUSION: Both techniques can provide more information than is available from conventional enhanced CT scans alone. An algorithm for the clinical application of perfusion CT is proposed. The ease with which these quantitative techniques can be performed and the extra information they provide could lead to improved staging of cancer and more appropriate patient management.
Contrast Media↗
A new non-invasive test for the detection of compartment syndromes.
Chronic exertional compartment syndrome (CECS) is currently diagnosed using invasive pressure measurements. We report the use of 99Tcm-methoxyisobutyl isonitrile (99Tcm-MIBI) scintigraphy as a new non-invasive method of diagnosis. Forty-six patients with suspected chronic compartment syndrome underwent graded treadmill exercise to reproduce the presenting symptoms. At peak exercise, 300 MBq of 99Tcm-MIBI were injected intravenously. Subsequent cross-sectional imaging provided by emission tomography demonstrated regional abnormalities in muscle perfusion in the calf. A repeat study was performed at rest the following day. All patients in whom there was a strong clinical suspicion of CECS were considered for invasive pressure measurements. Statistical analysis of the results for investigation of CECS using 99Tcm-MIBI versus pressure studies gave P = 0.06. A comparison of 99Tcm-MIBI versus outcome gave P < 0.0001. The sensitivity was 80% and the specificity 97% for 99Tcm-MIBI studies based on outcome. The positive predictive value was 89% and the negative predictive value 94%. Thus 99Tcm-MIBI can detect compartment syndromes with good positive and negative predictive values. It is relatively simple, cheap and less invasive than pressure measurements. This technique shows promise in the diagnosis of CECS.
Blood Pressure↗
CT derived Patlak images of the human kidney.
This study aimed to produce Patlak images of the kidney from dynamic CT data and to determine whether such images are substantially affected by fluid movement between renal tubular segments. Renal permeability was measured in 31 kidneys by applying Patlak analysis to time-density data from kidney and aorta during dynamic CT. Permeability parameters were correlated against plasma urea. The renal region (cortex or medulla) with the greatest permeability was determined from parametric images generated using pixel by pixel analysis. The mean value for whole kidney permeability was 517.5 microliters min-1 ml-1. A correlation was found between whole kidney permeability and plasma urea (p < 0.01). Permeability values were highest in the renal medulla in 24 (77%) kidneys. The higher medullary values of permeability are artefactual, resulting from movement of fluid and contrast medium between cortex and medulla. Although Patlak images do not reflect true intrarenal permeability values, the apparent medullary permeability may provide diagnostically useful information about the concentrating ability of the kidney. CT measurements of whole kidney permeability reflect filtration function but the apparent intrarenal variations in permeability will result in measurement errors dependent upon the relative amounts of renal cortex and medulla included in the CT slice studied.
Adolescent↗
Blood-brain barrier and blood volume imaging of cerebral glioma using functional CT: a pictorial review.
Five cases of cerebral glioma are presented here that illustrate the benefit of functional CT imaging of blood-brain barrier permeability and cerebral blood volume. Functional CT uses Patlak analysis of a single location dynamic sequence to extract physiological information that is useful clinically i the assessment of cerebral gliomas. Functional CT offers distinct advantages over other functional modalities including clearer delineation of tumour, tumour grading, measurement of tumour activity and monitoring response to therapy.
Aged↗
Ideal contrast medium bolus for perfusion measurement in dynamic lung CT.
Explore the source record for details and available documents.
Contrast Media↗
In vivo assessment of neovascularization of liver metastases using perfusion CT.
Neovascularization of tumours produces a high microvessel density. Although diagnostic imaging is unable to visualize microvessels directly, it is possible to demonstrate associated changes in tissue perfusion. The aim of this study was to use the quantitative functional information and high spatial resolution of perfusion computed tomography to study neovascularization of hepatic metastases. Perfusion CT was performed in 13 patients with hepatic metastases from various primary tumours. Arterial perfusion was measured in the metastasis; both arterial and portal perfusion were measured in a small rim of liver tissue immediately adjacent to the metastasis. Perfusion measurements were correlated against survival of the patient in nine cases. Arterial perfusion was increased above normal values, both in the metastasis (median: 0.62 ml min-1 ml-1; range: 0.26-3.05 ml min-1 ml-1) and in the adjacent liver (median: 0.51 ml min-1 ml-1; range: 0.14-1.60 ml min-1 ml-1). Portal perfusion of adjacent liver was highly variable (median: 0.30 ml min-1 ml-1; range: 0.05-1.85 ml min-1 ml-1). Arterial perfusion was positively correlated with portal perfusion within liver tissue adjacent to metastases (p < 0.05, r = 0.58), a reversal of the normal situation. Survival of the patient correlated with arterial perfusion within the metastasis (p < 0.05, r = 0.69) but more closely with arterial perfusion in the adjacent liver (p < 0.02, r = 0.78). In conclusion, alterations in perfusion within metastases and adjacent liver are in accordance with the histological features of neovascularization. Perfusion CT offers a method for studying neovascularization in the living patient and offers prognostic information.
Carcinoma↗
Altered perfusion adjacent to hepatic metastases.
Explore the source record for details and available documents.
Humans↗
How does gated SPET alter reporting of myocardial perfusion studies?
Gated single photon emission tomography (SPET) during myocardial perfusion scintigraphy has been proposed as a method for distinguishing artefact from myocardial infarction and for assessing myocardial viability. This study describes the alterations in the specialist report produced when gated SPET was included in 50 consecutive myocardial perfusion studies. Diagnostic confidence was scored following an initial assessment using non-gated images alone and then re-scored after a review of the gated SPET data. The change in diagnostic confidence and the presence of additional information about myocardial viability were recorded. These were correlated with various clinical parameters, including a subjective assessment of the likelihood of an attenuation artefact as determined by clinical examination prior to imaging. Diagnostic confidence was altered by identification of attenuation artefacts in 11 (22%) patients, moving towards normality in all cases. In three of these (6%), the change was sufficient to make coronary angiography potentially unnecessary. Attenuation artefacts were equally common in men and women. Whereas breast attenuation artefacts could be anticipated from clinical examination, this was not so far diaphragmatic attenuation artefacts, which occurred most commonly in men under 55 years of age. The gated study provided additional information about myocardial viability in 13 (26%) patients, most commonly those referred following myocardial infarction. In view of the frequent alterations in the specialist's final report and the difficulties in pre-selecting patients likely to benefit from the technique, the use of gated SPET can be justified for all patients undergoing sestamibi myocardial perfusion imaging.
Adult↗
Colorectal cancer: diagnostic potential of CT measurements of hepatic perfusion and implications for contrast enhancement protocols.
PURPOSE: To assess changes in hepatic perfusion in patients with colorectal cancer with computed tomography (CT), diagnostic potential of CT perfusion measurements, and implications for design of contrast enhancement protocols. MATERIALS AND METHODS: In 27 patients with colorectal cancer, arterial and portal perfusion were calculated from temporal changes in attenuation after intravenous administration of contrast material. RESULTS: Arterial perfusion greater than 0.25 mL/min/mL was seen in nine (82%) of the 11 patients with overt metastases versus six (38%) of the 16 patients with no overt metastases (P < .05). Portal perfusion of 0.25 mL/min/mL or less was found in five (46%) of the patients with overt metastases versus three (19%) of the patients with no overt metastases. Follow-up imaging showed progressive metastatic disease in three patients, all of whom had decreased portal perfusion. CONCLUSION: Increased arterial perfusion appears to be an indicator of liver metastases, whereas reduced portal perfusion may indicate progressive disease. Contrast enhancement protocols that are based on experience with normal livers may not be optimal for patients with metastases.
Aged↗
CT measurements of capillary permeability within nodal masses: a potential technique for assessing the activity of lymphoma.
Analysis of time-attenuation data has enabled CT to measure capillary permeability within the brain and kidney. As yet, such techniques have not been applied to nodal masses in patients with lymphoma. Tumour angiogenesis is known to produce capillaries that exhibit increased permeability and CT measurements of permeability could therefore potentially provide a marker of tumour viability. This study aims to determine the feasibility and limitations of CT measurement of capillary permeability within lymphoma nodal masses. Six patients with biopsy proven lymphoma have been studied. Time-attenuation curves from the aorta and nodal mass were generated from a single-location dynamic sequence of images acquired over 3 min following an intravenous bolus of iopamidol. A nuclear medicine data processing technique, Patlak analysis, was used to calculate capillary permeability and blood volume within the nodal mass. Renal blood vessel permeability was also determined in four patients. Median lymph node permeability to iopamidol was 88.5 microliters min-1 ml-1 (range 36.4-198.5 microliters min-1 ml-1). The correlation coefficient of the linear fit for the Patlak analysis ranged from 0.74 to 0.95 and was greater than 0.9 for regions of interest of 150 pixels or more (256 x 256 matrix). The values for renal permeability (442 microliters min-1 ml-1; range: 349-589 microliters min-1 ml-1) were comparable to those previously reported. Functional images of permeability were also obtained. The study has confirmed the feasibility of CT measurements of capillary permeability within nodal masses. The technique combines anatomical imaging and functional information within one examination and has potential application in monitoring the response of lymphoma to therapy.
Adult↗
Neuroradiological findings in primary progressive aphasia: CT MRI and cerebral perfusion SPECT.
Primary progressive aphasia (PPA) is defined as progressive decline in language for 2 or more years with preservation of activities of daily living and general cognitive functions. Whereas the clinical features of this syndrome have been well documented, the neuroradiological findings have not been studied systematically. We studied 13 patients with PPA retrospectively: 10 underwent CT, 12 MRI and 12 cerebral perfusion studies using 99mTc-HMPAO SPECT.CT and MR images were scored for focal atrophy by two independent assessors. Initial qualitative assessment of SPECT images was confirmed by quantitative analysis. CT was normal in 5 patients. Focal atrophy, affecting predominantly the left temporal lobe, was seen in 4 of 10 patients on CT, and 10 of 12 on MRI. Atrophy was localised primarily to the superior and middle temporal gyri on MRI. All 12 patients who underwent SPECT had unilateral temporal lobe perfusion defects, in 2 patients of whom MRI was normal. CT is relatively insensitive to focal abnormalities in PPA; MRI and SPECT are the imaging modalities of choice. MRI allows accurate, specific localisation of atrophy within the temporal neocortex. SPECT may reveal a functional decrease in cerebral perfusion prior to establishment of structural change.
Adult↗
Leucocyte scintigraphy or computed tomography for the febrile post-operative patient?
OBJECTIVE: The optimal initial investigation for the post-operative patient with suspected occult intra-abdominal sepsis is controversial, although the diagnostic accuracy of a variety of techniques is known. Our objective is to determine which investigation has the greatest positive effect on patient management. METHODS AND PATIENTS: We reviewed 67 consecutive post-operative patients investigated for suspected occult sepsis retrospectively and analysed the sequence of investigations required to achieve the diagnosis depending on the choice of initial investigation, and the interval between between initiating investigations and performing definitive percutaneous drainage. RESULTS: Forty patients had scintigraphy as the initial investigation and 21 of these went on to require CT. None of the 27 patients who had CT as the initial investigation required any other imaging (chi 2 = 20.6, P < 0.0001) and appropriate percutaneous drainage was offered immediately. Conversely, the average interval to drainage in those who had scintigraphy first was 3.1 days. Fourteen out of 20 patients (70%) who had scintigraphy as the initial investigation following recent surgery, and 7 of 20 (35%) following old surgery, needed subsequent CT. None of the 20 and 7 patients in the recent and old surgery groups respectively who had CT initially required further imaging. CONCLUSION: Our results suggest recommending CT as the initial investigation in the early post-operative period as this will reduce the total number of investigations required to achieve the diagnosis and the time to definitive drainage. In the late post-operative period, scintigraphy will resolve the majority of problems.
Abdomen↗
Dynamic contrast enhanced MR.
Explore the source record for details and available documents.
Contrast Media↗
Longitudinal distribution of O3 absorption in the lung: gender differences and intersubject variability.
Because the National Ambient Air Quality Standard for ozone (O3) is intended to protect the most sensitive individuals in the general population, it is necessary to identify sources of intersubject variation in the exposure-dose-response cascade. We hypothesize that differences in lung anatomy can modulate exposure-dose relationships between individuals, and this results in differences between their responsiveness to O3 at a fixed exposure condition. During quiet breathing, the conducting airways remove the majority of inhaled O3, so the volume of this region should have an important impact on O3 dose distribution. Employing the bolus inhalation method, we measured the distribution of O3 absorption with respect to penetration volume (Vp), and using the Fowler single-breath N2 washout method, we determined the dead space volume (VD) in the lungs of 10 men and 10 women at a fixed respiratory flow of 250 ml/s. On average, the women absorbed O3 at smaller Vp than the men, and the women had smaller VD than the men. When expressed in terms of Vp/VD, the absorption distribution of the men and women was indistinguishable. Moreover, an interpretation of the O3 distribution in terms of an intrinsic mass transfer parameter (Ka) indicated that differences between the O3 dosimetry in all subjects, whether men or women, could be explained by a unique correlation with anatomic dead space: Ka (in s-1) = 610 VD-105 (in ml). Application of this result to measurements of O3 exposure response indicated that previously reported gender differences may be due to a failure in properly accounting for tissue surface within the conducting airways.
Absorption↗