Phase- and size-adjusted CT cut-off for differentiating neoplastic lesions from normal colon in contrast-enhanced CT colonography

A computed tomography (CT) cut-off for differentiating neoplastic lesions (polyps/carcinoma) from normal colon in contrast-enhanced CT colonography (CTC) relating to the contrast phase and lesion size is determined. CT values of 64 colonic lesions (27 polyps <10 mm, 13 polyps 10 mm, 24 carcinomas) were determined by region-of-interest (ROI) measurements in 38 patients who underwent contrast-enhanced CTC. In addition, the height (H) of the colonic lesions was measured in CT. CT values were also measured in the aorta (A), superior mesenteric vein (V) and colonic wall. The contrast phase was defined by using x as a weighting factor for describing the different contrast phases ranging from the pure arterial phase (x=1) over the intermediate phases (x=0.9–0.1) to the pure venous phase (x=0). The CT values of the lesions were correlated with their height (H), the different phases ( ) and the ratio . The CT cut-off was linearly adjusted to the imaged contrast phase and height of the lesion by the line . The slope m was determined by linear regression in the correlation ( ) and the Y-intercept y₀ by the minimal shift of the line needed to maximize the accuracy of separating the colonic wall from the lesions. The CT value of the lesions correlated best with the intermediate phase: 0.4A + 0.6V (r=0.8 for polyps 10 mm, r=0.6 for carcinomas, r=0.4 for polyps <10 mm). The accuracy in the differentiation between lesions and normal colonic wall increased with the height implemented as divisor, reached 91% and was obtained by the dynamic cut-off described by the formula: . The CT value of colonic polyps or carcinomas can be increased extrinsically by scanning in the phase in which 0.4A + 0.6V reaches its maximum. Differentiating lesions from normal colon based on CT values is possible in contrast-enhanced CTC and improves when the cut-off is adjusted (normalized) to the contrast phase and lesion size.     

Determination of intestinal radiocalcium absorption by double tracer method with 85Sr i.v.

The intestinal absorption of radiocalcium can be estimated on the basis of serum radioactivity after an oral administration of ⁴⁷Ca (o.S(t)) and intravenous application of ⁸⁵Sr. High linear correlation (r=0.94) between the true absorption of ⁴⁷Ca and the absorption calculated from radioactivity of serum, was found in 42 subjects. The true absorption of ⁴⁷Ca was estimated by following up serum and faeces radioactivity during 7 days after oral administration of radiocalcium. Results of the radiocalcium absorption rate for a group of control subjects are also presented. The radiocalcium absorption rate (i(x)) is calculated by means of the following integral: $$\int\limits_{\text{0}}^H {i(x)dx = \frac{{\sin (IIb)}}{{II}}} (100/S_{1{\text{Ca}}} )\int\limits_{\text{0}}^H {{\text{o}}{\text{.S}}} (t)(H - t)^{b - 1} dt.$$ In order to solve this integral one should know numerical values of constants b and S _1Ca which determine the serum specific activity after i.v. application of ⁴⁷Ca, according to the power function: $${\text{i}}{\text{.v}}{\text{. }}S(t) = S_{{\text{ }}1{\text{Ca}}} t^{ - b} $$ The numerical value of the constant b can be estimated by following serum radioactivity o.S(t) between 6 and 24 h after an oral administration of ⁴⁷Ca. Because of the high linear correlation between the S ₁ constants obtained by ⁴⁷Ca and that obtained by ⁸⁵Sr, the value of the S _1Ca constant was estimated by following serum radioactivity of ⁸⁵Sr given intravenously. Determination of ⁴⁷Ca intestinal absorption by double-tracer technique with ⁸⁵Sr i.v. is quick and accurate.     

A method to quantitate cerebral blood flow using a rotating gamma camera and iodine-123 iodoamphetamine with one blood sampling

A method has been developed to quantitate regional cerebral blood blow (rCBF) using iodine-123-labelled N-isopropyl-p-iodoamphetamine (IMP). This technique requires only two single-photon emission tomography (SPET) scans and one blood sample. Based on a two-compartment model, radioactivity concentrations in the brain for each scan time (early: t _e ; delayed: td) aredescribed as: % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4qamaaBa% aaleaacaWG0baabeaakmaabmaabaGaamiDamaaBaaaleaacaWGLbaa% beaaaOGaayjkaiaawMcaaiabg2da9iaadAgacqWIpM+zcaWGdbWaaS% baaSqaaiaadggaaeqaaOWaaeWaaeaacaWG0bWaaSbaaSqaaiaadwga% aeqaaaGccaGLOaGaayzkaaGaey4LIqSaamyzamaalaaabaGaamOzaa% qaaiaadAfadaWgaaWcbaGaamizaaqabaaaaOGaamiDamaaBaaaleaa% caWGLbaabeaaaaa!4D64!\[C_t \left( {t_e } \right) = fC_a \left( {t_e } \right) \otimes e\frac{f}{{V_d }}t_e \] and % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn% hiov2DGi1BTfMBaeXatLxBI9gBaerbd9wDYLwzYbItLDharqqtubsr% 4rNCHbGeaGqiVu0Je9sqqrpepC0xbbL8F4rqqrFfpeea0xe9Lq-Jc9% vqaqpepm0xbba9pwe9Q8fs0-yqaqpepae9pg0FirpepeKkFr0xfr-x% fr-xb9adbaqaaeGaciGaaiaabeqaamaabaabaaGcbaGaam4qamaaBa% aaleaacaWG0baabeaakmaabmaabaGaamiDamaaBaaaleaacaWGKbaa% beaaaOGaayjkaiaawMcaaiabg2da9iaadAgacqWIpM+zcaWGdbWaaS% baaSqaaiaadggaaeqaaOWaaeWaaeaacaWG0bWaaSbaaSqaaiaadsga% aeqaaaGccaGLOaGaayzkaaGaey4LIqSaamyzamaalaaabaGaamOzaa% qaaiaadAfadaWgaaWcbaGaamizaaqabaaaaOGaamiDamaaBaaaleaa% caWGKbaabeaaaaa!4D61!\[C_t \left( {t_d } \right) = fC_a \left( {t_d } \right) \otimes e\frac{f}{{V_d }}t_d \] respectively, where denotes the convolution integral; C _a (t), the arterial input function; f rCBF; and V _d , the regional distribution volume of IMP. Calculation of the ratio of the above two equations and a table look-up procedure yield a unique pair of rCBF and V _d for each region of interest (ROI). A standard input function has been generated by combining the input functions from 12 independent studies prior to this work to avoid frequent arterial blood sampling, and one blood sample is taken at 10 min following IMP administration for calibration of the standard arterial input function. This calibration time was determined such that the integration of the first 40 min of the calibrated, combined input function agreed best with those from 12 individual input functions (the difference was 5.3% on average). This method was applied to eight subjects (two normals and six patients with cerebral infarction), and yielded rCBF values which agreed well with those obtained by a positron emission tomography H₂ ¹⁵O autoradiography method. This method was also found to provide rCBF values that were consistent with those obtained by the non-linear least squares fitting technique and those obtained by conventional microsphere model analysis. The optimum SPET scan times were found to be 40 and 180 min for the early and delayed scans, respectively. These scan times allow the use of a conventional rotating gamma camera for clinical purposes. V _d values ranged between 10 and 40 ml/g depending on the pathological condition, thereby suggesting the importance of measuring V _d for each ROI. In conclusion, optimization of the blood sampling time and the scanning time enabled quantitative measurement of rCBF with two SPET scans and one blood sample.     

Predictive value of [<Superscript>18</Superscript>F]-fluoride PET for monitoring bone remodeling in patients with orthopedic conditions treated with a Taylor spatial frame

Purpose

The Taylor Spatial Frame (TSF) is used to correct orthopedic conditions such as correction osteotomies in delayed fracture healing and pseudarthrosis. Long-term TSF-treatments are common and may lead to complications. Current conventional radiological methods are often unsatisfactory for therapy monitoring. Hence, an imaging technique capable of quantifying bone healing progression would be advantageous.

Methods

A cohort of 24 patients with different orthopedic conditions, pseudarthrosis (n?=?10), deformities subjected to correction osteotomy (n?=?9), and fracture (n?=?5) underwent dynamic [¹⁸F]-fluoride (Na¹⁸F) PET/CT at 8 weeks and 4 months, respectively, after application of a TSF. Parametric images, corresponding to the net transport rate of [¹⁸F]-fluoride from plasma to bone, K _i were calculated. The ratio of the maximum K _i at PET scan 2 and 1 (\( {\overline{K}}_{i, \max } \)) as well as the ratio of the maximum Standard Uptake Value at PET scan 2 and 1 (\( {\overline{SUV}}_{\max } \)) were calculated for each individual. Different treatment end-points were scored, and the overall treatment outcome score was compared with the osteoblastic activity progression as scored with \( {\overline{K}}_{i, \max } \) or \( {\overline{SUV}}_{\max } \).

Results

\( {\overline{K}}_{i, \max } \) and \( {\overline{SUV}}_{\max } \) were not correlated within each orthopedic group (p?>?0.1 for all groups), nor for the pooled population (p?=?0.12). The distribution of \( {\overline{K}}_{i, \max } \) was found significantly different among the different orthopedic groups (p?=?0.0046) -also for \( {\overline{SUV}}_{\max } \) (p?=?0.022). The positive and negative treatment predictive values for \( {\overline{K}}_{i, \max } \) were 66.7 % and 77.8 %, respectively. Corresponding values for \( {\overline{SUV}}_{\max } \) were 25 % and 33.3 %

Conclusions

The \( {\overline{K}}_{i, \max } \) obtained from dynamic [¹⁸F]-fluoride-PET imaging is a promising predictive factor to evaluate changes in bone healing in response to TSF treatment.

     

Differentiation of malignant and benign pulmonary nodules with first-pass dual-input perfusion CT

Objective

To assess diagnostic performance of dual-input CT perfusion for distinguishing malignant from benign solitary pulmonary nodules (SPNs).

Methods

Fifty-six consecutive subjects with SPNs underwent contrast-enhanced 320-row multidetector dynamic volume CT. The dual-input maximum slope CT perfusion analysis was employed to calculate the pulmonary flow (PF), bronchial flow (BF), and perfusion index $ \left( {\mathrm{PI},={{\mathrm{PF}} \left/ {{\left( {\mathrm{PF} + \mathrm{BF}} \right)}} \right.}} \right) $ . Differences in perfusion parameters between malignant and benign tumours were assessed with histopathological diagnosis as the gold standard. Diagnostic value of the perfusion parameters was calculated using the receiver-operating characteristic (ROC) curve analysis.

Results

Amongst 56 SPNs, statistically significant differences in all three perfusion parameters were revealed between malignant and benign tumours. The PI demonstrated the biggest difference between malignancy and benignancy: 0.30?±?0.07 vs. 0.51?±?0.13 , P?<?0.001. The area under the PI ROC curve was 0.92, the largest of the three perfusion parameters, producing a sensitivity of 0.95, specificity of 0.83, positive likelihood ratio (+LR) of 5.59, and negative likelihood ratio (?LR) of 0.06 in identifying malignancy.

Conclusions

The PI derived from the dual-input maximum slope CT perfusion analysis is a valuable biomarker for identifying malignancy in SPNs. PI may be potentially useful for lung cancer treatment planning and forecasting the therapeutic effect of radiotherapy treatment.

Key Points

? Modern CT equipment offers assessment of vascular parameters of solitary pulmonary nodules (SPNs) ? Dual vascular supply was investigated to differentiate malignant from benign SPNs. ? Different dual vascular supply patterns were found in malignant and benign SPNs. ? The perfusion index is a useful biomarker for differentiate malignancy from benignancy.     

Scintigraphy in the clinical evaluation of disorders of mineral and skeletal metabolism in renal failure

In patients with renal bone disease skeletal and extra-skeletal abnormalities can be visualised using conventional bone scintigraphy. Some of these abnormalities are associated with characteristic scintigraphic appearances, which are reviewed in detail, and the possible mechanisms involved are discussed. Specific imaging with iodine 123 serum amyloid P component and iodine 131 ₂-microglobulin is also discussed in the diagnosis of ₂-microglobulin amyloidosis specific to patients on dialysis. In the light of available evidence, it appears that bone scintigraphy plays, so far, a limited role in the clinical evaluation of skeletal and extra-skeletal abnormalities in chronic renal failure. The potential role of bone scintigraphy in identifying patients with aluminium-related bone disease needs to be investigated further, and in this respect special attention must be given to the problem of high soft-tissue activity associated with impaired renal function. Timing haemodialysis sessions before scintigraphic imaging deserves wider recognition as it reduces high soft-tissue activity, thereby allowing bone uptake to be assessed more accurately. Specific imaging of amyloidosis resulting from ₂-microglobulin deposition is a promising technique, but the relative value of the two proposed radiopharmaceuticals needs further clarification.Offprint requests to: E.K.J. Pauwels     

Age estimation in children by measurement of open apices in teeth: an Indian formula

The aim of this paper is twofold: first, to evaluate an Indian sample by Cameriere’s European formula; and second, if this formula turns out to be unsuitable, to study a specific formula for Indian children. Orthopantomographs taken from 480 Indian children (227 girls and 253 boys) aged between 3 and 15 years were analyzed. Following the pilot study, subjects’ age was modeled as a function of gender (g), region of country (C), and morphological variables (predictors: x ₅, the distance between the inner sides of the open apex of the second premolar divided by the tooth length; s = x₁ + x₂ + x₃ + x₄ + x₅ + x₆ + x₇ s = x_{1} + x_{2} + x_{3} + x_{4} + x_{5} + x_{6} + x_{7} , sum of normalized open apices; N _0, the number of teeth with root development complete. Results showed that all these variables except gender and second premolar contributed significantly to the fit so that all were included in the regression model, yielding the following linear regression formula:

Identification of fetal hemoglobin and simultaneous estimation of bloodstain age by high-performance liquid chromatography

Summary A method using reverse-phase high-performance liquid chromatography (HPLC) for the identification of fetal hemoglobin (Hb F) and the simultaneous estimation of bloodstain age is described. Umbilical cord and neonatal bloodstains can be differentiated from adult stains by the presence of -globin chains which are characteristic of Hb F. With this method, cord and neonatal blood could be distinguished from adult blood in stains up to 32 weeks old. The age of the stain was estimated from the ratio of the peak area of the -globin chain to that of heme on the same chromatogram. The ratio decreased gradually with an increase in the age of the stain up to 20 weeks old. Studies performed at each time period revealed no significant difference in the ratios of cord and neonatal bloodstains or in the ratios of cord and adult stains. The regression equation calculated from the ratios (y) and the ages of stains in weeks (x) expressed logarithmically isy = 2.5758 – 0.2497 ln(x) and the coefficient of correlation is –0.7491 (n = 252,P < 0.001). The present method, having the advantages of simplicity, speed and sensitivity, should be of great value to forensic science.     

Changes in deviation of absorbed dose to water among users by chamber calibration shift

Purpose

The JSMP01 dosimetry protocol had adopted the provisional ⁶⁰Co calibration coefficient \(N_{{{\text{D,w,Q}}_{ 0} }}^{{}}\), namely, the product of exposure calibration coefficient N _C and conversion coefficient k _D,X. After that, the absorbed dose to water D _w standard was established, and the JSMP12 protocol adopted the \(N_{{{\text{D,w,Q}}_{ 0} }}^{{}}\) calibration. In this study, the influence of the calibration shift on the measurement of D _w among users was analyzed.

Materials and methods

The intercomparison of the D _w using an ionization chamber was annually performed by visiting related hospitals. Intercomparison results before and after the calibration shift were analyzed, the deviation of D _w among users was re-evaluated, and the cause of deviation was estimated.

Results

As a result, the stability of LINAC, calibration of the thermometer and barometer, and collection method of ion recombination were confirmed. The statistical significance of standard deviation of D _w was not observed, but that of difference of D _w among users was observed between N _C and \(N_{{{\text{D,w,Q}}_{ 0} }}^{{}}\) calibration.

Conclusion

Uncertainty due to chamber-to-chamber variation was reduced by the calibration shift, consequently reducing the uncertainty among users regarding D _w. The result also pointed out uncertainty might be reduced by accurate and detailed instructions on the setup of an ionization chamber.

     

Post-Dilatation Intravascular Brachytherapy Trials on Hypercholesterolemic Rabbits Using 32P-Phosphate Solutions in Angioplasty Balloons

Response of peripheral arteries to post-dilatation intravascular brachytherapy (IVBT) using ³²P liquid sources was studied in a rabbit model. The applied sources were angioplasty balloons filled with aqueous solutions of Na₂H³²PO₄, NaCl and iodinated contrast. Dose distribution was calibrated by thermoluminescence dosimetry. The uncertainty of in vitro determinations of the activity–dose dependence was ± 15–30%. The animal experiments were performed on rabbits with induced hypercholesterolemia. The ³²P sources were introduced into a randomly chosen (left or right) iliac artery, immediately after balloon injury. Due to the low specific activity of the applied sources, the estimated 7–49 Gy doses on the internal artery surface required 30–100 min irradiations. A symmetric, balloon-occluded but non-irradiated artery of the same animal served as control. Radiation effects were evaluated by comparing the thicknesses of various components of irradiated versus untreated artery walls of each animal. The treatment was well tolerated by the animals. The effects of various dose ranges could be distinguished although differences in individual biological reactions were large. Only the 49 Gy dose at zero distance (16 Gy at 1.0 mm from the balloon surface) reduced hypertrophy in every active layer of the artery wall. The cross-sectional intimal thicknesses after 7, 12, 38 and 49 Gy doses were 0.277, 0.219, 0.357 and 0.196 mm² respectively, versus 0.114, 0.155, 0.421 and 0.256 mm² in controls (p < 0.05). The lowest radiation dose on the intima induced the opposite effect. Edge intimal hyperplasia was not avoided, which agrees with other reports. The edge restenosis and the variability of individual response to identical treatment conditions must be considered as limitations of the post-dilatation IVBT method. Only application of highest irradiation doses was effective. The irradiation dose should be planned and calculated for adventitia.     

Todeszeitbestimmung auf der Basis simultaner Messung von Hirn- und Rektaltemperatur

Zusammenfassung Die Analyse der Daten an 21 Leichen simultan registrierter Hirn- und Rektaltemperaturkurven ergab hinsichtlich separater oder kombinierter Todeszeitberechnungen folgende Ergebnisse und Schlußfolgerungen:Im Bereich einer normierten Hirntemperatur (Q _H) 0,5Q _H<1,0 (etwa bis 6,5 hpm) führt die alleinige Verwendung der Hirntemperatur zu den präzisesten Todeszeitrückrechnungen (Standardabweichung um dt=0 s ₀=±0,75; Variationsbreite 3,3 h). Im Bereich 0,3Q _H<0,5 (etwa 6,5–10,5 hpm) ist die kombinierte Todeszeitrückrechnung mit Wichtung im Verhältnis 6 (Hirn):4 (Rektum) vergleichsweise am präzisesten (s ₀=±1,18; Variationsbreite 5 h). Im Bereich 0,07Q _H<0,3 (jenseits 10,5 hpm) ergibt die alleinige Verwendung der Rektaltemperatur die präzisesten Todeszeitberechnungen (s ₀=±1,62; Variationsbreite 6,6 h).Ein integrierter Rechenansatz aus beiden Rückrechnungsformeln mit dadurch möglicher Elimination der Temperatur bei Todeseintritt scheint im Bereich um 0,7Q _H<1,0 geeignet zu sein, größere Fehler berechneter Todeszeiten in Fällen mit z.B Fieber bei Todeseintritt zu vermeiden (s ₀=±0,69; Variationsbreite 2,7 h).Herrn Prof. Dr. W. Janssen zum 60 Geburtstag gewidmet     

A simple method for the quantification of benzodiazepine receptors using iodine-123 iomazenil and single-photon emission tomography

Iodine-123 iomazenil (Iomazenil) is a ligand for central type benzodiazepine receptors that is suitable for single-photon emission tomography (SPET). The purpose of this study was to develop a simple method for the quantification of its binding potential (BP). The method is based on a two-compartment model (K ₁, influx rate constant;k ₂, efflux rate constant;V _T (=K ₁/k ₂), the total distribution volumes relative to the total arterial tracer concentration), and requires two SPET scans and one blood sampling. For a given input function, the radioactivity ratio of the early to delayed scans can be considered to tabulate as a function ofk ₂, and a table lookup procedure provides the correspondingk ₂ value, from whichK ₁ andV _T values are then calculated. The arterial input function is obtained by calibration of the standard input function by the single blood sampling. SPET studies were performed on 14 patients with cerebrovascular diseases, dementia or brain tumours (mean age±SD, 56.0±12.2). None of the patients had any heart, renal or liver disease. A dynamic SPET scan was performed following intravenous bolus injection of Iomazenil. A static SPET scan was performed at 180 min after injection. Frequent blood sampling from the brachial artery was performed on all subjects for determination of the arterial input function. Two-compartment model analysis was validated for calculation of theV _T value of Iomazenil. Good correlations were observed betweenV _T values calculated by three-compartment model analysis and those calculated by the present method, in which the scan time combinations (early scan/delayed scan) used were 15/180 min, 30/180 min or 45/180 min (all combinations:r=0.92), supporting the validity of this method. The present method is simple and applicable for clinical use.     

<Superscript>68</Superscript>Ga-DOTANOC: biodistribution and dosimetry in patients affected by neuroendocrine tumors

Objectives The aim of this work was the evaluation of biodistribution and radiation dosimetry of ⁶⁸Ga-DOTANOC in patients affected by neuroendocrine tumors. Materials and methods We enrolled nine patients (six male and three female) affected by different types of neuroendocrine tumors (NETs). Each patient underwent four whole body positron emission tomography (PET) scans, respectively, at 5, 20, 60, and 120 min after the intravenous injection of about 185 MBq of ⁶⁸Ga-DOTANOC. Blood and urine samples were taken at different time points post injection: respectively, at about 5, 18, 40, 60, and 120 min for blood and every 40–50 min from injection time up to 4 h for urine. The organs involved in the dosimetric evaluations were liver, heart, spleen, kidneys, lungs, pituitary gland, and urinary bladder. Dosimetric evaluations were done using the OLINDA/EXM 1.0 software. Results A physiological uptake of ⁶⁸Ga-DOTANOC was seen in all patients in the pituitary gland, the spleen, the liver, and the urinary tract (kidneys and urinary bladder). Organs with the highest absorbed doses were kidneys . The mean effective dose equivalent (EDE) was . Discussion and conclusions The excretion of the compound was principally via urine, giving dose to the kidney and the urinary bladder wall. As SSTR2 is the most frequently expressed somatostatin receptor and ⁶⁸Ga-DOTANOC has high affinity to it, this compound might play an important role in PET oncology in the future. The dosimetric evaluation carried out by our team demonstrated that ⁶⁸Ga-DOTANOC delivers a dose to organs comparable to, and even lower than, analogous diagnostic compounds.     

Validity of different gated equilibrium blood pool methods for determination of left ventricular ejection fraction

Left ventricular ejection fractions (EF) were determined in 37 patients by biplane cineventriculography (Angio) and by four modifications of the gated equilibrium blood pool (GBP) method:

1. Region of interest (ROI) in enddiastole (ED), correction by external background
2. ROI in ED, correction by internal background between ED and endsystole (ES)
3. ROI in ED (maximum) and ES (minimum); no background correction
4. ROI in ES, correction by background between ED and ES.

EF_GBP were determined after injection of 20 mCi ^99mTc human albumin (Anger-camera, all-purpose collimator, 16 ECG-segments, 64 x 64 matrix with 1.5 zoom). EF by biplane angiography (EF_angio) was calculated by the formula of Dodge. The following correlation between angiographically and scintigraphically determined EF's were found: $$\begin{gathered} EF_{GBP 1} = 0.504 EF_{angio} + 8.08, \hfill \\ EF_{GBP 2} = 0.847 EF_{angio} + 10.0, \hfill \\ EF_{GBP 3} = 0.911 EF_{angio} + 3.75, \hfill \\ EF_{GBP 4} = 0.648 EF_{angio} --- 3.51 \hfill \\\end{gathered}$$ Intraobserver variability of GBP method 2 and 3 was±5%. EFs determined by GBP methods 2 and 3 are as accurate as the EFs determined by cineventriculography.     

Validity of rapid estimation of erythrocyte volume in the diagnosis of polycytemia vera

In the diagnosis of polycytemia vera, estimation of erythrocyte volume (EV) from plasma volume (PV) and venous hematocrit (Hct _v ) is usually thought unadvisable, because the ratio of whole body hematocrit to venous hematocrit (f ratio) is higher in patients with splenomegaly than in normal subjects, and varies considerably between individuals. We determined the mean f ratio in 232 consecutive patients suspected of polycytemia vera ( ;SD 0.048) and used it with each patient's PV and Hct _v to calculate an estimated normalised EV _n . With measured EV as a reference value, EV _n was investigated as a diagnostic test. By means of two cut off levels the EV _n values could be divided into EV _n elevated, EV _n not elevated (both with high predictive values), and an EV _n borderline group. The size of the borderline EV _n group ranged from 5% to 46% depending on position of the cut off levels, i.e. with the efficiency demanded from the diagnostic test. EV can safely and rapidly be estimated from PV and Hct _v , if is determined from the relevant population, and if the results in an easily defineable borderline range of EV _n values are supplemented by direct EV determination.     

Dosimetry of intravenously administered oxygen-15 labelled water in man: a model based on experimental human data from 21 subjects

Models based on uniform distribution of tracer in total body water underestimate the absorbed dose from H₂ ¹⁵O because of the short half-life (2.04 min) of ¹⁵O, which leads to non-uniform distribution of absorbed dose and also complicates the direct measurement of organ retention curves. However, organ absorbed doses can be predicted by the present kinetic model based on the convolution technique. The measured time course of arterial H2150 concentration following intravenous administration represents the input function to organs. The impulse response of a given organ is its transit time function determined by blood flow and the partition of water between tissue and blood. Values of these two parameters were taken from the literature. Integrals of the arterial input function and organ transit time functions were used to derive integrals of organ retention functions (organ residence times). The latter were used with absorbed dose calculation software (MIRDOSE-2) to obtain estimates for 24 organs. From the mean values of organ absorbed doses, the effective dose equivalent (EDE) and effective dose (ED) were calculated. From measurements on 21 subjects, the average value for both EDE and ED was calculated to be 1.2 Sv · MBq^–1 compared with a value of about 0.5 Sv · MBq^–1 predicted by uniform water distribution models. Based on the human data, a method of approximating H₂ ¹⁵O absorbed dose values from body surface area is described. Correspondence to: T. Smith     

A contrast-oriented algorithm for FDG-PET-based delineation of tumour volumes for the radiotherapy of lung cancer: derivation from phantom measurements and validation in patient data

Purpose  An easily applicable algorithm for the FDG-PET-based delineation of tumour volumes for the radiotherapy of lung cancer was developed by phantom measurements and validated in patient data. Methods  PET scans were performed (ECAT-ART tomograph) on two cylindrical phantoms (phan1, phan2) containing glass spheres of different volumes (7.4–258 ml) which were filled with identical FDG concentrations. Gradually increasing the activity of the fillable background, signal-to-background ratios from 33:1 to 2.5:1 were realised. The mean standardised uptake value (SUV) of the region-of-interest (ROI) surrounded by a 70% isocontour (mSUV₇₀) was used to represent the FDG accumulation of each sphere (or tumour). Image contrast was defined as: where BG is the mean background − SUV. For the spheres of phan1, the threshold SUVs (TS) best matching the known sphere volumes were determined. A regression function representing the relationship between TS/(mSUV₇₀ − BG) and C was calculated and used for delineation of the spheres in phan2 and the gross tumour volumes (GTVs) of eight primary lung tumours. These GTVs were compared to those defined using CT. Results  The relationship between TS/(mSUV₇₀ − BG) and C is best described by an inverse regression function which can be converted to the linear relationship . Using this algorithm, the volumes delineated in phan2 differed by only −0.4 to +0.7 mm in radius from the true ones, whilst the PET-GTVs differed by only −0.7 to +1.2 mm compared with the values determined by CT. Conclusion  By the contrast-oriented algorithm presented in this study, a PET-based delineation of GTVs for primary tumours of lung cancer patients is feasible.