Direct deconvolution algorithms based on Laplace transforms in nuclear medicine applications.

A set of algorithms is presented for direct deconvolution of the residue signal of an organ with the input signal to the organ. The deconvolution process yields the residual impulse response from which the distribution of transit times and the important mean transit time can be readily determined. The deconvolution method is based on the Laplace transform and it requires that the input signal can be fitted with an expression consisting of one, two or three exponentials with or without a bolus term at zero time or a constant term. These types of exponential expressions for the input signal cover a wide range of the input signals encountered in nuclear medicine applications. Simulation studies of the residue signal by convolution of various input signals with a number of residual impulse response models yielded an excellent accuracy of the deconvoluted residual impulse response for a suitably small sampling time. The simulations provide an opportunity to understand further the shapes of the residue curves depending on the shape of the input signal and the distribution of transit times. Simulations with Gaussian-distributed noise and noise spikes superimposed on the residue signal were also made to investigate the robustness of the direct deconvolution algorithm using apparently real-life data.

Radix mesiolingualis and radix distolingualis in a collection of permanent maxillary molars.

Two lingual root structures are occasionally found on human permanent maxillary molars. One of these is the normal lingual root, which is always present, the other is a supernumerary structure which can be located either mesiolingually (radix mesiolingualis (RML)) or distolingually (radix distolingualis (RDL)). The available literature refers only to the existence and location of RML and RDL Very small materials have, quite simply, hitherto precluded a more detailed description of these roots. The large collection of extracted teeth at the School of Dentistry in Copenhagen now includes a non-random subcollection of 145 permanent maxillary molars, the root complex of which contains 2 lingual root structures. Based on this material it was possible to undertake a modern, systematic analysis of the macromorphological variation of RMLs and RDLs. In this study, which was mainly non-metric, criteria for the identification of RML and RDL were established. The analysis also showed that the lingual supernumerary roots were only rarely found on the first molar, but with increasing frequency on the second and third molars. Both separate and non-separate RML and RDL were observed. In the material, degrees of separation greater than 0.9 were registered, degrees of divergence up to approximately 45 degrees, an apical bend of approximately 90 degrees, and extreme apical slenderness. Even though the supernumerary roots described here do not occur very often, knowing about them is nevertheless clinically relevant in for example endodontic and surgical contexts.

Radix paramolaris and radix distomolaris in Danish permanent maxillary molars.

The School of Dentistry in Copenhagen possesses a collection of 96 human permanent maxillary molars (M sup) with a root complex, the macromorphology of which includes a facially located supernumerary root known as radix paramolaris (RP) and/or a distally located supernumerary root called radix distomolaris (RD). Systematic analysis of these teeth enabled the authors to establish precise criteria for the identification of RP and RD on M sup; 91.5% out of a total of 70 RP identified occurred on M3 sup, 7.2% on M2 sup, and 1.4% on M1 sup. The corresponding percentages for 29 RD identified were: 96.5% on M3 sup, 3.4% on M2 sup, and 0.0% on M1 sup; 50.0% of the 70 RP were separate in relation to the 2 facial root components and 31.5% non-separate; in 18.6% of the RP observed, it was impossible to establish whether or not they were separate. Corresponding frequencies for the 29 RD in relation to the distofacial and lingual root components were 41.3% separate and 37.9% non-separate; 20.7% of the roots could not be categorized. The following clinically relevant macromorphological variables regarding RP and RD were also observed: degree of separation in relation to the respective neighboring root components, degree of divergence in relation to the same macrostructures, apical bend, apical gracility, and pattern of fusion.

External and internal macromorphology in 3D-reconstructed maxillary molars using computerized X-ray microtomography.

AIM: The aim of this study was to perform a qualitative analysis of the relationship between the external and internal macromorphology of the root complex and to use fractal dimension analysis to determine the correlation between the shape of the outer surface of the root and the shape of the root canal. METHODOLOGY: On the basis of X-ray computed transaxial microtomography, a qualitative and quantitative analysis of the external and internal macromorphology of the root complex in permanent maxillary molars was performed using well-defined macromorphological variables and fractal dimension analysis. Five maxillary molars were placed between a microfocus X-ray tube with a focal spot size of 0.07 mm, a Thomson-SCF image intensifier, and a CCD camera compromising a detector for the tomograph. Between 100 and 240 tomographic 2D slices were made of each tooth. Assembling slices for 3D volume was carried out with subsequent median noise filtering. Segmentation into enamel, dentine and pulp space was achieved through thresholding followed by morphological filtering. Surface representations were then constructed. A useful visualization of the tooth was created by making the dental hard tissues transparent and the pulp chamber and root-canal system opaque. On this basis it became possible to assess the relationship between the external and internal macromorphology of the crown and root complex. RESULTS: There was strong agreement between the number, position and cross-section of the root canals and the number, position and degree of manifestation of the root complex macrostructures. Data from a fractal dimension analysis also showed a high correlation between the shape of the root canals and the corresponding roots. CONCLUSIONS: It is suggested that these types of 3D volumes constitute a platform for preclinical training in fundamental endodontic procedures.

The Ekman-Westborg-Julin syndrome: report of case.

The Ekman-Westborg-Julin Syndrome is reveiwed and a new case reported.

Uptake index and stimulated salivary gland response in 99Tcm-pertechnetate salivary gland scintigraphy in normal subjects.

With a view to improve the diagnosis of salivary gland diseases (in particular, Sjögrén's syndrome) associated with decreased salivary gland function and decreased stimulated salivary gland response, the normal range of radionuclide uptake function and the stimulated salivary gland response were established in 27 subjects without any known salivary gland disease. Following injection of 99Tcm-pertechnetate, sequential images were recorded for 40 min with oral administration of citric acid at 30 min. The total uptake index (TUI) was calculated as the sum of the background corrected count rates over the parotid and submandibular glands at 3 min divided by the injected dose. The TUI, expressed as a percentage of dose, was 0.55 +/- 0.12 (mean +/- S.D.). The stimulated salivary gland response (SSGR) was calculated as the difference between the rate constants (min-1) of monoexponential fits to the time-activity curves over the four salivary glands immediately after and before the administration of citric acid. The lower significance limit (P < 0.05) of the SSGR was a 2.4% decrease per min. The parameters TUI and SSGR can be used as a diagnostic tool in, for example, early Sjögren's syndrome.

Root canals in two-rooted maxillary second molars.

The aim of this study was to register the root canal number, root canal position, and root canal cross-section in human two-rooted, permanent maxillary second molars. One hundred and fifty-nine such teeth extracted in Denmark were cross-sectioned at the mid-root level and apically in accordance with precise guidelines. The observations were made in a stereomicroscope, corresponding to the above-mentioned section levels. At mid-root there were two canals present in 11% of the teeth examined; the canals were located mesially and distofacially, mesiofacially and distally, or facially and lingually. Three canals positioned mesiofacially, distofacially, and lingually were observed in 89% of the teeth. At the same level 62% of the canal cross-sections were noncircular, some being, for instance, C-shaped, whereas 38% of the cross-sections were circular. Apically, two canals were found, representing 19% of the teeth, with the canal position as at mid-root; 81% of the teeth were three-canaled with the same canal position as at mid-root. At the apical level 60% of the canal cross-sections were noncircular, whereas 40% of the cross-sections were circular.

Mandibular premolar differentiation.

The authors present a method for differentiating between human mandibular premolars: P1 inf and P2 inf. The material with which the method was developed consisted of 260 stone casts. On these, both premolars were present and were intact on at least one side. The study models represented 131 girls and 129 boys, mean age 14.6 yr. In a comprehensive pilot project, a whole range of macromorphologic criteria was tested that, in various combinations, could be expected to be usable for differentiation between P1 inf and P2 inf. On the basis of the pilot study, the total variation was reduced to four criteria-combinations, called types, which, in summary, can be characterized as the following: type 1: flattening of the mesiolingual part of the crown, no lingual lobe; type 2: at least one lingual lobe; type 3: lingual part of the crown symmetrically curved, no lingual lobe; type 4: other characteristics. After definition of the types, their occurrence on P1 inf and P2 inf was definitively registered. Observations were made with a stereomicroscope; 131 premolar pairs from the right side and 129 from the left were registered. Statistical tests showed that there was no significant difference in the distribution of types between variants from the right and left sides, or between girls and boys. These data were therefore pooled for P1 inf and P2 inf, respectively. A subsequent test revealed, as expected, a highly significant difference in the distribution of the four types among 1. and 2. premolar.(ABSTRACT TRUNCATED AT 250 WORDS)

Root canals in one-rooted maxillary second molars.

The Royal Dental College, Copenhagen, houses an extensive collection of human teeth extracted in Denmark. The collection currently contains 104 one-rooted, permanent maxillary second molars. The root complex on these teeth was sectioned at the junction between the coronal and the apical halves, i.e. mid-root, and at the junction between the middle and the apical thirds, i.e. apically. Using a stereomicroscope we then registered, mid-root and apically, the following variables: canal number, canal position, and canal cross-section. Mid-root there was 1 centrally located root canal in 25.96% of the teeth examined; 2 canals were observed either mesially and distofacially, mesiofacially and distally, or facially and lingually in 34.62%; 3 canals positioned mesiofacially, distofacially, and lingually were found in 39.42%. At the same level 63.51% of the canal cross-sections were non-circular, whereas 36.49% of the canals had a circular cross-section image. The non-circular canal cross-sections could more specifically be characterized as C-shaped, Y-shaped, hourglass-shaped or the root canal had a greater faciolingual than mesiodistal extension or, respectively, a greater mesiodistal than faciolingual extension. Apically there was 1 centrally located root canal in 35.58%; 2 canals were observed with a position either mesially and distofacially, mesiofacially and distally, or facially and lingually in 37.49%; 3 canals located mesiofacially, distofacially, and lingually were found in 26.92%. At the apical level, 64.32% of the root canal cross-sections were non-circular, whereas 35.68% of the canals showed a circular cross-section. The results presented here are aimed at: clinical dentists, endodontists, and dental morphologists.

Radix paramolaris in permanent mandibular molars: identification and morphology.

The Royal Dental College, Copenhagen, houses an extensive collection of human teeth which have been extracted in Denmark. The collection presently includes 203 permanent mandibular molars with a root complex containing a facially-located supernumerary root. This macrostructure is named radix paramolaris (RP). By analyzing the large number of specimens available it was possible to establish uniform and precise criteria for the identification of RP on M1 inf, M2 inf, and M3 inf. The analyses included both separate and non-separate RP. The representation of the RP variants according to tooth type was mapped. Furthermore, the following clinically relevant variables with respect to RP were registered: degree of separation, divergence, apical bend, apical gracility, and fusion. Because of the nature of the material, the study was mostly qualitative and non-metric. The results are aimed primarily at clinical dentists, dental morphologists, and dental anthropologists.

Morphometric analysis of occlusal groove-fossa-system in mandibular third molar.

Based on serially cut 200-microns-thick sections from 21 human mandibular third molars, a quantitative characterization was made of the morphology in the mesial and distal interlobal groove. Two parameters were used: depth of interlobal groove and structure angle. The interlobal groove depth varied between 0.13 and 0.55, taken in relation to the maximum crown height. The structure angle varied between 2 degrees and 170 degrees. If the structure angle was less than or equal to 25 degrees, the interlobal groove was classified as a fissure; if the angle was greater than 25 degrees, the interlobal groove was classified as a groove. Only in 18% of the sections did the interlobal groove manifest itself as a fissure. The study demonstrates that it was possible unambiguously to describe the two-dimensional profile of interlobal grooves by groove depth and structure angle.

Radix entomolaris: identification and morphology.

The Royal Dental College, Copenhagen, houses an extensive collection of human teeth, extracted in Denmark. At present, the collection includes 398 permanent mandibular molars with a root complex containing a lingually-located supernumerary root. This macrostructure is called radix entomolaris (RE). By analyzing the large number of available specimens it was possible to establish uniform and precise criteria for the identification of RE on M1 inf, M2 inf, and M3 inf. The analyses included separate as well as non-separate RE. The representation of the RE variants according to tooth types was mapped. Furthermore, the following relevant clinical variables with respect to RE were registered: degree of separation, divergence, apical bend, apical gracility, and fusion. Because of the nature of the material, the investigation was mostly qualitative and non-metric. The results should be of interest to clinical dentists, dental morphologists, and dental anthropologists.

Root complex and root canal system: a correlation analysis using one-rooted mandibular second molars.

The principal aim of this investigation was to verify an expected, probable correlation between certain variables, which are initially represented in the macrostructure of the root complex corresponding to the cemento-dentin junction, and certain variables that subsequently manifest themselves in the root canal system. A material consisting of 76 one-rooted, permanent mandibular second molars (M2 inf) was used. The specimens were cut at the mid-root level and all observations were made on the coronal root segment using a stereomicroscope. Relevant variables of the root complex were observed. The total macromorphologic variation of the root complex could be subdivided and classified in well-defined, distinguishable types. In accordance with the single root complex type an expected, logically deduced configuration of the root canal system was established. The relevant variables of the canal system were then recorded. Finally, the root complex morphology, as well as the expected and actually observed canal configuration, were compared type by type. In 76.3% of the teeth a good concordance could be shown between the expected and the actual canal configuration, whereas in 23.7% of the specimens there was a divergence. In 42.1% of the investigated teeth, 1 centrally localized main canal with varying cross section images, among them a C-shaped image, was found. In 30.3%, 2 main canals were found, which were often localized mesially and distally. In 23.7%, 3 main canals were observed: 1 mesiofacial, 1 mesiolingual and 1 distal. In the remaining 3.9%, 1 non-independent supernumerary canal was seen in a distolingual position.

A new method for determination of the rate constant for clearance of radioactive indicators in gamma camera hepatography. Clinical examples with 99mTc-diethyl-IDA and 99mTc-diethyl-iodo-IDA.

Application of Stewart-Hamilton's formula to the activity-time curve recorded over a left ventricular region of interest following an intravenous bolus injection of a radioactive indicator in gamma camera hepatography has resulted in a new method for determination of the clearance rate constant of the indicator (i.e. the ratio of the clearance to the plasma volume). In a group of 19 normal subjects the clearance rate constant was 0.116 +/- 0.036 min-1 (means +/- 1 S.D.) with 99mTc-diethyl-IDA (SOLCO HIDA) and 0.184 +/- 0.037 min-1 (means +/- 1 S.D.) with 99mTc-diethyl-iodo-IDA (SOLCO IODIDA) in 15 normal subjects. The clearance rate constant is assumed to represent mainly hepatic clearance of the radioactive indicator and to a much smaller extent renal clearance. The literature shows diverging results as to the clearance of 99mTc-diethyl-IDA and the reasons for this are discussed. The correlations between the clearance rate constant of 99mTc-diethyl-IDA and a number of laboratory variables with relation to liver function were moderate to non-existent in a group of 16 subjects with abnormal values of at least one of these variables. The rate constant for clearance as described in the paper represents a non-invasive method for rapid evaluation of the uptake capacity of the liver and, in particular, with regard to the polygonal cells of the liver parenchyma when IDA derivatives are employed. The clinical usefulness of the clearance rate constant is probably superior to the group of routine laboratory variables which also describe other functions than liver uptake.

A method for determination of normal or abnormal blood volume in patients subjected to radionuclide cardiography.

The blood volume can be measured after labelling of red blood cells with technetium-99m. In addition, the blood volume and its standard error of estimate can be calculated from the subject's sex, height and deviation from desired weight. By comparing the measured blood volume with the estimated normal blood volume and using a statistical test, it can be decided whether a measured blood volume is normal or not. This method was applied to a group of 36 patients with heart diseases. Four of the patients had abnormal blood volumes. In the remaining 32 patients the measured blood volumes were equally distributed around the estimated mean normal values. The method described for determination of normal/abnormal blood volumes can be considered a by-product of routine radionuclide cardiography.

A new, simple and precise method for the determination of right ventricule forward ejection fraction in first-pass radionuclide cardiography.

A new method is presented for the determination of right ventricular ejection fraction (RVEF) in first-pass radionuclide cardiography. The method is simple to apply and it provides RVEF values with an experimental standard deviation of 3.4% over the whole range of right ventricular ejection fractions. The method determines RVEF from analysis of time-activity curves from regions of interest (ROIs) over representative portions of the right atrium and the pulmonary artery (RVEFRAPA). Hence, the problem of demarcation of the right ventricle from adjacent structures is avoided. RVEFRAPA was 0.658 +/- 0.067 (mean +/- 1 S.D.) in a normal group of 36 adult women. This value was not significantly different from the RVEF of 0.641 +/- 0.072 (mean +/- 1 S.D.) determined by separate areas over the right ventricle in the end-diastole and end-systole (RVEFRVSA). In a repeatability study comprising 25 subjects covering a wide range of RVEF values, the standard deviation of RVEFRAPA was 4.4 times smaller than that of RVEFRVSA. The left ventricular ejection fraction (LVEF) determined in the equilibrium gated radionuclide cardiography following the first-pass study was 0.692 +/- 0.065 (mean +/- 1 S.D.) for the normal group. Hence, LVEF is slightly higher than RVEF in normals.

Glomerular filtration rate in adults estimated from 123iodine-hippuran and 99mtechnetium-diethylenetriaminepenta-acetic acid gamma camera renography.

In a retrospective study a close relationship was found between the rate constant for renal clearance of the radioactive indicator (lambda pk) and the glomerular filtration rate (GFR) measured by 51Cr-EDTA plasma clearance. The material comprised eighteen adult subjects submitted to 123I-hippuran gamma camera renography (IHGR) and twenty-two adult subjects to 99mTc-DTPA gamma camera renography (TDGR). The rate constant was calculated from a bi-exponential decomposition of the activity-time curve recorded within a small region of interest over the left ventricle. The total cleared renal fraction (TCRF) of the cardiac output with respect to the radioactive indicator has previously been shown to be closely related to GFR. A pooled estimate of GFR (GFRp) was calculated from the stochastically independent estimates of GFR based on lambda pk and TCRF. The comparison of GFRp with measured GFR was satisfactory and yielded substantially smaller standard deviations (SD) of GFRp than estimates based on lambda pk and TCRF separately. The standard deviations of GFRp were about 7 and 12 ml/min/1.73 m2 in IHGR for GFR equal to 50 and 100 ml/min/1.73 m2, respectively. The corresponding SD in TDGR were about 7 and 11 ml/min/1.73 m2. These standard deviations are sufficiently small for many clinical purposes and the method requires no blood samples or urine collections.

Absorbed radiation dose in adults from iodine-131 and iodine-123 orthoiodohippurate and technetium-99m DTPA renography.

A mathematic model for evaluation of absorbed dose in radionuclide renography has been developed and programmed for automatic calculation in the computer. Input data to the model are readily available from the results of the renography and, hence, the method described is suitable for individual dose determinations in adults. Apart from the situation with very considerable outflow obstructions [131I]OIH single probe renography involves a 15-20 times smaller dose to radiation sensitive organs than [123I]OIH gamma camera renography. Further, the latter examination results in a 2-10 times smaller dose than [99mTc]DTPA gamma camera renography under normal outflow conditions. Absorbed renal dose is large, approximately 70 mGy, in the three renographies in the borderline case with total outflow obstructions. For comparison, i.v. pyelography, which is the x-ray examination often used instead of radionuclide renography, involves an absorbed dose to ovaries 10-1000 times larger than in radionuclide renography.

Evaluation of forward stroke volume in first-pass radionuclide cardiography.

First-pass radionuclide cardiography and Zierler's area-over-height formula have been applied for determination of stroke volume. The method has three new features: (a) the region of interest comprises the entire cardiopulmonary circulation; (b) a prediction of (normal) blood volume based on deviation from desired weight; and (c) a correction of stroke volume in case of incomplete bolus injection. The method was verified in a pathological situation by an independent geometric method in equilibrium gated radionuclide cardiography. The variation of stroke volume was investigated in a normal group of 61 women, 40-80 years old. The result was in excellent agreement with values for normal variation of stroke volume in the literature.

Evaluation of regional cerebral circulation based on absolute mean transit times in radionuclide cerebral angiography.

In radionuclide cerebral angiography (RCA) the analysis of the activity-time curves recorded over the hemispheres following an intravenous bolus injection of a radioactive indicator permits the evaluation of absolute cerebral mean transit times (MTTcb). The inverse of MTTcb is an index of cerebral blood flow. The bolus parts of the cerebral activity curves were fitted with gamma-variate functions. The duration of the injection bolus and its subsequent dispersion through the cardiopulmonary circulation were corrected for using the activity curve over the aortic arch. In a control material of 52 subjects MTTcb was uncorrelated with age and equal to 3.2 +/- 0.67 s (means +/- 1 SEE) for the 37 subjects younger than 60. For the fifteen subjects older than 60, mean MTTcb showed a steep increase with age. The results were in close agreement with those obtained by other researchers using either correction of cerebral curves based on a physical flow model or direct injections into the internal carotid artery. Comparison of RCA with x-ray carotid angiography in 12 subjects was satisfactory. Repeated RCA examinations in nine subjects a few days apart yielded a reproducibility of 0.7 s for MTTcb. The RCA is non-invasive, rapid, easy to perform and without risk for the patient. The RCA is recommended for quantitative evaluation of major alterations in cerebral perfusion.