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Josef Machac

Publications and source records attributed to Josef Machac.

At least 19 recordsLinked to original sources
PubMed2006

Comparison of 18F SPECT with PET in myocardial imaging: a realistic thorax-cardiac phantom study.

BACKGROUND: Positron emission tomography (PET) imaging with fluorine-18 (18F) Fluorodeoxyglucose (FDG) and flow tracer such as Rubidium-82 (82Rb) is an established method for evaluating an ischemic but viable myocardium. However, the high cost of PET imaging restricts its wider clinical use. Therefore, less expensive 18F FDG single photon emission computed tomography (SPECT) imaging has been considered as an alternative to 18F FDG PET imaging. The purpose of the work is to compare SPECT with PET in myocardial perfusion/viability imaging. METHODS: A nonuniform RH-2 thorax-heart phantom was used in the SPECT and PET acquisitions. Three inserts, 3 cm, 2 cm and 1 cm in diameter, were placed in the left ventricular (LV) wall to simulate infarcts. The phantom acquisition was performed sequentially with 7.4 MBq of 18F and 22.2 MBq of Technetium-99m (99mTc) in the SPECT study and with 7.4 MBq of 18F and 370 MBq of 82Rb in the PET study. SPECT and PET data were processed using standard reconstruction software provided by vendors. Circumferential profiles of the short-axis slices, the contrast and viability of the inserts were used to evaluate the SPECT and PET images. RESULTS: The contrast for 3 cm, 2 cm and 1 cm inserts were for 18F PET data, 1.0 +/- 0.01, 0.67 +/- 0.02 and 0.25 +/- 0.01, respectively. For 82Rb PET data, the corresponding contrast values were 0.61 +/- 0.02, 0.37 +/- 0.02 and 0.19 +/- 0.01, respectively. For 18F SPECT the contrast values were, 0.31 +/- 0.03 and 0.20 +/- 0.05 for 3 cm and 2 cm inserts, respectively. For 99mTc SPECT the contrast values were, 0.63 +/- 0.04 and 0.24 +/- 0.05 for 3 cm and 2 cm inserts respectively. In SPECT, the 1 cm insert was not detectable. In the SPECT study, all three inserts were falsely diagnosed as "viable", while in the PET study, only the 1 cm insert was diagnosed falsely "viable". CONCLUSION: For smaller defects the 99mTc/18F SPECT imaging cannot entirely replace the more expensive 82Rb/18F PET for myocardial perfusion/viability imaging, due to poorer image spatial resolution and poorer defect contrast.

Journal Article↗
PubMed2006

Non-invasive imaging of atherosclerotic plaque macrophage in a rabbit model with F-18 FDG PET: a histopathological correlation.

BACKGROUND: Coronary atherosclerosis and its thrombotic complications are the major cause of mortality and morbidity throughout the industrialized world. Thrombosis on disrupted atherosclerotic plaques plays a key role in the onset of acute coronary syndromes. Macrophages density is one of the most critical compositions of plaque in both plaque vulnerability and thrombogenicity upon rupture. It has been shown that macrophages have a high uptake of 18F-FDG (FDG). We studied the correlation of FDG uptake with histopathological macrophage accumulation in atherosclerotic plaques in a rabbit model. METHODS: Atherosclerosis was induced in rabbits (n = 6) by a combination of atherogenic diet and balloon denudation of the aorta. PET imaging was performed at baseline and 2 months after atherogenic diet and coregistered with magnetic resonance (MR) imaging. Normal (n = 3) rabbits served as controls. FDG uptake by the thoracic aorta was expressed as concentration (muCi/ml) and the ratio of aortic uptake-to-blood radioactivity. FDG uptake and RAM-11 antibody positive areas were analyzed in descending aorta. RESULTS: Atherosclerotic aortas showed significantly higher uptake of FDG than normal aortas. The correlation of aortic FDG uptake with macrophage areas assessed by histopathology was statistically significant although it was not high (r = 0.48, p < 0.0001). When uptake was expressed as the ratio of aortic uptake-to-blood activity, it correlated better (r = 0.80, p < 0.0001) with the macrophage areas, due to the correction for residual blood FDG activity. CONCLUSION: PET FDG activity correlated with macrophage content within aortic atherosclerosis. This imaging approach might serve as a useful non-invasive imaging technique and potentially permit monitoring of relative changes in inflammation within the atherosclerotic lesion.

Journal Article↗
PubMed2006

Concomitant paravertebral FDG uptake helps differentiate supraclavicular and suprarenal brown fat uptake from malignant uptake when CT coregistration is not available.

OBJECTIVES: Fluorine-18 fluorodeoxyglucose (F-18 FDG) uptake in brown adipose tissue (BAT) in the supraclavicular, superior mediastinal, paravertebral, and suprarenal/perinephric regions has been recognized. Of these 4 areas, uptake in the supraclavicular, mediastinal, and suprarenal areas may be difficult to differentiate from malignancy for those who interpret PET images only without CT coregistration or fusion. We assessed the prevalence and concomitance of F-18 FDG uptake in these 4 BAT regions. METHODS: A total of 1495 F-18-FDG PET studies were reviewed. Distinct patterns compatible with BAT uptake in the 4 regions were graded and correlated with each other. RESULTS: Of the 1495 studies, supraclavicular uptake was seen in 40 (2.7%), paravertebral uptake in 29 (1.9%), mediastinal uptake in 23(1.5%), and suprarenal uptake in 11 (0.7%). Of the 40 studies showing supraclavicular uptake, paravertebral uptake was also seen in 27 (68%), mediastinal uptake in 23 (58%), and suprarenal uptake in 11 (28%). Alternatively, of the 29 studies showing paravertebral uptake, all but 2 studies (93%) also had concomitant supraclavicular uptake. No studies showed isolated mediastinal or suprarenal uptake. All studies with mediastinal uptake also had supraclavicular uptake, and all studies with suprarenal uptake also had paravertebral uptake. CONCLUSIONS: Virtually all of mediastinal and suprarenal BAT uptake was associated with supraclavicular and paravertebral uptake, respectively. Nearly all paravertebral uptake coexisted with supraclavicular uptake. Even when CT coregistration is not available, concomitant paravertebral uptake can help differentiate suprarenal uptake and somewhat less typical supraclavicular BAT uptake from malignant uptake, and concomitant supraclavicular uptake can help differentiate mediastinal uptake from malignant uptake.

Adipose Tissue, Brown↗
PubMed2006

Appearance of intrathymic parathyroid adenomas on pinhole sestamibi parathyroid imaging.

OBJECTIVES: Ectopic inferior parathyroid adenomas (PAs) are frequently located in the anterior mediastinum, quite often in the thymus gland. Correct preoperative localization is particularly helpful for surgical planning. Clinical follow up has shown that most intrathymic adenomas were visualized on pinhole views and located closer to the thyroid than expected. We reviewed the typical appearance of intrathymic PA on pinhole views. METHODS: We retrospectively reviewed sestamibi pinhole parathyroid imaging performed on 163 patients with primary hyperparathyroidism and final diagnoses established by surgery, histology, intraoperative PTH monitoring, and clinical follow up. Studies showing focal increased activity in the lower pole region of the thyroid were selected and divided into 2 groups, group A (foci that are visually not separable from the thyroid) and group B (foci that are completely separated from the thyroid), and correlated with the final diagnoses. RESULTS: Of the 163 patients, 102 had 103 clearly abnormal foci in the lower pole region (bilateral lower pole foci in one study). There were 93 foci in group A and 10 foci in group B. Of the 93 foci in group A, there were 80 normally situated inferior PA, 6 descended superior PA, 3 intrathyroidal PA, one hyperplastic parathyroid gland, one thyroid adenoma, one unidentified, and one intrathymic PA. Of the 10 foci in group B, 3 were eutopic inferior PA and 7 were intrathymic PA. CONCLUSION: Focal increased activity completely separated from the lower pole of thyroid (regardless of the distance of separation) on sestamibi pinhole images indicates a high probability of intrathymic parathyroid adenoma.

Adenoma↗
PubMed2006

Patterns of red marrow in the adult femur.

PURPOSE: Conversion of red marrow (RM) to fatty marrow in the skeleton of the lower extremities begins at the distal end, ie, feet, and progresses proximally with distal bone marrow (ie, tibia) being converted more rapidly than proximal bone marrow (ie, femur). However, in an individual long bone, conversion begins in the diaphysis and progresses both distally and proximally (more rapidly toward the distal side). In a normal adult's femur, RM is present in the proximal one third or less. Reconversion of fatty marrow to RM is reported to occur in the reverse order of conversion. We assessed the frequency of various patterns of RM in the adult femur on In-111 leukocyte scans for a better understanding of the bone marrow regeneration process in individual long bones. METHODS: The patterns of marrow activity in the femur shown on In-111 leukocyte scans performed in 354 adults were divided into a) RM limited to the proximal one third or less, b) to the proximal two thirds, c) to the proximal one third and distal one third with no activity in the middle shaft, and d) in the entire femur. RESULTS: There were 207 patients with pattern A, 91 pattern B, 14 pattern C, and 42 pattern D. CONCLUSIONS: A considerably higher number of adults showed pattern B than pattern C. This suggests that regeneration of diaphyseal marrow precedes that of the distal marrow in an individual long bone or possibly that conversion of the latter precedes the former, which is different from that proposed in the literature.

Adult↗
PubMed2005

Using the intraoperative hand held probe without lymphoscintigraphy or using only dye correlates with higher sensory morbidity following sentinel lymph node biopsy in breast cancer: a review of the literature.

BACKGROUND: There are no studies that have directly investigated the incremental reduction in sensory morbidity that lymphoscintigraphy images (LS) and triangulated body marking or other skin marking techniques provide during sentinel lymph node biopsy (SLNB) compared to using only the probe without LS and skin marking or using only dye. However, an indirect assessment of this potential for additional sensory morbidity reduction is possible by extracting morbidity data from studies comparing the morbidity of SLNB to that of axillary lymph node dissection. METHODS: A literature search yielded 13 articles that had data on sensory morbidity at specific time points on pain, numbness or paresthesia from SLNB that used radiotracer and probe or used only dye as a primary method of finding the sentinel node (SN). Of these, 10 utilized LS, while 3 did not utilize LS. By matching the data in studies not employing LS to the studies that did, comparisons regarding the percentage of patients experiencing pain, numbness/paresthesia after SLNB could be reasonably attempted at a cutoff of 9 months. RESULTS: In the 7 studies reporting on pain after 9 months (> 9 months) that used LS (1347 patients), 13.8% of patients reported these symptoms, while in the one study that did not use LS (143 patients), 28.7% of patients reported these symptoms at > 9 months (P < 0.0001). In the 6 studies reporting on numbness and/or paresthesia at > 9 months that used LS (601 patients), 12.5% of patients reported these symptoms, while in the 3 studies that did not use LS (229 patients), 23.1% of patients reported these symptoms at > 9 months (P = 0.0002). Similar trends were also noted for all these symptoms at < or = 9 months. CONCLUSION: Because of variations in techniques and time of assessing morbidity, direct comparisons between studies are difficult. Nevertheless at a minimum, a clear trend is present: having the LS images and skin markings to assist during SLNB appears to yield more favorable morbidity outcomes for the patients compared to performing SLNB with only the probe or performing SLNB with dye alone. These results are extremely pertinent, as the main reason for performing SLNB itself in the first place is to achieve reduced morbidity.

Journal Article↗
PubMed2005

Cardiac positron emission tomography imaging.

Cardiac positron emission tomography (PET) imaging has advanced from primarily a research tool to a practical, high-performance clinical imaging modality. The widespread availability of state-of-the-art PET gamma cameras, the commercial availability of perfusion and viability PET imaging tracers, reimbursement for PET perfusion and viability procedures by government and private health insurance plans, and the availability of computer software for image display of perfusion, wall motion, and viability images have all been a key to cardiac PET imaging becoming a routine clinical tool. Although myocardial perfusion PET imaging is an option for all patients requiring stress perfusion imaging, there are identifiable patient groups difficult to image with conventional single-photon emission computed tomography imaging that are particularly likely to benefit from PET imaging, such as obese patients, women, patients with previous nondiagnostic tests, and patients with poor left ventricular function attributable to coronary artery disease considered for revascularization. Myocardial PET perfusion imaging with rubidium-82 is noteworthy for high efficiency, rapid throughput, and in a high-volume setting, low operational costs. PET metabolic viability imaging continues to be a noninvasive standard for diagnosis of viability imaging. Cardiac PET imaging has been shown to be cost-effective. The potential of routine quantification of resting and stress blood flow and coronary flow reserve in response to pharmacologic and cold-pressor stress offers tantalizing possibilities of enhancing the power of PET myocardial perfusion imaging. This can be achieved by providing assurance of stress quality control, in enhancing diagnosis and risk stratification in patients with coronary artery disease, and expanding diagnostic imaging into the realm of detection of early coronary artery disease and endothelial dysfunction subject to risk factor modification. Combined PET and x-ray computed tomography imaging (PET-CT) results in enhanced patient throughput and efficiency. The combination of multislice computed tomography scanners with PET opens possibilities of adding coronary calcium scoring and noninvasive coronary angiography to myocardial perfusion imaging and quantification. Evaluation of the clinical role of these creative new possibilities warrants investigation.

Coronary Angiography↗
PubMed2005

Focally increased activity in the lateral aspect of the mid cervical spine on bone scintigraphy is almost always benign in nature.

OBJECTIVES: Abnormal bone scan findings in the spine are often nonspecific. The confidence level for the differential diagnosis between metastases and benign or degenerative changes may vary depending on their appearance, location or intensity. The recognition of a specific pattern for certain benign conditions and its subcategorization will increase the credibility of bone scan interpretation while retaining a high level of sensitivity. We report one such finding, focally increased activity on the lateral side of the cervical spine on the posterior view, most common at the C3-C5 level ("mid-cervical-lateral-focus"). METHODS: Of 481 patients with various cancers who had at least 2 whole-body bone scans, 6 months or more apart, 41 patients were judged to show this characteristic "mid-cervical-lateral-focus" on at least one scan. Final diagnosis (metastasis vs. benign) for each "mid-cervical-lateral-focus" was made based on clinical grounds and serial bone scans. RESULTS: The bone scan showed definite multiple metastases in 15 patients, and the differential diagnosis for the "mid-cervical-lateral-focus" was already clinically irrelevant in these patients. Nevertheless, the "mid-cervical-lateral-focus" was finally judged to be benign in 14 of these 15 patients and in all remaining 26 patients without other obvious metastases. The only "mid-cervical-lateral-focus" judged to be a metastatic focus was not only clinically redundant, but also the most intense among all the "mid-cervical-lateral-foci." in this series (too intense to be interpreted as benign). CONCLUSION: The typical "mid-cervical-lateral-focus" pattern is extremely unlikely to represent metastases (virtually 0% in patients without other obvious metastases). This knowledge helps exclude metastases on bone scans.

Aged↗
PubMed2004

Improving 3D PET imaging by restoration: a phantom study.

The main objective of our work is to improve 3D PET imaging. Compared with 2D PET, 3D PET imaging has slightly worse axial resolution and a significantly higher contribution of scatter and randoms, but 3D PET has much better sensitivity than 2D PET imaging. A Jaszczak deluxe phantom was acquired in 3D mode on our GE Advance PET system. Activity of 333 MBq of 18F was uniformly distributed. Prior to the emission scan, blank and transmission scans had been acquired. They were used for attenuation correction. The duration of the emission scan was 20 min, transmission 10 min, and blank 20 min. Standard FBP reconstruction software provided by the vendor was used to obtain slice images. Point spread function was also acquired in a 21 cm diameter cylinder phantom filled with water 6.0 cm from the center and used to create restoration filters. Two restoration filters were applied, medium and sharp. Results showed significant improvement in resolution, contrast and detectability of the cold rods. The artifacts outside the phantom were also significantly reduced. For 11.1 mm rods, average contrast was 0.49+/-0.02 in the original image, 0.52+/-0.04 in the medium restored image, and in the sharply restored image 0.75+/-0.05. For 7.9 mm rods, average contrast was 0.07+/-0.01 in the original image, 0.21+/-0.03 in the medium restored image, and 0.50+/-0.04 in the sharply restored image. The amount of noise in the uniform slices, measured as the coefficient of variation (COV), was 5.5, 7.1 and 10.8% in the original image and in the images restored with medium and sharp filters, respectively. In conclusion, restoration can significantly improve the resolution and contrast of 3D PET imaging.

Phantoms, Imaging↗
PubMed2003

Areolar-cutaneous "junction" injections to augment sentinel node count activity.

PURPOSE: The authors report on a modified lymphoscintigraphy protocol for increasing activity in the sentinel node (SN) through a specific technique (LymphoBoost). It consists of an areolar-cutaneous "junction" injection, using a very shallow, high-volume, high-specific-activity injection of 100% filtered Tc-99m sulfur colloid, as an adjunct to their standard protocol. MATERIALS AND METHODS: Results from a previously optimized protocol (group 1, n = 28) were compared with those from their new protocol (group 2, n = 85), which consisted of two sets of consecutively applied (within 12 to 20 minutes) injections: group 2A composed of perilesional and intradermal injections (similar to the previous group 1) followed by group 2B LymphoBoost injections within 12 to 20 minutes in the same patients. Regions of interest were drawn around the SN and the injection sites (IS) at the end of the studies to calculate the end-of-study SN:IS ratio for both group 1 and group 2 studies. The SN:IS ratio is generally independent of dose and is a measurement of the "efficiency" of getting activity from the IS to the SN. RESULTS: The mean SN:IS ratio in group 2 was 3.34 times greater than that in group 1 studies (P < 0.0005). The median SN:IS ratio was 3.53 times greater in the group 2 studies. Many cases showed a dramatic increase in SN counts before the LymphoBoost injection was even completed, with more than 5% of injected activity reaching nodes at the end of the study in some patients. Multiple different lymphatic pathways were noted, but all led to the same node(s). No significant disagreement between group 2A and group 2B results was noted. CONCLUSIONS: Areolar-cutaneous junction injections, performed under these conditions, augment SN activity dramatically in most patients. Hotter nodes provide several benefits, especially when next-day surgery is contemplated, and should also reduce the extent of dissection needed to remove the sentinel node.

Breast↗
PubMed2003

The usefulness of a repeat study for differentiating between bowel activity and local tumor recurrence on FDG PET scans.

The importance of fluorodeoxyglucose (FDG) positron emission tomography (PET) in the evaluation of colorectal cancer is well established. Activity in the rectosigmoid region on an FDG PET scan may vary significantly, which may occasionally lead to difficulties in interpretation when assessing local recurrence of colorectal cancer. The authors present a case in which a repeat PET study performed after an enema 1 week later was useful for differentiating between normal bowel activity and local tumor recurrence. This repeat study obviated the need for surgical intervention, although the role of the enema in this case is unclear.

Colon↗
PubMed2003

Comparison of 2-dimensional and 3-dimensional 82Rb myocardial perfusion PET imaging.

UNLABELLED: We compared 2-dimensional (2D) and 3-dimensional (3D) (82)Rb PET imaging in 3 different experiments: in a realistic heart-thorax phantom, in a uniformity-resolution phantom, and in 14 healthy volunteers. METHODS: A nonuniform heart-thorax phantom was filled with 111 MBq of (82)Rb injected into the left ventricular (LV) wall. In the LV wall of the cardiac phantom, 3 inserts-1, 2, and 3 cm in diameter-were placed to simulate infarcts. A standard rest cardiac PET imaging protocol in 2D and 3D modes was used. Following the same protocol, a uniformity-resolution phantom with uniformly distributed activity of 1,998 MBq and 740 MBq of (82)Rb in water was used to obtain 2D PET images and 3D PET images, respectively. All 2D volunteer studies were performed by injecting 2,220 MBq of (82)Rb intravenously. For half the volunteers, 3D studies were performed with a high dose (HD) (2,220 MBq) of (82)Rb; for the remainder of the 3D studies, a low dose (LD) (740 MBq) of (82)Rb was used. In the 2D and LD 3D studies, there was a delay of 2 min and 3 min, respectively, followed by a 6-min acquisition. In the HD 3D volunteer studies, there was a delay of 5 min followed by a 6-min acquisition. Circumferential profiles of the short-axis slices and the contrast of the inserts were used to evaluate the cardiac phantom PET images. The transaxial slices from the uniformity-resolution phantom were evaluated by visual inspection and by measuring uniformity. The human studies were evaluated by measuring the contrast between LV wall and LV cavity, using linear profiles and visual analysis. RESULTS: In the cardiac phantom study, circumferential profiles for the 2D and 3D images were similar. The contrast values for the 1-, 2-, and 3-cm inserts in the 2D study were 0.19 +/- 0.03, 0.34 +/- 0.05, and 0.61 +/- 0.03, respectively. The respective contrast values in the 3D study were 0.15 +/- 0.02, 0.36 +/- 0.04, and 0.52 +/- 0.05. In the uniformity-resolution phantom study, the coefficients of variation, calculated for a representative uniform slice, were 5.3% and 7.6% for the 2D and 3D studies, respectively. For the 7 volunteers on whom HD 3D was used, the mean 2D contrast was 0.33 +/- 0.08 and the mean HD 3D contrast was 0.35 +/- 0.08 (P = not statistically significant). For the other 7 volunteers, on whom LD 3D was used, the mean 2D contrast was 0.39 +/- 0.06 and the mean LD 3D contrast was 0.39 +/- 0.10 (P = not statistically significant). In the tomographic slices, the 2D and 3D images and polar plots were similar. CONCLUSION: When obtained with a PET system having a high counting-rate performance, 2D and 3D (82)Rb PET cardiac images are comparable. LD 3D imaging can make (82)Rb PET cardiac imaging more affordable.

Heart↗
PubMed2003

Factors affecting visualization rates of internal mammary sentinel nodes during lymphoscintigraphy.

UNLABELLED: There is great variation in the reported frequency of internal mammary (IM) sentinel node (SN) visualization. We observed a marked increase in our IM SN detection rate after 2 factors were changed simultaneously: depth of perilesional injection and dose. METHODS: A retrospective review of 82 consecutive patients (group 1) was compared with 61 consecutive patients (group 2) after changing the depth of perilesional injections and dose. Both groups had perilesional injections of (99m)Tc-sulfur colloid followed by intradermal injections at the areolar cutaneous junction. For group 2, activity was increased in all patients scheduled for next-day surgery. Group 2 had perilesional injections on top of, beside, and just below the estimated level of the tumor in an infiltrative manner, versus injections just on top of and beside the tumor as performed for group 1. RESULTS: The rates of IM SN visualization were 4.9% (4/82) for group 1 and 23.0% (14/61) for group 2 (P < 0.003). IM SNs were hotter in group 2 than in group 1. The total number of IM SNs detected per patient was also higher for group 2 than for group 1: 2.1 and 1.2, respectively. In group 2, patients with small breasts had an IM SN visualization rate of 46.2%; those with medium breasts, 21.1%; and those with large breasts, 0% (P < 0.017). In group 2, primary lesions located medially had a higher rate of IM SN visualization than did lesions located laterally: 38.9% (7/18) and 16.2% (6/37), respectively (P = 0.066). Dose was not a statistically significant factor within group 2 or group 1 when comparing IM SN visualization rate for doses above or below the mean or median. CONCLUSION: Modification of just these 2 factors resulted in a striking change in our IM SN detection rates. The injection depth was the most important factor. Breast size had a marked effect on the probability of detecting IM SNs. This suggests that the variation in detection rates reported in the literature could be at least partly dependent on variations in these factors, among others. Many surgeons do not routinely harvest IM SNs, but information about their presence can potentially alter treatment decisions.

Axilla↗