Motion compensation for fully 4D PET reconstruction using PET superset data.

Fully 4D PET image reconstruction is receiving increasing research interest due to its ability to significantly reduce spatiotemporal noise in dynamic PET imaging. However, thus far in the literature, the important issue of correcting for subject head motion has not been considered. Specifically, as a direct consequence of using temporally extensive basis functions, a single instance of movement propagates to impair the reconstruction of multiple time frames, even if no further movement occurs in those frames. Existing 3D motion compensation strategies have not yet been adapted to 4D reconstruction, and as such the benefits of 4D algorithms have not yet been reaped in a clinical setting where head movement undoubtedly occurs. This work addresses this need, developing a motion compensation method suitable for fully 4D reconstruction methods which exploits an optical tracking system to measure the head motion along with PET superset data to store the motion compensated data. List-mode events are histogrammed as PET superset data according to the measured motion, and a specially devised normalization scheme for motion compensated reconstruction from the superset data is required. This work proceeds to propose the corresponding time-dependent normalization modifications which are required for a major class of fully 4D image reconstruction algorithms (those which use linear combinations of temporal basis functions). Using realistically simulated as well as real high-resolution PET data from the HRRT, we demonstrate both the detrimental impact of subject head motion in fully 4D PET reconstruction and the efficacy of our proposed modifications to 4D algorithms. Benefits are shown both for the individual PET image frames as well as for parametric images of tracer uptake and volume of distribution for (18)F-FDG obtained from Patlak analysis.

Development of a THz spectroscopic imaging system.

We have developed a real-time THz imaging system based on the two-dimensional (2D) electro-optic (EO) sampling technique. Employing the 2D EO-sampling technique, we can obtain THz images using a CCD camera at a video rate of up to 30 frames per second. A spatial resolution of 1.4 mm was achieved. This resolution was reasonably close to the theoretical limit determined by diffraction. We observed not only static objects but also moving ones. To acquire spectroscopic information, time-domain images were collected. By processing these images on a computer, we can obtain spectroscopic images. Spectroscopy for silicon wafers was demonstrated.

Contractile properties of urethral smooth muscles of young and aged female dogs: morphological and pharmacological aspects.

BACKGROUND: Alpha1-adrenoceptors are highly concentrated in the urethral smooth muscles and may play an important role in the contraction of this area. However, detailed examinations of age-related changes of the properties of urethral smooth muscle have rarely been undertaken. METHODS: The contractile properties of urethras from young non-parous and old parous female beagles were determined with a urethral function study, macroscopic autoradiography for urethras using [3H]-labeled tamsulosin and morphometry of the urethral muscles. RESULTS: The antagonistic effect (pA2) of prazosin for norepinephrine was 7.76+/-0.13 in young dogs and 7.62+/-0.06 in aged dogs. The specific binding of [3H]-tamsulosin (a relatively selective alpha1A-adrenoceptor antagonist) was recognized diffusely in proximal urethras with in vitro autoradiography. The density of binding in smooth muscles was approximately 60 and 40% in circular longitudinal layers, respectively, for both dogs. CONCLUSIONS: The female canine urethra had alpha1A, and alpha1L-adrenoceptors. No age-related changes were seen in the function of the proximal urethra, distribution of alpha1-adrenoceptor binding sites and smooth muscle densities.

Distribution of alpha1-adrenoceptor subtype mRNAs in human renal cortex.

OBJECTIVE: To determine the quantity and distribution of alpha1-adrenoceptor subtype mRNAs in human renal cortex. MATERIALS AND METHODS: Specimens of renal cortex tissue were obtained at the time of radical nephrectomy or total nephroureterectomy from 46 patients (mean age 59.0 years, sd 14.7) with renal cell carcinoma, renal pelvic or ureteric tumour. Using the reverse-transcriptase polymerase chain reaction (RT-PCR), the RNase protection assay and in situ hybridization, the presentation, quantity and distribution of alpha1-adrenoceptor subtype mRNAs were determined. RESULTS: Expression of the three alpha1-adrenoceptor subtype mRNAs (alpha1a, alpha1b and alpha1d) was confirmed in the arteries of the renal cortex (arciform, interlobular, arteriole), but among the three subtypes, the alpha1b was less apparent by in situ hybridization. Intense alpha1-mRNA staining was apparent especially in the smooth muscle of arterial walls. In both proximal and distal renal tubules, each of the alpha1-mRNAs was less marked in cytoplasm than in the arteries. In the glomeruli weak staining was detected in the endothelium but there was no obvious staining in the veins. RT-PCR showed all three subtypes of alpha1-adrenoceptor. The RNase protection assay showed that the predominant alpha1-adrenoceptor subtype mRNA in human renal cortex was alpha1a. However, the abundance of alpha1a-mRNA in human kidney was much less than in the prostate. CONCLUSION: Three alpha1-adrenoceptor subtype mRNAs were recognized in human renal cortex and detected particularly in the smooth muscle of the arteries. There was more alpha1a-adrenoceptor subtype in human renal cortex than the other subtypes. It is not known how each subtype operates against adrenergic stimulation; further studies are needed to examine receptor density or receptor function.

The alpha1L-adrenoceptor subtype in the lower urinary tract: a comparison of human urethra and prostate.

OBJECTIVE: To identify the alpha1-adrenoceptor subtypes present in the human urethra, by comparing the affinity of prazosin for alpha1-adrenoceptors in the rabbit, dog and human prostatic urethra, and in the dog and human prostate. MATERIALS AND METHODS: The study comprised samples of human prostate and prostatic urethra, obtained by open prostatectomy of patients with benign prostatic hyperplasia, and of the proximal urethra and prostate from male Beagle dogs and rabbits. Specimens were homogenized, filtered and pelleted by centrifugation. Nonspecific binding was determined in the presence of 1 mmol/L prazosin when assessing [3H]YM-617 (tamsulosin) binding, and 10 mmol/L phentolamine when assessing [3H]prazosin binding. Specific binding was defined as the difference between total binding and nonspecific binding. RESULTS: The dissociation constant for [3H]prazosin in the human prostate (0.088 nmol/L) was less than that in the rabbit urethra (0.299 nmol/L), dog urethra (0.604 nmol/L), dog prostate (0.482 nmol/L) and human urethra (0.254 nmol/L). The affinity of prazosin was also investigated by determining the potency of the inhibition of [3H]YM-617 binding. The affinity of prazosin for alpha1-adrenoceptors in the human urethra (Ki, 2.5 nmol/L) was lower than its affinity for alpha1-adrenoceptors in the human prostate (Ki, 0.25 nmol/L) and all of the cloned subtypes (Ki, 0.26-0.44 nmol/L). CONCLUSION: The alpha1L-adrenoceptor subtype is more prominent in the human, rabbit and dog urethra and dog prostate than in the human prostate.

Quantification and distribution of alpha1-adrenoceptor subtype mRNAs in human proximal urethra.

1. We performed RNase protection assays and in situ hybridization to investigate the ratio of the three alpha1-adrenoceptor subtype mRNAs, alpha1a, alpha1b and alpha1d, in human proximal urethra, and their localization in urethral cross-sections. As revealed by the RNase protection assays, alpha1a was the predominant subtype mRNA in both male and female urethral samples. Alpha1d mRNA was detected only in the female sample, and alpha1b mRNA was not detected in any of the samples tested. The ratio of the abundance of the subtype mRNAs, alpha1a:alpha1b:alpha1d, was 100:0:0 in the male urethra and 90:0:10 in the female urethra. 2. In situ hybridization studies showed no significant differences in the cross-sectional distribution of alpha1-adrenoceptor subtype mRNAs between male and female urethras. Intense alpha1a staining was observed in the smooth muscle of the urethra, but alpha1b and alpha1d staining was much less intense. 3. Of the three cloned alpha1 subtypes, alpha1a is the most likely to be responsible for the contraction of the human urethra. Owing to the side effects of nonselective alpha1 drugs, alpha1-selective drugs may be clinically superior to nonselective drugs for the treatment of urethral disorders.

[Retrograde radical cystectomy. Advantages of our "vesico-rectal tunnel" method].

BACKGROUND: The facilitation of dissecting the vesical pedicles and undisturbed preservation of the membranous urethra were investigated during radical cystectomy using the retrograde technique. METHODS: First, just as with radical prostatectomy, the prostate and the rectum were separated by blunt digital dissection. After the deep dorsal vein complex and the urethra were cut, the bladder and the rectum were also separated in a retrograde manner towards the Denonvillier's fascia. Then the peritoneum was opened and its lowest part was incised above the cul-de-sac. A tunnel was made beginning at the cut-end of the urethra to the cul-de-sac. Consequently, the bladder was lifted up by hand inserted this "vesico-rectal tunnel" and the bilateral remaining lateral pedicles were ligated and transsected without difficulty. RESULTS: Fourteen patients underwent radical cystectomy using this technique. Among them, the average operating time and blood loss in 4 patients received retrograde radical cystectomy accompanied with ileal conduit were 5 hours 15 minutes and 1606 ml, respectively. These in 9 patients received retrograde radical cystectomy followed by bowel orthotopic urinary reservoir were 7 hours and 6 minutes and 1086 ml, respectively. Another patient received ureterocutaneoustomy. CONCLUSION: Creating a "vesico-rectal tunnel" during radical cystectomy primarily by the retrograde extraperitoneal technique can afford to preserve the urethral sphincter and to ligate the pedicles easily. This method is fundamentally familiar to us because retrograde radical prostatectomy is now widely adopted and it may help to reduce the operating time even when there is a shortage of manpower.

Prostatic cancer presenting monoclonal gammopathy: report of two cases.

Two cases of prostatic cancer accompanied by monoclonal gammopathy of undetermined significance (MGUS) are reported. Both cases presented IgG-lambda type hyperimmunoglobulinemia and Bence Jones protein (BJP) in the urine. A characteristic of both cases was significant multiple bone metastasis, and one case also demonstrated a severe immunological disorder. During the treatment, one patient recovered from MGUS. We recommend that elderly male patients manifesting MGUS be examined for prostatic cancer.