Optimal leaf sequencing with elimination of tongue-and-groove underdosage

The individual leaves of a multileaf collimator (MLC) have a tongue-and-groove or stepped-edge design to minimize leakage radiation between adjacent leaves. This design element has a drawback in that it creates areas of underdosages in intensity-modulated photon beams unless a leaf trajectory is specifically designed such that for any two adjacent leaf pairs, the direct exposure under the tongue-and-groove is equal to the lower of the direct exposures of the leaf pairs. In this work, we present a systematic study of the optimization of a leaf sequencing algorithm for segmental multileaf collimator beam delivery that completely eliminates areas of underdosages due to tongue-and-groove or stepped-edge design of the MLC. Simultaneous elimination of tongue-and-groove effect and leaf interdigitation is also studied. This is an extension of our previous work (Kamath et al 2003a Phys. Med. Biol. 48 307) in which we described a leaf sequencing algorithm that is optimal for monitor unit (MU) efficiency under most common leaf movement constraints that include minimum leaf separation. Compared to our previously published algorithm (without constraints), the new algorithms increase the number of sub-fields by approximately 21% and 25%, respectively, but are optimal in MU efficiency for unidirectional schedules.     

Recurrent diffuse lipomatosis of the neck--a case report

Diffuse lipomatosis is a rare disorder of adipose tissue occurring in young people . It has a predilection for trunk and proximal extremities where it presents as poorly circumscribed overgrowth of fatty tissue. Definite diagnosis is established by histological examination of tumor. Though it attains extensive size and has a high tendency to recur, the clinical course is benign.     

Short-term impact of COVID-19 on quality of life,perceived stress,and serious psychological distress in an adult population in the midwest United States

Quality of Life Research - This study aimed to investigate changes over time in quality of life, perceived stress, and serious psychological distress for individuals diagnosed with COVID-19 in an...     

Elevated serum PAR-1 levels as an emerging biomarker of inflammation to predict the dengue infection severity

The present study was designed to check the serum levels of protease-activated receptor (PAR-1) in patients during different phases of dengue severity. Moreover, a correlation between serum PAR-1 levels and hematological parameters, inflammatory cytokine levels, and liver functional changes was also determined. Based on the World Health Organization criteria, the study population was divided into: nonsevere dengue fever (DF; n = 30), severe dengue hemorrhagic fever (DHF; n = 19), and severe dengue shock syndrome (DSS; n = 11). The platelet count (PLT) and hematocrit (HCT) were analyzed using an automated hematology analyzer and liver function enzymes aspartate transaminase (AST), alanine transaminase (ALT), and alkaline phosphate (ALP), bilirubin were checked by auto-analyzer using diagnostic kits. Moreover, the levels of inflammatory mediators C-reactive protein (CRP), tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), interleukin-17 (IL-17), and PAR-1 were determined using respective ELISA kits. The HCT levels were elevated and platelet count decreased significantly during dengue complications (DHF and DSS) compared to the DF patients, while the levels of liver functional biomarkers AST, ALT, ALP, and bilirubin remained elevated in DHF and DSS groups than in the corresponding DF group. Similarly, the inflammatory cytokine levels of CRP, TNF-α, IL-6, and IL-17 in DHF and DSS subjects were markedly increased when observed against DF subjects. Notably, the PAR-1 levels were significantly elevated in DHF and DSS groups than in the DF group and positively correlated with changes in HCT levels, inflammatory biomarkers, and liver enzymes. Our findings conclude that PAR-1 levels persistently increased with the severity of the dengue infection and are strongly associated with various clinical manifestations. Thus, PAR-1 levels can be used as a diagnostic marker for assessing dengue severity.     

Limb salvage surgery in bone tumour with modular endoprosthesis

 Thirty-three patients with bone tumours were treated by resection of the growth and reconstruction with a Kotz modular endoprosthesis. The average follow-up was for 50 months, ranging from 14 to 79 months. At the last review, 12 patients (36%) had died due to the tumour and 9 others (27%) had metastases. All 4 patients with proximal tibial reconstruction had poor functional results, due to an extension lag or to knee stiffness. Four of the six tumours of the proximal femur were complicated by local recurrence or dislocation of the hip, and had poor or fair functional results. Of the patients with distal femoral reconstruction, 17 out of 22 had excellent or good functional results. Reconstruction with a modular prosthesis after resection of a tumour gives excellent or good functional results in more than three-fourths of the cases of distal femur reconstruction, but it should be used with caution in the proximal tibia and proximal femur.

---

Resumé  33 patients avec une tumeur(s) osseuse(s) ont ete traites par résection chirurgicale suivie d’une reconstruction avec endoprothese modulaire de Kotz. Les patients étaient suivis pour une periode allant de 14 a 79 mois (50 mois). Au dernier bilan 12 malades (36%) avaient une mort liee a la-tumeur. Le resultat fonctionnel a ete insatisfaisant chez tous les patients ayant subi une reconstruction tibiale proximale: soit un deficit de l’extension due genou ou la raideur. Dans les deux-tiers des cas (4 sur 6) avec reconstruction femorale proximale, des complications ont été observees: recidive locale, luxation de la tete femorale et mauvais voir mediocre resultat fonctionnel. Plus des trois quarts des patients avec reconstruction femorale distale (17/22) ont eu un bon voir excellent resultat fonctionnel. Le type de reconstruction avec prothèse modulaire apres résection tumorale parait bien indiquée chez des patients avec grosse tumeur osseuse et souhaitant preserver une mobilité adequate. Cette chirurgie peut donner un bon ou excellent resultat fonctionnel dans plus de 3/4 des cas de reconstruction distale du femur, mais elle doit être utilisée avec précaution dans la reconstruction tibiale et femorale proximales vu le risque de complications a type de luxation de la tête femorale et de déficit de l’extension.

---

---

Accepted: 8 July 1998